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* bignum.c (bitlength_bdigit): New function.

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(rb_big_pow): Use bitlength_bdigit instead of ffs.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41050 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
This commit is contained in:
akr 2013-06-03 14:49:33 +00:00
parent bf386e580f
commit 935d39a5b8
2 changed files with 24 additions and 1 deletions
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5
ChangeLog
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@ -1,3 +1,8 @@
Mon Jun 3 23:47:55 2013 Tanaka Akira <akr@fsij.org>
* bignum.c (bitlength_bdigit): New function.
(rb_big_pow): Use bitlength_bdigit instead of ffs.
Mon Jun 3 23:11:19 2013 Ayumu AIZAWA <ayumu.aizawa@gmail.com>
* lib/fileutils.rb: fix behavior when mkdir/mkdir_p accepted "/".

20
bignum.c
View File

@ -3178,6 +3178,24 @@ bigsqr(VALUE x)
return bigtrunc(bigmul0(x, x));
}
static int
bitlength_bdigit(BDIGIT v)
{
if (v == 0)
return 0;
v |= v >> 1;
v |= v >> 2;
v |= v >> 4;
v |= v >> 8;
#if 2 < SIZEOF_BDIGITS
v |= v >> 16;
#endif
v++;
if (v == 0)
return SIZEOF_BDIGITS*CHAR_BIT;
return ffs(v); /* assumption: sizeof(BDIGIT) <= sizeof(int) */
}
/*
* call-seq:
* big ** exponent -> numeric
@ -3219,7 +3237,7 @@ rb_big_pow(VALUE x, VALUE y)
VALUE z = 0;
SIGNED_VALUE mask;
const long xlen = RBIGNUM_LEN(x) - 1;
const long xbits = ffs(RBIGNUM_DIGITS(x)[xlen]) + SIZEOF_BDIGITS*BITSPERDIG*xlen;
const long xbits = bitlength_bdigit(RBIGNUM_DIGITS(x)[xlen]) + SIZEOF_BDIGITS*BITSPERDIG*xlen;
const long BIGLEN_LIMIT = BITSPERDIG*1024*1024;
if ((xbits > BIGLEN_LIMIT) || (xbits * yy > BIGLEN_LIMIT)) {