mirror of https://gerrit.osmocom.org/libosmocore
314 lines
9.8 KiB
C
314 lines
9.8 KiB
C
/*
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* (C) 2011 by Harald Welte <laforge@gnumonks.org>
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* (C) 2011 by Sylvain Munaut <tnt@246tNt.com>
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*
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* All Rights Reserved
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*
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* SPDX-License-Identifier: GPL-2.0+
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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*/
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#include <stdint.h>
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#include <osmocom/core/bits.h>
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/*! \addtogroup bits
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* @{
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* Osmocom bit level support code.
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*
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* This module implements the notion of different bit-fields, such as
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* - unpacked bits (\ref ubit_t), i.e. 1 bit per byte
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* - packed bits (\ref pbit_t), i.e. 8 bits per byte
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* - soft bits (\ref sbit_t), 1 bit per byte from -127 to 127
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*
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* \file bits.c */
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/*! convert unpacked bits to packed bits, return length in bytes
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* \param[out] out output buffer of packed bits
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* \param[in] in input buffer of unpacked bits
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* \param[in] num_bits number of bits
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*/
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int osmo_ubit2pbit(pbit_t *out, const ubit_t *in, unsigned int num_bits)
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{
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unsigned int i;
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uint8_t curbyte = 0;
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pbit_t *outptr = out;
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for (i = 0; i < num_bits; i++) {
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uint8_t bitnum = 7 - (i % 8);
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curbyte |= (in[i] << bitnum);
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if(i % 8 == 7){
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*outptr++ = curbyte;
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curbyte = 0;
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}
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}
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/* we have a non-modulo-8 bitcount */
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if (i % 8)
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*outptr++ = curbyte;
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return outptr - out;
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}
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/*! Shift unaligned input to octet-aligned output
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* \param[out] out output buffer, unaligned
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* \param[in] in input buffer, octet-aligned
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* \param[in] num_nibbles number of nibbles
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*/
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void osmo_nibble_shift_right(uint8_t *out, const uint8_t *in,
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unsigned int num_nibbles)
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{
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unsigned int i, num_whole_bytes = num_nibbles / 2;
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if (!num_whole_bytes)
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return;
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/* first byte: upper nibble empty, lower nibble from src */
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out[0] = (in[0] >> 4);
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/* bytes 1.. */
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for (i = 1; i < num_whole_bytes; i++)
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out[i] = ((in[i - 1] & 0xF) << 4) | (in[i] >> 4);
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/* shift the last nibble, in case there's an odd count */
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i = num_whole_bytes;
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if (num_nibbles & 1)
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out[i] = ((in[i - 1] & 0xF) << 4) | (in[i] >> 4);
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else
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out[i] = (in[i - 1] & 0xF) << 4;
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}
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/*! Shift unaligned input to octet-aligned output
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* \param[out] out output buffer, octet-aligned
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* \param[in] in input buffer, unaligned
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* \param[in] num_nibbles number of nibbles
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*/
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void osmo_nibble_shift_left_unal(uint8_t *out, const uint8_t *in,
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unsigned int num_nibbles)
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{
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unsigned int i, num_whole_bytes = num_nibbles / 2;
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if (!num_whole_bytes)
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return;
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for (i = 0; i < num_whole_bytes; i++)
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out[i] = ((in[i] & 0xF) << 4) | (in[i + 1] >> 4);
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/* shift the last nibble, in case there's an odd count */
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i = num_whole_bytes;
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if (num_nibbles & 1)
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out[i] = (in[i] & 0xF) << 4;
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}
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/*! convert unpacked bits to soft bits
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* \param[out] out output buffer of soft bits
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* \param[in] in input buffer of unpacked bits
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* \param[in] num_bits number of bits
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*/
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void osmo_ubit2sbit(sbit_t *out, const ubit_t *in, unsigned int num_bits)
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{
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unsigned int i;
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for (i = 0; i < num_bits; i++)
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out[i] = in[i] ? -127 : 127;
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}
