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* bignum.c (absint_numwords_bytes): New function.

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(absint_numwords_generic): Extracted from rb_absint_numwords.
  (rb_absint_numwords): Use absint_numwords_bytes if possible.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41199 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
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akr 2013-06-09 16:08:54 +00:00
parent d395be138c
commit f30d662c24
2 changed files with 108 additions and 26 deletions
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6
ChangeLog
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@ -1,3 +1,9 @@
Mon Jun 10 01:07:57 2013 Tanaka Akira <akr@fsij.org>
* bignum.c (absint_numwords_bytes): New function.
(absint_numwords_generic): Extracted from rb_absint_numwords.
(rb_absint_numwords): Use absint_numwords_bytes if possible.
Sun Jun 9 21:33:15 2013 Tanaka Akira <akr@fsij.org>
* bignum.c (rb_absint_numwords): Return (size_t)-1 when overflow.

128
bignum.c
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@ -516,6 +516,94 @@ rb_absint_size(VALUE val, int *nlz_bits_ret)
return (de - dp) * SIZEOF_BDIGITS - num_leading_zeros / CHAR_BIT;
}
size_t
absint_numwords_bytes(size_t numbytes, int nlz_bits_in_msbyte, size_t word_numbits, size_t *nlz_bits_ret)
{
/*
* word_numbytes = word_numbits / CHAR_BIT
* div, mod = val_numbits.divmod(word_numbits)
*
* q, r = numbytes.divmod(word_numbytes)
* s = q if r * CHAR_BIT >= nlz_bits_in_msbyte
* = q - 1 if otherwise
* t = r * CHAR_BIT - nlz_bits_in_msbyte if r * CHAR_BIT >= nlz_bits_in_msbyte
* = word_numbits + r * CHAR_BIT - nlz_bits_in_msbyte if otherwise
*
* div = (numbytes * CHAR_BIT - nlz_bits_in_msbyte) / word_numbits
* = ((q * word_numbytes + r) * CHAR_BIT - nlz_bits_in_msbyte) / word_numbits
* = (q * word_numbytes * CHAR_BIT + r * CHAR_BIT - nlz_bits_in_msbyte) / word_numbits
* = q + (r * CHAR_BIT - nlz_bits_in_msbyte) / word_numbits if r * CHAR_BIT >= nlz_bits_in_msbyte
* q - 1 + (word_numbits + r * CHAR_BIT - nlz_bits_in_msbyte) / word_numbits if r * CHAR_BIT < nlz_bits_in_msbyte
* = s + t / word_numbits
* mod = (r * CHAR_BIT - nlz_bits_in_msbyte) % word_numbits if r * CHAR_BIT >= nlz_bits_in_msbyte
* (word_numbits + r * CHAR_BIT - nlz_bits_in_msbyte) % word_numbits if r * CHAR_BIT < nlz_bits_in_msbyte
* = t % word_numbits
*
* numwords = mod == 0 ? div : div + 1
* nlz_bits = mod == 0 ? 0 : word_numbits - mod
*/
size_t word_numbytes = word_numbits / CHAR_BIT;
size_t q = numbytes / word_numbytes;
size_t r = numbytes % word_numbytes;
size_t s, t;
size_t div, mod;
size_t numwords;
size_t nlz_bits;
if (r * CHAR_BIT >= (size_t)nlz_bits_in_msbyte) {
s = q;
t = r * CHAR_BIT - nlz_bits_in_msbyte;
}
else {
s = q - 1;
t = word_numbits + r * CHAR_BIT - nlz_bits_in_msbyte;
}
div = s + t / word_numbits;
mod = t % word_numbits;
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;
VALUE div_mod, div, mod;
int sign;
size_t numwords;
size_t nlz_bits;
/*
* val_numbits = numbytes * CHAR_BIT - nlz_bits_in_msbyte
* div, mod = val_numbits.divmod(word_numbits)
* numwords = mod == 0 ? div : div + 1
* nlz_bits = mod == 0 ? 0 : word_numbits - mod
*/
val_numbits = SIZET2NUM(numbytes);
val_numbits = rb_funcall(val_numbits, '*', 1, LONG2FIX(CHAR_BIT));
if (nlz_bits_in_msbyte)
val_numbits = rb_funcall(val_numbits, '-', 1, LONG2FIX(nlz_bits_in_msbyte));
word_numbits_v = SIZET2NUM(word_numbits);
div_mod = rb_funcall(val_numbits, rb_intern("divmod"), 1, word_numbits_v);
div = RARRAY_AREF(div_mod, 0);
mod = RARRAY_AREF(div_mod, 1);
if (mod == LONG2FIX(0)) {
nlz_bits = 0;
}
else {
div = rb_funcall(div, '+', 1, LONG2FIX(1));
nlz_bits = word_numbits - NUM2SIZET(mod);
}
rb_integer_pack(div, &sign, &numwords, 1, sizeof(numwords), 0,
INTEGER_PACK_MSWORD_FIRST|INTEGER_PACK_NATIVE_BYTE_ORDER);
if (sign == 2)
return (size_t)-1;
*nlz_bits_ret = nlz_bits;
return numwords;
}
/*
* Calculate a number of words to be required to represent
* the absolute value of the integer given as _val_.
@ -537,45 +625,33 @@ size_t
rb_absint_numwords(VALUE val, size_t word_numbits, size_t *nlz_bits_ret)
{
size_t numbytes;
int nlz_bits_in_msbyte;
size_t numwords;
size_t nlz_bits;
int nlz_bits_in_msbyte;
VALUE val_numbits, word_numbits_v;
VALUE div_mod, div, mod;
int sign;
if (word_numbits == 0)
return (size_t)-1;
numbytes = rb_absint_size(val, &nlz_bits_in_msbyte);
/*
* val_numbits = numbytes * CHAR_BIT - nlz_bits_in_msbyte
* div, mod = val_numbits.divmod(word_numbits)
* numwords = mod == 0 ? div : div + 1
* nlz_bits = mod == 0 ? 0 : word_numbits - mod
*/
val_numbits = SIZET2NUM(numbytes);
val_numbits = rb_funcall(val_numbits, '*', 1, LONG2FIX(CHAR_BIT));
if (nlz_bits_in_msbyte)
val_numbits = rb_funcall(val_numbits, '-', 1, LONG2FIX(nlz_bits_in_msbyte));
word_numbits_v = SIZET2NUM(word_numbits);
div_mod = rb_funcall(val_numbits, rb_intern("divmod"), 1, word_numbits_v);
div = RARRAY_AREF(div_mod, 0);
mod = RARRAY_AREF(div_mod, 1);
if (mod == LONG2FIX(0)) {
nlz_bits = 0;
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;
numwords0 = absint_numwords_generic(numbytes, nlz_bits_in_msbyte, word_numbits, &nlz_bits0);
assert(numwords0 == numwords);
assert(nlz_bits0 == nlz_bits);
#endif
}
else {
div = rb_funcall(div, '+', 1, LONG2FIX(1));
nlz_bits = word_numbits - NUM2SIZET(mod);
numwords = absint_numwords_generic(numbytes, nlz_bits_in_msbyte, word_numbits, &nlz_bits);
}
rb_integer_pack(div, &sign, &numwords, 1, sizeof(numwords), 0,
INTEGER_PACK_MSWORD_FIRST|INTEGER_PACK_NATIVE_BYTE_ORDER);
if (sign == 2)
return (size_t)-1;
if (numwords == (size_t)-1)
return numwords;
if (nlz_bits_ret)
*nlz_bits_ret = nlz_bits;
return numwords;
}