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refactor: cleanup & optimize reflect*

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douniwan5788 2024-09-17 23:19:30 +08:00
parent eda204bf87
commit 11353044ca
1 changed files with 5 additions and 32 deletions
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37
common/commonutil.c
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@ -98,39 +98,13 @@ uint8_t reflect8(uint8_t b) {
return (b * 0x0202020202ULL & 0x010884422010ULL) % 1023;
}
// Reverse the bits in a byte with 4 operations (64-bit multiply, no division):
/*
uint8_t reflect8(uint8_t b) {
return ((b * 0x80200802ULL) & 0x0884422110ULL) * 0x0101010101ULL >> 32;
}
*/
uint16_t reflect16(uint16_t b) {
uint16_t v = 0;
v |= (b & 0x8000) >> 15;
v |= (b & 0x4000) >> 13;
v |= (b & 0x2000) >> 11;
v |= (b & 0x1000) >> 9;
v |= (b & 0x0800) >> 7;
v |= (b & 0x0400) >> 5;
v |= (b & 0x0200) >> 3;
v |= (b & 0x0100) >> 1;
v |= (b & 0x0080) << 1;
v |= (b & 0x0040) << 3;
v |= (b & 0x0020) << 5;
v |= (b & 0x0010) << 7;
v |= (b & 0x0008) << 9;
v |= (b & 0x0004) << 11;
v |= (b & 0x0002) << 13;
v |= (b & 0x0001) << 15;
uint16_t reflect16(uint16_t v) {
v = (reflect8(v) << 8) | (reflect8(v >> 8) & 0xFF);
return v;
}
uint32_t reflect32(uint32_t b) {
uint32_t reflect32(uint32_t v) {
// https://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable
uint32_t v = b; // 32-bit word to reverse bit order
// swap odd and even bits
v = ((v >> 1) & 0x55555555) | ((v & 0x55555555) << 1);
// swap consecutive pairs
@ -140,7 +114,7 @@ uint32_t reflect32(uint32_t b) {
// swap bytes
v = ((v >> 8) & 0x00FF00FF) | ((v & 0x00FF00FF) << 8);
// swap 2-byte long pairs
v = (v >> 16) | (v << 16);
v = ( v >> 16 ) | ( v << 16);
return v;
}
@ -151,9 +125,8 @@ uint64_t reflect48(uint64_t v) {
return v;
}
uint64_t reflect64(uint64_t b) {
uint64_t reflect64(uint64_t v) {
// https://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable
uint64_t v = b; // 64-bit word to reverse bit order
// swap 4-byte long pairs
uint64_t v1 = reflect32(v >> 32);
uint64_t v2 = reflect32(v);