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