summaryrefslogtreecommitdiff
path: root/src/encode.c
blob: dd7223980629f3400e220a3547584604e133fde1 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
/**
 * @file encode.c
 *
 * @section LICENSE
 * Copyright 2012 - 2014
 *
 * Mathis Rosenhauer, Moritz Hanke, Joerg Behrens
 * Deutsches Klimarechenzentrum GmbH
 * Bundesstr. 45a
 * 20146 Hamburg Germany
 *
 * Luis Kornblueh
 * Max-Planck-Institut fuer Meteorologie
 * Bundesstr. 53
 * 20146 Hamburg
 * Germany
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above
 *    copyright notice, this list of conditions and the following
 *    disclaimer in the documentation and/or other materials provided
 *    with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * @section DESCRIPTION
 *
 * Adaptive Entropy Encoder
 * Based on CCSDS documents 121.0-B-2 and 120.0-G-3
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "libaec.h"
#include "encode.h"
#include "encode_accessors.h"

static int m_get_block(struct aec_stream *strm);

static inline void emit(struct internal_state *state,
                        uint32_t data, int bits)
{
    /**
       Emit sequence of bits.
     */

    if (bits <= state->bits) {
        state->bits -= bits;
        *state->cds += (uint8_t)(data << state->bits);
    } else {
        bits -= state->bits;
        *state->cds++ += (uint8_t)((uint64_t)data >> bits);

        while (bits > 8) {
            bits -= 8;
            *state->cds++ = (uint8_t)(data >> bits);
        }

        state->bits = 8 - bits;
        *state->cds = (uint8_t)(data << state->bits);
    }
}

static inline void emitfs(struct internal_state *state, int fs)
{
    /**
       Emits a fundamental sequence.

       fs zero bits followed by one 1 bit.
     */

    for(;;) {
        if (fs < state->bits) {
            state->bits -= fs + 1;
            *state->cds += 1U << state->bits;
            break;
        } else {
            fs -= state->bits;
            *++state->cds = 0;
            state->bits = 8;
        }
    }
}

static inline void copy64(uint8_t *dst, uint64_t src)
{
    dst[0] = (uint8_t)(src >> 56);
    dst[1] = (uint8_t)(src >> 48);
    dst[2] = (uint8_t)(src >> 40);
    dst[3] = (uint8_t)(src >> 32);
    dst[4] = (uint8_t)(src >> 24);
    dst[5] = (uint8_t)(src >> 16);
    dst[6] = (uint8_t)(src >> 8);
    dst[7] = (uint8_t)src;
}

static inline void emitblock_fs(struct aec_stream *strm, int k, int ref)
{
    uint32_t i;
    uint32_t used; /* used bits in 64 bit accumulator */
    uint64_t acc; /* accumulator */
    struct internal_state *state = strm->state;

    acc = (uint64_t)*state->cds << 56;
    used = 7 - state->bits;

    for (i = ref; i < strm->block_size; i++) {
        used += (state->block[i] >> k) + 1;
        while (used > 63) {
            copy64(state->cds, acc);
            state->cds += 8;
            acc = 0;
            used -= 64;
        }
        acc |= UINT64_C(1) << (63 - used);
    }

    copy64(state->cds, acc);
    state->cds += used >> 3;
    state->bits = 7 - (used & 7);
}

static inline void emitblock(struct aec_stream *strm, int k, int ref)
{
    /**
       Emit the k LSB of a whole block of input data.
    */

    uint64_t a;
    struct internal_state *state = strm->state;
    uint32_t *in = state->block + ref;
    uint32_t *in_end = state->block + strm->block_size;
    uint64_t mask = (UINT64_C(1) << k) - 1;
    uint8_t *o = state->cds;
    int p = state->bits;

    a = *o;

    while(in < in_end) {
        a <<= 56;
        p = (p % 8) + 56;

        while (p > k && in < in_end) {
            p -= k;
            a += ((uint64_t)(*in++) & mask) << p;
        }

