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authorMark Adler <madler@alumni.caltech.edu>2011-09-09 23:26:40 -0700
committerMark Adler <madler@alumni.caltech.edu>2011-09-09 23:26:40 -0700
commitf6194ef39af5864f792412460c354cc339dde7d1 (patch)
tree5ea1e6849128e9b2194c66ee3d82afa36b4ac07c /examples
parent639be997883d9016baaf46017a2802b2ce1698bd (diff)
downloadzlib-f6194ef39af5864f792412460c354cc339dde7d1.tar.gz
zlib 1.2.3.4v1.2.3.4
Diffstat (limited to 'examples')
-rw-r--r--examples/README.examples21
-rw-r--r--examples/enough.c569
-rw-r--r--examples/gzlog.c1303
-rw-r--r--examples/gzlog.h93
-rw-r--r--examples/pigz.c452
5 files changed, 2074 insertions, 364 deletions
diff --git a/examples/README.examples b/examples/README.examples
index 5632d7a..146919c 100644
--- a/examples/README.examples
+++ b/examples/README.examples
@@ -1,4 +1,10 @@
-This directory contains examples of the use of zlib.
+This directory contains examples of the use of zlib and other relevant
+programs and documentation.
+
+enough.c
+ calculation and justification of ENOUGH parameter in inftrees.h
+ - calculates the maximum table space used in inflate tree
+ construction over all possible Huffman codes
fitblk.c
compress just enough input to nearly fill a requested output size
@@ -23,9 +29,16 @@ gzjoin.c
gzlog.c
gzlog.h
- efficiently maintain a message log file in gzip format
- - illustrates use of raw deflate and Z_SYNC_FLUSH
- - illustrates use of gzip header extra field
+ efficiently and robustly maintain a message log file in gzip format
+ - illustrates use of raw deflate, Z_PARTIAL_FLUSH, deflatePrime(),
+ and deflateSetDictionary()
+ - illustrates use of a gzip header extra field
+
+pigz.c
+ parallel implementation of gzip compression
+ - uses pthreads to speed up compression on multiple core machines
+ - illustrates the use of deflateSetDictionary() with raw deflate
+ - illustrates the use of crc32_combine()
zlib_how.html
painfully comprehensive description of zpipe.c (see below)
diff --git a/examples/enough.c b/examples/enough.c
new file mode 100644
index 0000000..b570707
--- /dev/null
+++ b/examples/enough.c
@@ -0,0 +1,569 @@
+/* enough.c -- determine the maximum size of inflate's Huffman code tables over
+ * all possible valid and complete Huffman codes, subject to a length limit.
+ * Copyright (C) 2007, 2008 Mark Adler
+ * Version 1.3 17 February 2008 Mark Adler
+ */
+
+/* Version history:
+ 1.0 3 Jan 2007 First version (derived from codecount.c version 1.4)
+ 1.1 4 Jan 2007 Use faster incremental table usage computation
+ Prune examine() search on previously visited states
+ 1.2 5 Jan 2007 Comments clean up
+ As inflate does, decrease root for short codes
+ Refuse cases where inflate would increase root
+ 1.3 17 Feb 2008 Add argument for initial root table size
+ Fix bug for initial root table size == max - 1
+ Use a macro to compute the history index
+ */
+
+/*
+ Examine all possible Huffman codes for a given number of symbols and a
+ maximum code length in bits to determine the maximum table size for zilb's
+ inflate. Only complete Huffman codes are counted.
+
+ Two codes are considered distinct if the vectors of the number of codes per
+ length are not identical. So permutations of the symbol assignments result
+ in the same code for the counting, as do permutations of the assignments of
+ the bit values to the codes (i.e. only canonical codes are counted).
+
+ We build a code from shorter to longer lengths, determining how many symbols
+ are coded at each length. At each step, we have how many symbols remain to
+ be coded, what the last code length used was, and how many bit patterns of
+ that length remain unused. Then we add one to the code length and double the
+ number of unused patterns to graduate to the next code length. We then
+ assign all portions of the remaining symbols to that code length that
+ preserve the properties of a correct and eventually complete code. Those
+ properties are: we cannot use more bit patterns than are available; and when
+ all the symbols are used, there are exactly zero possible bit patterns
+ remaining.
+
+ The inflate Huffman decoding algorithm uses two-level lookup tables for
+ speed. There is a single first-level table to decode codes up to root bits
+ in length (root == 9 in the current inflate implementation). The table
+ has 1 << root entries and is indexed by the next root bits of input. Codes
+ shorter than root bits have replicated table entries, so that the correct
+ entry is pointed to regardless of the bits that follow the short code. If
+ the code is longer than root bits, then the table entry points to a second-
+ level table. The size of that table is determined by the longest code with
+ that root-bit prefix. If that longest code has length len, then the table
+ has size 1 << (len - root), to index the remaining bits in that set of
+ codes. Each subsequent root-bit prefix then has its own sub-table. The
+ total number of table entries required by the code is calculated
+ incrementally as the number of codes at each bit length is populated. When
+ all of the codes are shorter than root bits, then root is reduced to the
+ longest code length, resulting in a single, smaller, one-level table.
+
+ The inflate algorithm also provides for small values of root (relative to
+ the log2 of the number of symbols), where the shortest code has more bits
+ than root. In that case, root is increased to the length of the shortest
+ code. This program, by design, does not handle that case, so it is verified
+ that the number of symbols is less than 2^(root + 1).
+
+ In order to speed up the examination (by about ten orders of magnitude for
+ the default arguments), the intermediate states in the build-up of a code
+ are remembered and previously visited branches are pruned. The memory
+ required for this will increase rapidly with the total number of symbols and
+ the maximum code length in bits. However this is a very small price to pay
+ for the vast speedup.
+
+ First, all of the possible Huffman codes are counted, and reachable
+ intermediate states are noted by a non-zero count in a saved-results array.
+ Second, the intermediate states that lead to (root + 1) bit or longer codes
+ are used to look at all sub-codes from those junctures for their inflate
+ memory usage. (The amount of memory used is not affected by the number of
+ codes of root bits or less in length.) Third, the visited states in the
+ construction of those sub-codes and the associated calculation of the table
+ size is recalled in order to avoid recalculating from the same juncture.
+ Beginning the code examination at (root + 1) bit codes, which is enabled by
+ identifying the reachable nodes, accounts for about six of the orders of
+ magnitude of improvement for the default arguments. About another four
+ orders of magnitude come from not revisiting previous states. Out of
+ approximately 2x10^16 possible Huffman codes, only about 2x10^6 sub-codes
+ need to be examined to cover all of the possible table memory usage cases
+ for the default arguments of 286 symbols limited to 15-bit codes.
+
+ Note that an unsigned long long type is used for counting. It is quite easy
+ to exceed the capacity of an eight-byte integer with a large number of
+ symbols and a large maximum code length, so multiple-precision arithmetic
+ would need to replace the unsigned long long arithmetic in that case. This
+ program will abort if an overflow occurs. The big_t type identifies where
+ the counting takes place.
+
+ An unsigned long long type is also used for calculating the number of
+ possible codes remaining at the maximum length. This limits the maximum
+ code length to the number of bits in a long long minus the number of bits
+ needed to represent the symbols in a flat code. The code_t type identifies
+ where the bit pattern counting takes place.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+#define local static
+
+/* special data types */
+typedef unsigned long long big_t; /* type for code counting */
+typedef unsigned long long code_t; /* type for bit pattern counting */
+struct tab { /* type for been here check */
+ size_t len; /* length of bit vector in char's */
+ char *vec; /* allocated bit vector */
+};
+
+/* The array for saving results, num[], is indexed with this triplet:
+
+ syms: number of symbols remaining to code
+ left: number of available bit patterns at length len
+ len: number of bits in the codes currently being assigned
+
+ Those indices are constrained thusly when saving results:
+
+ syms: 3..totsym (totsym == total symbols to code)
+ left: 2..syms - 1, but only the evens (so syms == 8 -> 2, 4, 6)
+ len: 1..max - 1 (max == maximum code length in bits)
+
+ syms == 2 is not saved since that immediately leads to a single code. left
+ must be even, since it represents the number of available bit patterns at
+ the current length, which is double the number at the previous length.
+ left ends at syms-1 since left == syms immediately results in a single code.
+ (left > sym is not allowed since that would result in an incomplete code.)
+ len is less than max, since the code completes immediately when len == max.
+
+ The offset into the array is calculated for the three indices with the
+ first one (syms) being outermost, and the last one (len) being innermost.
+ We build the array with length max-1 lists for the len index, with syms-3
+ of those for each symbol. There are totsym-2 of those, with each one
+ varying in length as a function of sym. See the calculation of index in
+ count() for the index, and the calculation of size in main() for the size
+ of the array.
+
+ For the deflate example of 286 symbols limited to 15-bit codes, the array
+ has 284,284 entries, taking up 2.17 MB for an 8-byte big_t. More than
+ half of the space allocated for saved results is actually used -- not all
+ possible triplets are reached in the generation of valid Huffman codes.
+ */
+
+/* The array for tracking visited states, done[], is itself indexed identically
+ to the num[] array as described above for the (syms, left, len) triplet.
+ Each element in the array is further indexed by the (mem, rem) doublet,
+ where mem is the amount of inflate table space used so far, and rem is the
+ remaining unused entries in the current inflate sub-table. Each indexed
+ element is simply one bit indicating whether the state has been visited or
+ not. Since the ranges for mem and rem are not known a priori, each bit
+ vector is of a variable size, and grows as needed to accommodate the visited
+ states. mem and rem are used to calculate a single index in a triangular
+ array. Since the range of mem is expected in the default case to be about
+ ten times larger than the range of rem, the array is skewed to reduce the
+ memory usage, with eight times the range for mem than for rem. See the
+ calculations for offset and bit in beenhere() for the details.
+
+ For the deflate example of 286 symbols limited to 15-bit codes, the bit
+ vectors grow to total approximately 21 MB, in addition to the 4.3 MB done[]
+ array itself.
+ */
+
+/* Globals to avoid propagating constants or constant pointers recursively */
+local int max; /* maximum allowed bit length for the codes */
+local int root; /* size of base code table in bits */
+local int large; /* largest code table so far */
+local size_t size; /* number of elements in num and done */
+local int *code; /* number of symbols assigned to each bit length */
+local big_t *num; /* saved results array for code counting */
+local struct tab *done; /* states already evaluated array */
+
+/* Index function for num[] and done[] */
+#define INDEX(i,j,k) (((size_t)((i-1)>>1)*((i-2)>>1)+(j>>1)-1)*(max-1)+k-1)
+
+/* Free allocated space. Uses globals code, num, and done. */
+local void cleanup(void)
+{
+ size_t n;
+
+ if (done != NULL) {
+ for (n = 0; n < size; n++)
+ if (done[n].len)
+ free(done[n].vec);
+ free(done);
+ }
+ if (num != NULL)
+ free(num);
+ if (code != NULL)
+ free(code);
+}
+
+/* Return the number of possible Huffman codes using bit patterns of lengths
+ len through max inclusive, coding syms symbols, with left bit patterns of
+ length len unused -- return -1 if there is an overflow in the counting.
