1f28698998
* Hashing functions rely on integer overflow behavior. Mark those functions as safe. * abort() if a passed in size_t value is greater than UINT32_MAX. This can occur on 64 bit builds where size_t is larger than uint32_t. * Special case the index lookup for an empty sorted vector. Without the special case, size() == 0, and size()-1 underflows. Change-Id: I343a14b589fc8f0d221c1998ae5d6f0b9e2781f8
74 lines
2.1 KiB
C++
74 lines
2.1 KiB
C++
/*
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* Copyright (C) 2012 The Android Open Source Project
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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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/* Implementation of Jenkins one-at-a-time hash function. These choices are
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* optimized for code size and portability, rather than raw speed. But speed
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* should still be quite good.
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**/
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#include <stdlib.h>
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#include <utils/JenkinsHash.h>
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namespace android {
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#ifdef __clang__
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__attribute__((no_sanitize("integer")))
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#endif
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hash_t JenkinsHashWhiten(uint32_t hash) {
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hash += (hash << 3);
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hash ^= (hash >> 11);
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hash += (hash << 15);
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return hash;
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}
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uint32_t JenkinsHashMixBytes(uint32_t hash, const uint8_t* bytes, size_t size) {
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if (size > UINT32_MAX) {
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abort();
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}
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hash = JenkinsHashMix(hash, (uint32_t)size);
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size_t i;
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for (i = 0; i < (size & -4); i += 4) {
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uint32_t data = bytes[i] | (bytes[i+1] << 8) | (bytes[i+2] << 16) | (bytes[i+3] << 24);
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hash = JenkinsHashMix(hash, data);
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}
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if (size & 3) {
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uint32_t data = bytes[i];
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data |= ((size & 3) > 1) ? (bytes[i+1] << 8) : 0;
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data |= ((size & 3) > 2) ? (bytes[i+2] << 16) : 0;
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hash = JenkinsHashMix(hash, data);
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}
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return hash;
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}
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uint32_t JenkinsHashMixShorts(uint32_t hash, const uint16_t* shorts, size_t size) {
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if (size > UINT32_MAX) {
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abort();
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}
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hash = JenkinsHashMix(hash, (uint32_t)size);
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size_t i;
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for (i = 0; i < (size & -2); i += 2) {
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uint32_t data = shorts[i] | (shorts[i+1] << 16);
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hash = JenkinsHashMix(hash, data);
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}
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if (size & 1) {
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uint32_t data = shorts[i];
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hash = JenkinsHashMix(hash, data);
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}
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return hash;
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}
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}
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