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Diffstat (limited to 'include/core/SkChecksum.h')
-rw-r--r-- | include/core/SkChecksum.h | 70 |
1 files changed, 70 insertions, 0 deletions
diff --git a/include/core/SkChecksum.h b/include/core/SkChecksum.h new file mode 100644 index 0000000000..76f1461ed9 --- /dev/null +++ b/include/core/SkChecksum.h @@ -0,0 +1,70 @@ +/* + * 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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