        switch (p & ~7) {
        case 0:
            o[0] = (uint8_t)(a >> 56);
            o[1] = (uint8_t)(a >> 48);
            o[2] = (uint8_t)(a >> 40);
            o[3] = (uint8_t)(a >> 32);
            o[4] = (uint8_t)(a >> 24);
            o[5] = (uint8_t)(a >> 16);
            o[6] = (uint8_t)(a >> 8);
            o += 7;
            break;
        case 8:
            o[0] = (uint8_t)(a >> 56);
            o[1] = (uint8_t)(a >> 48);
            o[2] = (uint8_t)(a >> 40);
            o[3] = (uint8_t)(a >> 32);
            o[4] = (uint8_t)(a >> 24);
            o[5] = (uint8_t)(a >> 16);
            a >>= 8;
            o += 6;
            break;
        case 16:
            o[0] = (uint8_t)(a >> 56);
            o[1] = (uint8_t)(a >> 48);
            o[2] = (uint8_t)(a >> 40);
            o[3] = (uint8_t)(a >> 32);
            o[4] = (uint8_t)(a >> 24);
            a >>= 16;
            o += 5;
            break;
        case 24:
            o[0] = (uint8_t)(a >> 56);
            o[1] = (uint8_t)(a >> 48);
            o[2] = (uint8_t)(a >> 40);
            o[3] = (uint8_t)(a >> 32);
            a >>= 24;
            o += 4;
            break;
        case 32:
            o[0] = (uint8_t)(a >> 56);
            o[1] = (uint8_t)(a >> 48);
            o[2] = (uint8_t)(a >> 40);
            a >>= 32;
            o += 3;
            break;
        case 40:
            o[0] = (uint8_t)(a >> 56);
            o[1] = (uint8_t)(a >> 48);
            a >>= 40;
            o += 2;
            break;
        case 48:
            *o++ = (uint8_t)(a >> 56);
            a >>= 48;
            break;
        default:
            a >>= 56;
            break;
        }
    }

    *o = (uint8_t)a;
    state->cds = o;
    state->bits = p % 8;
}

static void preprocess_unsigned(struct aec_stream *strm)
{
    /**
       Preprocess RSI of unsigned samples.

       Combining preprocessing and converting to uint32_t in one loop
       is slower due to the data dependance on x_i-1.
    */

    uint32_t D;
    struct internal_state *state = strm->state;
    const uint32_t *restrict x = state->data_raw;
    uint32_t *restrict d = state->data_pp;
    uint32_t xmax = state->xmax;
    uint32_t rsi = strm->rsi * strm->block_size - 1;
    unsigned int i;

    state->ref = 1;
    state->ref_sample = x[0];
    d[0] = 0;
    for (i = 0; i < rsi; i++) {
        if (x[i + 1] >= x[i]) {
            D = x[i + 1] - x[i];
            if (D <= x[i])
                d[i + 1] = 2 * D;
            else
                d[i + 1] = x[i + 1];
        } else {
            D = x[i] - x[i + 1];
            if (D <= xmax - x[i])
                d[i + 1] = 2 * D - 1;
            else
                d[i + 1] = xmax - x[i + 1];
        }
    }
    state->uncomp_len = (strm->block_size - 1) * strm->bits_per_sample;
}

static void preprocess_signed(struct aec_stream *strm)
{
    /**
       Preprocess RSI of signed samples.
    */

    uint32_t D;
    struct internal_state *state = strm->state;
    int32_t *restrict x = (int32_t *)state->data_raw;
    uint32_t *restrict d = state->data_pp;
    int32_t xmax = (int32_t)state->xmax;
    int32_t xmin = (int32_t)state->xmin;
    uint32_t rsi = strm->rsi * strm->block_size - 1;
    uint32_t m = UINT64_C(1) << (strm->bits_per_sample - 1);
    unsigned int i;

    state->ref = 1;
    state->ref_sample = x[0];
    d[0] = 0;
    x[0] = (x[0] ^ m) - m;

    for (i = 0; i < rsi; i++) {
        x[i + 1] = (x[i + 1] ^ m) - m;
        if (x[i + 1] < x[i]) {
            D = (uint32_t)(x[i] - x[i + 1]);
            if (D <= (uint32_t)(xmax - x[i]))
                d[i + 1] = 2 * D - 1;
            else
                d[i + 1] = xmax - x[i + 1];
        } else {
            D = (uint32_t)(x[i + 1] - x[i]);
            if (D <= (uint32_t)(x[i] - xmin))
                d[i + 1] = 2 * D;
            else
                d[i + 1] = x[i + 1] - xmin;
        }
    }
    state->uncomp_len = (strm->block_size - 1) * strm->bits_per_sample;
}

static inline uint64_t block_fs(struct aec_stream *strm, int k)
{
    /**
       Sum FS of all samples in block for given splitting position.
    */

    uint32_t i;
    uint64_t fs = 0;
    struct internal_state *state = strm->state;

    for (i = 0; i < strm->block_size; i++)
        fs += (uint64_t)(state->block[i] >> k);

    return fs;
}

static uint32_t assess_splitting_option(struct aec_stream *strm)
{
    /**
       Length of CDS encoded with splitting option and optimal k.

