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libosmocore/src/bitcomp.c

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/* bit compression routines */
/* (C) 2016 sysmocom s.f.m.c. GmbH by Max Suraev <msuraev@sysmocom.de>
*
* All Rights Reserved
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*
*/
/*! \defgroup bitcomp Bit compression
* @{
*/
/*! \file bitcomp.c
* \brief Osmocom bit compression routines
*/
#include <stdint.h>
#include <stdbool.h>
#include <errno.h>
#include <string.h>
#include <osmocom/core/bitvec.h>
#include <osmocom/core/bitcomp.h>
/*
* Terminating codes for uninterrupted sequences of 0 and 1 up to 64 bit length
* according to TS 44.060 9.1.10
*/
static const unsigned t4_term[2][64] = {
{
0b0000110111,
0b10,
0b11,
0b010,
0b011,
0b0011,
0b0010,
0b00011,
0b000101,
0b000100,
0b0000100,
0b0000101,
0b0000111,
0b00000100,
0b00000111,
0b000011000,
0b0000010111,
0b0000011000,
0b0000001000,
0b00001100111,
0b00001101000,
0b00001101100,
0b00000110111,
0b00000101000,
0b00000010111,
0b00000011000,
0b000011001010,
0b000011001011,
0b000011001100,
0b000011001101,
0b000001101000,
0b000001101001,
0b000001101010,
0b000001101011,
0b000011010010,
0b000011010011,
0b000011010100,
0b000011010101,
0b000011010110,
0b000011010111,
0b000001101100,
0b000001101101,
0b000011011010,
0b000011011011,
0b000001010100,
0b000001010101,
0b000001010110,
0b000001010111,
0b000001100100,
0b000001100101,
0b000001010010,
0b000001010011,
0b000000100100,
0b000000110111,
0b000000111000,
0b000000100111,
0b000000101000,
0b000001011000,
0b000001011001,
0b000000101011,
0b000000101100,
0b000001011010,
0b000001100110,
0b000001100111
},
{
0b00110101,
0b000111,
0b0111,
0b1000,
0b1011,
0b1100,
0b1110,
0b1111,
0b10011,
0b10100,
0b00111,
0b01000,
0b001000,
0b000011,
0b110100,
0b110101,
0b101010,
0b101011,
0b0100111,
0b0001100,
0b0001000,
0b0010111,
0b0000011,
0b0000100,
0b0101000,
0b0101011,
0b0010011,
0b0100100,
0b0011000,
0b00000010,
0b00000011,
0b00011010,
0b00011011,
0b00010010,
0b00010011,
0b00010100,
0b00010101,
0b00010110,
0b00010111,
0b00101000,
0b00101001,
0b00101010,
0b00101011,
0b00101100,
0b00101101,
0b00000100,
0b00000101,
0b00001010,
0b00001011,
0b01010010,
0b01010011,
0b01010100,
0b01010101,
0b00100100,
0b00100101,
0b01011000,
0b01011001,
0b01011010,
0b01011011,
0b01001010,
0b01001011,
0b00110010,
0b00110011,
0b00110100
}
};
static const unsigned t4_term_length[2][64] = {
{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},
{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}
};
static const unsigned t4_min_term_length[] = {2, 4};
static const unsigned t4_min_make_up_length[] = {10, 5};
static const unsigned t4_max_term_length[] = {12, 8};
static const unsigned t4_max_make_up_length[] = {13, 9};
static const unsigned t4_make_up_length[2][15] = {
{10, 12, 12, 12, 12, 12, 12, 13, 13, 13, 13, 13, 13, 13, 13},
{5, 5, 6, 7, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9}
};
static const unsigned t4_make_up_ind[15] = {64, 128, 192, 256, 320, 384, 448, 512, 576, 640, 704, 768, 832, 896, 960};
static const unsigned t4_make_up[2][15] = {
{
0b0000001111,
0b000011001000,
0b000011001001,
0b000001011011,
0b000000110011,
0b000000110100,
0b000000110101,
0b0000001101100,
0b0000001101101,
0b0000001001010,
0b0000001001011,
0b0000001001100,
0b0000001001101,
0b0000001110010,
0b0000001110011
},
{
0b11011,
0b10010,
0b010111,
0b0110111,
0b00110110,
0b00110111,
0b01100100,
0b01100101,
0b01101000,
0b01100111,
0b011001100,
0b011001101,
0b011010010,
0b011010011,
0b011010100
}
};
/*! \brief Attempt to decode compressed bit vector
*
* Return length of RLE according to modified ITU-T T.4 from TS 44.060 Table 9.1.10.2
* or -1 if no applicable RLE found
* N. B: we need explicit bit length to make decoding unambiguous
*/
static inline int t4_rle_term(unsigned w, bool b, unsigned bits)
{
unsigned i;
for (i = 0; i < 64; i++)