+ Keep a record of previous results in num to prevent repeating the same
+ calculation. Uses the globals max and num. */
+local big_t count(int syms, int len, int left)
+{
+ big_t sum; /* number of possible codes from this juncture */
+ big_t got; /* value returned from count() */
+ int least; /* least number of syms to use at this juncture */
+ int most; /* most number of syms to use at this juncture */
+ int use; /* number of bit patterns to use in next call */
+ size_t index; /* index of this case in *num */
+
+ /* see if only one possible code */
+ if (syms == left)
+ return 1;
+
+ /* note and verify the expected state */
+ assert(syms > left && left > 0 && len < max);
+
+ /* see if we've done this one already */
+ index = INDEX(syms, left, len);
+ got = num[index];
+ if (got)
+ return got; /* we have -- return the saved result */
+
+ /* we need to use at least this many bit patterns so that the code won't be
+ incomplete at the next length (more bit patterns than symbols) */
+ least = (left << 1) - syms;
+ if (least < 0)
+ least = 0;
+
+ /* we can use at most this many bit patterns, lest there not be enough
+ available for the remaining symbols at the maximum length (if there were
+ no limit to the code length, this would become: most = left - 1) */
+ most = (((code_t)left << (max - len)) - syms) /
+ (((code_t)1 << (max - len)) - 1);
+
+ /* count all possible codes from this juncture and add them up */
+ sum = 0;
+ for (use = least; use <= most; use++) {
+ got = count(syms - use, len + 1, (left - use) << 1);
+ sum += got;
+ if (got == -1 || sum < got) /* overflow */
+ return -1;
+ }
+
+ /* verify that all recursive calls are productive */
+ assert(sum != 0);
+
+ /* save the result and return it */
+ num[index] = sum;
+ return sum;
+}
+
+/* Return true if we've been here before, set to true if not. Set a bit in a
+ bit vector to indicate visiting this state. Each (syms,len,left) state
+ has a variable size bit vector indexed by (mem,rem). The bit vector is
+ lengthened if needed to allow setting the (mem,rem) bit. */
+local int beenhere(int syms, int len, int left, int mem, int rem)
+{
+ size_t index; /* index for this state's bit vector */
+ size_t offset; /* offset in this state's bit vector */
+ int bit; /* mask for this state's bit */
+ size_t length; /* length of the bit vector in bytes */
+ char *vector; /* new or enlarged bit vector */
+
+ /* point to vector for (syms,left,len), bit in vector for (mem,rem) */
+ index = INDEX(syms, left, len);
+ mem -= 1 << root;
+ offset = (mem >> 3) + rem;
+ offset = ((offset * (offset + 1)) >> 1) + rem;
+ bit = 1 << (mem & 7);
+
+ /* see if we've been here */
+ length = done[index].len;
+ if (offset < length && (done[index].vec[offset] & bit) != 0)
+ return 1; /* done this! */
+
+ /* we haven't been here before -- set the bit to show we have now */
+
+ /* see if we need to lengthen the vector in order to set the bit */
+ if (length <= offset) {
+ /* if we have one already, enlarge it, zero out the appended space */
+ if (length) {
+ do {
+ length <<= 1;
+ } while (length <= offset);
+ vector = realloc(done[index].vec, length);
+ if (vector != NULL)
+ memset(vector + done[index].len, 0, length - done[index].len);
+ }
+
+ /* otherwise we need to make a new vector and zero it out */
+ else {
+ length = 1 << (len - root);
+ while (length <= offset)
+ length <<= 1;
+ vector = calloc(length, sizeof(char));
+ }
+
+ /* in either case, bail if we can't get the memory */
+ if (vector == NULL) {
+ fputs("abort: unable to allocate enough memory\n", stderr);
+ cleanup();
+ exit(1);
+ }
+
+ /* install the new vector */
+ done[index].len = length;
+ done[index].vec = vector;
+ }
+
+ /* set the bit */
+ done[index].vec[offset] |= bit;
+ return 0;
+}
+
+/* Examine all possible codes from the given node (syms, len, left). Compute
+ the amount of memory required to build inflate's decoding tables, where the
+ number of code structures used so far is mem, and the number remaining in
+ the current sub-table is rem. Uses the globals max, code, root, large, and
+ done. */
+local void examine(int syms, int len, int left, int mem, int rem)
+{
+ int least; /* least number of syms to use at this juncture */
+ int most; /* most number of syms to use at this juncture */
+ int use; /* number of bit patterns to use in next call */
+
+ /* see if we have a complete code */
+ if (syms == left) {
+ /* set the last code entry */
+ code[len] = left;
+
+ /* complete computation of memory used by this code */
+ while (rem < left) {
+ left -= rem;
+ rem = 1 << (len - root);
+ mem += rem;
+ }
+ assert(rem == left);
+
+ /* if this is a new maximum, show the entries used and the sub-code */
+ if (mem > large) {
+ large = mem;
+ printf("max %d: ", mem);
+ for (use = root + 1; use <= max; use++)
+ if (code[use])
+ printf("%d[%d] ", code[use], use);
+ putchar('\n');
+ fflush(stdout);
+ }
+
+ /* remove entries as we drop back down in the recursion */
+ code[len] = 0;
+ return;
+ }
+
+ /* prune the tree if we can */
+ if (beenhere(syms, len, left, mem, rem))
+ return;
+
+ /* we need to use at least this many bit patterns so that the code won't be
+ incomplete at the next length (more bit patterns than symbols) */
+ least = (left << 1) - syms;
+ if (least < 0)
+ least = 0;
+
+ /* we can use at most this many bit patterns, lest there not be enough
+ available for the remaining symbols at the maximum length (if there were
+ no limit to the code length, this would become: most = left - 1) */
+ most = (((code_t)left << (max - len)) - syms) /
+ (((code_t)1 << (max - len)) - 1);
+
+ /* occupy least table spaces, creating new sub-tables as needed */
+ use = least;
+ while (rem < use) {
+ use -= rem;
+ rem = 1 << (len - root);
+ mem += rem;
+ }
+ rem -= use;
+
+ /* examine codes from here, updating table space as we go */
+ for (use = least; use <= most; use++) {
+ code[len] = use;
+ examine(syms - use, len + 1, (left - use) << 1,
+ mem + (rem ? 1 << (len - root) : 0), rem << 1);
+ if (rem == 0) {
+ rem = 1 << (len - root);
+ mem += rem;
+ }
+ rem--;
+ }
+
+ /* remove entries as we drop back down in the recursion */
+ code[len] = 0;
+}
+
+/* Look at all sub-codes starting with root + 1 bits. Look at only the valid
+ intermediate code states (syms, left, len). For each completed code,
+ calculate the amount of memory required by inflate to build the decoding
+ tables. Find the maximum amount of memory required and show the code that
+ requires that maximum. Uses the globals max, root, and num. */
+local void enough(int syms)
+{
+ int n; /* number of remaing symbols for this node */
+ int left; /* number of unused bit patterns at this length */
+ size_t index; /* index of this case in *num */
+
+ /* clear code */
+ for (n = 0; n <= max; n++)
+ code[n] = 0;
+
+ /* look at all (root + 1) bit and longer codes */
+ large = 1 << root; /* base table */
+ if (root < max) /* otherwise, there's only a base table */
+ for (n = 3; n <= syms; n++)
+ for (left = 2; left < n; left += 2)
+ {
+ /* look at all reachable (root + 1) bit nodes, and the
+ resulting codes (complete at root + 2 or more) */
+ index = INDEX(n, left, root + 1);
+ if (root + 1 < max && num[index]) /* reachable node */
+ examine(n, root + 1, left, 1 << root, 0);
+
+ /* also look at root bit codes with completions at root + 1
+ bits (not saved in num, since complete), just in case */
+ if (num[index - 1] && n <= left << 1)
+ examine((n - left) << 1, root + 1, (n - left) << 1,
+ 1 << root, 0);
+ }
+
+ /* done */
+ printf("done: maximum of %d table entries\n", large);
+}
+
+/*
+ Examine and show the total number of possible Huffman codes for a given
+ maximum number of symbols, initial root table size, and maximum code length
+ in bits -- those are the command arguments in that order. The default
+ values are 286, 9, and 15 respectively, for the deflate literal/length code.
+ The possible codes are counted for each number of coded symbols from two to
+ the maximum. The counts for each of those and the total number of codes are
+ shown. The maximum number of inflate table entires is then calculated
+ across all possible codes. Each new maximum number of table entries and the
+ associated sub-code (starting at root + 1 == 10 bits) is shown.
+
+ To count and examine Huffman codes that are not length-limited, provide a
+ maximum length equal to the number of symbols minus one.
+
+ For the deflate literal/length code, use "enough". For the deflate distance
+ code, use "enough 30 6".
+
+ This uses the %llu printf format to print big_t numbers, which assumes that
+ big_t is an unsigned long long. If the big_t type is changed (for example
+ to a multiple precision type), the method of printing will also need to be
+ updated.
+ */
+int main(int argc, char **argv)
+{
+ int syms; /* total number of symbols to code */
+ int n; /* number of symbols to code for this run */
+ big_t got; /* return value of count() */
+ big_t sum; /* accumulated number of codes over n */
+
+ /* set up globals for cleanup() */
+ code = NULL;
+ num = NULL;
+ done = NULL;
+
+ /* get arguments -- default to the deflate literal/length code */
+ syms = 286;
+ root = 9;
+ max = 15;
+ if (argc > 1) {
+ syms = atoi(argv[1]);
+ if (argc > 2) {
+ root = atoi(argv[2]);
+ if (argc > 3)
+ max = atoi(argv[3]);
+ }
+ }
+ if (argc > 4 || syms < 2 || root < 1 || max < 1) {
+ fputs("invalid arguments, need: [sym >= 2 [root >= 1 [max >= 1]]]\n",
+ stderr);
+ return 1;
+ }
+
+ /* if not restricting the code length, the longest is syms - 1 */
+ if (max > syms - 1)
+ max = syms - 1;
+
+ /* determine the number of bits in a code_t */
+ n = 0;
+ while (((code_t)1 << n) != 0)
+ n++;
+
+ /* make sure that the calculation of most will not overflow */
+ if (max > n || syms - 2 >= (((code_t)0 - 1) >> (max - 1))) {
+ fputs("abort: code length too long for internal types\n", stderr);
+ return 1;
+ }
+
+ /* reject impossible code requests */
+ if (syms - 1 > ((code_t)1 << max) - 1) {
+ fprintf(stderr, "%d symbols cannot be coded in %d bits\n",
+ syms, max);
+ return 1;
+ }
+
+ /* allocate code vector */
+ code = calloc(max + 1, sizeof(int));
+ if (code == NULL) {
+ fputs("abort: unable to allocate enough memory\n", stderr);
+ return 1;
+ }
+
+ /* determine size of saved results array, checking for overflows,
+ allocate and clear the array (set all to zero with calloc()) */
+ if (syms == 2) /* iff max == 1 */
+ num = NULL; /* won't be saving any results */
+ else {
+ size = syms >> 1;
+ if (size > ((size_t)0 - 1) / (n = (syms - 1) >> 1) ||
+ (size *= n, size > ((size_t)0 - 1) / (n = max - 1)) ||
+ (size *= n, size > ((size_t)0 - 1) / sizeof(big_t)) ||
+ (num = calloc(size, sizeof(big_t))) == NULL) {
+ fputs("abort: unable to allocate enough memory\n", stderr);
+ cleanup();
+ return 1;
+ }
+ }
+
+ /* count possible codes for all numbers of symbols, add up counts */
+ sum = 0;
+ for (n = 2; n <= syms; n++) {
+ got = count(n, 1, 2);
+ sum += got;
+ if (got == -1 || sum < got) { /* overflow */
+ fputs("abort: can't count that high!\n", stderr);
+ cleanup();
+ return 1;
+ }
+ printf("%llu %d-codes\n", got, n);
+ }
+ printf("%llu total codes for 2 to %d symbols", sum, syms);
+ if (max < syms - 1)
+ printf(" (%d-bit length limit)\n", max);
+ else
+ puts(" (no length limit)");
+
+ /* allocate and clear done array for beenhere() */
+ if (syms == 2)
+ done = NULL;
+ else if (size > ((size_t)0 - 1) / sizeof(struct tab) ||
+ (done = calloc(size, sizeof(struct tab))) == NULL) {
+ fputs("abort: unable to allocate enough memory\n", stderr);
+ cleanup();
+ return 1;
+ }
+
+ /* find and show maximum inflate table usage */
+ if (root > max) /* reduce root to max length */
+ root = max;
+ if (syms < ((code_t)1 << (root + 1)))
+ enough(syms);
+ else
+ puts("cannot handle minimum code lengths > root");
+
+ /* done */
+ cleanup();
+ return 0;
+}
diff --git a/examples/gzlog.c b/examples/gzlog.c
index b6acdef..4daf1c2 100644
--- a/examples/gzlog.c
+++ b/examples/gzlog.c
@@ -1,413 +1,1058 @@
/*
* gzlog.c
- * Copyright (C) 2004 Mark Adler
+ * Copyright (C) 2004, 2008 Mark Adler, all rights reserved
* For conditions of distribution and use, see copyright notice in gzlog.h
- * version 1.0, 26 Nov 2004
- *
+ * version 2.0, 25 Apr 2008
*/
-#include <string.h> /* memcmp() */
-#include <stdlib.h> /* malloc(), free(), NULL */
-#include <sys/types.h> /* size_t, off_t */
-#include <unistd.h> /* read(), close(), sleep(), ftruncate(), */
- /* lseek() */
-#include <fcntl.h> /* open() */
-#include <sys/file.h> /* flock() */
-#include "zlib.h" /* deflateInit2(), deflate(), deflateEnd() */
+/*
+ gzlog provides a mechanism for frequently appending short strings to a gzip
+ file that is efficient both in execution time and compression ratio. The
+ strategy is to write the short strings in an uncompressed form to the end of
+ the gzip file, only compressing when the amount of uncompressed data has
+ reached a given threshold.