       In Rice coding each sample in a block of samples is split at
       the same position into k LSB and bits_per_sample - k MSB. The
       LSB part is left binary and the MSB part is coded as a
       fundamental sequence a.k.a. unary (see CCSDS 121.0-B-2). The
       function of the length of the Coded Data Set (CDS) depending on
       k has exactly one minimum (see A. Kiely, IPN Progress Report
       42-159).

       To find that minimum with only a few costly evaluations of the
       CDS length, we start with the k of the previous CDS. K is
       increased and the CDS length evaluated. If the CDS length gets
       smaller, then we are moving towards the minimum. If the length
       increases, then the minimum will be found with smaller k.

       For increasing k we know that we will gain block_size bits in
       length through the larger binary part. If the FS lenth is less
       than the block size then a reduced FS part can't compensate the
       larger binary part. So we know that the CDS for k+1 will be
       larger than for k without actually computing the length. An
       analogue check can be done for decreasing k.
     */

    int k;
    int k_min;
    int this_bs; /* Block size of current block */
    int no_turn; /* 1 if we shouldn't reverse */
    int dir; /* Direction, 1 means increasing k, 0 decreasing k */
    uint64_t len; /* CDS length for current k */
    uint64_t len_min; /* CDS length minimum so far */
    uint64_t fs_len; /* Length of FS part (not including 1s) */

    struct internal_state *state = strm->state;

    this_bs = strm->block_size - state->ref;
    len_min = UINT64_MAX;
    k = k_min = state->k;
    no_turn = k == 0;
    dir = 1;

    for (;;) {
        fs_len = block_fs(strm, k);
        len = fs_len + this_bs * (k + 1);

        if (len < len_min) {
            if (len_min < UINT64_MAX)
                no_turn = 1;

            len_min = len;
            k_min = k;

            if (dir) {
                if (fs_len < this_bs || k >= state->kmax) {
                    if (no_turn)
                        break;
                    k = state->k - 1;
                    dir = 0;
                    no_turn = 1;
                } else {
                    k++;
                }
            } else {
                if (fs_len >= this_bs || k == 0)
                    break;
                k--;
            }
        } else {
            if (no_turn)
                break;
            k = state->k - 1;
            dir = 0;
            no_turn = 1;
        }
    }
    state->k = k_min;

    return (uint32_t)len_min;
}

static uint32_t assess_se_option(struct aec_stream *strm)
{
    /**
       Length of CDS encoded with Second Extension option.

       If length is above limit just return UINT32_MAX.
    */

    uint32_t i;
    uint64_t len, d;
    struct internal_state *state = strm->state;
    uint32_t *block = state->block;

    len = 1;

    for (i = 0; i < strm->block_size; i += 2) {
        d = (uint64_t)block[i] + (uint64_t)block[i + 1];
        len += d * (d + 1) / 2 + block[i + 1] + 1;
        if (len > state->uncomp_len)
            return UINT32_MAX;
    }
    return (uint32_t)len;
}

static void init_output(struct aec_stream *strm)
{
    /**
       Direct output to next_out if next_out can hold a Coded Data
       Set, use internal buffer otherwise.
    */

    struct internal_state *state = strm->state;

    if (strm->avail_out > CDSLEN) {
        if (!state->direct_out) {
            state->direct_out = 1;
            *strm->next_out = *state->cds;
            state->cds = strm->next_out;
        }
    } else {
        if (state->zero_blocks == 0 || state->direct_out) {
            /* copy leftover from last block */
            *state->cds_buf = *state->cds;
            state->cds = state->cds_buf;
        }
        state->direct_out = 0;
    }
}

/*
 *
 * FSM functions
 *
 */

static int m_flush_block_resumable(struct aec_stream *strm)
{
    /**
       Slow and restartable flushing
    */
    struct internal_state *state = strm->state;

    int n = (int)MIN((size_t)(state->cds - state->cds_buf - state->i),
                     strm->avail_out);
    memcpy(strm->next_out, state->cds_buf + state->i, n);
    strm->next_out += n;
    strm->avail_out -= n;
    state->i += n;

    if (strm->avail_out == 0) {
        return M_EXIT;
    } else {
        state->mode = m_get_block;
        return M_CONTINUE;
    }
}

static int m_flush_block(struct aec_stream *strm)
{
    /**
       Flush block in direct_out mode by updating counters.

