152 lines
4.4 KiB
C
152 lines
4.4 KiB
C
/***********************************************************************/
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/* */
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/* Objective Caml */
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/* */
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/* Xavier Leroy, projet Cristal, INRIA Rocquencourt */
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/* */
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/* Copyright 1996 Institut National de Recherche en Informatique et */
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/* en Automatique. All rights reserved. This file is distributed */
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/* under the terms of the GNU Library General Public License, with */
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/* the special exception on linking described in file ../LICENSE. */
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/* */
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/***********************************************************************/
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/* $Id$ */
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/* The generic hashing primitive */
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#include "mlvalues.h"
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#include "custom.h"
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#include "memory.h"
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static unsigned long hash_accu;
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static long hash_univ_limit, hash_univ_count;
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static void hash_aux(value obj);
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CAMLprim value hash_univ_param(value count, value limit, value obj)
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{
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hash_univ_limit = Long_val(limit);
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hash_univ_count = Long_val(count);
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hash_accu = 0;
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hash_aux(obj);
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return Val_long(hash_accu & 0x3FFFFFFF);
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/* The & has two purposes: ensure that the return value is positive
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and give the same result on 32 bit and 64 bit architectures. */
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}
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#define Alpha 65599
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#define Beta 19
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#define Combine(new) (hash_accu = hash_accu * Alpha + (new))
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#define Combine_small(new) (hash_accu = hash_accu * Beta + (new))
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static void hash_aux(value obj)
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{
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unsigned char * p;
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mlsize_t i, j;
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tag_t tag;
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hash_univ_limit--;
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if (hash_univ_count < 0 || hash_univ_limit < 0) return;
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if (Is_long(obj)) {
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hash_univ_count--;
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Combine(Long_val(obj));
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return;
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}
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/* Pointers into the heap are well-structured blocks. So are atoms.
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We can inspect the block contents. */
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if (Is_atom(obj) || Is_young(obj) || Is_in_heap(obj)) {
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tag = Tag_val(obj);
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switch (tag) {
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case String_tag:
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hash_univ_count--;
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i = string_length(obj);
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for (p = &Byte_u(obj, 0); i > 0; i--, p++)
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Combine_small(*p);
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break;
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case Double_tag:
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/* For doubles, we inspect their binary representation, LSB first.
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The results are consistent among all platforms with IEEE floats. */
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hash_univ_count--;
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#ifdef ARCH_BIG_ENDIAN
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for (p = &Byte_u(obj, sizeof(double) - 1), i = sizeof(double);
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i > 0;
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p--, i--)
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#else
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for (p = &Byte_u(obj, 0), i = sizeof(double);
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i > 0;
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p++, i--)
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#endif
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Combine_small(*p);
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break;
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case Double_array_tag:
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hash_univ_count--;
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for (j = 0; j < Bosize_val(obj); j += sizeof(double)) {
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#ifdef ARCH_BIG_ENDIAN
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for (p = &Byte_u(obj, j + sizeof(double) - 1), i = sizeof(double);
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i > 0;
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p--, i--)
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#else
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for (p = &Byte_u(obj, j), i = sizeof(double);
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i > 0;
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p++, i--)
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#endif
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Combine_small(*p);
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}
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break;
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case Abstract_tag:
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/* We don't know anything about the contents of the block.
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Better do nothing. */
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break;
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case Infix_tag:
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hash_aux(obj - Infix_offset_val(obj));
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break;
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case Object_tag:
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hash_univ_count--;
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Combine(Oid_val(obj));
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break;
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case Custom_tag:
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/* If no hashing function provided, do nothing */
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if (Custom_ops_val(obj)->hash != NULL) {
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hash_univ_count--;
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Combine(Custom_ops_val(obj)->hash(obj));
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}
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break;
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default:
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hash_univ_count--;
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Combine_small(tag);
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i = Wosize_val(obj);
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while (i != 0) {
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i--;
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hash_aux(Field(obj, i));
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}
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break;
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}
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return;
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}
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/* Otherwise, obj is a pointer outside the heap, to an object with
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a priori unknown structure. Use its physical address as hash key. */
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Combine((long) obj);
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}
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/* Hashing variant tags */
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CAMLexport value hash_variant(char * tag)
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{
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value accu;
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/* Same hashing algorithm as in ../typing/btype.ml, function hash_variant */
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for (accu = Val_int(0); *tag != 0; tag++)
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accu = Val_int(223 * Int_val(accu) + *((unsigned char *) tag));
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#ifdef ARCH_SIXTYFOUR
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accu = accu & Val_long(0x7FFFFFFFL);
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#endif
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/* Force sign extension of bit 31 for compatibility between 32 and 64-bit
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platforms */
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return (int32) accu;
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}
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