if (w == t4_term[b][i] && bits == t4_term_length[b][i])
return i;
return -1;
}
static inline int t4_rle_makeup(unsigned w, bool b, unsigned bits)
{
unsigned i;
for (i = 0; i < 15; i++)
if (w == t4_make_up[b][i] && bits == t4_make_up_length[b][i])
return t4_make_up_ind[i];
return -1;
}
/*! \brief Make-up codes for a given length
*
* Return proper make-up code word for an uninterrupted sequence of b bits
* of length len according to modified ITU-T T.4 from TS 44.060 Table 9.1.10.2 */
static inline int t4_rle(struct bitvec *bv, unsigned len, bool b)
{
if (len >= 960) {
bitvec_set_uint(bv, t4_make_up[b][14], t4_make_up_length[b][14]);
return bitvec_set_uint(bv, t4_term[b][len - 960], t4_term_length[b][len - 960]);
}
if (len >= 896) {
bitvec_set_uint(bv, t4_make_up[b][13], t4_make_up_length[b][13]);
return bitvec_set_uint(bv, t4_term[b][len - 896], t4_term_length[b][len - 896]);
}
if (len >= 832) {
bitvec_set_uint(bv, t4_make_up[b][12], t4_make_up_length[b][12]);
return bitvec_set_uint(bv, t4_term[b][len - 832], t4_term_length[b][len - 832]);
}
if (len >= 768) {
bitvec_set_uint(bv, t4_make_up[b][11], t4_make_up_length[b][11]);
return bitvec_set_uint(bv, t4_term[b][len - 768], t4_term_length[b][len - 768]);
}
if (len >= 704) {
bitvec_set_uint(bv, t4_make_up[b][10], t4_make_up_length[b][10]);
return bitvec_set_uint(bv, t4_term[b][len - 704], t4_term_length[b][len - 704]);
}
if (len >= 640) {
bitvec_set_uint(bv, t4_make_up[b][9], t4_make_up_length[b][9]);
return bitvec_set_uint(bv, t4_term[b][len - 640], t4_term_length[b][len - 640]);
}
if (len >= 576) {
bitvec_set_uint(bv, t4_make_up[b][8], t4_make_up_length[b][8]);
return bitvec_set_uint(bv, t4_term[b][len - 576], t4_term_length[b][len - 576]);
}
if (len >= 512) {
bitvec_set_uint(bv, t4_make_up[b][7], t4_make_up_length[b][7]);
return bitvec_set_uint(bv, t4_term[b][len - 512], t4_term_length[b][len - 512]);
}
if (len >= 448) {
bitvec_set_uint(bv, t4_make_up[b][6], t4_make_up_length[b][6]);
return bitvec_set_uint(bv, t4_term[b][len - 448], t4_term_length[b][len - 448]);
}
if (len >= 384) {
bitvec_set_uint(bv, t4_make_up[b][5], t4_make_up_length[b][5]);
return bitvec_set_uint(bv, t4_term[b][len - 384], t4_term_length[b][len - 384]);
}
if (len >= 320) {
bitvec_set_uint(bv, t4_make_up[b][4], t4_make_up_length[b][4]);
return bitvec_set_uint(bv, t4_term[b][len - 320], t4_term_length[b][len - 320]);
}
if (len >= 256) {
bitvec_set_uint(bv, t4_make_up[b][3], t4_make_up_length[b][3]);
return bitvec_set_uint(bv, t4_term[b][len - 256], t4_term_length[b][len - 256]);
}
if (len >= 192) {
bitvec_set_uint(bv, t4_make_up[b][2], t4_make_up_length[b][2]);
return bitvec_set_uint(bv, t4_term[b][len - 192], t4_term_length[b][len - 192]);
}
if (len >= 128) {
bitvec_set_uint(bv, t4_make_up[b][1], t4_make_up_length[b][1]);
return bitvec_set_uint(bv, t4_term[b][len - 128], t4_term_length[b][len - 128]);
}
if (len >= 64) {
bitvec_set_uint(bv, t4_make_up[b][0], t4_make_up_length[b][0]);
return bitvec_set_uint(bv, t4_term[b][len - 64], t4_term_length[b][len - 64]);
}
return bitvec_set_uint(bv, t4_term[b][len], t4_term_length[b][len]);
}
enum dec_state {
EXPECT_TERM,
TOO_LONG,
NEED_MORE_BITS,
CORRUPT,
OK
};
static inline enum dec_state _t4_step(struct bitvec *v, uint16_t w, bool b, unsigned bits, bool term_only)
{
if (bits > t4_max_make_up_length[b])
return TOO_LONG;
if (bits < t4_min_term_length[b])
return NEED_MORE_BITS;
if (term_only) {
if (bits > t4_max_term_length[b])
return CORRUPT;
int t = t4_rle_term(w, b, bits);
if (-1 != t) {
bitvec_fill(v, t, b ? ONE : ZERO);
return OK;
}
return NEED_MORE_BITS;
}
int m = t4_rle_makeup(w, b, bits);
if (-1 != m) {
bitvec_fill(v, m, b ? ONE : ZERO);
return EXPECT_TERM;
}
m = t4_rle_term(w, b, bits);
if (-1 != m) {
bitvec_fill(v, m, b ? ONE : ZERO);
return OK;
}
return NEED_MORE_BITS;
}
/*! \brief decode T4-encoded bit vector
* Assumes MSB first encoding.