+
+ gzlog also provides protection against interruptions in the process due to
+ system crashes. The status of the operation is recorded in an extra field
+ in the gzip file, and is only updated once the gzip file is brought to a
+ valid state. The last data to be appended or compressed is saved in an
+ auxiliary file, so that if the operation is interrupted, it can be completed
+ the next time an append operation is attempted.
+
+ gzlog maintains another auxiliary file with the last 32K of data from the
+ compressed portion, which is preloaded for the compression of the subsequent
+ data. This minimizes the impact to the compression ratio of appending.
+ */
+
+/*
+ Operations Concept:
+
+ Files (log name "foo"):
+ foo.gz -- gzip file with the complete log
+ foo.add -- last message to append or last data to compress
+ foo.dict -- dictionary of the last 32K of data for next compression
+ foo.temp -- temporary dictionary file for compression after this one
+ foo.lock -- lock file for reading and writing the other files
+ foo.repairs -- log file for log file recovery operations (not compressed)
+
+ gzip file structure:
+ - fixed-length (no file name) header with extra field (see below)
+ - compressed data ending initially with empty stored block
+ - uncompressed data filling out originally empty stored block and
+ subsequent stored blocks as needed (16K max each)
+ - gzip trailer
+ - no junk at end (no other gzip streams)
+
+ When appending data, the information in the first three items above plus the
+ foo.add file are sufficient to recover an interrupted append operation. The
+ extra field has the necessary information to restore the start of the last
+ stored block and determine where to append the data in the foo.add file, as
+ well as the crc and length of the gzip data before the append operation.
+
+ The foo.add file is created before the gzip file is marked for append, and
+ deleted after the gzip file is marked as complete. So if the append
+ operation is interrupted, the data to add will still be there. If due to
+ some external force, the foo.add file gets deleted between when the append
+ operation was interrupted and when recovery is attempted, the gzip file will
+ still be restored, but without the appended data.
+
+ When compressing data, the information in the first two items above plus the
+ foo.add file are sufficient to recover an interrupted compress operation.
+ The extra field has the necessary information to find the end of the
+ compressed data, and contains both the crc and length of just the compressed
+ data and of the complete set of data including the contents of the foo.add
+ file.
+
+ Again, the foo.add file is maintained during the compress operation in case
+ of an interruption. If in the unlikely event the foo.add file with the data
+ to be compressed is missing due to some external force, a gzip file with
+ just the previous compressed data will be reconstructed. In this case, all
+ of the data that was to be compressed is lost (approximately one megabyte).
+ This will not occur if all that happened was an interruption of the compress
+ operation.
+
+ The third state that is marked is the replacement of the old dictionary with
+ the new dictionary after a compress operation. Once compression is
+ complete, the gzip file is marked as being in the replace state. This
+ completes the gzip file, so an interrupt after being so marked does not
+ result in recompression. Then the dictionary file is replaced, and the gzip
+ file is marked as completed. This state prevents the possibility of
+ restarting compression with the wrong dictionary file.
+
+ All three operations are wrapped by a lock/unlock procedure. In order to
+ gain exclusive access to the log files, first a foo.lock file must be
+ exclusively created. When all operations are complete, the lock is
+ released by deleting the foo.lock file. If when attempting to create the
+ lock file, it already exists and the modify time of the lock file is more
+ than five minutes old (set by the PATIENCE define below), then the old
+ lock file is considered stale and deleted, and the exclusive creation of
+ the lock file is retried. To assure that there are no false assessments
+ of the staleness of the lock file, the operations periodically touch the
+ lock file to update the modified date.
+
+ Following is the definition of the extra field with all of the information
+ required to enable the above append and compress operations and their
+ recovery if interrupted. Multi-byte values are stored little endian
+ (consistent with the gzip format). File pointers are eight bytes long.
+ The crc's and lengths for the gzip trailer are four bytes long. (Note that
+ the length at the end of a gzip file is used for error checking only, and
+ for large files is actually the length modulo 2^32.) The stored block
+ length is two bytes long. The gzip extra field two-byte identification is
+ "ap" for append. It is assumed that writing the extra field to the file is
+ an "atomic" operation. That is, either all of the extra field is written
+ to the file, or none of it is, if the operation is interrupted right at the
+ point of updating the extra field. This is a reasonable assumption, since
+ the extra field is within the first 52 bytes of the file, which is smaller
+ than any expected block size for a mass storage device (usually 512 bytes or
+ larger).
+
+ Extra field (35 bytes):
+ - Pointer to first stored block length -- this points to the two-byte length
+ of the first stored block, which is followed by the two-byte, one's
+ complement of that length. The stored block length is preceded by the
+ three-bit header of the stored block, which is the actual start of the
+ stored block in the deflate format. See the bit offset field below.
+ - Pointer to the last stored block length. This is the same as above, but
+ for the last stored block of the uncompressed data in the gzip file.
+ Initially this is the same as the first stored block length pointer.
+ When the stored block gets to 16K (see the MAX_STORE define), then a new
+ stored block as added, at which point the last stored block length pointer
+ is different from the first stored block length pointer. When they are
+ different, the first bit of the last stored block header is eight bits, or
+ one byte back from the block length.
+ - Compressed data crc and length. This is the crc and length of the data
+ that is in the compressed portion of the deflate stream. These are used
+ only in the event that the foo.add file containing the data to compress is
+ lost after a compress operation is interrupted.
+ - Total data crc and length. This is the crc and length of all of the data
+ stored in the gzip file, compressed and uncompressed. It is used to
+ reconstruct the gzip trailer when compressing, as well as when recovering
+ interrupted operations.
+ - Final stored block length. This is used to quickly find where to append,
+ and allows the restoration of the original final stored block state when
+ an append operation is interrupted.
+ - First stored block start as the number of bits back from the final stored
+ block first length byte. This value is in the range of 3..10, and is
+ stored as the low three bits of the final byte of the extra field after
+ subtracting three (0..7). This allows the last-block bit of the stored
+ block header to be updated when a new stored block is added, for the case
+ when the first stored block and the last stored block are the same. (When
+ they are different, the numbers of bits back is known to be eight.) This
+ also allows for new compressed data to be appended to the old compressed
+ data in the compress operation, overwriting the previous first stored
+ block, or for the compressed data to be terminated and a valid gzip file
+ reconstructed on the off chance that a compression operation was
+ interrupted and the data to compress in the foo.add file was deleted.
+ - The operation in process. This is the next two bits in the last byte (the
+ bits under the mask 0x18). The are interpreted as 0: nothing in process,
+ 1: append in process, 2: compress in process, 3: replace in process.
+ - The top three bits of the last byte in the extra field are reserved and
+ are currently set to zero.
+
+ Main procedure:
+ - Exclusively create the foo.lock file using the O_CREAT and O_EXCL modes of
+ the system open() call. If the modify time of an existing lock file is
+ more than PATIENCE seconds old, then the lock file is deleted and the
+ exclusive create is retried.
+ - Load the extra field from the foo.gz file, and see if an operation was in
+ progress but not completed. If so, apply the recovery procedure below.
+ - Perform the append procedure with the provided data.
+ - If the uncompressed data in the foo.gz file is 1MB or more, apply the
+ compress procedure.
+ - Delete the foo.lock file.
+
+ Append procedure:
+ - Put what to append in the foo.add file so that the operation can be
+ restarted if this procedure is interrupted.
+ - Mark the foo.gz extra field with the append operation in progress.
+ + Restore the original last-block bit and stored block length of the last
+ stored block from the information in the extra field, in case a previous
+ append operation was interrupted.
+ - Append the provided data to the last stored block, creating new stored
+ blocks as needed and updating the stored blocks last-block bits and
+ lengths.
+ - Update the crc and length with the new data, and write the gzip trailer.
+ - Write over the extra field (with a single write operation) with the new
+ pointers, lengths, and crc's, and mark the gzip file as not in process.
+ Though there is still a foo.add file, it will be ignored since nothing
+ is in process. If a foo.add file is leftover from a previously
+ completed operation, it is truncated when writing new data to it.
+ - Delete the foo.add file.
+
+ Compress and replace procedures:
+ - Read all of the uncompressed data in the stored blocks in foo.gz and write
+ it to foo.add. Also write foo.temp with the last 32K of that data to
+ provide a dictionary for the next invocation of this procedure.
+ - Rewrite the extra field marking foo.gz with a compression in process.
+ * If there is no data provided to compress (due to a missing foo.add file
+ when recovering), reconstruct and truncate the foo.gz file to contain
+ only the previous compressed data and proceed to the step after the next
+ one. Otherwise ...
+ - Compress the data with the dictionary in foo.dict, and write to the
+ foo.gz file starting at the bit immediately following the last previously
+ compressed block. If there is no foo.dict, proceed anyway with the
+ compression at slightly reduced efficiency. (For the foo.dict file to be
+ missing requires some external failure beyond simply the interruption of
+ a compress operation.) During this process, the foo.lock file is
+ periodically touched to assure that that file is not considered stale by
+ another process before we're done. The deflation is terminated with a
+ non-last empty static block (10 bits long), that is then located and
+ written over by a last-bit-set empty stored block.
+ - Append the crc and length of the data in the gzip file (previously
+ calculated during the append operations).
+ - Write over the extra field with the updated stored block offsets, bits
+ back, crc's, and lengths, and mark foo.gz as in process for a replacement
+ of the dictionary.
+ @ Delete the foo.add file.
+ - Replace foo.dict with foo.temp.
+ - Write over the extra field, marking foo.gz as complete.
+
+ Recovery procedure:
+ - If not a replace recovery, read in the foo.add file, and provide that data
+ to the appropriate recovery below. If there is no foo.add file, provide
+ a zero data length to the recovery. In that case, the append recovery
+ restores the foo.gz to the previous compressed + uncompressed data state.
+ For the the compress recovery, a missing foo.add file results in foo.gz
+ being restored to the previous compressed-only data state.
