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added new function reflect32

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tharexde 2020-09-27 12:53:52 +02:00
parent e8abcb9b23
commit d0d6317c33
2 changed files with 18 additions and 1 deletions
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18
common/commonutil.c
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@ -97,6 +97,22 @@ uint16_t reflect16(uint16_t b) {
return v;
}
uint32_t reflect32(uint32_t b) {
// 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
v = ((v >> 2) & 0x33333333) | ((v & 0x33333333) << 2);
// swap nibbles ...
v = ((v >> 4) & 0x0F0F0F0F) | ((v & 0x0F0F0F0F) << 4);
// swap bytes
v = ((v >> 8) & 0x00FF00FF) | ((v & 0x00FF00FF) << 8);
// swap 2-byte long pairs
v = ( v >> 16 ) | ( v << 16);
return v;
}
void num_to_bytes(uint64_t n, size_t len, uint8_t *dest) {
while (len--) {
dest[len] = (uint8_t) n;
@ -153,4 +169,4 @@ uint32_t rotl(uint32_t a, uint8_t n) {
uint32_t rotr(uint32_t a, uint8_t n) {
n &= 31;
return (a >> n) | (a << (32 - n));
}
}

1
common/commonutil.h
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@ -47,6 +47,7 @@ void FormatVersionInformation(char *dst, int len, const char *prefix, void *vers
uint32_t reflect(uint32_t v, int b); // used in crc.c ...
uint8_t reflect8(uint8_t b); // dedicated 8bit reversal
uint16_t reflect16(uint16_t b); // dedicated 16bit reversal
uint32_t reflect32(uint32_t b); // dedicated 32bit reversal
void num_to_bytes(uint64_t n, size_t len, uint8_t *dest);
uint64_t bytes_to_num(uint8_t *src, size_t len);