Add T4 bit map compression routines
Add bit map encoder and decoder functions: decoder is fully functional
while encoder is good enough for testing - no backtracking to find
the best possible compression is implemented. If somebody is willing to
implement MS side of EDGE than this has to be expanded.
Add corresponding tests.
N. B: the encoding is implemented according to ETSI TS 44.060 which is
slightly different from T4 used for fax according to CCITT G31D (RFC 804).
Ticket: OW#2407
Sponsored-by: On-Waves ehf
Signed-off-by: Max <msuraev@sysmocom.de>
diff --git a/src/bitcomp.c b/src/bitcomp.c
new file mode 100644
index 0000000..bf35927
--- /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;
+}
+
+