diff options
Diffstat (limited to 'deflate.c')
| -rw-r--r-- | deflate.c | 293 |
1 files changed, 215 insertions, 78 deletions
@@ -1,5 +1,5 @@ /* deflate.c -- compress data using the deflation algorithm - * Copyright (C) 1995-2013 Jean-loup Gailly and Mark Adler + * Copyright (C) 1995-2016 Jean-loup Gailly and Mark Adler * For conditions of distribution and use, see copyright notice in zlib.h */ @@ -52,7 +52,7 @@ #include "deflate.h" const char deflate_copyright[] = - " deflate 1.2.8.1 Copyright 1995-2013 Jean-loup Gailly and Mark Adler "; + " deflate 1.2.8.1 Copyright 1995-2016 Jean-loup Gailly and Mark Adler "; /* If you use the zlib library in a product, an acknowledgment is welcome in the documentation of your product. If for some reason you cannot @@ -74,6 +74,7 @@ typedef block_state (*compress_func) OF((deflate_state *s, int flush)); /* Compression function. Returns the block state after the call. */ local int deflateStateCheck OF((z_streamp strm)); +local void slide_hash OF((deflate_state *s)); local void fill_window OF((deflate_state *s)); local block_state deflate_stored OF((deflate_state *s, int flush)); local block_state deflate_fast OF((deflate_state *s, int flush)); @@ -191,6 +192,37 @@ local const config configuration_table[10] = { s->head[s->hash_size-1] = NIL; \ zmemzero((Bytef *)s->head, (unsigned)(s->hash_size-1)*sizeof(*s->head)); +/* =========================================================================== + * Slide the hash table when sliding the window down (could be avoided with 32 + * bit values at the expense of memory usage). We slide even when level == 0 to + * keep the hash table consistent if we switch back to level > 0 later. + */ +local void slide_hash(s) + deflate_state *s; +{ + unsigned n, m; + Posf *p; + uInt wsize = s->w_size; + + n = s->hash_size; + p = &s->head[n]; + do { + m = *--p; + *p = (Pos)(m >= wsize ? m - wsize : NIL); + } while (--n); + n = wsize; +#ifndef FASTEST + p = &s->prev[n]; + do { + m = *--p; + *p = (Pos)(m >= wsize ? m - wsize : NIL); + /* If n is not on any hash chain, prev[n] is garbage but + * its value will never be used. + */ + } while (--n); +#endif +} + /* ========================================================================= */ int ZEXPORT deflateInit_(strm, level, version, stream_size) z_streamp strm; @@ -540,6 +572,13 @@ int ZEXPORT deflateParams(strm, level, strategy) return Z_BUF_ERROR; } if (s->level != level) { + if (s->level == 0 && s->matches != 0) { + if (s->matches == 1) + slide_hash(s); + else + CLEAR_HASH(s); + s->matches = 0; + } s->level = level; s->max_lazy_match = configuration_table[level].max_lazy; s->good_match = configuration_table[level].good_length; @@ -659,10 +698,10 @@ local void putShortMSB (s, b) } /* ========================================================================= - * Flush as much pending output as possible. All deflate() output goes - * through this function so some applications may wish to modify it - * to avoid allocating a large strm->next_out buffer and copying into it. - * (See also read_buf()). + * Flush as much pending output as possible. All deflate() output, except for + * some deflate_stored() output, goes through this function so some + * applications may wish to modify it to avoid allocating a large + * strm->next_out buffer and copying into it. (See also read_buf()). */ local void flush_pending(strm) z_streamp strm; @@ -1420,8 +1459,7 @@ local void check_match(s, start, match, length) local void fill_window(s) deflate_state *s; { - register unsigned n, m; - register Posf *p; + unsigned n; unsigned more; /* Amount of free space at the end of the window. */ uInt wsize = s->w_size; @@ -1448,35 +1486,11 @@ local void fill_window(s) */ if (s->strstart >= wsize+MAX_DIST(s)) { - zmemcpy(s->window, s->window+wsize, (unsigned)wsize); + zmemcpy(s->window, s->window+wsize, (unsigned)wsize - more); s->match_start -= wsize; s->strstart -= wsize; /* we now have strstart >= MAX_DIST */ s->block_start -= (long) wsize; - - /* Slide the hash table (could be avoided with 32 bit values - at the expense of memory usage). We slide even when level == 0 - to keep the hash table consistent if we switch back to level > 0 - later. (Using level 0 permanently is not an optimal usage of - zlib, so we don't care about this pathological case.) - */ - n = s->hash_size; - p = &s->head[n]; - do { - m = *--p; - *p = (Pos)(m >= wsize ? m-wsize : NIL); - } while (--n); - - n = wsize; -#ifndef FASTEST - p = &s->prev[n]; - do { - m = *--p; - *p = (Pos)(m >= wsize ? m-wsize : NIL); - /* If n is not on any hash chain, prev[n] is garbage but - * its value will