       Fall back to slow flushing if in buffered mode.
    */
    int n;
    struct internal_state *state = strm->state;

#ifdef ENABLE_RSI_PADDING
    if (state->blocks_avail == 0
        && strm->flags & AEC_PAD_RSI
        && state->block_nonzero == 0
        )
        emit(state, 0, state->bits % 8);
#endif

    if (state->direct_out) {
        n = (int)(state->cds - strm->next_out);
        strm->next_out += n;
        strm->avail_out -= n;
        state->mode = m_get_block;
        return M_CONTINUE;
    }

    state->i = 0;
    state->mode = m_flush_block_resumable;
    return M_CONTINUE;
}

static int m_encode_splitting(struct aec_stream *strm)
{
    struct internal_state *state = strm->state;
    int k = state->k;

    emit(state, k + 1, state->id_len);
    if (state->ref)
        emit(state, state->ref_sample, strm->bits_per_sample);

    emitblock_fs(strm, k, state->ref);
    if (k)
        emitblock(strm, k, state->ref);

    return m_flush_block(strm);
}

static int m_encode_uncomp(struct aec_stream *strm)
{
    struct internal_state *state = strm->state;

    emit(state, (1U << state->id_len) - 1, state->id_len);
    if (state->ref)
        state->block[0] = state->ref_sample;
    emitblock(strm, strm->bits_per_sample, 0);
    return m_flush_block(strm);
}

static int m_encode_se(struct aec_stream *strm)
{
    uint32_t i;
    uint32_t d;
    struct internal_state *state = strm->state;

    emit(state, 1, state->id_len + 1);
    if (state->ref)
        emit(state, state->ref_sample, strm->bits_per_sample);

    for (i = 0; i < strm->block_size; i+= 2) {
        d = state->block[i] + state->block[i + 1];
        emitfs(state, d * (d + 1) / 2 + state->block[i + 1]);
    }

    return m_flush_block(strm);
}

static int m_encode_zero(struct aec_stream *strm)
{
    struct internal_state *state = strm->state;

    emit(state, 0, state->id_len + 1);

    if (state->zero_ref)
        emit(state, state->zero_ref_sample, strm->bits_per_sample);

    if (state->zero_blocks == ROS)
        emitfs(state, 4);
    else if (state->zero_blocks >= 5)
        emitfs(state, state->zero_blocks);
    else
        emitfs(state, state->zero_blocks - 1);

    state->zero_blocks = 0;
    return m_flush_block(strm);
}

static int m_select_code_option(struct aec_stream *strm)
{
    /**
       Decide which code option to use.
    */

    uint32_t split_len;
    uint32_t se_len;
    struct internal_state *state = strm->state;

    if (state->id_len > 1)
        split_len = assess_splitting_option(strm);
    else
        split_len = UINT32_MAX;
    se_len = assess_se_option(strm);

    if (split_len < state->uncomp_len) {
        if (split_len < se_len)
            return m_encode_splitting(strm);
        else
            return m_encode_se(strm);
    } else {
        if (state->uncomp_len <= se_len)
            return m_encode_uncomp(strm);
        else
            return m_encode_se(strm);
    }
}

static int m_check_zero_block(struct aec_stream *strm)
{
    /**
       Check if input block is all zero.

       Aggregate consecutive zero blocks until we find !0 or reach the
       end of a segment or RSI.
    */

    uint32_t i;
    struct internal_state *state = strm->state;
    uint32_t *p = state->block;

    for (i = 0; i < strm->block_size; i++)
        if (p[i] != 0)
            break;

    if (i < strm->block_size) {
        if (state->zero_blocks) {
            /* The current block isn't zero but we have to emit a
             * previous zero block first. The current block will be
             * flagged and handled later.
             */
            state->block_nonzero = 1;
            state->mode = m_encode_zero;
            return M_CONTINUE;
        }
        state->mode = m_select_code_option;
        return M_CONTINUE;
    } else {
        state->zero_blocks++;
        if (state->zero_blocks == 1) {
            state->zero_ref = state->ref;
            state->zero_ref_sample = state->ref_sample;
        }
        if (state->blocks_avail == 0
            || (strm->rsi - state->blocks_avail) % 64 == 0) {
            if (state->zero_blocks > 4)
                state->zero_blocks = ROS;
            state->mode = m_encode_zero;
            return M_CONTINUE;
        }
        state->mode = m_get_block;
        return M_CONTINUE;
    }
}

static int m_get_rsi_resumable(struct aec_stream *strm)
{
    /**
       Get RSI while input buffer is short.

