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/*
* 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
// 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
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