diff options
Diffstat (limited to 'examples/enough.c')
| -rw-r--r-- | examples/enough.c | 39 |
1 files changed, 21 insertions, 18 deletions
diff --git a/examples/enough.c b/examples/enough.c index c40410b..b991144 100644 --- a/examples/enough.c +++ b/examples/enough.c @@ -1,7 +1,7 @@ /* 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 + * Copyright (C) 2007, 2008, 2012 Mark Adler + * Version 1.4 18 August 2012 Mark Adler */ /* Version history: @@ -14,6 +14,9 @@ 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 + 1.4 18 Aug 2012 Avoid shifts more than bits in type (caused endless loop!) + Clean up comparisons of different types + Clean up code indentation */ /* @@ -236,8 +239,8 @@ local big_t count(int syms, int len, int left) 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; + if (got == (big_t)0 - 1 || sum < got) /* overflow */ + return (big_t)0 - 1; } /* verify that all recursive calls are productive */ @@ -458,6 +461,7 @@ int main(int argc, char **argv) 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 */ + code_t word; /* for counting bits in code_t */ /* set up globals for cleanup() */ code = NULL; @@ -466,19 +470,19 @@ int main(int argc, char **argv) /* get arguments -- default to the deflate literal/length code */ syms = 286; - root = 9; + 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 > 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); + stderr); return 1; } @@ -487,18 +491,17 @@ int main(int argc, char **argv) max = syms - 1; /* determine the number of bits in a code_t */ - n = 0; - while (((code_t)1 << n) != 0) - n++; + for (n = 0, word = 1; word; n++, word <<= 1) + ; /* make sure that the calculation of most will not overflow */ - if (max > n || syms - 2 >= (((code_t)0 - 1) >> (max - 1))) { + if (max > n || (code_t)(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) { + if ((code_t)(syms - 1) > ((code_t)1 << max) - 1) { fprintf(stderr, "%d symbols cannot be coded in %d bits\n", syms, max); return 1; @@ -532,7 +535,7 @@ int main(int argc, char **argv) for (n = 2; n <= syms; n++) { got = count(n, 1, 2); sum += got; - if (got == -1 || sum < got) { /* overflow */ + if (got == (big_t)0 - 1 || sum < got) { /* overflow */ fputs("abort: can't count that high!\n", stderr); cleanup(); return 1; @@ -556,9 +559,9 @@ int main(int argc, char **argv) } /* find and show maximum inflate table usage */ - if (root > max) /* reduce root to max length */ - root = max; - if (syms < ((code_t)1 << (root + 1))) + if (root > max) /* reduce root to max length */ + root = max; + if ((code_t)syms < ((code_t)1 << (root + 1))) enough(syms); else puts("cannot handle minimum code lengths > root"); |