       Let user provide more input. Once we got all input pad buffer
       to full RSI.
    */

    struct internal_state *state = strm->state;

    do {
        if (strm->avail_in >= state->bytes_per_sample) {
            state->data_raw[state->i] = state->get_sample(strm);
        } else {
            if (state->flush == AEC_FLUSH) {
                if (state->i > 0) {
                    state->blocks_avail = state->i / strm->block_size - 1;
                    if (state->i % strm->block_size)
                        state->blocks_avail++;
                    do
                        state->data_raw[state->i] =
                            state->data_raw[state->i - 1];
                    while(++state->i < strm->rsi * strm->block_size);
                } else {
                    /* Finish encoding by padding the last byte with
                     * zero bits. */
                    emit(state, 0, state->bits);
                    if (strm->avail_out > 0) {
                        if (!state->direct_out)
                            *strm->next_out++ = *state->cds;
                        strm->avail_out--;
                        state->flushed = 1;
                    }
                    return M_EXIT;
                }
            } else {
                return M_EXIT;
            }
        }
    } while (++state->i < strm->rsi * strm->block_size);

    if (strm->flags & AEC_DATA_PREPROCESS)
        state->preprocess(strm);

    return m_check_zero_block(strm);
}

static int m_get_block(struct aec_stream *strm)
{
    /**
       Provide the next block of preprocessed input data.

       Pull in a whole Reference Sample Interval (RSI) of data if
       block buffer is empty.
    */

    struct internal_state *state = strm->state;

    init_output(strm);

    if (state->block_nonzero) {
        state->block_nonzero = 0;
        state->mode = m_select_code_option;
        return M_CONTINUE;
    }

    if (state->blocks_avail == 0) {
        state->blocks_avail = strm->rsi - 1;
        state->block = state->data_pp;

        if (strm->avail_in >= state->rsi_len) {
            state->get_rsi(strm);
            if (strm->flags & AEC_DATA_PREPROCESS)
                state->preprocess(strm);

            return m_check_zero_block(strm);
        } else {
            state->i = 0;
            state->mode = m_get_rsi_resumable;
        }
    } else {
        if (state->ref) {
            state->ref = 0;
            state->uncomp_len = strm->block_size * strm->bits_per_sample;
        }
        state->block += strm->block_size;
        state->blocks_avail--;
        return m_check_zero_block(strm);
    }
    return M_CONTINUE;
}

static void cleanup(struct aec_stream *strm)
{
    struct internal_state *state = strm->state;

    if (strm->flags & AEC_DATA_PREPROCESS && state->data_raw)
        free(state->data_raw);
    if (state->data_pp)
        free(state->data_pp);
    free(state);
}

/*
 *
 * API functions
 *
 */

int aec_encode_init(struct aec_stream *strm)
{
    struct internal_state *state;

    if (strm->bits_per_sample > 32 || strm->bits_per_sample == 0)
        return AEC_CONF_ERROR;

    if (strm->block_size != 8
        && strm->block_size != 16
        && strm->block_size != 32
        && strm->block_size != 64)
        return AEC_CONF_ERROR;

    if (strm->rsi > 4096)
        return AEC_CONF_ERROR;

    state = malloc(sizeof(struct internal_state));
    if (state == NULL)
        return AEC_MEM_ERROR;

    memset(state, 0, sizeof(struct internal_state));
    strm->state = state;
    state->uncomp_len = strm->block_size * strm->bits_per_sample;

    if (strm->bits_per_sample > 16) {
        /* 24/32 input bit settings */
        state->id_len = 5;

