9  *  http://www.apache.org/licenses/LICENSE-2.0
22  * - Arthmetic coder put bits while increasing memory addresses
25  * - Plain bits are puts starting the end of the buffer, with memeory
28  *       .---------------------------------------------------.
30  *       '---------------------------------------------------'
31  *       |---------------------> - - - - - - - - - - - - - ->|
32  *                              |< - - - <-------------------|
36  * - The forward writing is protected against buffer overflow, it cannot
40  * - The backward writing is protected against overwrite of the arithmetic
44  *       .---------------------------------------------------.
46  *       '---------------------------------------------------'
47  *       |---------------------> - - - - - - - - - - - - - ->|
48  *       |< - - - - - - - - - - -  - - - <-------------------|
52  * - Reading is limited to read of the complementary end of the buffer.
54  * - The procedure `lc3_check_bits()` returns indication that read has been
114     struct lc3_bits_ac ac;  member
139  * return          0: Ok  -1: Bitstream overflow or AC reading error
153  * v, n            Value, in range 0 to 2^n - 1, and bits count (1 to 32)
196 /* ----------------------------------------------------------------------------
198  * -------------------------------------------------------------------------- */
221     struct lc3_bits_accu *accu = &bits->accu;  in lc3_put_bits()
223     if (accu->n + n <= LC3_ACCU_BITS) {  in lc3_put_bits()
224         accu->v |= v << accu->n;  in lc3_put_bits()
225         accu->n += n;  in lc3_put_bits()
244     struct lc3_bits_accu *accu = &bits->accu;  in lc3_get_bits()
246     if (accu->n + n <= LC3_ACCU_BITS) {  in lc3_get_bits()
247         int v = (accu->v >> accu->n) & ((1u << n) - 1);  in lc3_get_bits()
248         return (accu->n += n), v;  in lc3_get_bits()
261     const struct lc3_ac_symbol *symbols = model->s;  in lc3_put_symbol()
262     struct lc3_bits_ac *ac = &bits->ac;  in lc3_put_symbol()  local
263     unsigned range = ac->range >> 10;  in lc3_put_symbol()
265     ac->low += range * symbols[s].low;  in lc3_put_symbol()
266     ac->range = range * symbols[s].range;  in lc3_put_symbol()
268     ac->carry |= ac->low >> 24;  in lc3_put_symbol()
269     ac->low &= 0xffffff;  in lc3_put_symbol()
271     if (ac->range < 0x10000)  in lc3_put_symbol()
281     const struct lc3_ac_symbol *symbols = model->s;  in lc3_get_symbol()
282     struct lc3_bits_ac *ac = &bits->ac;  in lc3_get_symbol()  local
284     unsigned range = (ac->range >> 10) & 0xffff;  in lc3_get_symbol()
286     ac->error |= (ac->low >= (range << 10));  in lc3_get_symbol()
287     if (ac->error)  in lc3_get_symbol()
288         ac->low = 0;  in lc3_get_symbol()
292     if (ac->low < range * symbols[s].low) {  in lc3_get_symbol()
294         s -= ac->low < range * symbols[s].low ? 4 : -4;  in lc3_get_symbol()
295         s -= ac->low < range * symbols[s].low ? 2 : -2;  in lc3_get_symbol()
296         s -= ac->low < range * symbols[s].low ? 1 : -1;  in lc3_get_symbol()
297         s -= ac->low < range * symbols[s].low;  in lc3_get_symbol()
300     ac->low -= range * symbols[s].low;  in lc3_get_symbol()
301     ac->range = range * symbols[s].range;  in lc3_get_symbol()
303     if (ac->range < 0x10000)  in lc3_get_symbol()