Method: Object#hash
- Defined in:
- gc.c
#hash ⇒ Fixnum
Generates a Fixnum
hash value for this object. This function must have the property that a.eql?(b)
implies a.hash == b.hash
. The hash value is used by class Hash
. Any hash value that exceeds the capacity of a Fixnum
will be truncated before being used.
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# File 'gc.c'
/*
* call-seq:
* obj.hash => fixnum
*
* Generates a <code>Fixnum</code> hash value for this object. This
* function must have the property that <code>a.eql?(b)</code> implies
* <code>a.hash == b.hash</code>. The hash value is used by class
* <code>Hash</code>. Any hash value that exceeds the capacity of a
* <code>Fixnum</code> will be truncated before being used.
*/
VALUE
rb_obj_id(VALUE obj)
{
/*
* 32-bit VALUE space
* MSB ------------------------ LSB
* false 00000000000000000000000000000000
* true 00000000000000000000000000000010
* nil 00000000000000000000000000000100
* undef 00000000000000000000000000000110
* symbol ssssssssssssssssssssssss00001110
* object oooooooooooooooooooooooooooooo00 = 0 (mod sizeof(RVALUE))
* fixnum fffffffffffffffffffffffffffffff1
*
* object_id space
* LSB
* false 00000000000000000000000000000000
* true 00000000000000000000000000000010
* nil 00000000000000000000000000000100
* undef 00000000000000000000000000000110
* symbol 000SSSSSSSSSSSSSSSSSSSSSSSSSSS0 S...S % A = 4 (S...S = s...s * A + 4)
* object oooooooooooooooooooooooooooooo0 o...o % A = 0
* fixnum fffffffffffffffffffffffffffffff1 bignum if required
*
* where A = sizeof(RVALUE)/4
*
* sizeof(RVALUE) is
* 20 if 32-bit, double is 4-byte aligned
* 24 if 32-bit, double is 8-byte aligned
* 40 if 64-bit
*/
if (TYPE(obj) == T_SYMBOL) {
return (SYM2ID(obj) * sizeof(RVALUE) + (4 << 2)) | FIXNUM_FLAG;
}
if (SPECIAL_CONST_P(obj)) {
return LONG2NUM((long)obj);
}
return (VALUE)((long)obj|FIXNUM_FLAG);
}
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