41 lines
1.3 KiB
C++
41 lines
1.3 KiB
C++
/** @file hash.h */
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/* Copyright 2009 10gen Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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namespace mongoutils {
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/** @return hash of a pointer to an unsigned. so you get a 32 bit hash out, regardless of whether
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pointers are 32 or 64 bit on the particular platform.
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is there a faster way to impl this that hashes just as well?
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*/
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inline unsigned hashPointer(void *v) {
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unsigned x = 0;
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unsigned char *p = (unsigned char *) &v;
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for( unsigned i = 0; i < sizeof(void*); i++ ) {
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x = x * 131 + p[i];
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}
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return x;
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}
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inline unsigned hash(unsigned u) {
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unsigned char *p = (unsigned char *) &u;
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return (((((p[3] * 131) + p[2]) * 131) + p[1]) * 131) + p[0];
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}
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}
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