diff options
| -rw-r--r-- | ChangeLog | 5 | ||||
| -rw-r--r-- | bignum.c | 27 |
2 files changed, 30 insertions, 2 deletions
@@ -1,3 +1,8 @@ +Mon Jun 10 05:38:23 2013 Tanaka Akira <akr@fsij.org> + + * bignum.c (absint_numwords_small): New function. + (absint_numwords_generic): Use absint_numwords_small if possible. + Mon Jun 10 01:07:57 2013 Tanaka Akira <akr@fsij.org> * bignum.c (absint_numwords_bytes): New function. @@ -555,7 +555,7 @@ absint_numwords_bytes(size_t numbytes, int nlz_bits_in_msbyte, size_t word_numbi } else { s = q - 1; - t = word_numbits + r * CHAR_BIT - nlz_bits_in_msbyte; + t = word_numbits - nlz_bits_in_msbyte + r * CHAR_BIT; } div = s + t / word_numbits; mod = t % word_numbits; @@ -566,6 +566,20 @@ absint_numwords_bytes(size_t numbytes, int nlz_bits_in_msbyte, size_t word_numbi } size_t +absint_numwords_small(size_t numbytes, int nlz_bits_in_msbyte, size_t word_numbits, size_t *nlz_bits_ret) +{ + size_t val_numbits = numbytes * CHAR_BIT - nlz_bits_in_msbyte; + size_t div = val_numbits / word_numbits; + size_t mod = val_numbits % word_numbits; + size_t numwords; + size_t nlz_bits; + numwords = mod == 0 ? div : div + 1; + nlz_bits = mod == 0 ? 0 : word_numbits - mod; + *nlz_bits_ret = nlz_bits; + return numwords; +} + +size_t absint_numwords_generic(size_t numbytes, int nlz_bits_in_msbyte, size_t word_numbits, size_t *nlz_bits_ret) { VALUE val_numbits, word_numbits_v; @@ -634,7 +648,16 @@ rb_absint_numwords(VALUE val, size_t word_numbits, size_t *nlz_bits_ret) numbytes = rb_absint_size(val, &nlz_bits_in_msbyte); - if (word_numbits % CHAR_BIT == 0) { + if (numbytes <= SIZE_MAX / CHAR_BIT) { + numwords = absint_numwords_small(numbytes, nlz_bits_in_msbyte, word_numbits, &nlz_bits); +#if 0 + size_t numwords0, nlz_bits0; + numwords0 = absint_numwords_generic(numbytes, nlz_bits_in_msbyte, word_numbits, &nlz_bits0); + assert(numwords0 == numwords); + assert(nlz_bits0 == nlz_bits); +#endif + } + else if (word_numbits % CHAR_BIT == 0) { numwords = absint_numwords_bytes(numbytes, nlz_bits_in_msbyte, word_numbits, &nlz_bits); #if 0 size_t numwords0, nlz_bits0; |