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add: reflect16

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rem:  swapbits, reflect
This commit is contained in:
iceman1001 2018-01-28 10:46:46 +01:00
commit cf44d04be1
2 changed files with 22 additions and 29 deletions
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45
armsrc/util.c
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@ -13,34 +13,29 @@ size_t nbytes(size_t nbits) {
return (nbits >> 3)+((nbits % 8) > 0);
}
// Swap bit order on a uint32_t value. Can be limited by 'b' just use say 8 bits reversal
// note: function clears the rest of the bits.
uint32_t SwapBits(uint32_t v, int b) {
uint32_t newvalue = 0;
for(int i = 0; i < b; i++) {
newvalue ^= ((v >> i) & 1) << (b - 1 - i);
}
return newvalue;
}
uint8_t reflect8(uint8_t b) {
return ((b * 0x80200802ULL) & 0x0884422110ULL) * 0x0101010101ULL >> 32;
}
/*
ref http://www.csm.ornl.gov/~dunigan/crc.html
Returns the value v with the bottom b [0,32] bits reflected.
Example: reflect(0x3e23L,3) == 0x3e26
*/
uint32_t reflect(uint32_t v, int b) {
uint32_t t = v;
for ( int i = 0; i < b; ++i) {
if (t & 1)
v |= BITMASK((b-1)-i);
else
v &= ~BITMASK((b-1)-i);
t >>= 1;
}
return v;
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;
return v;
}
void num_to_bytes(uint64_t n, size_t len, uint8_t* dest) {