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Feature #8700 » bit_length.patch

akr (Akira Tanaka), 08/05/2013 09:48 PM

View differences:

bignum.c (working copy)
/*
* call-seq:
* big.bit_length -> integer
*
* Returns the number of bits of the absolute value of <i>big</i>.
*
* (-2**10000-1).bit_length #=> 10001
* (-2**10000).bit_length #=> 10001
* (-2**10000+1).bit_length #=> 10000
*
* (-2**1000-1).bit_length #=> 1001
* (-2**1000).bit_length #=> 1001
* (-2**1000+1).bit_length #=> 1000
*
* (2**1000-1).bit_length #=> 1000
* (2**1000).bit_length #=> 1001
* (2**1000+1).bit_length #=> 1001
*
* (2**10000-1).bit_length #=> 10000
* (2**10000).bit_length #=> 10001
* (2**10000+1).bit_length #=> 10001
*
*/
static VALUE
rb_big_bit_length(VALUE big)
{
int nlz_bits;
size_t numbytes;
static const BDIGIT char_bit[1] = { CHAR_BIT };
BDIGIT numbytes_bary[bdigit_roomof(sizeof(size_t))];
BDIGIT nlz_bary[1];
BDIGIT result_bary[bdigit_roomof(sizeof(size_t)+1)];
numbytes = rb_absint_size(big, &nlz_bits);
if (numbytes <= SIZE_MAX / CHAR_BIT) {
return SIZET2NUM(numbytes * CHAR_BIT - nlz_bits);
}
nlz_bary[0] = nlz_bits;
bary_unpack(BARY_ARGS(numbytes_bary), &numbytes, 1, sizeof(numbytes), 0,
INTEGER_PACK_NATIVE_BYTE_ORDER);
BARY_MUL1(result_bary, numbytes_bary, char_bit);
BARY_SUB(result_bary, result_bary, nlz_bary);
return rb_integer_unpack(result_bary, numberof(result_bary), sizeof(BDIGIT), 0,
INTEGER_PACK_LSWORD_FIRST|INTEGER_PACK_NATIVE_BYTE_ORDER);
}
/*
* call-seq:
* fix.bit_length -> integer
*
* Returns the number of bits of the absolute value of <i>fix</i>.
*
* (-2**12-1).bit_length) #=> 13
* (-2**12).bit_length) #=> 13
* (-2**12+1).bit_length) #=> 12
* -0x100.bit_length #=> 9
* -0xff.bit_length #=> 8
* -1.bit_length #=> 1
* 0.bit_length #=> 0
* 1.bit_length #=> 1
* 0xff.bit_length #=> 8
* 0x100.bit_length #=> 9
* (2**12-1).bit_length #=> 12
* (2**12).bit_length #=> 13
* (2**12+1).bit_length #=> 13
*/
static VALUE
rb_fix_bit_length(VALUE fix)
{
long v = FIX2LONG(fix);
if (v < 0)
v = -v;
return LONG2FIX(bitsize(v));
}
/*
* call-seq:
* big.odd? -> true or false
*
* Returns <code>true</code> if <i>big</i> is an odd number.
......
rb_define_method(rb_cBignum, "abs", rb_big_abs, 0);
rb_define_method(rb_cBignum, "magnitude", rb_big_abs, 0);
rb_define_method(rb_cBignum, "size", rb_big_size, 0);
rb_define_method(rb_cBignum, "bit_length", rb_big_bit_length, 0);
rb_define_method(rb_cBignum, "odd?", rb_big_odd_p, 0);
rb_define_method(rb_cBignum, "even?", rb_big_even_p, 0);
rb_define_method(rb_cFixnum, "bit_length", rb_fix_bit_length, 0);
power_cache_init();
}
test/ruby/test_integer.rb (working copy)
end
assert_equal(3 ^ 10, 3 ^ obj)
end
def test_bit_length
assert_equal(13, (-2**12-1).bit_length)
assert_equal(13, (-2**12).bit_length)
assert_equal(12, (-2**12+1).bit_length)
assert_equal(9, -0x100.bit_length)
assert_equal(8, -0xff.bit_length)
assert_equal(1, -1.bit_length)
assert_equal(0, 0.bit_length)
assert_equal(1, 1.bit_length)
assert_equal(8, 0xff.bit_length)
assert_equal(9, 0x100.bit_length)
assert_equal(12, (2**12-1).bit_length)
assert_equal(13, (2**12).bit_length)
assert_equal(13, (2**12+1).bit_length)
assert_equal(10001, (-2**10000-1).bit_length)
assert_equal(10001, (-2**10000).bit_length)
assert_equal(10000, (-2**10000+1).bit_length)
assert_equal(10000, (2**10000-1).bit_length)
assert_equal(10001, (2**10000).bit_length)
assert_equal(10001, (2**10000+1).bit_length)
1.upto(1000) {|i|
n = 2**i
assert_equal(i+1, (-n-1).bit_length)
assert_equal(i+1, (-n).bit_length)
assert_equal(i, (-n+1).bit_length)
assert_equal(i, (n-1).bit_length)
assert_equal(i+1, (n).bit_length)
assert_equal(i+1, (n+1).bit_length)
}
end
end
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