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+/*! \file bitcomp.c
+ * Osmocom bit compression routines */
+/*
+ * (C) 2016 by sysmocom - s.f.m.c. GmbH
+ * Author: Max Suraev <msuraev@sysmocom.de>
+ *
+ * All Rights Reserved
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ *
+ * 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.
+ *
+ */
+
+/*! \defgroup bitcomp Bit compression
+ * @{
+ * \file bitcomp.c */
+
+#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_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[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
+ }
+};
+
+/*! Make-up codes for a given length
+ *
+ * \return 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]);
+}
+
+/*! encode bit vector in-place using T4 encoding
+ * Assumes MSB first encoding.
+ * \param[in] bv bit vector to be encoded
+ * \return 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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