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Diffstat (limited to 'src/bitcomp.c')
| -rw-r--r-- | src/bitcomp.c | 480 |
1 files changed, 480 insertions, 0 deletions
diff --git a/src/bitcomp.c b/src/bitcomp.c new file mode 100644 index 00000000..bf359274 --- /dev/null +++ b/src/bitcomp.c @@ -0,0 +1,480 @@ +/* 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; +} + + |