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#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;
}
/*! \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;
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;
}
/*! \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;
x = (x & 0x33333333) << 2 | (x & 0xCCCCCCCC) >> 2;
x = (x & 0x0F0F0F0F) << 4 | (x & 0xF0F0F0F0) >> 4;
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;
x = (x & 0x33) << 2 | (x & 0xCC) >> 2;
x = (x & 0x0F) << 4 | (x & 0xF0) >> 4;
return x;
}
/*! \brief reverse bit-order of each byte in a buffer
* \param[in] buf buffer containing bytes to be bit-reversed
* \param[in] len 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;
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 + 3 < 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--;
}
}
/*! @} */
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