5ccbe38285
git-svn-id: http://skia.googlecode.com/svn/trunk@4422 2bbb7eff-a529-9590-31e7-b0007b416f81
72 lines
1.9 KiB
C
72 lines
1.9 KiB
C
/*
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* Copyright 2012 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#ifndef SkChecksum_DEFINED
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#define SkChecksum_DEFINED
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#include "SkTypes.h"
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#if !defined(SK_PREFER_32BIT_CHECKSUM)
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#define SK_PREFER_32BIT_CHECKSUM 0
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#endif
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enum {
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ChecksumRotateBits = 17
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};
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#define SkCHECKSUM_MASH(CHECKSUM, NEW_CHUNK) \
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CHECKSUM = (((CHECKSUM) >> (sizeof(CHECKSUM)*8 - ChecksumRotateBits)) + \
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((CHECKSUM) << ChecksumRotateBits)) ^ (NEW_CHUNK);
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/**
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* Compute a 64-bit checksum for a given data block
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*
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* @param data Memory address of the data block to be processed. Must be
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* 32-bit aligned
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* @param size Size of the data block in bytes. Must be a multiple of 8.
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* @return checksum result
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*/
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inline uint64_t SkComputeChecksum64(const uint64_t* ptr, size_t size) {
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SkASSERT(SkIsAlign8(size));
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// Strict 8-byte alignment is not required on ptr. On current
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// CPUs there is no measurable performance difference between 32-bit
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// and 64-bit aligned access to uint64_t data
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SkASSERT(SkIsAlign4((intptr_t)ptr));
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const uint64_t* stop = ptr + (size >> 3);
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uint64_t result = 0;
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while (ptr < stop) {
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SkCHECKSUM_MASH(result, *ptr);
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ptr++;
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}
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return result;
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}
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/**
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* Compute a 32-bit checksum for a given data block
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*
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* @param data Memory address of the data block to be processed. Must be
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* 32-bit aligned.
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* @param size Size of the data block in bytes. Must be a multiple of 4.
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* @return checksum result
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*/
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inline uint32_t SkComputeChecksum32(const uint32_t* ptr, size_t size) {
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SkASSERT(SkIsAlign4(size));
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SkASSERT(SkIsAlign4((intptr_t)ptr));
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const uint32_t* stop = ptr + (size >> 2);
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uint32_t result = 0;
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while (ptr < stop) {
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SkCHECKSUM_MASH(result, *ptr);
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ptr++;
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}
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return result;
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}
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#endif
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