+ - Append recovery:
+ - Pick up append at + step above
+ - Compress recovery:
+ - Pick up compress at * step above
+ - Replace recovery:
+ - Pick up compress at @ step above
+ - Log the repair with a date stamp in foo.repairs
+ */
+
+#include <sys/types.h>
+#include <stdio.h> /* rename, fopen, fprintf, fclose */
+#include <stdlib.h> /* malloc, free */
+#include <string.h> /* strlen, strrchr, strcpy, strncpy, strcmp */
+#include <fcntl.h> /* open */
+#include <unistd.h> /* lseek, read, write, close, unlink, sleep, */
+ /* ftruncate, fsync */
+#include <errno.h> /* errno */
+#include <time.h> /* time, ctime */
+#include <sys/stat.h> /* stat */
+#include <sys/time.h> /* utimes */
+#include "zlib.h" /* crc32 */
+
+#include "gzlog.h" /* header for external access */
-#include "gzlog.h" /* interface */
#define local static
+typedef unsigned int uint;
+typedef unsigned long ulong;
+
+/* Macro for debugging to deterministically force recovery operations */
+#ifdef DEBUG
+ #include <setjmp.h> /* longjmp */
+ jmp_buf gzlog_jump; /* where to go back to */
+ int gzlog_bail = 0; /* which point to bail at (1..8) */
+ int gzlog_count = -1; /* number of times through to wait */
+# define BAIL(n) do { if (n == gzlog_bail && gzlog_count-- == 0) \
+ longjmp(gzlog_jump, gzlog_bail); } while (0)
+#else
+# define BAIL(n)
+#endif
+
+/* how old the lock file can be in seconds before considering it stale */
+#define PATIENCE 300
+
+/* maximum stored block size in Kbytes -- must be in 1..63 */
+#define MAX_STORE 16
-/* log object structure */
-typedef struct {
- int id; /* object identifier */
- int fd; /* log file descriptor */
- off_t extra; /* offset of extra "ap" subfield */
- off_t mark_off; /* offset of marked data */
- off_t last_off; /* offset of last block */
- unsigned long crc; /* uncompressed crc */
- unsigned long len; /* uncompressed length (modulo 2^32) */
- unsigned stored; /* length of current stored block */
-} gz_log;
-
-#define GZLOGID 19334 /* gz_log object identifier */
-
-#define LOCK_RETRY 1 /* retry lock once a second */
-#define LOCK_PATIENCE 1200 /* try about twenty minutes before forcing */
-
-/* acquire a lock on a file */
-local int lock(int fd)
+/* number of stored Kbytes to trigger compression (must be >= 32 to allow
+ dictionary construction, and <= 204 * MAX_STORE, in order for >> 10 to
+ discard the stored block headers contribution of five bytes each) */
+#define TRIGGER 1024
+
+/* size of a deflate dictionary (this cannot be changed) */
+#define DICT 32768U
+
+/* values for the operation (2 bits) */
+#define NO_OP 0
+#define APPEND_OP 1
+#define COMPRESS_OP 2
+#define REPLACE_OP 3
+
+/* macros to extract little-endian integers from an unsigned byte buffer */
+#define PULL2(p) ((p)[0]+((uint)((p)[1])<<8))
+#define PULL4(p) (PULL2(p)+((ulong)PULL2(p+2)<<16))
+#define PULL8(p) (PULL4(p)+((off_t)PULL4(p+4)<<32))
+
+/* macros to store integers into a byte buffer in little-endian order */
+#define PUT2(p,a) do {(p)[0]=a;(p)[1]=(a)>>8;} while(0)
+#define PUT4(p,a) do {PUT2(p,a);PUT2(p+2,a>>16);} while(0)
+#define PUT8(p,a) do {PUT4(p,a);PUT4(p+4,a>>32);} while(0)
+
+/* internal structure for log information */
+#define LOGID "\106\035\172" /* should be three non-zero characters */
+struct log {
+ char id[4]; /* contains LOGID to detect inadvertent overwrites */
+ int fd; /* file descriptor for .gz file, opened read/write */
+ char *path; /* allocated path, e.g. "/var/log/foo" or "foo" */
+ char *end; /* end of path, for appending suffices such as ".gz" */
+ off_t first; /* offset of first stored block first length byte */
+ int back; /* location of first block id in bits back from first */
+ uint stored; /* bytes currently in last stored block */
+ off_t last; /* offset of last stored block first length byte */
+ ulong ccrc; /* crc of compressed data */
+ ulong clen; /* length (modulo 2^32) of compressed data */
+ ulong tcrc; /* crc of total data */
+ ulong tlen; /* length (modulo 2^32) of total data */
+ time_t lock; /* last modify time of our lock file */
+};
+
+/* gzip header for gzlog */
+local unsigned char log_gzhead[] = {
+ 0x1f, 0x8b, /* magic gzip id */
+ 8, /* compression method is deflate */
+ 4, /* there is an extra field (no file name) */
+ 0, 0, 0, 0, /* no modification time provided */
+ 0, 0xff, /* no extra flags, no OS specified */
+ 39, 0, 'a', 'p', 35, 0 /* extra field with "ap" subfield */
+ /* 35 is EXTRA, 39 is EXTRA + 4 */
+};
+
+#define HEAD sizeof(log_gzhead) /* should be 16 */
+
+/* initial gzip extra field content (52 == HEAD + EXTRA + 1) */
+local unsigned char log_gzext[] = {
+ 52, 0, 0, 0, 0, 0, 0, 0, /* offset of first stored block length */
+ 52, 0, 0, 0, 0, 0, 0, 0, /* offset of last stored block length */
+ 0, 0, 0, 0, 0, 0, 0, 0, /* compressed data crc and length */
+ 0, 0, 0, 0, 0, 0, 0, 0, /* total data crc and length */
+ 0, 0, /* final stored block data length */
+ 5 /* op is NO_OP, last bit 8 bits back */
+};
+
+#define EXTRA sizeof(log_gzext) /* should be 35 */
+
+/* initial gzip data and trailer */
+local unsigned char log_gzbody[] = {
+ 1, 0, 0, 0xff, 0xff, /* empty stored block (last) */
+ 0, 0, 0, 0, /* crc */
+ 0, 0, 0, 0 /* uncompressed length */
+};
+
+#define BODY sizeof(log_gzbody)
+
+/* Exclusively create foo.lock in order to negotiate exclusive access to the
+ foo.* files. If the modify time of an existing lock file is greater than
+ PATIENCE seconds in the past, then consider the lock file to have been
+ abandoned, delete it, and try the exclusive create again. Save the lock
+ file modify time for verification of ownership. Return 0 on success, or -1
+ on failure, usually due to an access restriction or invalid path. Note that
+ if stat() or unlink() fails, it may be due to another process noticing the
+ abandoned lock file a smidge sooner and deleting it, so those are not
+ flagged as an error. */
+local int log_lock(struct log *log)
{
- int patience;
+ int fd;
+ struct stat st;
- /* try to lock every LOCK_RETRY seconds for LOCK_PATIENCE seconds */
- patience = LOCK_PATIENCE;
- do {
- if (flock(fd, LOCK_EX + LOCK_NB) == 0)
- return 0;
- (void)sleep(LOCK_RETRY);
- patience -= LOCK_RETRY;
- } while (patience > 0);
+ strcpy(log->end, ".lock");
+ while ((fd = open(log->path, O_CREAT | O_EXCL, 0644)) < 0) {
+ if (errno != EEXIST)
+ return -1;
+ if (stat(log->path, &st) == 0 && time(NULL) - st.st_mtime > PATIENCE) {
+ unlink(log->path);
+ continue;
+ }
+ sleep(2); /* relinquish the CPU for two seconds while waiting */
+ }
+ close(fd);
+ if (stat(log->path, &st) == 0)
+ log->lock = st.st_mtime;
+ return 0;
+}
- /* we've run out of patience -- give up */
- return -1;
+/* Update the modify time of the lock file to now, in order to prevent another
+ task from thinking that the lock is stale. Save the lock file modify time
+ for verification of ownership. */
+local void log_touch(struct log *log)
+{
+ struct stat st;
+
+ strcpy(log->end, ".lock");
+ utimes(log->path, NULL);
+ if (stat(log->path, &st) == 0)
+ log->lock = st.st_mtime;
}
-/* release lock */
-local void unlock(int fd)
+/* Check the log file modify time against what is expected. Return true if
+ this is not our lock. If it is our lock, touch it to keep it. */
+local int log_check(struct log *log)
{
- (void)flock(fd, LOCK_UN);
+ struct stat st;
+
+ strcpy(log->end, ".lock");
+ if (stat(log->path, &st) || st.st_mtime != log->lock)
+ return 1;
+ log_touch(log);
+ return 0;
}
-/* release a log object */
-local void log_clean(gz_log *log)
+/* Unlock a previously acquired lock, but only if it's ours. */
+local void log_unlock(struct log *log)
{
- unlock(log->fd);
- (void)close(log->fd);
- free(log);
+ if (log_check(log))
+ return;
+ strcpy(log->end, ".lock");
+ unlink(log->path);
+ log->lock = 0;
}
-/* read an unsigned long from a byte buffer little-endian */
-local unsigned long make_ulg(unsigned char *buf)
+/* Check the gzip header and read in the extra field, filling in the values in
+ the log structure. Return op on success or -1 if the gzip header was not as
+ expected. op is the current operation in progress last written to the extra
+ field. This assumes that the gzip file has already been opened, with the
+ file descriptor log->fd. */
+local int log_head(struct log *log)
{
- int n;
- unsigned long val;
+ int op;
+ unsigned char buf[HEAD + EXTRA];
- val = (unsigned long)(*buf++);
- for (n = 8; n < 32; n += 8)
- val += (unsigned long)(*buf++) << n;
- return val;
+ if (lseek(log->fd, 0, SEEK_SET) < 0 ||
+ read(log->fd, buf, HEAD + EXTRA) != HEAD + EXTRA ||
+ memcmp(buf, log_gzhead, HEAD)) {
+ return -1;
+ }
+ log->first = PULL8(buf + HEAD);
+ log->last = PULL8(buf + HEAD + 8);
+ log->ccrc = PULL4(buf + HEAD + 16);
+ log->clen = PULL4(buf + HEAD + 20);
+ log->tcrc = PULL4(buf + HEAD + 24);
+ log->tlen = PULL4(buf + HEAD + 28);
+ log->stored = PULL2(buf + HEAD + 32);
+ log->back = 3 + (buf[HEAD + 34] & 7);
+ op = (buf[HEAD + 34] >> 3) & 3;
+ return op;
}
-/* read an off_t from a byte buffer little-endian */
-local off_t make_off(unsigned char *buf)
+/* Write over the extra field contents, marking the operation as op. Use fsync
+ to assure that the device is written to, and in the requested order. This
+ operation, and only this operation, is assumed to be atomic in order to
+ assure that the log is recoverable in the event of an interruption at any
+ point in the process. Return -1 if the write to foo.gz failed. */
+local int log_mark(struct log *log, int op)
{
- int n;
- off_t val;
+ int ret;
+ unsigned char ext[EXTRA];
- val = (off_t)(*buf++);
- for (n = 8; n < 64; n += 8)
- val += (off_t)(*buf++) << n;
- return val;
+ PUT8(ext, log->first);
+ PUT8(ext + 8, log->last);
+ PUT4(ext + 16, log->ccrc);
+ PUT4(ext + 20, log->clen);
+ PUT4(ext + 24, log->tcrc);
+ PUT4(ext + 28, log->tlen);
+ PUT2(ext + 32, log->stored);
+ ext[34] = log->back - 3 + (op << 3);
+ fsync(log->fd);
+ ret = lseek(log->fd, HEAD, SEEK_SET) < 0 ||
+ write(log->fd, ext, EXTRA) != EXTRA ? -1 : 0;
+ fsync(log->fd);
+ return ret;
}
-/* write an unsigned long little-endian to byte buffer */
-local void dice_ulg(unsigned long val, unsigned char *buf)
+/* Rewrite the last block header bits and subsequent zero bits to get to a byte
+ boundary, setting the last block bit if last is true, and then write the
+ remainder of the stored block header (length and one's complement). Leave
+ the file pointer after the end of the last stored block data. Return -1 if
+ there is a read or write failure on the foo.gz file */
+local int log_last(struct log *log, int last)
{
- int n;
+ int back, len, mask;
+ unsigned char buf[6];
+
+ /* determine the locations of the bytes and bits to modify */
+ back = log->last == log->first ? log->back : 8;
+ len = back > 8 ? 2 : 1; /* bytes back from log->last */
+ mask = 0x80 >> ((back - 1) & 7); /* mask for block last-bit */
+
+ /* get the byte to modify (one or two back) into buf[0] -- don't need to
+ read the byte if the last-bit is eight bits back, since in that case
+ the entire byte will be modified */
+ buf[0] = 0;
+ if (back != 8 && (lseek(log->fd, log->last - len, SEEK_SET) < 0 ||
+ read(log->fd, buf, 1) != 1))
+ return -1;
+
+ /* change the last-bit of the last stored block as requested -- note
+ that all bits above the last-bit are set to zero, per the type bits
