diff options
| -rw-r--r-- | huffman.c | 15 |
1 files changed, 13 insertions, 2 deletions
@@ -274,11 +274,22 @@ void build_huffman_tree(int *freqs, unsigned char *lengths, * ---------------------------------- * maxprob - nactivesyms * - * rounded up, of course. And we'll only even be trying - * this if + * rounded up, of course. And we'll only even be trying this if + * smallestfreq <= totalfreq / maxprob, which is precisely the + * condition under which the numerator of this fraction is + * positive. + * + * (As for the denominator, that could only be negative if there + * were more than F_{n+2} symbols overall, in which case it + * _wouldn't_ be possible to avoid having a symbol with + * probability at most 1/F_{n+2}. So that is a constraint on the + * input parameters to this function, which we enforce by + * assertion.) */ num = totalfreq - smallestfreq * maxprob; denom = maxprob - nactivesyms; + assert(num > 0); /* this just restates the assert above */ + assert(denom > 0); /* this is a constraint on the function parameters */ adjust = (num + denom - 1) / denom; /* |