diff options
Diffstat (limited to 'src/bits.c')
| -rw-r--r-- | src/bits.c | 188 |
1 files changed, 188 insertions, 0 deletions
diff --git a/src/bits.c b/src/bits.c new file mode 100644 index 00000000..4c67bddb --- /dev/null +++ b/src/bits.c @@ -0,0 +1,188 @@ + +#include <stdint.h> + +#include <osmocom/core/bits.h> + +/*! \addtogroup bits + * @{ + */ + +/*! \file bits.c + * \brief Osmocom bit level support code + */ + + +/*! \brief convert unpacked bits to packed bits, return length in bytes + * \param[out] out output buffer of packed bits + * \param[in] in input buffer of unpacked bits + * \param[in] num_bits number of bits + */ +int osmo_ubit2pbit(pbit_t *out, const ubit_t *in, unsigned int num_bits) +{ + unsigned int i; + uint8_t curbyte = 0; + pbit_t *outptr = out; + + for (i = 0; i < num_bits; i++) { + uint8_t bitnum = 7 - (i % 8); + + curbyte |= (in[i] << bitnum); + + if(i % 8 == 7){ + *outptr++ = curbyte; + curbyte = 0; + } + } + /* we have a non-modulo-8 bitcount */ + if (i % 8) + *outptr++ = curbyte; + + return outptr - out; +} + +/*! \brief convert packed bits to unpacked bits, return length in bytes + * \param[out] out output buffer of unpacked bits + * \param[in] in input buffer of packed bits + * \param[in] num_bits number of bits + */ +int osmo_pbit2ubit(ubit_t *out, const pbit_t *in, unsigned int num_bits) +{ + unsigned int i; + ubit_t *cur = out; + ubit_t *limit = out + num_bits; + + for (i = 0; i < (num_bits/8)+1; i++) { + pbit_t byte = in[i]; + *cur++ = (byte >> 7) & 1; + if (cur >= limit) + break; + *cur++ = (byte >> 6) & 1; + if (cur >= limit) + break; + *cur++ = (byte >> 5) & 1; + if (cur >= limit) + break; + *cur++ = (byte >> 4) & 1; + if (cur >= limit) + break; + *cur++ = (byte >> 3) & 1; + if (cur >= limit) + break; + *cur++ = (byte >> 2) & 1; + if (cur >= limit) + break; + *cur++ = (byte >> 1) & 1; + if (cur >= limit) + break; + *cur++ = (byte >> 0) & 1; + if (cur >= limit) + break; + } + return cur - out; +} + +/*! \brief convert unpacked bits to packed bits (extended options) + * \param[out] out output buffer of packed bits + * \param[in] out_ofs offset into output buffer + * \param[in] in input buffer of unpacked bits + * \param[in] in_ofs offset into input buffer + * \param[in] num_bits number of bits + * \param[in] lsb_mode Encode bits in LSB orde instead of MSB + * \returns length in bytes (max written offset of output buffer + 1) + */ +int osmo_ubit2pbit_ext(pbit_t *out, unsigned int out_ofs, + const ubit_t *in, unsigned int in_ofs, + unsigned int num_bits, int lsb_mode) +{ + int i, op, bn; + for (i=0; i<num_bits; i++) { + op = out_ofs + i; + bn = lsb_mode ? (op&7) : (7-(op&7)); + if (in[in_ofs+i]) + out[op>>3] |= 1 << bn; + else + out[op>>3] &= ~(1 << bn); + } + return ((out_ofs + num_bits - 1) >> 3) + 1; +} + +/*! \brief convert packed bits to unpacked bits (extended options) + * \param[out] out output buffer of unpacked bits + * \param[in] out_ofs offset into output buffer + * \param[in] in input buffer of packed bits + * \param[in] in_ofs offset into input buffer + * \param[in] num_bits number of bits + * \param[in] lsb_mode Encode bits in LSB orde instead of MSB + * \returns length in bytes (max written offset of output buffer + 1) + */ +int osmo_pbit2ubit_ext(ubit_t *out, unsigned int out_ofs, + const pbit_t *in, unsigned int in_ofs, + unsigned int num_bits, int lsb_mode) +{ + int i, ip, bn; + for (i=0; i<num_bits; i++) { + ip = in_ofs + i; + bn = lsb_mode ? (ip&7) : (7-(ip&7)); + out[out_ofs+i] = !!(in[ip>>3] & (1<<bn)); + } + 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--; + } +} + +/*! @} */ |