diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/bits.c | 57 |
1 files changed, 57 insertions, 0 deletions
@@ -128,4 +128,61 @@ int osmo_pbit2ubit_ext(ubit_t *out, unsigned int out_ofs, return out_ofs + num_bits; } +/* generalized bit reversal function, Chapter 7 "Hackers Delight" */ +uint32_t osmo_bit_reversal(uint32_t x, enum osmo_br_mode k) +{ + if (k & 1) x = (x & 0x55555555) << 1 | (x & 0xAAAAAAAA) >> 1; + if (k & 2) x = (x & 0x33333333) << 2 | (x & 0xCCCCCCCC) >> 2; + if (k & 4) x = (x & 0x0F0F0F0F) << 4 | (x & 0xF0F0F0F0) >> 4; + if (k & 8) x = (x & 0x00FF00FF) << 8 | (x & 0xFF00FF00) >> 8; + if (k & 16) x = (x & 0x0000FFFF) << 16 | (x & 0xFFFF0000) >> 16; + + return x; +} + +/* generalized bit reversal function, Chapter 7 "Hackers Delight" */ +uint32_t osmo_revbytebits_32(uint32_t x) +{ + x = (x & 0x55555555) << 1 | (x & 0xAAAAAAAA) >> 1; + x = (x & 0x33333333) << 2 | (x & 0xCCCCCCCC) >> 2; + x = (x & 0x0F0F0F0F) << 4 | (x & 0xF0F0F0F0) >> 4; + + return x; +} + +uint32_t osmo_revbytebits_8(uint8_t x) +{ + x = (x & 0x55) << 1 | (x & 0xAA) >> 1; + x = (x & 0x33) << 2 | (x & 0xCC) >> 2; + x = (x & 0x0F) << 4 | (x & 0xF0) >> 4; + + return x; +} + +void osmo_revbytebits_buf(uint8_t *buf, int len) +{ + unsigned int i; + unsigned int unaligned_cnt; + int len_remain = len; + + unaligned_cnt = ((unsigned long)buf & 3); + for (i = 0; i < unaligned_cnt; i++) { + buf[i] = osmo_revbytebits_8(buf[i]); + len_remain--; + if (len_remain <= 0) + return; + } + + for (i = unaligned_cnt; i < len; i += 4) { + uint32_t *cur = (uint32_t *) (buf + i); + *cur = osmo_revbytebits_32(*cur); + len_remain -= 4; + } + + for (i = len - len_remain; i < len; i++) { + buf[i] = osmo_revbytebits_8(buf[i]); + len_remain--; + } +} + /*! }@ */ |