diff options
Diffstat (limited to 'src/bits.c')
| -rw-r--r-- | src/bits.c | 30 |
1 files changed, 28 insertions, 2 deletions
@@ -128,7 +128,16 @@ int osmo_pbit2ubit_ext(ubit_t *out, unsigned int out_ofs, return out_ofs + num_bits; } -/* generalized bit reversal function, Chapter 7 "Hackers Delight" */ +/*! \brief generalized bit reversal function + * \param[in] x the 32bit value to be reversed + * \param[in] k the type of reversal requested + * \returns the reversed 32bit dword + * + * This function reverses the bit order within a 32bit word. Depending + * on "k", it either reverses all bits in a 32bit dword, or the bytes in + * the dword, or the bits in each byte of a dword, or simply swaps the + * two 16bit words in a dword. See 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; @@ -140,7 +149,12 @@ uint32_t osmo_bit_reversal(uint32_t x, enum osmo_br_mode k) return x; } -/* generalized bit reversal function, Chapter 7 "Hackers Delight" */ +/*! \brief reverse the bit-order in each byte of a dword + * \param[in] x 32bit input value + * \returns 32bit value where bits of each byte have been reversed + * + * See Chapter 7 "Hackers Delight" + */ uint32_t osmo_revbytebits_32(uint32_t x) { x = (x & 0x55555555) << 1 | (x & 0xAAAAAAAA) >> 1; @@ -150,6 +164,12 @@ uint32_t osmo_revbytebits_32(uint32_t x) return x; } +/*! \brief reverse the bit order in a byte + * \param[in] x 8bit input value + * \returns 8bit value where bits order has been reversed + * + * See Chapter 7 "Hackers Delight" + */ uint32_t osmo_revbytebits_8(uint8_t x) { x = (x & 0x55) << 1 | (x & 0xAA) >> 1; @@ -159,6 +179,12 @@ uint32_t osmo_revbytebits_8(uint8_t x) return x; } +/*! \brief reverse bit-order of each byte in a buffer + * \param buf buffer containing bytes to be bit-reversed + * \param[in] length of buffer in bytes + * + * This function reverses the bits in each byte of the buffer + */ void osmo_revbytebits_buf(uint8_t *buf, int len) { unsigned int i; |