* \param[in] in bit vector with encoded data
* \param[in] cc color code (whether decoding should start with 1 or 0)
* \param[out] out the bit vector to store result into
* returns 0 on success, negative value otherwise
*/
int osmo_t4_decode(const struct bitvec *in, bool cc, struct bitvec *out)
{
uint8_t orig[in->data_len];
struct bitvec vec;
vec.data = orig;
vec.data_len = in->data_len;
bitvec_zero(&vec);
memcpy(vec.data, in->data, in->data_len);
vec.cur_bit = in->cur_bit;
/* init decoder using known color code: */
unsigned bits = t4_min_term_length[cc];
enum dec_state d;
int16_t w = bitvec_get_int16_msb(&vec, bits);
bool b = cc;
bool term_only = false;
while (vec.cur_bit > 0) {
d = _t4_step(out, w, b, bits, term_only);
switch (d) {
case EXPECT_TERM:
bitvec_shiftl(&vec, bits);
bits = t4_min_term_length[b];
w = bitvec_get_int16_msb(&vec, bits);
term_only = true;
break;
case OK:
bitvec_shiftl(&vec, bits);
bits = t4_min_term_length[!b];
w = bitvec_get_int16_msb(&vec, bits);
b = !b;
term_only = false;
break;
case NEED_MORE_BITS:
bits++;
w = bitvec_get_int16_msb(&vec, bits);
break;
case TOO_LONG:
return -E2BIG;
case CORRUPT:
return -EINVAL;
}
}
return 0;
}
/*! \brief encode bit vector in-place using T4 encoding
* Assumes MSB first encoding.
* \param[in] bv bit vector to be encoded
* returns color code (if the encoding started with 0 or 1) or -1 on failure (encoded is bigger than original)
*/
int osmo_t4_encode(struct bitvec *bv)
{
unsigned rl0 = bitvec_rl(bv, false), rl1 = bitvec_rl(bv, true);
int r = (rl0 > rl1) ? 0 : 1;
uint8_t orig[bv->data_len], tmp[bv->data_len * 2]; /* FIXME: better estimate max possible encoding overhead */
struct bitvec comp, vec;
comp.data = tmp;
comp.data_len = bv->data_len * 2;
bitvec_zero(&comp);
vec.data = orig;
vec.data_len = bv->data_len;
bitvec_zero(&vec);
memcpy(vec.data, bv->data, bv->data_len);
vec.cur_bit = bv->cur_bit;
while (vec.cur_bit > 0) {
if (rl0 > rl1) {
bitvec_shiftl(&vec, rl0);
t4_rle(&comp, rl0, false);
} else {
bitvec_shiftl(&vec, rl1);
t4_rle(&comp, rl1, true);
}
/*
TODO: implement backtracking for optimal encoding
printf(" -> [%d/%d]", comp.cur_bit + vec.cur_bit, bv->cur_bit);
*/
rl0 = bitvec_rl(&vec, false);
rl1 = bitvec_rl(&vec, true);
}
if (comp.cur_bit < bv->cur_bit) {
memcpy(bv->data, tmp, bv->data_len);
bv->cur_bit = comp.cur_bit;
return r;
}
return -1;
}
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