never be used. - */ - } while (--n); -#endif + slide_hash(s); more += wsize; } if (s->strm->avail_in == 0) break; @@ -1582,70 +1596,193 @@ local void fill_window(s) if (s->strm->avail_out == 0) return (last) ? finish_started : need_more; \ } +/* Maximum stored block length in deflate format (not including header). */ +#define MAX_STORED 65535 + +/* Minimum of a and b. */ +#define MIN(a, b) ((a) > (b) ? (b) : (a)) + /* =========================================================================== * Copy without compression as much as possible from the input stream, return * the current block state. - * This function does not insert new strings in the dictionary since - * uncompressible data is probably not useful. This function is used - * only for the level=0 compression option. - * NOTE: this function should be optimized to avoid extra copying from - * window to pending_buf. + * + * In case deflateParams() is used to later switch to a non-zero compression + * level, s->matches (otherwise unused when storing) keeps track of the number + * of hash table slides to perform. If s->matches is 1, then one hash table + * slide will be done when switching. If s->matches is 2, the maximum value + * allowed here, then the hash table will be cleared, since two or more slides + * is the same as a clear. + * + * deflate_stored() is written to minimize the number of times an input byte is + * copied. It is most efficient with large input and output buffers, which + * maximizes the opportunites to have a single copy from next_in to next_out. */ local block_state deflate_stored(s, flush) deflate_state *s; int flush; { - /* Stored blocks are limited to 0xffff bytes, pending_buf is limited - * to pending_buf_size, and each stored block has a 5 byte header: + /* Smallest worthy block size when not flushing or finishing. By default + * this is 32K. This can be as small as 507 bytes for memLevel == 1. For + * large input and output buffers, the stored block size will be larger. */ - ulg max_block_size = 0xffff; - ulg max_start; + unsigned min_block = MIN(s->pending_buf_size - 5, s->w_size); - if (max_block_size > s->pending_buf_size - 5) { - max_block_size = s->pending_buf_size - 5; - } - - /* Copy as much as possible from input to output: */ + /* Copy as many min_block or larger stored blocks directly to next_out as + * possible. If flushing, copy the remaining available input to next_out as + * stored blocks, if there is enough space. + */ + unsigned len, left, have, last; + unsigned used = s->strm->avail_in; for (;;) { - /* Fill the window as much as possible: */ - if (s->lookahead <= 1) { + /* Set len to the maximum size block that we can copy directly with the + * available input data and output space. Set left to how much of that + * would be copied from what's left in the window. + */ + len = MAX_STORED; /* maximum deflate stored block length */ + have = (s->bi_valid + 42) >> 3; /* number of header bytes */ + /* maximum stored block length that will fit in avail_out: */ + have = s->strm->avail_out > have ? s->strm->avail_out - have : 0; + left = s->strstart - s->block_start; /* bytes left in window */ + if (len > (ulg)left + s->strm->avail_in) + len = left + s->strm->avail_in; /* limit len to the input */ + if (len > have) + len = have; /* limit len to the output */ + if (left > len) + left = len; /* limit window pull to len */ + + /* If the stored block would be less than min_block in length, or if + * unable to copy all of the available input when flushing, then try + * copying to the window and the pending buffer instead. Also don't + * write an empty block when flushing -- deflate() does that. + */ + if (len < min_block && (len == 0 || flush == Z_NO_FLUSH || + len - left != s->strm->avail_in)) + break; - Assert(s->strstart < s->w_size+MAX_DIST(s) || - s->block_start >= (long)s->w_size, "slide too late"); + /* Make a dummy stored block in pending to get the header bytes, + * including any pending bits. This also updates the debugging counts. + */ + last = flush == Z_FINISH && len - left == s->strm->avail_in ? 