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-rw-r--r--ChangeLog9
-rw-r--r--bignum.c86
-rw-r--r--internal.h4
3 files changed, 75 insertions, 24 deletions
diff --git a/ChangeLog b/ChangeLog
index 3e9778e98c..31f16adae7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+Sun Jun 9 21:33:15 2013 Tanaka Akira <akr@fsij.org>
+
+ * bignum.c (rb_absint_numwords): Return (size_t)-1 when overflow.
+ Refine variable names.
+ (rb_absint_size): Refine variable names.
+
+ * internal.h (rb_absint_size): Refine an argument name.
+ (rb_absint_numwords): Ditto.
+
Sun Jun 9 16:51:41 2013 Tanaka Akira <akr@fsij.org>
* bignum.c (rb_absint_numwords): Renamed from rb_absint_size_in_word.
diff --git a/bignum.c b/bignum.c
index 78cc893a78..ae91f46ad0 100644
--- a/bignum.c
+++ b/bignum.c
@@ -452,8 +452,25 @@ rb_big_unpack(unsigned long *buf, long num_longs)
}
/* number of bytes of abs(val). additionaly number of leading zeros can be returned. */
+
+/*
+ * Calculate a number of bytes to be required to represent
+ * the absolute value of the integer given as _val_.
+ *
+ * [val] an integer.
+ * [nlz_bits_ret] number of leading zero bits in the most significant byte is returned if not NULL.
+ *
+ * This function returns ((val_numbits * CHAR_BIT + CHAR_BIT - 1) / CHAR_BIT)
+ * where val_numbits is the number of bits of abs(val).
+ * This function should not overflow.
+ *
+ * If nlz_bits_ret is not NULL,
+ * (return_value * CHAR_BIT - val_numbits) is stored in *nlz_bits_ret.
+ * In this case, 0 <= *nlz_bits_ret < CHAR_BIT.
+ *
+ */
size_t
-rb_absint_size(VALUE val, int *number_of_leading_zero_bits)
+rb_absint_size(VALUE val, int *nlz_bits_ret)
{
BDIGIT *dp;
BDIGIT *de;
@@ -489,51 +506,76 @@ rb_absint_size(VALUE val, int *number_of_leading_zero_bits)
while (dp < de && de[-1] == 0)
de--;
if (dp == de) {
- if (number_of_leading_zero_bits)
- *number_of_leading_zero_bits = 0;
+ if (nlz_bits_ret)
+ *nlz_bits_ret = 0;
return 0;
}
num_leading_zeros = nlz(de[-1]);
- if (number_of_leading_zero_bits)
- *number_of_leading_zero_bits = num_leading_zeros % CHAR_BIT;
+ if (nlz_bits_ret)
+ *nlz_bits_ret = num_leading_zeros % CHAR_BIT;
return (de - dp) * SIZEOF_BDIGITS - num_leading_zeros / CHAR_BIT;
}
+/*
+ * Calculate a number of words to be required to represent
+ * the absolute value of the integer given as _val_.
+ *
+ * [val] an integer.
+ * [word_numbits] number of bits in a word.
+ * [nlz_bits_ret] number of leading zero bits in the most significant word is returned if not NULL.
+ *
+ * This function returns ((val_numbits * CHAR_BIT + word_numbits - 1) / word_numbits)
+ * where val_numbits is the number of bits of abs(val).
+ * If it overflows, (size_t)-1 is returned.
+ *
+ * If nlz_bits_ret is not NULL and overflow is not occur,
+ * (return_value * word_numbits - val_numbits) is stored in *nlz_bits_ret.
+ * In this case, 0 <= *nlz_bits_ret < word_numbits.
+ *
+ */
size_t
-rb_absint_numwords(VALUE val, size_t word_numbits_arg, size_t *number_of_leading_zero_bits)
+rb_absint_numwords(VALUE val, size_t word_numbits, size_t *nlz_bits_ret)
{
size_t numbytes;
size_t numwords;
- int zerobits_in_byte;
- VALUE val_numbits, word_numbits;
+ size_t nlz_bits;
+ int nlz_bits_in_msbyte;
+ VALUE val_numbits, word_numbits_v;
VALUE div_mod, div, mod;
+ int sign;
- numbytes = rb_absint_size(val, &zerobits_in_byte);
+ if (word_numbits == 0)
+ return (size_t)-1;
+
+ numbytes = rb_absint_size(val, &nlz_bits_in_msbyte);
/*
- * val_numbits = numbytes * CHAR_BIT - zerobits_in_byte
+ * val_numbits = numbytes * CHAR_BIT - nlz_bits_in_msbyte
* div, mod = val_numbits.divmod(word_numbits)
* numwords = mod == 0 ? div : div + 1
- * number_of_leading_zero_bits_in_word = mod == 0 ? 0 : word_numbits - mod
+ * nlz_bits = mod == 0 ? 0 : word_numbits - mod
*/
val_numbits = SIZET2NUM(numbytes);
val_numbits = rb_funcall(val_numbits, '*', 1, LONG2FIX(CHAR_BIT));
- if (zerobits_in_byte)
- val_numbits = rb_funcall(val_numbits, '-', 1, LONG2FIX(zerobits_in_byte));
- word_numbits = SIZET2NUM(word_numbits_arg);
- div_mod = rb_funcall(val_numbits, rb_intern("divmod"), 1, word_numbits);
+ 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)) {
- numwords = NUM2SIZET(div);
- if (number_of_leading_zero_bits)
- *number_of_leading_zero_bits = 0;
+ nlz_bits = 0;
}
else {
- numwords = NUM2SIZET(rb_funcall(div, '+', 1, LONG2FIX(1)));
- if (number_of_leading_zero_bits)
- *number_of_leading_zero_bits = word_numbits_arg - NUM2SIZET(mod);
- }
+ 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;
+ if (nlz_bits_ret)
+ *nlz_bits_ret = nlz_bits;
return numwords;
}
diff --git a/internal.h b/internal.h
index da0ee34be5..7f42ee0269 100644
--- a/internal.h
+++ b/internal.h
@@ -119,8 +119,8 @@ VALUE rb_big_fdiv(VALUE x, VALUE y);
VALUE rb_big_uminus(VALUE x);
VALUE rb_integer_float_cmp(VALUE x, VALUE y);
VALUE rb_integer_float_eq(VALUE x, VALUE y);
-size_t rb_absint_size(VALUE val, int *number_of_leading_zero_bits);
-size_t rb_absint_numwords(VALUE val, size_t word_numbits, size_t *number_of_leading_zero_bits);
+size_t rb_absint_size(VALUE val, int *nlz_bits_ret);
+size_t rb_absint_numwords(VALUE val, size_t word_numbits, size_t *nlz_bits_ret);
int rb_absint_singlebit_p(VALUE val);
/* class.c */
generated by cgit v1.2.3 (git 2.39.1) at 2024-08-25 07:27:57 +0000