diff options
| -rw-r--r-- | ChangeLog | 6 | ||||
| -rw-r--r-- | bignum.c | 28 |
2 files changed, 23 insertions, 11 deletions
@@ -1,3 +1,9 @@ +Wed Jul 31 19:55:33 2013 Tanaka Akira <akr@fsij.org> + + * bignum.c (MAX_BIG2STR_TABLE_ENTRIES): Use SIZEOF_SIZE_T. + (power_cache_get_power0): Add rb_bug call for too bit i argument. + (power_cache_get_power): Simplified. + Wed Jul 31 18:32:25 2013 Akinori MUSHA <knu@iDaemons.org> * lib/uri/common.rb (URI.decode_www_form_component): Use String#b. @@ -4082,7 +4082,7 @@ big_rshift(VALUE x, unsigned long shift) #define LOG2_KARATSUBA_BIG2STR_DIGITS 7 #define KARATSUBA_BIG2STR_DIGITS (1L<<LOG2_KARATSUBA_BIG2STR_DIGITS) -#define MAX_BIG2STR_TABLE_ENTRIES 64 +#define MAX_BIG2STR_TABLE_ENTRIES (SIZEOF_SIZE_T * CHAR_BIT) static VALUE big2str_power_cache[35][MAX_BIG2STR_TABLE_ENTRIES]; @@ -4100,6 +4100,21 @@ power_cache_init(void) static inline VALUE power_cache_get_power0(int base, int i) { + /* MAX_BIG2STR_TABLE_ENTRIES is big enough to that + * big2str_power_cache[base][MAX_BIG2STR_TABLE_ENTRIES-1] fills whole memory. + * So MAX_BIG2STR_TABLE_ENTRIES <= i is not possible to calculate. + * + * big2str_power_cache[base][MAX_BIG2STR_TABLE_ENTRIES-1] = + * (base**KARATSUBA_BIG2STR_DIGITS)**(MAX_BIG2STR_TABLE_ENTRIES-1) = + * (base**KARATSUBA_BIG2STR_DIGITS)**(SIZEOF_SIZE_T*CHAR_BIT-1) = + * base**(KARATSUBA_BIG2STR_DIGITS*(SIZEOF_SIZE_T*CHAR_BIT-1)) > 2**(SIZEOF_SIZE_T*CHAR_BIT-1) + * where + * 2 <= base + * 1 < KARATSUBA_BIG2STR_DIGITS + */ + if (MAX_BIG2STR_TABLE_ENTRIES <= i) + rb_bug("too big power number requested: (%d**%ld)**(2**%d)", base, KARATSUBA_BIG2STR_DIGITS, i); + if (NIL_P(big2str_power_cache[base - 2][i])) { big2str_power_cache[base - 2][i] = i == 0 ? rb_big_pow(rb_int2big(base), INT2FIX(KARATSUBA_BIG2STR_DIGITS)) @@ -4113,24 +4128,15 @@ static VALUE power_cache_get_power(int base, long n1, long* m1) { int i, m; - long j; VALUE t; if (n1 <= KARATSUBA_BIG2STR_DIGITS) rb_bug("n1 > KARATSUBA_BIG2STR_DIGITS"); m = bitsize(n1-1); /* ceil(log2(n1)) */ - if (m1) *m1 = 1 << m; + if (m1) *m1 = 1 << m; /* smallest x which n1 <= x and x is a power of 2. */ i = m - LOG2_KARATSUBA_BIG2STR_DIGITS; - if (i >= MAX_BIG2STR_TABLE_ENTRIES) - i = MAX_BIG2STR_TABLE_ENTRIES - 1; t = power_cache_get_power0(base, i); - - j = KARATSUBA_BIG2STR_DIGITS*(1 << i); - while (n1 > j) { - t = bigsq(t); - j *= 2; - } return t; } |