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Estimated hours taken: 1 runtime/*.h: runtime/*.c: runtime/mercury_conf.h.in: Remove old .h files. Update #includes to refer to mercury_*.h Update #ifdef MODULE_H to be #ifdef MERCURY_MODULE_H
49 lines
1.1 KiB
C
49 lines
1.1 KiB
C
/*
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** Copyright (C) 1997 The University of Melbourne.
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** This file may only be copied under the terms of the GNU Library General
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** Public License - see the file COPYING.LIB in the Mercury distribution.
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*/
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#include "mercury_imp.h"
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/*
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** The function `hash_float()' is used by the library predicate `float__hash'
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** and also for hashing floats for `pragma fact_table' indexing.
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** It computes a non-negative Integer hash value for a Float.
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** The exact hash function used depend on the relative sizes of Float and
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** Integer.
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*/
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union FloatInteger {
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Float f;
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Integer i;
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Integer j[(sizeof(Float)/sizeof(Integer) > 0
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? sizeof(Float)/sizeof(Integer) : 1)];
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char c[sizeof(Float)/sizeof(char)];
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};
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Integer
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hash_float(Float f)
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{
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union FloatInteger fi;
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size_t i;
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Integer h = 0;
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fi.i = 0;
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fi.f = f;
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if (sizeof(Float) <= sizeof(Integer)) {
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h = fi.i;
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} else if (sizeof(Float) % sizeof(Integer) == 0) {
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for (i = 0; i < sizeof(Float)/sizeof(Integer); i++) {
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h ^= fi.j[i];
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}
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} else {
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for (i = 0; i < sizeof(Float)/sizeof(char); i++) {
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h ^= (h << 5);
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h ^= fi.c[i];
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}
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}
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return (h >= 0 ? h : -h);
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}
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