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/* compare256_rle.h -- 256 byte run-length encoding comparison
* Copyright (C) 2022 Nathan Moinvaziri
* For conditions of distribution and use, see copyright notice in zlib.h
*/
#include "zbuild.h"
#include "zendian.h"
#include "zmemory.h"
#include "fallback_builtins.h"
typedef uint32_t (*compare256_rle_func)(const uint8_t* src0, const uint8_t* src1);
/* 8-bit RLE comparison for hardware without unaligned loads */
static inline uint32_t compare256_rle_8(const uint8_t *src0, const uint8_t *src1) {
uint32_t len = 0;
uint8_t val = *src0;
do {
if (val != src1[0])
return len;
if (val != src1[1])
return len + 1;
if (val != src1[2])
return len + 2;
if (val != src1[3])
return len + 3;
if (val != src1[4])
return len + 4;
if (val != src1[5])
return len + 5;
if (val != src1[6])
return len + 6;
if (val != src1[7])
return len + 7;
src1 += 8, len += 8;
} while (len < 256);
return 256;
}
/* 64-bit RLE comparison for hardware with unaligned loads */
static inline uint32_t compare256_rle_64(const uint8_t *src0, const uint8_t *src1) {
uint32_t src0_cmp32, len = 0;
uint16_t src0_cmp;
uint64_t sv, mv, diff;
src0_cmp = zng_memread_2(src0);
src0_cmp32 = ((uint32_t)src0_cmp << 16) | src0_cmp;
sv = ((uint64_t)src0_cmp32 << 32) | src0_cmp32;
do {
mv = zng_memread_8(src1);
diff = sv ^ mv;
if (diff)
return len + zng_ctz64(Z_U64_TO_LE(diff)) / 8;
src1 += 8, len += 8;
} while (len < 256);
return 256;
}
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