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43 lines
1.2 KiB
Objective-C
43 lines
1.2 KiB
Objective-C
//
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// ASHashing.m
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// Texture
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//
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// Copyright (c) 2017-present, Pinterest, Inc. All rights reserved.
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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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#import <AsyncDisplayKit/ASHashing.h>
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#define ELF_STEP(B) T1 = (H << 4) + B; T2 = T1 & 0xF0000000; if (T2) T1 ^= (T2 >> 24); T1 &= (~T2); H = T1;
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/**
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* The hashing algorithm copied from CoreFoundation CFHashBytes function.
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* https://opensource.apple.com/source/CF/CF-1153.18/CFUtilities.c.auto.html
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*/
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NSUInteger ASHashBytes(void *bytesarg, size_t length) {
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/* The ELF hash algorithm, used in the ELF object file format */
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uint8_t *bytes = (uint8_t *)bytesarg;
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UInt32 H = 0, T1, T2;
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SInt32 rem = (SInt32)length;
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while (3 < rem) {
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ELF_STEP(bytes[length - rem]);
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ELF_STEP(bytes[length - rem + 1]);
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ELF_STEP(bytes[length - rem + 2]);
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ELF_STEP(bytes[length - rem + 3]);
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rem -= 4;
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}
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switch (rem) {
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case 3: ELF_STEP(bytes[length - 3]);
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case 2: ELF_STEP(bytes[length - 2]);
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case 1: ELF_STEP(bytes[length - 1]);
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case 0: ;
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}
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return H;
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}
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#undef ELF_STEP
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