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/*! convert soft bits to unpacked bits
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* \param[out] out output buffer of unpacked bits
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* \param[in] in input buffer of soft bits
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* \param[in] num_bits number of bits
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*/
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void osmo_sbit2ubit(ubit_t *out, const sbit_t *in, unsigned int num_bits)
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{
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unsigned int i;
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for (i = 0; i < num_bits; i++)
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out[i] = in[i] < 0;
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}
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/*! convert packed bits to unpacked bits, return length in bytes
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* \param[out] out output buffer of unpacked bits
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* \param[in] in input buffer of packed bits
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* \param[in] num_bits number of bits
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* \return number of bytes used in \ref out
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*/
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int osmo_pbit2ubit(ubit_t *out, const pbit_t *in, unsigned int num_bits)
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{
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unsigned int i;
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ubit_t *cur = out;
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ubit_t *limit = out + num_bits;
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for (i = 0; i < (num_bits/8)+1; i++) {
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pbit_t byte = in[i];
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*cur++ = (byte >> 7) & 1;
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if (cur >= limit)
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break;
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*cur++ = (byte >> 6) & 1;
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if (cur >= limit)
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break;
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*cur++ = (byte >> 5) & 1;
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if (cur >= limit)
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break;
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*cur++ = (byte >> 4) & 1;
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if (cur >= limit)
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break;
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*cur++ = (byte >> 3) & 1;
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if (cur >= limit)
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break;
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*cur++ = (byte >> 2) & 1;
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if (cur >= limit)
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break;
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*cur++ = (byte >> 1) & 1;
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if (cur >= limit)
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break;
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*cur++ = (byte >> 0) & 1;
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if (cur >= limit)
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break;
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}
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return cur - out;
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}
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/*! convert unpacked bits to packed bits (extended options)
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* \param[out] out output buffer of packed bits
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* \param[in] out_ofs offset into output buffer
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* \param[in] in input buffer of unpacked bits
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* \param[in] in_ofs offset into input buffer
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* \param[in] num_bits number of bits
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* \param[in] lsb_mode Encode bits in LSB orde instead of MSB
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* \returns length in bytes (max written offset of output buffer + 1)
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*/
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int osmo_ubit2pbit_ext(pbit_t *out, unsigned int out_ofs,
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const ubit_t *in, unsigned int in_ofs,
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unsigned int num_bits, int lsb_mode)
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{
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unsigned int i, op, bn;
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for (i=0; i<num_bits; i++) {
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op = out_ofs + i;
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bn = lsb_mode ? (op&7) : (7-(op&7));
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if (in[in_ofs+i])
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out[op>>3] |= 1 << bn;
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else
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out[op>>3] &= ~(1 << bn);
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}
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return ((out_ofs + num_bits - 1) >> 3) + 1;
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}
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/*! convert packed bits to unpacked bits (extended options)
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* \param[out] out output buffer of unpacked bits
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* \param[in] out_ofs offset into output buffer
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* \param[in] in input buffer of packed bits
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* \param[in] in_ofs offset into input buffer
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* \param[in] num_bits number of bits
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* \param[in] lsb_mode Encode bits in LSB orde instead of MSB
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* \returns length in bytes (max written offset of output buffer + 1)
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*/
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int osmo_pbit2ubit_ext(ubit_t *out, unsigned int out_ofs,
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const pbit_t *in, unsigned int in_ofs,
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unsigned int num_bits, int lsb_mode)
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{
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unsigned int i, ip, bn;
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for (i=0; i<num_bits; i++) {
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ip = in_ofs + i;
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bn = lsb_mode ? (ip&7) : (7-(ip&7));
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out[out_ofs+i] = !!(in[ip>>3] & (1<<bn));
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}
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return out_ofs + num_bits;
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}
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/* look-up table for bit-reversal within a byte. Generated using:
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int i,k;
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for (i = 0 ; i < 256 ; i++) {
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uint8_t sample = 0 ;
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for (k = 0; k<8; k++) {
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if ( i & 1 << k ) sample |= 0x80 >> k;
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}
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flip_table[i] = sample;
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}
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*/
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static const uint8_t flip_table[256] = {
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0x00, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0, 0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0,
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0x08, 0x88, 0x48, 0xc8, 0x28, 0xa8, 0x68, 0xe8, 0x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, 0xf8,
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0x04, 0x84, 0x44, 0xc4, 0x24, 0xa4, 0x64, 0xe4, 0x14, 0x94, 0x54, 0xd4, 0x34, 0xb4, 0x74, 0xf4,
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0x0c, 0x8c, 0x4c, 0xcc, 0x2c, 0xac, 0x6c, 0xec, 0x1c, 0x9c, 0x5c, 0xdc, 0x3c, 0xbc, 0x7c, 0xfc,
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0x02, 0x82, 0x42, 0xc2, 0x22, 0xa2, 0x62, 0xe2, 0x12, 0x92, 0x52, 0xd2, 0x32, 0xb2, 0x72, 0xf2,
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0x0a, 0x8a, 0x4a, 0xca, 0x2a, 0xaa, 0x6a, 0xea, 0x1a, 0x9a, 0x5a, 0xda, 0x3a, 0xba, 0x7a, 0xfa,
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0x06, 0x86, 0x46, 0xc6, 0x26, 0xa6, 0x66, 0xe6, 0x16, 0x96, 0x56, 0xd6, 0x36, 0xb6, 0x76, 0xf6,
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0x0e, 0x8e, 0x4e, 0xce, 0x2e, 0xae, 0x6e, 0xee, 0x1e, 0x9e, 0x5e, 0xde, 0x3e, 0xbe, 0x7e, 0xfe,
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0x01, 0x81, 0x41, 0xc1, 0x21, 0xa1, 0x61, 0xe1, 0x11, 0x91, 0x51, 0xd1, 0x31, 0xb1, 0x71, 0xf1,
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0x09, 0x89, 0x49, 0xc9, 0x29, 0xa9, 0x69, 0xe9, 0x19, 0x99, 0x59, 0xd9, 0x39, 0xb9, 0x79, 0xf9,
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0x05, 0x85, 0x45, 0xc5, 0x25, 0xa5, 0x65, 0xe5, 0x15, 0x95, 0x55, 0xd5, 0x35, 0xb5, 0x75, 0xf5,
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0x0d, 0x8d, 0x4d, 0xcd, 0x2d, 0xad, 0x6d, 0xed, 0x1d, 0x9d, 0x5d, 0xdd, 0x3d, 0xbd, 0x7d, 0xfd,
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0x03, 0x83, 0x43, 0xc3, 0x23, 0xa3, 0x63, 0xe3, 0x13, 0x93, 0x53, 0xd3, 0x33, 0xb3, 0x73, 0xf3,
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0x0b, 0x8b, 0x4b, 0xcb, 0x2b, 0xab, 0x6b, 0xeb, 0x1b, 0x9b, 0x5b, 0xdb, 0x3b, 0xbb, 0x7b, 0xfb,
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0x07, 0x87, 0x47, 0xc7, 0x27, 0xa7, 0x67, 0xe7, 0x17, 0x97, 0x57, 0xd7, 0x37, 0xb7, 0x77, 0xf7,
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0x0f, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef, 0x1f, 0x9f, 0x5f, 0xdf, 0x3f, 0xbf, 0x7f, 0xff,
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};
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/*! generalized bit reversal function
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* \param[in] x the 32bit value to be reversed
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* \param[in] k the type of reversal requested
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* \returns the reversed 32bit dword
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*
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* This function reverses the bit order within a 32bit word. Depending
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* on "k", it either reverses all bits in a 32bit dword, or the bytes in
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* the dword, or the bits in each byte of a dword, or simply swaps the
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* two 16bit words in a dword. See Chapter 7 "Hackers Delight"
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*/
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uint32_t osmo_bit_reversal(uint32_t x, enum osmo_br_mode k)
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{
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if (k & 1) x = (x & 0x55555555) << 1 | (x & 0xAAAAAAAA) >> 1;
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if (k & 2) x = (x & 0x33333333) << 2 | (x & 0xCCCCCCCC) >> 2;
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if (k & 4) x = (x & 0x0F0F0F0F) << 4 | (x & 0xF0F0F0F0) >> 4;
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if (k & 8) x = (x & 0x00FF00FF) << 8 | (x & 0xFF00FF00) >> 8;
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if (k & 16) x = (x & 0x0000FFFF) << 16 | (x & 0xFFFF0000) >> 16;
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return x;
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}
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/*! reverse the bit-order in each byte of a dword
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* \param[in] x 32bit input value
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* \returns 32bit value where bits of each byte have been reversed
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*
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* See Chapter 7 "Hackers Delight"
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*/
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uint32_t osmo_revbytebits_32(uint32_t x)
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{
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x = (x & 0x55555555) << 1 | (x & 0xAAAAAAAA) >> 1;
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x = (x & 0x33333333) << 2 | (x & 0xCCCCCCCC) >> 2;
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x = (x & 0x0F0F0F0F) << 4 | (x & 0xF0F0F0F0) >> 4;
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return x;
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}
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/*! reverse the bit order in a byte
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* \param[in] x 8bit input value
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* \returns 8bit value where bits order has been reversed
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*/
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uint32_t osmo_revbytebits_8(uint8_t x)
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{
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return flip_table[x];
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}
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/*! reverse bit-order of each byte in a buffer
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* \param[in] buf buffer containing bytes to be bit-reversed
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* \param[in] len length of buffer in bytes
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*
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* This function reverses the bits in each byte of the buffer
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*/
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void osmo_revbytebits_buf(uint8_t *buf, int len)
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{
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int i;
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for (i = 0; i < len; i++)
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buf[i] = flip_table[buf[i]];
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}
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/*! @} */
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