        if (strm->bits_per_sample <= 24
            && strm->flags & AEC_DATA_3BYTE) {
            state->bytes_per_sample = 3;
            if (strm->flags & AEC_DATA_MSB) {
                state->get_sample = aec_get_msb_24;
                state->get_rsi = aec_get_rsi_msb_24;
            } else {
                state->get_sample = aec_get_lsb_24;
                state->get_rsi = aec_get_rsi_lsb_24;
            }
        } else {
            state->bytes_per_sample = 4;
            if (strm->flags & AEC_DATA_MSB) {
                state->get_sample = aec_get_msb_32;
                state->get_rsi = aec_get_rsi_msb_32;
            } else {
                state->get_sample = aec_get_lsb_32;
                state->get_rsi = aec_get_rsi_lsb_32;
            }
        }
    }
    else if (strm->bits_per_sample > 8) {
        /* 16 bit settings */
        state->id_len = 4;
        state->bytes_per_sample = 2;

        if (strm->flags & AEC_DATA_MSB) {
            state->get_sample = aec_get_msb_16;
            state->get_rsi = aec_get_rsi_msb_16;
        } else {
            state->get_sample = aec_get_lsb_16;
            state->get_rsi = aec_get_rsi_lsb_16;
        }
    } else {
        /* 8 bit settings */
        if (strm->flags & AEC_RESTRICTED) {
            if (strm->bits_per_sample <= 4) {
                if (strm->bits_per_sample <= 2)
                    state->id_len = 1;
                else
                    state->id_len = 2;
            } else {
                return AEC_CONF_ERROR;
            }
        } else {
            state->id_len = 3;
        }
        state->bytes_per_sample = 1;

        state->get_sample = aec_get_8;
        state->get_rsi = aec_get_rsi_8;
    }
    state->rsi_len = strm->rsi * strm->block_size * state->bytes_per_sample;

    if (strm->flags & AEC_DATA_SIGNED) {
        state->xmax = (UINT64_C(1) << (strm->bits_per_sample - 1)) - 1;
        state->xmin = ~state->xmax;
        state->preprocess = preprocess_signed;
    } else {
        state->xmin = 0;
        state->xmax = (UINT64_C(1) << strm->bits_per_sample) - 1;
        state->preprocess = preprocess_unsigned;
    }

    state->kmax = (1U << state->id_len) - 3;

    state->data_pp = malloc(strm->rsi
                            * strm->block_size
                            * sizeof(uint32_t));
    if (state->data_pp == NULL) {
        cleanup(strm);
        return AEC_MEM_ERROR;
    }

    if (strm->flags & AEC_DATA_PREPROCESS) {
        state->data_raw = malloc(strm->rsi
                                 * strm->block_size
                                 * sizeof(uint32_t));
        if (state->data_raw == NULL) {
            cleanup(strm);
            return AEC_MEM_ERROR;
        }
    } else {
        state->data_raw = state->data_pp;
    }

    state->block = state->data_pp;

    state->ref = 0;
    strm->total_in = 0;
    strm->total_out = 0;
    state->flushed = 0;

    state->cds = state->cds_buf;
    *state->cds = 0;
    state->bits = 8;
    state->mode = m_get_block;

    return AEC_OK;
}

int aec_encode(struct aec_stream *strm, int flush)
{
    /**
       Finite-state machine implementation of the adaptive entropy
       encoder.
    */
    int n;
    struct internal_state *state = strm->state;

    state->flush = flush;
    strm->total_in += strm->avail_in;
    strm->total_out += strm->avail_out;

    while (state->mode(strm) == M_CONTINUE);

    if (state->direct_out) {
        n = (int)(state->cds - strm->next_out);
        strm->next_out += n;
        strm->avail_out -= n;

        *state->cds_buf = *state->cds;
        state->cds = state->cds_buf;
        state->direct_out = 0;
    }
    strm->total_in -= strm->avail_in;
    strm->total_out -= strm->avail_out;
    return AEC_OK;
}

int aec_encode_end(struct aec_stream *strm)
{
    struct internal_state *state = strm->state;
    int status;

    status = AEC_OK;
    if (state->flush == AEC_FLUSH && state->flushed == 0)
        status = AEC_STREAM_ERROR;
    cleanup(strm);
    return status;
}

int aec_buffer_encode(struct aec_stream *strm)
{
    int status;

    status = aec_encode_init(strm);
    if (status != AEC_OK)
        return status;
    status = aec_encode(strm, AEC_FLUSH);
    if (status != AEC_OK) {
        cleanup(strm);
        return status;
    }
    return aec_encode_end(strm);
}