+ of a stored block being 00 and per the convention that the bits to
+ bring the stream to a byte boundary are also zeros */
+ buf[1] = 0;
+ buf[2 - len] = (*buf & (mask - 1)) + (last ? mask : 0);
- for (n = 0; n < 4; n++) {
- *buf++ = val & 0xff;
- val >>= 8;
+ /* write the modified stored block header and lengths, move the file
+ pointer to after the last stored block data */
+ PUT2(buf + 2, log->stored);
+ PUT2(buf + 4, log->stored ^ 0xffff);
+ return lseek(log->fd, log->last - len, SEEK_SET) < 0 ||
+ write(log->fd, buf + 2 - len, len + 4) != len + 4 ||
+ lseek(log->fd, log->stored, SEEK_CUR) < 0 ? -1 : 0;
+}
+
+/* Append len bytes from data to the locked and open log file. len may be zero
+ if recovering and no .add file was found. In that case, the previous state
+ of the foo.gz file is restored. The data is appended uncompressed in
+ deflate stored blocks. Return -1 if there was an error reading or writing
+ the foo.gz file. */
+local int log_append(struct log *log, unsigned char *data, size_t len)
+{
+ uint put;
+ off_t end;
+ unsigned char buf[8];
+
+ /* set the last block last-bit and length, in case recovering an
+ interrupted append, then position the file pointer to append to the
+ block */
+ if (log_last(log, 1))
+ return -1;
+
+ /* append, adding stored blocks and updating the offset of the last stored
+ block as needed, and update the total crc and length */
+ while (len) {
+ /* append as much as we can to the last block */
+ put = (MAX_STORE << 10) - log->stored;
+ if (put > len)
+ put = (uint)len;
+ if (put) {
+ if (write(log->fd, data, put) != put)
+ return -1;
+ BAIL(1);
+ log->tcrc = crc32(log->tcrc, data, put);
+ log->tlen += put;
+ log->stored += put;
+ data += put;
+ len -= put;
+ }
+
+ /* if we need to, add a new empty stored block */
+ if (len) {
+ /* mark current block as not last */
+ if (log_last(log, 0))
+ return -1;
+
+ /* point to new, empty stored block */
+ log->last += 4 + log->stored + 1;
+ log->stored = 0;
+ }
+
+ /* mark last block as last, update its length */
+ if (log_last(log, 1))
+ return -1;
+ BAIL(2);
}
+
+ /* write the new crc and length trailer, and truncate just in case (could
+ be recovering from partial append with a missing foo.add file) */
+ PUT4(buf, log->tcrc);
+ PUT4(buf + 4, log->tlen);
+ if (write(log->fd, buf, 8) != 8 ||
+ (end = lseek(log->fd, 0, SEEK_CUR)) < 0 || ftruncate(log->fd, end))
+ return -1;
+
+ /* write the extra field, marking the log file as done, delete .add file */
+ if (log_mark(log, NO_OP))
+ return -1;
+ strcpy(log->end, ".add");
+ unlink(log->path); /* ignore error, since may not exist */
+ return 0;
}
-/* write an off_t little-endian to byte buffer */
-local void dice_off(off_t val, unsigned char *buf)
+/* Replace the foo.dict file with the foo.temp file. Also delete the foo.add
+ file, since the compress operation may have been interrupted before that was
+ done. Returns 1 if memory could not be allocated, or -1 if reading or
+ writing foo.gz fails, or if the rename fails for some reason other than
+ foo.temp not existing. foo.temp not existing is a permitted error, since
+ the replace operation may have been interrupted after the rename is done,
+ but before foo.gz is marked as complete. */
+local int log_replace(struct log *log)
{
- int n;
+ int ret;
+ char *dest;
+
+ /* delete foo.add file */
+ strcpy(log->end, ".add");
+ unlink(log->path); /* ignore error, since may not exist */
+ BAIL(3);
+
+ /* rename foo.name to foo.dict, replacing foo.dict if it exists */
+ strcpy(log->end, ".dict");
+ dest = malloc(strlen(log->path) + 1);
+ if (dest == NULL)
+ return -2;
+ strcpy(dest, log->path);
+ strcpy(log->end, ".temp");
+ ret = rename(log->path, dest);
+ free(dest);
+ if (ret && errno != ENOENT)
+ return -1;
+ BAIL(4);
- for (n = 0; n < 8; n++) {
- *buf++ = val & 0xff;
- val >>= 8;
+ /* mark the foo.gz file as done */
+ return log_mark(log, NO_OP);
+}
+
+/* Compress the len bytes at data and append the compressed data to the
+ foo.gz deflate data immediately after the previous compressed data. This
+ overwrites the previous uncompressed data, which was stored in foo.add
+ and is the data provided in data[0..len-1]. If this operation is
+ interrupted, it picks up at the start of this routine, with the foo.add
+ file read in again. If there is no data to compress (len == 0), then we
+ simply terminate the foo.gz file after the previously compressed data,
+ appending a final empty stored block and the gzip trailer. Return -1 if
+ reading or writing the log.gz file failed, or -2 if there was a memory
+ allocation failure. */
+local int log_compress(struct log *log, unsigned char *data, size_t len)
+{
+ int fd;
+ uint got, max;
+ ssize_t dict;
+ off_t end;
+ z_stream strm;
+ unsigned char buf[DICT];
+
+ /* compress and append compressed data */
+ if (len) {
+ /* set up for deflate, allocating memory */
+ strm.zalloc = Z_NULL;
+ strm.zfree = Z_NULL;
+ strm.opaque = Z_NULL;
+ if (deflateInit2(&strm, Z_DEFAULT_COMPRESSION, Z_DEFLATED, -15, 8,
+ Z_DEFAULT_STRATEGY) != Z_OK)
+ return -2;
+
+ /* read in dictionary (last 32K of data that was compressed) */
+ strcpy(log->end, ".dict");
+ fd = open(log->path, O_RDONLY, 0);
+ if (fd >= 0) {
+ dict = read(fd, buf, DICT);
+ close(fd);
+ if (dict < 0) {
+ deflateEnd(&strm);
+ return -1;
+ }
+ if (dict)
+ deflateSetDictionary(&strm, buf, (uint)dict);
+ }
+ log_touch(log);
+
+ /* prime deflate with last bits of previous block, position write
+ pointer to write those bits and overwrite what follows */
+ if (lseek(log->fd, log->first - (log->back > 8 ? 2 : 1),
+ SEEK_SET) < 0 ||
+ read(log->fd, buf, 1) != 1 || lseek(log->fd, -1, SEEK_CUR) < 0) {
+ deflateEnd(&strm);
+ return -1;
+ }
+ deflatePrime(&strm, (8 - log->back) & 7, *buf);
+
+ /* compress, finishing with a partial non-last empty static block */
+ strm.next_in = data;
+ max = (((uint)0 - 1) >> 1) + 1; /* in case int smaller than size_t */
+ do {
+ strm.avail_in = len > max ? max : (uint)len;
+ len -= strm.avail_in;
+ do {
+ strm.avail_out = DICT;
+ strm.next_out = buf;
+ deflate(&strm, len ? Z_NO_FLUSH : Z_PARTIAL_FLUSH);
+ got = DICT - strm.avail_out;
+ if (got && write(log->fd, buf, got) != got) {
+ deflateEnd(&strm);
+ return -1;
+ }
+ log_touch(log);
+ } while (strm.avail_out == 0);
+ } while (len);
+ deflateEnd(&strm);
+ BAIL(5);
+
+ /* find start of empty static block -- scanning backwards the first one
+ bit is the second bit of the block, if the last byte is zero, then
+ we know the byte before that has a one in the top bit, since an
+ empty static block is ten bits long */
+ if ((log->first = lseek(log->fd, -1, SEEK_CUR)) < 0 ||
+ read(log->fd, buf, 1) != 1)
+ return -1;
+ log->first++;
+ if (*buf) {
+ log->back = 1;
+ while ((*buf & ((uint)1 << (8 - log->back++))) == 0)
+ ; /* guaranteed to terminate, since *buf != 0 */
+ }
+ else
+ log->back = 10;
+
+ /* update compressed crc and length */
+ log->ccrc = log->tcrc;
+ log->clen = log->tlen;
+ }
+ else {
+ /* no data to compress -- fix up existing gzip stream */
+ log->tcrc = log->ccrc;
+ log->tlen = log->clen;
}
+
+ /* complete and truncate gzip stream */
+ log->last = log->first;
+ log->stored = 0;
+ PUT4(buf, log->tcrc);
+ PUT4(buf + 4, log->tlen);
+ if (log_last(log, 1) || write(log->fd, buf, 8) != 8 ||
+ (end = lseek(log->fd, 0, SEEK_CUR)) < 0 || ftruncate(log->fd, end))
+ return -1;
+ BAIL(6);
+
+ /* mark as being in the replace operation */
+ if (log_mark(log, REPLACE_OP))
+ return -1;
+
+ /* execute the replace operation and mark the file as done */
+ return log_replace(log);
}
-/* initial, empty gzip file for appending */
-local char empty_gz[] = {
- 0x1f, 0x8b, /* magic gzip id */
- 8, /* compression method is deflate */
- 4, /* there is an extra field */
- 0, 0, 0, 0, /* no modification time provided */
- 0, 0xff, /* no extra flags, no OS */
- 20, 0, 'a', 'p', 16, 0, /* extra field with "ap" subfield */
- 32, 0, 0, 0, 0, 0, 0, 0, /* offset of uncompressed data */
- 32, 0, 0, 0, 0, 0, 0, 0, /* offset of last block */
- 1, 0, 0, 0xff, 0xff, /* empty stored block (last) */
- 0, 0, 0, 0, /* crc */
- 0, 0, 0, 0 /* uncompressed length */
-};
+/* log a repair record to the .repairs file */
+local void log_log(struct log *log, int op, char *record)
+{
+ time_t now;
+ FILE *rec;
-/* initialize a log object with locking */
-void *gzlog_open(char *path)
+ now = time(NULL);
+ strcpy(log->end, ".repairs");
+ rec = fopen(log->path, "a");
+ if (rec == NULL)
+ return;
+ fprintf(rec, "%.24s %s recovery: %s\n", ctime(&now), op == APPEND_OP ?
+ "append" : (op == COMPRESS_OP ? "compress" : "replace"), record);
+ fclose(rec);
+ return;
+}
+
+/* Recover the interrupted operation op. First read foo.add for recovering an
+ append or compress operation. Return -1 if there was an error reading or
+ writing foo.gz or reading an existing foo.add, or -2 if there was a memory
+ allocation failure. */
+local int log_recover(struct log *log, int op)
{
- unsigned xlen;
- unsigned char temp[20];
- unsigned sub_len;
- int good;
- gz_log *log;
-
- /* allocate log structure */
- log = malloc(sizeof(gz_log));
- if (log == NULL)
- return NULL;
- log->id = GZLOGID;
+ int fd, ret = 0;
+ unsigned char *data = NULL;
+ size_t len = 0;
+ struct stat st;
- /* open file, creating it if necessary, and locking it */
- log->fd = open(path, O_RDWR | O_CREAT, 0600);
- if (log->fd < 0) {
- free(log);
- return NULL;
+ /* log recovery */
+ log_log(log, op, "start");
+
+ /* load foo.add file if expected and present */
+ if (op == APPEND_OP || op == COMPRESS_OP) {
+ strcpy(log->end, ".add");
+ if (stat(log->path, &st) == 0 && st.st_size) {
+ len = (size_t)(st.st_size);
+ if (len != st.st_size || (data = malloc(st.st_size)) == NULL) {
+ log_log(log, op, "allocation failure");
+ return -2;
+ }
+ if ((fd = open(log->path, O_RDONLY, 0)) < 0) {
+ log_log(log, op, ".add file read failure");
+ return -1;
+ }
+ ret = read(fd, data, len) != len;
+ close(fd);
+ if (ret) {
+ log_log(log, op, ".add file read failure");
+ return -1;
+ }
+ log_log(log, op, "loaded .add file");
+ }
+ else
+ log_log(log, op, "missing .add file!");
+ }
+
+ /* recover the interrupted operation */
+ switch (op) {
+ case APPEND_OP:
+ ret = log_append(log, data, len);
+ break;
+ case COMPRESS_OP:
+ ret = log_compress(log, data, len);
+ break;
+ case REPLACE_OP:
+ ret = log_replace(log);
}
- if (lock(log->fd)) {
+
+ /* log status */
+ log_log(log, op, ret ? "failure" : "complete");
+
+ /* clean up */
+ if (data != NULL)
+ free(data);
+ return ret;
+}
+
+/* Close the foo.gz file (if open) and release the lock. */
+local void log_close(struct log *log)
+{
+ if (log->fd >= 0)
close(log->fd);
- free(log);
- return NULL;
+ log->fd = -1;
+ log_unlock(log);
+}
+
+/* Open foo.gz, verify the header, and load the extra field contents, after
+ first creating the foo.lock file to gain exclusive access to the foo.*
+ files. If foo.gz does not exist or is empty, then write the initial header,
+ extra, and body content of an empty foo.gz log file. If there is an error
+ creating the lock file due to access restrictions, or an error reading or
+ writing the foo.gz file, or if the foo.gz file is not a proper log file for
+ this object (e.g. not a gzip file or does not contain the expected extra
+ field), then return true. If there is an error, the lock is released.
