208 lines
4.0 KiB
C
208 lines
4.0 KiB
C
/*
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* Copyright (C) 2014 Andreas Steffen
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* HSR Hochschule fuer Technik Rapperswil
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* option) any later version. See <http://www.fsf.org/copyleft/gpl.txt>.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY;https://www.hsr.ch/HSR-intern-Anmeldung.4409.0.html?&no_cache=1 without even the implied warranty of MERCHANTABILITY
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* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*/
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#include "bliss_bitpacker.h"
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typedef struct private_bliss_bitpacker_t private_bliss_bitpacker_t;
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/**
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* Private data structure for bliss_bitpacker_t object
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*/
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struct private_bliss_bitpacker_t {
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/**
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* Public interface.
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*/
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bliss_bitpacker_t public;
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/**
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* Current number of bits written to buffer
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*/
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size_t bits;
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/**
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* Bit buffer for up to 32 bits
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*/
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uint32_t bits_buf;
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/**
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* Bits left in the bit buffer
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*/
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size_t bits_left;
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/**
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* Buffer
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*/
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chunk_t buf;
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/**
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* Read/Write pointer into buffer
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*/
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chunk_t pos;
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};
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METHOD(bliss_bitpacker_t, get_bits, size_t,
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private_bliss_bitpacker_t *this)
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{
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return this->bits;
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}
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METHOD(bliss_bitpacker_t, write_bits, bool,
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private_bliss_bitpacker_t *this, uint32_t value, size_t bits)
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{
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if (bits == 0)
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{
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return TRUE;
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}
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if (bits > 32)
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{
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return FALSE;
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}
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if (bits < 32)
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{
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value &= (1 << bits) - 1;
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}
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this->bits += bits;
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while (TRUE)
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{
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if (bits <= this->bits_left)
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{
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this->bits_buf |= value << (this->bits_left - bits);
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this->bits_left -= bits;
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return TRUE;
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}
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this->bits_buf |= value >> (bits - this->bits_left);
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value &= (1 << (bits - this->bits_left)) - 1;
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bits -= this->bits_left;
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if (this->pos.len < 8)
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{
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return FALSE;
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}
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htoun32(this->pos.ptr, this->bits_buf);
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this->pos = chunk_skip(this->pos, 4);
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this->bits_buf = 0;
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this->bits_left = 32;
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}
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}
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METHOD(bliss_bitpacker_t, read_bits, bool,
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private_bliss_bitpacker_t *this, uint32_t *value, size_t bits)
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{
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if (bits > 32)
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{
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return FALSE;
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}
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*value = 0;
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while (TRUE)
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{
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if (this->bits_left == 0)
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{
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if (this->pos.len < 4)
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{
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return FALSE;
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}
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this->bits_buf = untoh32(this->pos.ptr);
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this->pos = chunk_skip(this->pos, 4);
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this->bits_left = 32;
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}
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if (bits <= this->bits_left)
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{
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*value |= this->bits_buf >> (this->bits_left - bits);
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this->bits_buf &= (1 << (this->bits_left - bits)) - 1;
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this->bits_left -= bits;
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return TRUE;
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}
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*value |= this->bits_buf << (bits - this->bits_left);
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bits -= this->bits_left;
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this->bits_left = 0;
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}
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}
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METHOD(bliss_bitpacker_t, extract_buf, chunk_t,
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private_bliss_bitpacker_t *this)
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{
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chunk_t buf;
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htoun32(this->pos.ptr, this->bits_buf);
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this->pos.len -= 4;
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buf = this->buf;
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buf.len = this->buf.len - this->pos.len - this->bits_left/8;
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this->buf = this->pos = chunk_empty;
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return buf;
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}
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METHOD(bliss_bitpacker_t, destroy, void,
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private_bliss_bitpacker_t *this)
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{
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free(this->buf.ptr);
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free(this);
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}
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/**
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* See header.
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*/
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bliss_bitpacker_t *bliss_bitpacker_create(uint16_t max_bits)
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{
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private_bliss_bitpacker_t *this;
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INIT(this,
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.public = {
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.get_bits = _get_bits,
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.write_bits = _write_bits,
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.read_bits = _read_bits,
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.extract_buf = _extract_buf,
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.destroy = _destroy,
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},
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.bits_left = 32,
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.buf = chunk_alloc(round_up(max_bits, 32)/8),
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);
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this->pos = this->buf;
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return &this->public;
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}
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/**
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* See header.
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*/
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bliss_bitpacker_t *bliss_bitpacker_create_from_data(chunk_t data)
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{
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private_bliss_bitpacker_t *this;
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INIT(this,
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.public = {
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.get_bits = _get_bits,
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.write_bits = _write_bits,
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.read_bits = _read_bits,
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.extract_buf = _extract_buf,
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.destroy = _destroy,
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},
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.bits = 8 * data.len,
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.buf = chunk_alloc(round_up(data.len, 4)),
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);
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memset(this->buf.ptr + this->buf.len - 4, 0x00, 4);
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memcpy(this->buf.ptr, data.ptr, data.len);
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this->pos = this->buf;
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return &this->public;
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}
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