ref: f6a002f2a67579cce9d53a4314f0676228517c12
dir: /third_party/libyuv/source/compare_common.cc/
/* * Copyright 2012 The LibYuv Project Authors. All rights reserved. * * Use of this source code is governed by a BSD-style license * that can be found in the LICENSE file in the root of the source * tree. An additional intellectual property rights grant can be found * in the file PATENTS. All contributing project authors may * be found in the AUTHORS file in the root of the source tree. */ #include "libyuv/basic_types.h" #include "libyuv/compare_row.h" #ifdef __cplusplus namespace libyuv { extern "C" { #endif #if ORIGINAL_OPT uint32_t HammingDistance_C1(const uint8_t* src_a, const uint8_t* src_b, int count) { uint32_t diff = 0u; int i; for (i = 0; i < count; ++i) { int x = src_a[i] ^ src_b[i]; if (x & 1) ++diff; if (x & 2) ++diff; if (x & 4) ++diff; if (x & 8) ++diff; if (x & 16) ++diff; if (x & 32) ++diff; if (x & 64) ++diff; if (x & 128) ++diff; } return diff; } #endif // Hakmem method for hamming distance. uint32_t HammingDistance_C(const uint8_t* src_a, const uint8_t* src_b, int count) { uint32_t diff = 0u; int i; for (i = 0; i < count - 3; i += 4) { uint32_t x = *((const uint32_t*)src_a) ^ *((const uint32_t*)src_b); uint32_t u = x - ((x >> 1) & 0x55555555); u = ((u >> 2) & 0x33333333) + (u & 0x33333333); diff += ((((u + (u >> 4)) & 0x0f0f0f0f) * 0x01010101) >> 24); src_a += 4; src_b += 4; } for (; i < count; ++i) { uint32_t x = *src_a ^ *src_b; uint32_t u = x - ((x >> 1) & 0x55); u = ((u >> 2) & 0x33) + (u & 0x33); diff += (u + (u >> 4)) & 0x0f; src_a += 1; src_b += 1; } return diff; } uint32_t SumSquareError_C(const uint8_t* src_a, const uint8_t* src_b, int count) { uint32_t sse = 0u; int i; for (i = 0; i < count; ++i) { int diff = src_a[i] - src_b[i]; sse += (uint32_t)(diff * diff); } return sse; } // hash seed of 5381 recommended. // Internal C version of HashDjb2 with int sized count for efficiency. uint32_t HashDjb2_C(const uint8_t* src, int count, uint32_t seed) { uint32_t hash = seed; int i; for (i = 0; i < count; ++i) { hash += (hash << 5) + src[i]; } return hash; } #ifdef __cplusplus } // extern "C" } // namespace libyuv #endif