+ Otherwise, the lock is left in place. */
+local int log_open(struct log *log)
+{
+ int op;
+
+ /* release open file resource if left over -- can occur if lock lost
+ between gzlog_open() and gzlog_write() */
+ if (log->fd >= 0)
+ close(log->fd);
+ log->fd = -1;
+
+ /* negotiate exclusive access */
+ if (log_lock(log) < 0)
+ return -1;
+
+ /* open the log file, foo.gz */
+ strcpy(log->end, ".gz");
+ log->fd = open(log->path, O_RDWR | O_CREAT, 0644);
+ if (log->fd < 0) {
+ log_close(log);
+ return -1;
}
- /* if file is empty, write new gzip stream */
+ /* if new, initialize foo.gz with an empty log, delete old dictionary */
if (lseek(log->fd, 0, SEEK_END) == 0) {
- if (write(log->fd, empty_gz, sizeof(empty_gz)) != sizeof(empty_gz)) {
- log_clean(log);
- return NULL;
+ if (write(log->fd, log_gzhead, HEAD) != HEAD ||
+ write(log->fd, log_gzext, EXTRA) != EXTRA ||
+ write(log->fd, log_gzbody, BODY) != BODY) {
+ log_close(log);
+ return -1;
}
+ strcpy(log->end, ".dict");
+ unlink(log->path);
}
- /* check gzip header */
- (void)lseek(log->fd, 0, SEEK_SET);
- if (read(log->fd, temp, 12) != 12 || temp[0] != 0x1f ||
- temp[1] != 0x8b || temp[2] != 8 || (temp[3] & 4) == 0) {
- log_clean(log);
- return NULL;
+ /* verify log file and load extra field information */
+ if ((op = log_head(log)) < 0) {
+ log_close(log);
+ return -1;
}
- /* process extra field to find "ap" sub-field */
- xlen = temp[10] + (temp[11] << 8);
- good = 0;
- while (xlen) {
- if (xlen < 4 || read(log->fd, temp, 4) != 4)
- break;
- sub_len = temp[2];
- sub_len += temp[3] << 8;
- xlen -= 4;
- if (memcmp(temp, "ap", 2) == 0 && sub_len == 16) {
- good = 1;
- break;
- }
- if (xlen < sub_len)
- break;
- (void)lseek(log->fd, sub_len, SEEK_CUR);
- xlen -= sub_len;
+ /* check for interrupted process and if so, recover */
+ if (op != NO_OP && log_recover(log, op)) {
+ log_close(log);
+ return -1;
}
- if (!good) {
- log_clean(log);
+
+ /* touch the lock file to prevent another process from grabbing it */
+ log_touch(log);
+ return 0;
+}
+
+/* See gzlog.h for the description of the external methods below */
+gzlog *gzlog_open(char *path)
+{
+ size_t n;
+ struct log *log;
+
+ /* check arguments */
+ if (path == NULL || *path == 0)
return NULL;
- }
- /* read in "ap" sub-field */
- log->extra = lseek(log->fd, 0, SEEK_CUR);
- if (read(log->fd, temp, 16) != 16) {
- log_clean(log);
+ /* allocate and initialize log structure */
+ log = malloc(sizeof(struct log));
+ if (log == NULL)
+ return NULL;
+ strcpy(log->id, LOGID);
+ log->fd = -1;
+
+ /* save path and end of path for name construction */
+ n = strlen(path);
+ log->path = malloc(n + 9); /* allow for ".repairs" */
+ if (log->path == NULL) {
+ free(log);
return NULL;
}
- log->mark_off = make_off(temp);
- log->last_off = make_off(temp + 8);
-
- /* get crc, length of gzip file */
- (void)lseek(log->fd, log->last_off, SEEK_SET);
- if (read(log->fd, temp, 13) != 13 ||
- memcmp(temp, "\001\000\000\377\377", 5) != 0) {
- log_clean(log);
+ strcpy(log->path, path);
+ log->end = log->path + n;
+
+ /* gain exclusive access and verify log file -- may perform a
+ recovery operation if needed */
+ if (log_open(log)) {
+ free(log->path);
+ free(log);
return NULL;
}
- log->crc = make_ulg(temp + 5);
- log->len = make_ulg(temp + 9);
- /* set up to write over empty last block */
- (void)lseek(log->fd, log->last_off + 5, SEEK_SET);
- log->stored = 0;
- return (void *)log;
+ /* return pointer to log structure */
+ return log;
}
-/* maximum amount to put in a stored block before starting a new one */
-#define MAX_BLOCK 16384
-
-/* write a block to a log object */
-int gzlog_write(void *obj, char *data, size_t len)
+/* gzlog_compress() return values:
+ 0: all good
+ -1: file i/o error (usually access issue)
+ -2: memory allocation failure
+ -3: invalid log pointer argument */
+int gzlog_compress(gzlog *logd)
{
- size_t some;
- unsigned char temp[5];
- gz_log *log;
+ int fd, ret;
+ uint block;
+ size_t len, next;
+ unsigned char *data, buf[5];
+ struct log *log = logd;
- /* check object */
- log = (gz_log *)obj;
- if (log == NULL || log->id != GZLOGID)
- return 1;
+ /* check arguments */
+ if (log == NULL || strcmp(log->id, LOGID) || len < 0)
+ return -3;
- /* write stored blocks until all of the input is written */
- do {
- some = MAX_BLOCK - log->stored;
- if (some > len)
- some = len;
- if (write(log->fd, data, some) != some)
- return 1;
- log->crc = crc32(log->crc, (unsigned char *)data, some);
- log->len += some;
- len -= some;
- data += some;
- log->stored += some;
-
- /* if the stored block is full, end it and start another */
- if (log->stored == MAX_BLOCK) {
- (void)lseek(log->fd, log->last_off, SEEK_SET);
- temp[0] = 0;
- dice_ulg(log->stored + ((unsigned long)(~log->stored) << 16),
- temp + 1);
- if (write(log->fd, temp, 5) != 5)
- return 1;
- log->last_off = lseek(log->fd, log->stored, SEEK_CUR);
- (void)lseek(log->fd, 5, SEEK_CUR);
- log->stored = 0;
- }
- } while (len);
- return 0;
-}
+ /* see if we lost the lock -- if so get it again and reload the extra
+ field information (it probably changed), recover last operation if
+ necessary */
+ if (log_check(log) && log_open(log))
+ return -1;
-/* recompress the remaining stored deflate data in place */
-local int recomp(gz_log *log)
-{
- z_stream strm;
- size_t len, max;
- unsigned char *in;
- unsigned char *out;
- unsigned char temp[16];
-
- /* allocate space and read it all in (it's around 1 MB) */
- len = log->last_off - log->mark_off;
- max = len + (len >> 12) + (len >> 14) + 11;
- out = malloc(max);
- if (out == NULL)
- return 1;
- in = malloc(len);
- if (in == NULL) {
- free(out);
- return 1;
- }
- (void)lseek(log->fd, log->mark_off, SEEK_SET);
- if (read(log->fd, in, len) != len) {
- free(in);
- free(out);
- return 1;
- }
+ /* create space for uncompressed data */
+ len = ((size_t)(log->last - log->first) & ~(((size_t)1 << 10) - 1)) +
+ log->stored;
+ if ((data = malloc(len)) == NULL)
+ return -2;
- /* recompress in memory, decoding stored data as we go */
- /* note: this assumes that unsigned is four bytes or more */
- /* consider not making that assumption */
- strm.zalloc = Z_NULL;
- strm.zfree = Z_NULL;
- strm.opaque = Z_NULL;
- if (deflateInit2(&strm, Z_BEST_COMPRESSION, Z_DEFLATED, -15, 8,
- Z_DEFAULT_STRATEGY) != Z_OK) {
- free(in);
- free(out);
- return 1;
- }
- strm.next_in = in;
- strm.avail_out = max;
- strm.next_out = out;
- while (len >= 5) {
- if (strm.next_in[0] != 0)
+ /* do statement here is just a cheap trick for error handling */
+ do {
+ /* read in the uncompressed data */
+ if (lseek(log->fd, log->first - 1, SEEK_SET) < 0)
break;
- strm.avail_in = strm.next_in[1] + (strm.next_in[2] << 8);
- strm.next_in += 5;
- len -= 5;
- if (strm.avail_in != 0) {
- if (len < strm.avail_in)
+ next = 0;
+ while (next < len) {
+ if (read(log->fd, buf, 5) != 5)
break;
- len -= strm.avail_in;
- (void)deflate(&strm, Z_NO_FLUSH);
- if (strm.avail_in != 0 || strm.avail_out == 0)
+ block = PULL2(buf + 1);
+ if (next + block > len ||
+ read(log->fd, (char *)data + next, block) != block)
break;
+ next += block;
}
- }
- (void)deflate(&strm, Z_SYNC_FLUSH);
- (void)deflateEnd(&strm);
- free(in);
- if (len != 0 || strm.avail_out == 0) {
- free(out);
- return 1;
- }
+ if (lseek(log->fd, 0, SEEK_CUR) != log->last + 4 + log->stored)
+ break;
+ log_touch(log);
- /* overwrite stored data with compressed data */
- (void)lseek(log->fd, log->mark_off, SEEK_SET);
- len = max - strm.avail_out;
- if (write(log->fd, out, len) != len) {
- free(out);
- return 1;
- }
- free(out);
-
- /* write last empty block, crc, and length */
- log->mark_off = log->last_off = lseek(log->fd, 0, SEEK_CUR);
- temp[0] = 1;
- dice_ulg(0xffffL << 16, temp + 1);
- dice_ulg(log->crc, temp + 5);
- dice_ulg(log->len, temp + 9);
- if (write(log->fd, temp, 13) != 13)
- return 1;
+ /* write the uncompressed data to the .add file */
+ strcpy(log->end, ".add");
+ fd = open(log->path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
+ if (fd < 0)
+ break;
+ ret = write(fd, data, len) != len;
+ if (ret | close(fd))
+ break;
+ log_touch(log);
- /* truncate file to discard remaining stored data and old trailer */
- ftruncate(log->fd, lseek(log->fd, 0, SEEK_CUR));
+ /* write the dictionary for the next compress to the .temp file */
+ strcpy(log->end, ".temp");
+ fd = open(log->path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
+ if (fd < 0)
+ break;
+ next = DICT > len ? len : DICT;
+ ret = write(fd, (char *)data + len - next, next) != next;
+ if (ret | close(fd))
+ break;
+ log_touch(log);
- /* update extra field to point to new last empty block */
- (void)lseek(log->fd, log->extra, SEEK_SET);
- dice_off(log->mark_off, temp);
- dice_off(log->last_off, temp + 8);
- if (write(log->fd, temp, 16) != 16)
- return 1;
- return 0;
-}
+ /* roll back to compressed data, mark the compress in progress */
+ log->last = log->first;
+ log->stored = 0;
+ if (log_mark(log, COMPRESS_OP))
+ break;
+ BAIL(7);
+
+ /* compress and append the data (clears mark) */
+ ret = log_compress(log, data, len);
+ free(data);
+ return ret;
+ } while (0);
-/* maximum accumulation of stored blocks before compressing */
-#define MAX_STORED 1048576
+ /* broke out of do above on i/o error */
+ free(data);
+ return -1;
+}
-/* close log object */
-int gzlog_close(void *obj)
+/* gzlog_write() return values:
+ 0: all good
+ -1: file i/o error (usually access issue)
+ -2: memory allocation failure
+ -3: invalid log pointer argument */
+int gzlog_write(gzlog *logd, void *data, size_t len)
{
- unsigned char temp[8];
- gz_log *log;
+ int fd, ret;
+ struct log *log = logd;
- /* check object */
- log = (gz_log *)obj;
- if (log == NULL || log->id != GZLOGID)
- return 1;
+ /* check arguments */
+ if (log == NULL || strcmp(log->id, LOGID) || len < 0)
+ return -3;
+ if (data == NULL || len == 0)
+ return 0;
