lib/decoding/osmocom/core/bits.h

/*! \file bits.h
 *  Osmocom bit level support code.
 *
 */

#pragma once

#include <stdint.h>
#include <stddef.h>

#include <osmocom/core/bit16gen.h>
#include <osmocom/core/bit32gen.h>
#include <osmocom/core/bit64gen.h>

/*! \defgroup bits soft, unpacked and packed bits
 *  @{
 * \file bits.h */

/*! soft bit with value (-127...127), as commonly used in
 * communications receivers such as [viterbi] decoders */
typedef int8_t  sbit_t;

/*! unpacked bit (0 or 1): 1 bit per byte */
typedef uint8_t ubit_t;

/*! packed bits (8 bits in a byte).
 *  NOTE on the endian-ness of \ref pbit_t:
 *  - Bits in a \ref pbit_t are ordered MSB first, i.e. 0x80 is the first bit.
 *  - Bit i in a \ref pbit_t array is array[i/8] & (1<<(7-i%8)) */
typedef uint8_t pbit_t;

/*! determine how many bytes we would need for \a num_bits packed bits
 *  \param[in] num_bits Number of packed bits
 *  \returns number of bytes needed for \a num_bits packed bits
 */
static inline unsigned int osmo_pbit_bytesize(unsigned int num_bits)
{
	unsigned int pbit_bytesize = num_bits / 8;

	if (num_bits % 8)
		pbit_bytesize++;

	return pbit_bytesize;
}

int osmo_ubit2pbit(pbit_t *out, const ubit_t *in, unsigned int num_bits);

int osmo_pbit2ubit(ubit_t *out, const pbit_t *in, unsigned int num_bits);

void osmo_nibble_shift_right(uint8_t *out, const uint8_t *in,
			     unsigned int num_nibbles);
void osmo_nibble_shift_left_unal(uint8_t *out, const uint8_t *in,
				 unsigned int num_nibbles);

void osmo_ubit2sbit(sbit_t *out, const ubit_t *in, unsigned int num_bits);
void osmo_sbit2ubit(ubit_t *out, const sbit_t *in, unsigned int num_bits);

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 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);

#define OSMO_BIN_SPEC "%d%d%d%d%d%d%d%d"
#define OSMO_BIN_PRINT(byte)  \
  (byte & 0x80 ? 1 : 0), \
  (byte & 0x40 ? 1 : 0), \
  (byte & 0x20 ? 1 : 0), \
  (byte & 0x10 ? 1 : 0), \
  (byte & 0x08 ? 1 : 0), \
  (byte & 0x04 ? 1 : 0), \
  (byte & 0x02 ? 1 : 0), \
  (byte & 0x01 ? 1 : 0)

#define OSMO_BIT_SPEC "%c%c%c%c%c%c%c%c"
#define OSMO_BIT_PRINT_EX(byte, ch)		\
  (byte & 0x80 ? ch : '.'), \
  (byte & 0x40 ? ch : '.'), \
  (byte & 0x20 ? ch : '.'), \
  (byte & 0x10 ? ch : '.'), \
  (byte & 0x08 ? ch : '.'), \
  (byte & 0x04 ? ch : '.'), \
  (byte & 0x02 ? ch : '.'), \
  (byte & 0x01 ? ch : '.')

#define OSMO_BIT_PRINT(byte)  OSMO_BIT_PRINT_EX(byte, '1')

/* BIT REVERSAL */

/*! bit-reversal mode for osmo_bit_reversal() */
enum osmo_br_mode {
	/*! reverse all bits in a 32bit dword */
	OSMO_BR_BITS_IN_DWORD	= 31,
	/*! reverse byte order in a 32bit dword */
	OSMO_BR_BYTES_IN_DWORD	= 24,
	/*! reverse bits of each byte in a 32bit dword */
	OSMO_BR_BITS_IN_BYTE	= 7,
	/*! swap the two 16bit words in a 32bit dword */
	OSMO_BR_WORD_SWAP	= 16,
};

uint32_t osmo_bit_reversal(uint32_t x, enum osmo_br_mode k);

uint32_t osmo_revbytebits_32(uint32_t x);

uint32_t osmo_revbytebits_8(uint8_t x);

void osmo_revbytebits_buf(uint8_t *buf, int len);

/*! left circular shift
 *  \param[in] in The 16 bit unsigned integer to be rotated
 *  \param[in] shift Number of bits to shift \a in to, [0;16] bits
 *  \returns shifted value
 */
static inline uint16_t osmo_rol16(uint16_t in, unsigned shift)
{
	return (in << shift) | (in >> (16 - shift));
}

/*! @} */