mirror of https://gerrit.osmocom.org/libosmocore
355 lines
8.4 KiB
C
355 lines
8.4 KiB
C
/* bit compression routines */
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/* (C) 2016 sysmocom s.f.m.c. GmbH by Max Suraev <msuraev@sysmocom.de>
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*
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* All Rights Reserved
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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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/*! \defgroup bitcomp Bit compression
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* @{
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*/
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/*! \file bitcomp.c
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* \brief Osmocom bit compression routines
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*/
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#include <stdint.h>
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#include <stdbool.h>
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#include <errno.h>
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#include <string.h>
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#include <osmocom/core/bitvec.h>
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#include <osmocom/core/bitcomp.h>
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/*
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* Terminating codes for uninterrupted sequences of 0 and 1 up to 64 bit length
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* according to TS 44.060 9.1.10
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*/
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static const unsigned t4_term[2][64] = {
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{
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0b0000110111,
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0b10,
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0b11,
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0b010,
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0b011,
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0b0011,
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0b0010,
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0b00011,
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0b000101,
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0b000100,
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0b0000100,
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0b0000101,
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0b0000111,
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0b00000100,
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0b00000111,
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0b000011000,
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0b0000010111,
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0b0000011000,
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0b0000001000,
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0b00001100111,
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0b00001101000,
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0b00001101100,
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0b00000110111,
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0b00000101000,
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0b00000010111,
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0b00000011000,
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0b000011001010,
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0b000011001011,
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0b000011001100,
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0b000011001101,
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0b000001101000,
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0b000001101001,
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0b000001101010,
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0b000001101011,
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0b000011010010,
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0b000011010011,
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0b000011010100,
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0b000011010101,
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0b000011010110,
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0b000011010111,
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0b000001101100,
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0b000001101101,
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0b000011011010,
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0b000011011011,
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0b000001010100,
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0b000001010101,
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0b000001010110,
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0b000001010111,
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0b000001100100,
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0b000001100101,
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0b000001010010,
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0b000001010011,
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0b000000100100,
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0b000000110111,
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0b000000111000,
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0b000000100111,
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0b000000101000,
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0b000001011000,
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0b000001011001,
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0b000000101011,
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0b000000101100,
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0b000001011010,
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0b000001100110,
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0b000001100111
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},
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{
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0b00110101,
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0b000111,
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0b0111,
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0b1000,
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0b1011,
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0b1100,
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0b1110,
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0b1111,
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0b10011,
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0b10100,
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0b00111,
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0b01000,
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0b001000,
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0b000011,
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0b110100,
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0b110101,
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0b101010,
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0b101011,
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0b0100111,
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0b0001100,
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0b0001000,
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0b0010111,
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0b0000011,
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0b0000100,
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0b0101000,
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0b0101011,
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0b0010011,
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0b0100100,
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0b0011000,
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0b00000010,
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0b00000011,
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0b00011010,
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0b00011011,
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0b00010010,
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0b00010011,
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0b00010100,
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0b00010101,
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0b00010110,
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0b00010111,
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0b00101000,
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0b00101001,
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0b00101010,
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0b00101011,
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0b00101100,
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0b00101101,
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0b00000100,
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0b00000101,
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0b00001010,
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0b00001011,
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0b01010010,
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0b01010011,
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0b01010100,
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0b01010101,
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0b00100100,
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0b00100101,
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0b01011000,
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0b01011001,
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0b01011010,
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0b01011011,
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0b01001010,
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0b01001011,
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0b00110010,
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0b00110011,
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0b00110100
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}
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};
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static const unsigned t4_term_length[2][64] = {
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{10, 2, 2, 3, 3, 4, 4, 5, 6, 6, 7, 7, 7, 8, 8, 9, 10, 10, 10, 11, 11, 11, 11, 11, 11, 11, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12},
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{8, 6, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8}
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};
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static const unsigned t4_make_up_length[2][15] = {
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{10, 12, 12, 12, 12, 12, 12, 13, 13, 13, 13, 13, 13, 13, 13},
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{5, 5, 6, 7, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9}
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};
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static const unsigned t4_make_up[2][15] = {
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{
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0b0000001111,
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0b000011001000,
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0b000011001001,
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0b000001011011,
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0b000000110011,