- /* go to start of most recent block being written */
- (void)lseek(log->fd, log->last_off, SEEK_SET);
-
- /* if some stuff was put there, update block */
- if (log->stored) {
- temp[0] = 0;
- dice_ulg(log->stored + ((unsigned long)(~log->stored) << 16),
- temp + 1);
- if (write(log->fd, temp, 5) != 5)
- return 1;
- log->last_off = lseek(log->fd, log->stored, SEEK_CUR);
- }
+ /* see if we lost the lock -- if so get it again and reload the extra
+ field information (it probably changed), recover last operation if
+ necessary */
+ if (log_check(log) && log_open(log))
+ return -1;
- /* write last block (empty) */
- if (write(log->fd, "\001\000\000\377\377", 5) != 5)
- return 1;
+ /* create and write .add file */
+ strcpy(log->end, ".add");
+ fd = open(log->path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
+ if (fd < 0)
+ return -1;
+ ret = write(fd, data, len) != len;
+ if (ret | close(fd))
+ return -1;
+ log_touch(log);
- /* write updated crc and uncompressed length */
- dice_ulg(log->crc, temp);
- dice_ulg(log->len, temp + 4);
- if (write(log->fd, temp, 8) != 8)
- return 1;
+ /* mark log file with append in progress */
+ if (log_mark(log, APPEND_OP))
+ return -1;
+ BAIL(8);
- /* put offset of that last block in gzip extra block */
- (void)lseek(log->fd, log->extra + 8, SEEK_SET);
- dice_off(log->last_off, temp);
- if (write(log->fd, temp, 8) != 8)
- return 1;
+ /* append data (clears mark) */
+ if (log_append(log, data, len))
+ return -1;
- /* if more than 1 MB stored, then time to compress it */
- if (log->last_off - log->mark_off > MAX_STORED) {
- if (recomp(log))
- return 1;
- }
+ /* check to see if it's time to compress -- if not, then done */
+ if (((log->last - log->first) >> 10) + (log->stored >> 10) < TRIGGER)
+ return 0;
+
+ /* time to compress */
+ return gzlog_compress(log);
+}
+
+/* gzlog_close() return values:
+ 0: ok
+ -3: invalid log pointer argument */
+int gzlog_close(gzlog *logd)
+{
+ struct log *log = logd;
- /* unlock and close file */
- log_clean(log);
+ /* check arguments */
+ if (log == NULL || strcmp(log->id, LOGID))
+ return -3;
+
+ /* close the log file and release the lock */
+ log_close(log);
+
+ /* free structure and return */
+ if (log->path != NULL)
+ free(log->path);
+ strcpy(log->id, "bad");
+ free(log);
return 0;
}
diff --git a/examples/gzlog.h b/examples/gzlog.h
index a800bd5..c461426 100644
--- a/examples/gzlog.h
+++ b/examples/gzlog.h
@@ -1,6 +1,6 @@
/* gzlog.h
- Copyright (C) 2004 Mark Adler, all rights reserved
- version 1.0, 26 Nov 2004
+ Copyright (C) 2004, 2008 Mark Adler, all rights reserved
+ version 2.0, 25 Apr 2008
This software is provided 'as-is', without any express or implied
warranty. In no event will the author be held liable for any damages
@@ -21,38 +21,69 @@
Mark Adler madler@alumni.caltech.edu
*/
+/* Version History:
+ 1.0 26 Nov 2004 First version
+ 2.0 25 Apr 2008 Complete redesign for recovery of interrupted operations
+ Interface changed slightly in that now path is a prefix
+ Compression now occurs as needed during gzlog_write()
+ gzlog_write() now always leaves the log file as valid gzip
+ */
+
/*
The gzlog object allows writing short messages to a gzipped log file,
opening the log file locked for small bursts, and then closing it. The log
- object works by appending stored data to the gzip file until 1 MB has been
- accumulated. At that time, the stored data is compressed, and replaces the
- uncompressed data in the file. The log file is truncated to its new size at
- that time. After closing, the log file is always valid gzip file that can
- decompressed to recover what was written.
-
- A gzip header "extra" field contains two file offsets for appending. The
- first points to just after the last compressed data. The second points to
- the last stored block in the deflate stream, which is empty. All of the
- data between those pointers is uncompressed.
+ object works by appending stored (uncompressed) data to the gzip file until
+ 1 MB has been accumulated. At that time, the stored data is compressed, and
+ replaces the uncompressed data in the file. The log file is truncated to
+ its new size at that time. After each write operation, the log file is a
+ valid gzip file that can decompressed to recover what was written.
+
+ The gzlog operations can be interupted at any point due to an application or
+ system crash, and the log file will be recovered the next time the log is
+ opened with gzlog_open().
*/
+#ifndef GZLOG_H
+#define GZLOG_H
+
+/* gzlog object type */
+typedef void gzlog;
+
/* Open a gzlog object, creating the log file if it does not exist. Return
- NULL on error. Note that gzlog_open() could take a long time to return if
- there is difficulty in locking the file. */
-void *gzlog_open(char *path);
-
-/* Write to a gzlog object. Return non-zero on error. This function will
- simply write data to the file uncompressed. Compression of the data
- will not occur until gzlog_close() is called. It is expected that
- gzlog_write() is used for a short message, and then gzlog_close() is
- called. If a large amount of data is to be written, then the application
- should write no more than 1 MB at a time with gzlog_write() before
- calling gzlog_close() and then gzlog_open() again. */
-int gzlog_write(void *log, char *data, size_t len);
-
-/* Close a gzlog object. Return non-zero on error. The log file is locked
- until this function is called. This function will compress stored data
- at the end of the gzip file if at least 1 MB has been accumulated. Note
- that the file will not be a valid gzip file until this function completes.
- */
-int gzlog_close(void *log);
+ NULL on error. Note that gzlog_open() could take a while to complete if it
+ has to wait to verify that a lock is stale (possibly for five minutes), or
+ if there is significant contention with other instantiations of this object
+ when locking the resource. path is the prefix of the file names created by
+ this object. If path is "foo", then the log file will be "foo.gz", and
+ other auxiliary files will be created and destroyed during the process:
+ "foo.dict" for a compression dictionary, "foo.temp" for a temporary (next)
+ dictionary, "foo.add" for data being added or compressed, "foo.lock" for the
+ lock file, and "foo.repairs" to log recovery operations performed due to
+ interrupted gzlog operations. A gzlog_open() followed by a gzlog_close()
+ will recover a previously interrupted operation, if any. */
+gzlog *gzlog_open(char *path);
+
+/* Write to a gzlog object. Return zero on success, -1 if there is a file i/o
+ error on any of the gzlog files (this should not happen if gzlog_open()
+ succeeded, unless the device has run out of space or leftover auxiliary
+ files have permissions or ownership that prevent their use), -2 if there is
+ a memory allocation failure, or -3 if the log argument is invalid (e.g. if
+ it was not created by gzlog_open()). This function will write data to the
+ file uncompressed, until 1 MB has been accumulated, at which time that data
+ will be compressed. The log file will be a valid gzip file upon successful
+ return. */
+int gzlog_write(gzlog *log, void *data, size_t len);
+
+/* Force compression of any uncompressed data in the log. This should be used
+ sparingly, if at all. The main application would be when a log file will
+ not be appended to again. If this is used to compress frequently while
+ appending, it will both significantly increase the execution time and
+ reduce the compression ratio. The return codes are the same as for
+ gzlog_write(). */
+int gzlog_compress(gzlog *log);
+
+/* Close a gzlog object. Return zero on success, -3 if the log argument is
+ invalid. The log object is freed, and so cannot be referenced again. */
+int gzlog_close(gzlog *log);
+
+#endif
diff --git a/examples/pigz.c b/examples/pigz.c
new file mode 100644
index 0000000..42794d0
--- /dev/null
+++ b/examples/pigz.c
@@ -0,0 +1,452 @@
+/* pigz.c -- parallel implementation of gzip
+ * Copyright (C) 2007 Mark Adler
+ * Version 1.1 28 January 2007 Mark Adler
+ */
+
+/* Version history:
+ 1.0 17 Jan 2007 First version
+ 1.1 28 Jan 2007 Avoid void * arithmetic (some compilers don't get that)
+ Add note about requiring zlib 1.2.3
+ Allow compression level 0 (no compression)
+ Completely rewrite parallelism -- add a write thread
+ Use deflateSetDictionary() to make use of history
+ Tune argument defaults to best performance on four cores
+ */
+
+/*
+ pigz compresses from stdin to stdout using threads to make use of multiple
+ processors and cores. The input is broken up into 128 KB chunks, and each
+ is compressed separately. The CRC for each chunk is also calculated
+ separately. The compressed chunks are written in order to the output,
+ and the overall CRC is calculated from the CRC's of the chunks.
+
+ The compressed data format generated is the gzip format using the deflate
+ compression method. First a gzip header is written, followed by raw deflate
+ partial streams. They are partial, in that they do not have a terminating
+ block. At the end, the deflate stream is terminated with a final empty
+ static block, and lastly a gzip trailer is written with the CRC and the
+ number of input bytes.
+
+ Each raw deflate partial stream is terminated by an empty stored block
+ (using the Z_SYNC_FLUSH option of zlib), in order to end that partial
+ bit stream at a byte boundary. That allows the partial streams to be
+ concantenated simply as sequences of bytes. This adds a very small four
+ or five byte overhead to the output for each input chunk.
+
+ zlib's crc32_combine() routine allows the calcuation of the CRC of the
+ entire input using the independent CRC's of the chunks. pigz requires zlib
+ version 1.2.3 or later, since that is the first version that provides the
+ crc32_combine() function.