1 : 0; + _tr_stored_block(s, (char *)0, 0L, last); - fill_window(s); - if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more; + /* Replace the lengths in the dummy stored block with len. */ + s->pending_buf[s->pending - 4] = len; + s->pending_buf[s->pending - 3] = len >> 8; + s->pending_buf[s->pending - 2] = ~len; + s->pending_buf[s->pending - 1] = ~len >> 8; - if (s->lookahead == 0) break; /* flush the current block */ + /* Write the stored block header bytes. */ + flush_pending(s->strm); + + /* Update debugging counts for the data about to be copied. */ +#ifdef ZLIB_DEBUG + s->compressed_len += len << 3; + s->bits_sent += len << 3; +#endif + + /* Copy uncompressed bytes from the window to next_out. */ + if (left) { + zmemcpy(s->strm->next_out, s->window + s->block_start, left); + s->strm->next_out += left; + s->strm->avail_out -= left; + s->strm->total_out += left; + s->block_start += left; + len -= left; } - Assert(s->block_start >= 0L, "block gone"); - - s->strstart += s->lookahead; - s->lookahead = 0; - - /* Emit a stored block if pending_buf will be full: */ - max_start = max_block_size + (ulg)s->block_start; - if (s->strstart == 0 || (ulg)s->strstart >= max_start) { - /* strstart == 0 is possible when wraparound on 16-bit machine */ - s->lookahead = (uInt)(s->strstart - max_start); - s->strstart = (uInt)max_start; - FLUSH_BLOCK(s, 0); + + /* Copy uncompressed bytes directly from next_in to next_out, updating + * the check value. + */ + if (len) { + read_buf(s->strm, s->strm->next_out, len); + s->strm->next_out += len; + s->strm->avail_out -= len; + s->strm->total_out += len; } - /* Flush if we may have to slide, otherwise block_start may become - * negative and the data will be gone: + } + + /* Update the sliding window with the last s->w_size bytes of the copied + * data, or append all of the copied data to the existing window if less + * than s->w_size bytes were copied. Also update the number of bytes to + * insert in the hash tables, in the event that deflateParams() switches to + * a non-zero compression level. + */ + used -= s->strm->avail_in; /* number of input bytes directly copied */ + if (used) { + /* If any input was used, then no unused input remains in the window, + * therefore s->block_start == s->strstart. */ - if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) { - FLUSH_BLOCK(s, 0); + if (used >= s->w_size) { /* supplant the previous history */ + s->matches = 2; /* clear hash */ + zmemcpy(s->window, s->strm->next_in - s->w_size, s->w_size); + s->strstart = s->w_size; } + else { + if (s->window_size - s->strstart <= used) { + /* Slide the window down. */ + s->strstart -= s->w_size; + zmemcpy(s->window, s->window + s->w_size, s->strstart); + if (s->matches < 2) + s->matches++; /* add a pending slide_hash() */ + } + zmemcpy(s->window + s->strstart, s->strm->next_in - used, used); + s->strstart += used; + } + s->block_start = s->strstart; + s->insert += MIN(used, s->w_size - s->insert); } - s->insert = 0; - if (flush == Z_FINISH) { - FLUSH_BLOCK(s, 1); - return finish_done; + + /* If flushing or finishing and all input has been consumed, then done. If + * the code above couldn't write a complete block to next_out, then the + * code following this won't be able to either. + */ + if (flush != Z_NO_FLUSH && s->strm->avail_in == 0 && + s->strstart == s->block_start) + return flush == Z_FINISH ? finish_done : block_done; + + /* Fill the window with any remaining input. */ + have = s->window_size - s->strstart - 1; + if (s->strm->avail_in > have && s->block_start >= s->w_size) { + /* Slide the window down. */ + s->block_start -= s->w_size; + s->strstart -= s->w_size; + zmemcpy(s->window, s->window + s->w_size, s->strstart); + if (s->matches < 2) + s->matches++; /* add a pending slide_hash() */ + have += s->w_size; /* more space now */ } - if ((long)s->strstart > s->block_start) - FLUSH_BLOCK(s, 0); - return block_done; + if (have > s->strm->avail_in) + have = s->strm->avail_in; + if (have) { + read_buf(s->strm, s->window + s->strstart, have); + s->strstart += have; + } + + /* There was not enough avail_out to write a complete worthy or flushed + * stored block to next_out. Write a stored block to pending instead, if we + * have enough input for a worthy block, or if flushing and there is enough + * room for the remaining input as a stored block in the pending buffer. + */ + have = (s->bi_valid + 42) >> 3; /* number of header bytes */ + /* maximum stored block length that will fit in pending: */ + have = MIN(s->pending_buf_size - have, MAX_STORED); + min_block = MIN(have, s->w_size); + left = s->strstart - s->block_start; + if (left >= min_block || + (left && flush != Z_NO_FLUSH && s->strm->avail_in == 0 && + left <= have)) { + len = MIN(left, have); + last = flush == Z_FINISH && s->strm->avail_in == 0 && + len == left ? 1 : 0; + _tr_stored_block(s, (charf *)s->window + s->block_start, len, last); + s->block_start += len; + flush_pending(s->strm); + if (last) + return finish_started; + } + + /* We've done all we can with the available input and output. */ + return need_more; } /* =========================================================================== |