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0b000000110100,
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0b000000110101,
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0b0000001101100,
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0b0000001101101,
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0b0000001001010,
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0b0000001001011,
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0b0000001001100,
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0b0000001001101,
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0b0000001110010,
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0b0000001110011
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},
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{
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0b11011,
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0b10010,
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0b010111,
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0b0110111,
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0b00110110,
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0b00110111,
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0b01100100,
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0b01100101,
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0b01101000,
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0b01100111,
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0b011001100,
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0b011001101,
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0b011010010,
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0b011010011,
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0b011010100
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}
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};
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/*! \brief Make-up codes for a given length
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*
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* \return Return proper make-up code word for an uninterrupted
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* sequence of b bits of length len according to modified ITU-T T.4
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* from TS 44.060 Table 9.1.10.2 */
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static inline int t4_rle(struct bitvec *bv, unsigned len, bool b)
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{
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if (len >= 960) {
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bitvec_set_uint(bv, t4_make_up[b][14], t4_make_up_length[b][14]);
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return bitvec_set_uint(bv, t4_term[b][len - 960], t4_term_length[b][len - 960]);
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}
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if (len >= 896) {
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bitvec_set_uint(bv, t4_make_up[b][13], t4_make_up_length[b][13]);
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return bitvec_set_uint(bv, t4_term[b][len - 896], t4_term_length[b][len - 896]);
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}
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if (len >= 832) {
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bitvec_set_uint(bv, t4_make_up[b][12], t4_make_up_length[b][12]);
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return bitvec_set_uint(bv, t4_term[b][len - 832], t4_term_length[b][len - 832]);
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}
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if (len >= 768) {
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bitvec_set_uint(bv, t4_make_up[b][11], t4_make_up_length[b][11]);
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return bitvec_set_uint(bv, t4_term[b][len - 768], t4_term_length[b][len - 768]);
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}
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if (len >= 704) {
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bitvec_set_uint(bv, t4_make_up[b][10], t4_make_up_length[b][10]);
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return bitvec_set_uint(bv, t4_term[b][len - 704], t4_term_length[b][len - 704]);
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}
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if (len >= 640) {
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bitvec_set_uint(bv, t4_make_up[b][9], t4_make_up_length[b][9]);
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return bitvec_set_uint(bv, t4_term[b][len - 640], t4_term_length[b][len - 640]);
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}
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if (len >= 576) {
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bitvec_set_uint(bv, t4_make_up[b][8], t4_make_up_length[b][8]);
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return bitvec_set_uint(bv, t4_term[b][len - 576], t4_term_length[b][len - 576]);
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}
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if (len >= 512) {
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bitvec_set_uint(bv, t4_make_up[b][7], t4_make_up_length[b][7]);
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return bitvec_set_uint(bv, t4_term[b][len - 512], t4_term_length[b][len - 512]);
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}
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if (len >= 448) {
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bitvec_set_uint(bv, t4_make_up[b][6], t4_make_up_length[b][6]);
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return bitvec_set_uint(bv, t4_term[b][len - 448], t4_term_length[b][len - 448]);
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}
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if (len >= 384) {
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bitvec_set_uint(bv, t4_make_up[b][5], t4_make_up_length[b][5]);
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return bitvec_set_uint(bv, t4_term[b][len - 384], t4_term_length[b][len - 384]);
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}
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if (len >= 320) {
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bitvec_set_uint(bv, t4_make_up[b][4], t4_make_up_length[b][4]);
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return bitvec_set_uint(bv, t4_term[b][len - 320], t4_term_length[b][len - 320]);
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}
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if (len >= 256) {
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bitvec_set_uint(bv, t4_make_up[b][3], t4_make_up_length[b][3]);
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return bitvec_set_uint(bv, t4_term[b][len - 256], t4_term_length[b][len - 256]);
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}
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if (len >= 192) {
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bitvec_set_uint(bv, t4_make_up[b][2], t4_make_up_length[b][2]);
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return bitvec_set_uint(bv, t4_term[b][len - 192], t4_term_length[b][len - 192]);
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}
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if (len >= 128) {
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bitvec_set_uint(bv, t4_make_up[b][1], t4_make_up_length[b][1]);
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return bitvec_set_uint(bv, t4_term[b][len - 128], t4_term_length[b][len - 128]);
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}
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if (len >= 64) {
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bitvec_set_uint(bv, t4_make_up[b][0], t4_make_up_length[b][0]);
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return bitvec_set_uint(bv, t4_term[b][len - 64], t4_term_length[b][len - 64]);
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}
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return bitvec_set_uint(bv, t4_term[b][len], t4_term_length[b][len]);
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}
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/*! \brief encode bit vector in-place using T4 encoding
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* Assumes MSB first encoding.
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* \param[in] bv bit vector to be encoded
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* \return color code (if the encoding started with 0 or 1) or -1 on
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* failure (encoded is bigger than original)
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*/
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int osmo_t4_encode(struct bitvec *bv)
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{
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unsigned rl0 = bitvec_rl(bv, false), rl1 = bitvec_rl(bv, true);
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int r = (rl0 > rl1) ? 0 : 1;
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uint8_t orig[bv->data_len], tmp[bv->data_len * 2]; /* FIXME: better estimate max possible encoding overhead */
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struct bitvec comp, vec;
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comp.data = tmp;
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comp.data_len = bv->data_len * 2;
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bitvec_zero(&comp);
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vec.data = orig;
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vec.data_len = bv->data_len;
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bitvec_zero(&vec);
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memcpy(vec.data, bv->data, bv->data_len);
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vec.cur_bit = bv->cur_bit;
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while (vec.cur_bit > 0) {
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if (rl0 > rl1) {
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bitvec_shiftl(&vec, rl0);
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t4_rle(&comp, rl0, false);
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} else {
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bitvec_shiftl(&vec, rl1);
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t4_rle(&comp, rl1, true);
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}
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/*
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TODO: implement backtracking for optimal encoding
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printf(" -> [%d/%d]", comp.cur_bit + vec.cur_bit, bv->cur_bit);
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*/
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rl0 = bitvec_rl(&vec, false);
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rl1 = bitvec_rl(&vec, true);
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}
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if (comp.cur_bit < bv->cur_bit) {
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memcpy(bv->data, tmp, bv->data_len);
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bv->cur_bit = comp.cur_bit;
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return r;
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}
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return -1;
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}
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