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/***********************************************************************/
/* */
/* Objective Caml */
/* */
/* Xavier Leroy, projet Cristal, INRIA Rocquencourt */
/* */
/* Copyright 1996 Institut National de Recherche en Informatique et */
/* Automatique. Distributed only by permission. */
/* */
/***********************************************************************/
/* $Id$ */
/* The generic hashing primitive */
#include "mlvalues.h"
#include "memory.h"
#include "str.h"
static unsigned long hash_accu;
static long hash_univ_limit, hash_univ_count;
static void hash_aux(value obj);
value hash_univ_param(value count, value limit, value obj) /* ML */
{
hash_univ_limit = Long_val(limit);
hash_univ_count = Long_val(count);
hash_accu = 0;
hash_aux(obj);
return Val_long(hash_accu & 0x3FFFFFFF);
/* The & has two purposes: ensure that the return value is positive
and give the same result on 32 bit and 64 bit architectures. */
}
#define Alpha 65599
#define Beta 19
#define Combine(new) (hash_accu = hash_accu * Alpha + (new))
#define Combine_small(new) (hash_accu = hash_accu * Beta + (new))
static void hash_aux(value obj)
{
unsigned char * p;
mlsize_t i, j;
tag_t tag;
hash_univ_limit--;
if (hash_univ_count < 0 || hash_univ_limit < 0) return;
if (Is_long(obj)) {
hash_univ_count--;
Combine(Long_val(obj));
return;
}
/* Pointers into the heap are well-structured blocks. So are atoms.
We can inspect the block contents. */
if (Is_atom(obj) || Is_young(obj) || Is_in_heap(obj)) {
tag = Tag_val(obj);
switch (tag) {
case String_tag:
hash_univ_count--;
i = string_length(obj);
for (p = &Byte_u(obj, 0); i > 0; i--, p++)
Combine_small(*p);
break;
case Double_tag:
/* For doubles, we inspect their binary representation, LSB first.
The results are consistent among all platforms with IEEE floats. */
hash_univ_count--;
#ifdef ARCH_BIG_ENDIAN
for (p = &Byte_u(obj, sizeof(double) - 1), i = sizeof(double);
i > 0;
p--, i--)
#else
for (p = &Byte_u(obj, 0), i = sizeof(double);
i > 0;
p++, i--)
#endif
Combine_small(*p);
break;
case Double_array_tag:
hash_univ_count--;
for (j = 0; j < Bosize_val(obj); j += sizeof(double)) {
#ifdef ARCH_BIG_ENDIAN
for (p = &Byte_u(obj, j + sizeof(double) - 1), i = sizeof(double);
i > 0;
p--, i--)
#else
for (p = &Byte_u(obj, j), i = sizeof(double);
i > 0;
p++, i--)
#endif
Combine_small(*p);
}
break;
case Abstract_tag:
case Final_tag:
/* We don't know anything about the contents of the block.
Better do nothing. */
break;
case Infix_tag:
hash_aux(obj - Infix_offset_val(obj));
break;
case Object_tag:
hash_univ_count--;
Combine(Oid_val(obj));
break;
default:
hash_univ_count--;
Combine_small(tag);
i = Wosize_val(obj);
while (i != 0) {
i--;
hash_aux(Field(obj, i));
}
break;
}
return;
}
/* Otherwise, obj is a pointer outside the heap, to an object with
a priori unknown structure. Use its physical address as hash key. */
Combine((long) obj);
}
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