+
+ pigz uses the POSIX pthread library for thread control and communication.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <pthread.h>
+#include <sys/types.h>
+#include <sys/uio.h>
+#include <unistd.h>
+#include "zlib.h"
+
+#define local static
+
+/* exit with error */
+local void bail(char *msg)
+{
+ fprintf(stderr, "pigz abort: %s\n", msg);
+ exit(1);
+}
+
+/* read up to len bytes into buf, repeating read() calls as needed */
+local size_t readn(int desc, unsigned char *buf, size_t len)
+{
+ ssize_t ret;
+ size_t got;
+
+ got = 0;
+ while (len) {
+ ret = read(desc, buf, len);
+ if (ret < 0)
+ bail("read error");
+ if (ret == 0)
+ break;
+ buf += ret;
+ len -= ret;
+ got += ret;
+ }
+ return got;
+}
+
+/* write len bytes, repeating write() calls as needed */
+local void writen(int desc, unsigned char *buf, size_t len)
+{
+ ssize_t ret;
+
+ while (len) {
+ ret = write(desc, buf, len);
+ if (ret < 1)
+ bail("write error");
+ buf += ret;
+ len -= ret;
+ }
+}
+
+/* a flag variable for communication between two threads */
+struct flag {
+ int value; /* value of flag */
+ pthread_mutex_t lock; /* lock for checking and changing flag */
+ pthread_cond_t cond; /* condition for signaling on flag change */
+};
+
+/* initialize a flag for use, starting with value val */
+local void flag_init(struct flag *me, int val)
+{
+ me->value = val;
+ pthread_mutex_init(&(me->lock), NULL);
+ pthread_cond_init(&(me->cond), NULL);
+}
+
+/* set the flag to val, signal another process that may be waiting for it */
+local void flag_set(struct flag *me, int val)
+{
+ pthread_mutex_lock(&(me->lock));
+ me->value = val;
+ pthread_cond_signal(&(me->cond));
+ pthread_mutex_unlock(&(me->lock));
+}
+
+/* if it isn't already, wait for some other thread to set the flag to val */
+local void flag_wait(struct flag *me, int val)
+{
+ pthread_mutex_lock(&(me->lock));
+ while (me->value != val)
+ pthread_cond_wait(&(me->cond), &(me->lock));
+ pthread_mutex_unlock(&(me->lock));
+}
+
+/* if flag is equal to val, wait for some other thread to change it */
+local void flag_wait_not(struct flag *me, int val)
+{
+ pthread_mutex_lock(&(me->lock));
+ while (me->value == val)
+ pthread_cond_wait(&(me->cond), &(me->lock));
+ pthread_mutex_unlock(&(me->lock));
+}
+
+/* clean up the flag when done with it */
+local void flag_done(struct flag *me)
+{
+ pthread_cond_destroy(&(me->cond));
+ pthread_mutex_destroy(&(me->lock));
+}
+
+/* a unit of work to feed to compress_thread() -- it is assumed that the out
+ buffer is large enough to hold the maximum size len bytes could deflate to,
+ plus five bytes for the final sync marker */
+struct work {
+ size_t len; /* length of input */
+ unsigned long crc; /* crc of input */
+ unsigned char *buf; /* input */
+ unsigned char *out; /* space for output (guaranteed big enough) */
+ z_stream strm; /* pre-initialized z_stream */
+ struct flag busy; /* busy flag indicating work unit in use */
+ pthread_t comp; /* this compression thread */
+};
+
+/* busy flag values */
+#define IDLE 0 /* compress and writing done -- can start compress */
+#define COMP 1 /* compress -- input and output buffers in use */
+#define WRITE 2 /* compress done, writing output -- can read input */
+
+/* read-only globals (set by main/read thread before others started) */
+local int ind; /* input file descriptor */
+local int outd; /* output file descriptor */
+local int level; /* compression level */
+local int procs; /* number of compression threads (>= 2) */
+local size_t size; /* uncompressed input size per thread (>= 32K) */
+local struct work *jobs; /* work units: jobs[0..procs-1] */
+
+/* next and previous jobs[] indices */
+#define NEXT(n) ((n) == procs - 1 ? 0 : (n) + 1)
+#define PREV(n) ((n) == 0 ? procs - 1 : (n) - 1)
+
+/* sliding dictionary size for deflate */
+#define DICT 32768U
+
+/* largest power of 2 that fits in an unsigned int -- used to limit requests
+ to zlib functions that use unsigned int lengths */
+#define MAX ((((unsigned)-1) >> 1) + 1)
+
+/* compress thread: compress the input in the provided work unit and compute
+ its crc -- assume that the amount of space at job->out is guaranteed to be
+ enough for the compressed output, as determined by the maximum expansion
+ of deflate compression -- use the input in the previous work unit (if there
+ is one) to set the deflate dictionary for better compression */
+local void *compress_thread(void *arg)
+{
+ size_t len; /* input length for this work unit */
+ unsigned long crc; /* crc of input data */
+ struct work *prev; /* previous work unit */
+ struct work *job = arg; /* work unit for this thread */
+ z_stream *strm = &(job->strm); /* zlib stream for this work unit */
+
+ /* reset state for a new compressed stream */
+ (void)deflateReset(strm);
+
+ /* initialize input, output, and crc */
+ strm->next_in = job->buf;
+ strm->next_out = job->out;
+ len = job->len;
+ crc = crc32(0L, Z_NULL, 0);
+
+ /* set dictionary if this isn't the first work unit, and if we will be
+ compressing something (the read thread assures that the dictionary
+ data in the previous work unit is still there) */
+ prev = jobs + PREV(job - jobs);
+ if (prev->buf != NULL && len != 0)
+ deflateSetDictionary(strm, prev->buf + (size - DICT), DICT);
+
+ /* run MAX-sized amounts of input through deflate and crc32 -- this loop
+ is needed for those cases where the integer type is smaller than the
+ size_t type, or when len is close to the limit of the size_t type */
+ while (len > MAX) {
+ strm->avail_in = MAX;
+ strm->avail_out = (unsigned)-1;
+ crc = crc32(crc, strm->next_in, strm->avail_in);
+ (void)deflate(strm, Z_NO_FLUSH);
+ len -= MAX;
+ }
+
+ /* run last piece through deflate and crc32, follow with a sync marker */
+ if (len) {
+ strm->avail_in = len;
+ strm->avail_out = (unsigned)-1;
+ crc = crc32(crc, strm->next_in, strm->avail_in);
+ (void)deflate(strm, Z_SYNC_FLUSH);
+ }
+
+ /* don't need to Z_FINISH, since we'd delete the last two bytes anyway */
+
+ /* return result */
+ job->crc = crc;
+ return NULL;
+}
+
+/* put a 4-byte integer into a byte array in LSB order */
+#define PUT4(a,b) (*(a)=(b),(a)[1]=(b)>>8,(a)[2]=(b)>>16,(a)[3]=(b)>>24)
+
+/* write thread: wait for compression threads to complete, write output in
+ order, also write gzip header and trailer around the compressed data */
+local void *write_thread(void *arg)
+{
+ int n; /* compress thread index */
+ size_t len; /* length of input processed */
+ unsigned long tot; /* total uncompressed size (overflow ok) */
+ unsigned long crc; /* CRC-32 of uncompressed data */
+ unsigned char wrap[10]; /* gzip header or trailer */
+
+ /* write simple gzip header */
+ memcpy(wrap, "\037\213\10\0\0\0\0\0\0\3", 10);
+ wrap[8] = level == 9 ? 2 : (level == 1 ? 4 : 0);
+ writen(outd, wrap, 10);
+
+ /* process output of compress threads until end of input */
+ tot = 0;
+ crc = crc32(0L, Z_NULL, 0);
+ n = 0;
+ do {
+ /* wait for compress thread to start, then wait to complete */
+ flag_wait(&(jobs[n].busy), COMP);
+ pthread_join(jobs[n].comp, NULL);
+
+ /* now that compress is done, allow read thread to use input buffer */
+ flag_set(&(jobs[n].busy), WRITE);
+
+ /* write compressed data and update length and crc */
+ writen(outd, jobs[n].out, jobs[n].strm.next_out - jobs[n].out);
+ len = jobs[n].len;
+ tot += len;
+ crc = crc32_combine(crc, jobs[n].crc, len);
+
+ /* release this work unit and go to the next work unit */
+ flag_set(&(jobs[n].busy), IDLE);
+ n = NEXT(n);
+
+ /* an input buffer less than size in length indicates end of input */
+ } while (len == size);
+
+ /* write final static block and gzip trailer (crc and len mod 2^32) */
+ wrap[0] = 3; wrap[1] = 0;
+ PUT4(wrap + 2, crc);
+ PUT4(wrap + 6, tot);
+ writen(outd, wrap, 10);
+ return NULL;
+}
+
+/* one-time initialization of a work unit -- this is where we set the deflate
+ compression level and request raw deflate, and also where we set the size
+ of the output buffer to guarantee enough space for a worst-case deflate
+ ending with a Z_SYNC_FLUSH */
+local void job_init(struct work *job)
+{
+ int ret; /* deflateInit2() return value */
+
+ job->buf = malloc(size);
+ job->out = malloc(size + (size >> 11) + 10);
+ job->strm.zfree = Z_NULL;
+ job->strm.zalloc = Z_NULL;
+ job->strm.opaque = Z_NULL;
+ ret = deflateInit2(&(job->strm), level, Z_DEFLATED, -15, 8,
+ Z_DEFAULT_STRATEGY);
+ if (job->buf == NULL || job->out == NULL || ret != Z_OK)
+ bail("not enough memory");
+}
+
+/* compress ind to outd in the gzip format, using multiple threads for the
+ compression and crc calculation and another thread for writing the output --
+ the read thread is the main thread */
+local void read_thread(void)
+{
+ int n; /* general index */
+ size_t got; /* amount read */
+ pthread_attr_t attr; /* thread attributes (left at defaults) */
+ pthread_t write; /* write thread */
+
+ /* set defaults (not all pthread implementations default to joinable) */
+ pthread_attr_init(&attr);
+ pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);
+
+ /* allocate and set up work list (individual work units will be initialized
+ as needed, in case the input is short), assure that allocation size
+ arithmetic does not overflow */
+ if (size + (size >> 11) + 10 < (size >> 11) + 10 ||
+ (ssize_t)(size + (size >> 11) + 10) < 0 ||
+ ((size_t)0 - 1) / procs <= sizeof(struct work) ||
+ (jobs = malloc(procs * sizeof(struct work))) == NULL)
+ bail("not enough memory");
+ for (n = 0; n < procs; n++) {
+ jobs[n].buf = NULL;
+ flag_init(&(jobs[n].busy), IDLE);
+ }
+
+ /* start write thread */
+ pthread_create(&write, &attr, write_thread, NULL);
+
+ /* read from input and start compress threads (write thread will pick up
+ the output of the compress threads) */
+ n = 0;
+ do {
+ /* initialize this work unit if it's the first time it's used */
+ if (jobs[n].buf == NULL)
+ job_init(jobs + n);
+
+ /* read input data, but wait for last compress on this work unit to be
+ done, and wait for the dictionary to be used by the last compress on
+ the next work unit */
+ flag_wait_not(&(jobs[n].busy), COMP);
+ flag_wait_not(&(jobs[NEXT(n)].busy), COMP);
+ got = readn(ind, jobs[n].buf, size);
+
+ /* start compress thread, but wait for write to be done first */
+ flag_wait(&(jobs[n].busy), IDLE);
+ jobs[n].len = got;
+ pthread_create(&(jobs[n].comp), &attr, compress_thread, jobs + n);
+
+ /* mark work unit so write thread knows compress was started */
+ flag_set(&(jobs[n].busy), COMP);
+
+ /* go to the next work unit */
+ n = NEXT(n);
+
+ /* do until end of input, indicated by a read less than size */
+ } while (got == size);
+
+ /* wait for the write thread to complete -- the write thread will join with
+ all of the compress threads, so this waits for all of the threads to
+ complete */
+ pthread_join(write, NULL);
+
+ /* free up all requested resources and return */
+ for (n = procs - 1; n >= 0; n--) {
+ flag_done(&(jobs[n].busy));
+ (void)deflateEnd(&(jobs[n].strm));
+ free(jobs[n].out);
+ free(jobs[n].buf);
+ }
+ free(jobs);
+ pthread_attr_destroy(&attr);
+}
+
+/* Process arguments for level, size, and procs, compress from stdin to
+ stdout in the gzip format. Note that procs must be at least two in
+ order to provide a dictionary in one work unit for the other work
+ unit, and that size must be at least 32K to store a full dictionary. */
+int main(int argc, char **argv)
+{
+ int n; /* general index */
+ int get; /* command line parameters to get */
+ char *arg; /* command line argument */
+
+ /* set defaults -- 32 processes and 128K buffers was found to provide
+ good utilization of four cores (about 97%) and balanced the overall
+ execution time impact of more threads against more dictionary
+ processing for a fixed amount of memory -- the memory usage for these
+ settings and full use of all work units (at least 4 MB of input) is
+ 16.2 MB
+ */
+ level = Z_DEFAULT_COMPRESSION;
+ procs = 32;
+ size = 131072UL;
+
+ /* process command-line arguments */
+ get = 0;
+ for (n = 1; n < argc; n++) {
+ arg = argv[n];
+ if (*arg == '-') {
+ while (*++arg)
+ if (*arg >= '0' && *arg <= '9') /* compression level */
+ level = *arg - '0';
+ else if (*arg == 'b') /* chunk size in K */
+ get |= 1;
+ else if (*arg == 'p') /* number of processes */
+ get |= 2;
+ else if (*arg == 'h') { /* help */
+ fputs("usage: pigz [-0..9] [-b blocksizeinK]", stderr);
+ fputs(" [-p processes] < foo > foo.gz\n", stderr);
+ return 0;
+ }
+ else
+ bail("invalid option");
+ }
+ else if (get & 1) {
+ if (get & 2)
+ bail("you need to separate the -b and -p options");
+ size = (size_t)(atol(arg)) << 10; /* chunk size */
+ if (size < DICT)
+ bail("invalid option");
+ get = 0;
+ }
+ else if (get & 2) {
+ procs = atoi(arg); /* processes */
+ if (procs < 2)
+ bail("invalid option");
+ get = 0;
+ }
+ else
+ bail("invalid option (you need to pipe input and output)");
+ }
+ if (get)
+ bail("missing option argument");
+
+ /* do parallel compression from stdin to stdout (the read thread starts up
+ the write thread and the compression threads, and they all join before
+ the read thread returns) */
+ ind = 0;
+ outd = 1;
+ read_thread();
+
+ /* done */
+ return 0;
+}