mirror of https://gerrit.osmocom.org/libosmocore
312 lines
8.7 KiB
C
312 lines
8.7 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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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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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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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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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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/*! 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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* See Chapter 7 "Hackers Delight"
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*/
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uint32_t osmo_revbytebits_8(uint8_t x)
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{
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x = (x & 0x55) << 1 | (x & 0xAA) >> 1;
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x = (x & 0x33) << 2 | (x & 0xCC) >> 2;
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x = (x & 0x0F) << 4 | (x & 0xF0) >> 4;
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return 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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unsigned int i;
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unsigned int unaligned_cnt;
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int len_remain = len;
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unaligned_cnt = ((unsigned long)buf & 3);
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for (i = 0; i < unaligned_cnt; i++) {
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buf[i] = osmo_revbytebits_8(buf[i]);
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len_remain--;
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if (len_remain <= 0)
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return;
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}
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for (i = unaligned_cnt; i + 3 < len; i += 4) {
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osmo_store32be(osmo_revbytebits_32(osmo_load32be(buf + i)), buf + i);
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len_remain -= 4;
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}
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for (i = len - len_remain; i < len; i++) {
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buf[i] = osmo_revbytebits_8(buf[i]);
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len_remain--;
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}
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}
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/*! @} */
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