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
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
//! This module contains functionality for doing lz77 compression of data.
#![macro_use]
use std::cmp;
use std::ops::{Range, RangeFrom};
use std::iter::{self, Iterator};
use std::slice::Iter;
use std::fmt;

use input_buffer::InputBuffer;
use matching::longest_match;
#[cfg(test)]
use lzvalue::{LZValue, LZType};
use huffman_table;
use chained_hash_table::ChainedHashTable;
#[cfg(test)]
use compression_options::{HIGH_MAX_HASH_CHECKS, HIGH_LAZY_IF_LESS_THAN};
use output_writer::{BufferStatus, DynamicWriter};
use compress::Flush;
use rle::process_chunk_greedy_rle;

const MAX_MATCH: usize = huffman_table::MAX_MATCH as usize;
const MIN_MATCH: usize = huffman_table::MIN_MATCH as usize;

const NO_RLE: u16 = 43212;

/// An enum describing whether we use lazy or greedy matching.
#[derive(Clone, Copy, Debug, Eq, PartialEq, Ord, PartialOrd, Hash)]
pub enum MatchingType {
    /// Use greedy matching: the matching algorithm simply uses a match right away
    /// if found.
    Greedy,
    /// Use lazy matching: after finding a match, the next input byte is checked, to see
    /// if there is a better match starting at that byte.
    ///
    /// As a special case, if max_hash_checks is set to 0, compression using only run-length
    /// (i.e maximum match distance of 1) is performed instead.
    Lazy,
}

impl fmt::Display for MatchingType {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            MatchingType::Greedy => write!(f, "Greedy matching"),
            MatchingType::Lazy => write!(f, "Lazy matching"),
        }
    }
}

/// A struct that contains the hash table, and keeps track of where we are in the input data
pub struct LZ77State {
    /// Struct containing hash chains that will be used to find matches.
    hash_table: ChainedHashTable,
    /// True if this is the first window that is being processed.
    is_first_window: bool,
    /// Set to true when the last block has been processed.
    is_last_block: bool,
    /// How many bytes the last match in the previous window extended into the current one.
    overlap: usize,
    /// How many bytes of input the current block contains.
    current_block_input_bytes: u64,
    /// The maximum number of hash entries to search.
    max_hash_checks: u16,
    /// Only lazy match if we have a match length less than this.
    lazy_if_less_than: u16,
    /// Whether to use greedy or lazy parsing
    matching_type: MatchingType,
    /// Keep track of the previous match and byte in case the buffer is full when lazy matching.
    match_state: ChunkState,
    /// Keep track of how many bytes in the lookahead that was part of a match, but has not been
    /// added to the hash chain yet.
    bytes_to_hash: usize,
    /// Keep track of if sync flush was used. If this is the case, the two first bytes needs to be
    /// hashed.
    was_synced: bool,
}

impl LZ77State {
    /// Creates a new LZ77 state
    pub fn new(
        max_hash_checks: u16,
        lazy_if_less_than: u16,
        matching_type: MatchingType,
    ) -> LZ77State {
        LZ77State {
            hash_table: ChainedHashTable::new(),
            is_first_window: true,
            is_last_block: false,
            overlap: 0,
            current_block_input_bytes: 0,
            max_hash_checks: max_hash_checks,
            lazy_if_less_than: lazy_if_less_than,
            matching_type: matching_type,
            match_state: ChunkState::new(),
            bytes_to_hash: 0,
            was_synced: false,
        }
    }

    /// Resets the state excluding max_hash_checks and lazy_if_less_than
    pub fn reset(&mut self) {
        self.hash_table.reset();
        self.is_first_window = true;
        self.is_last_block = false;
        self.overlap = 0;
        self.current_block_input_bytes = 0;
        self.match_state = ChunkState::new();
        self.bytes_to_hash = 0
    }

    pub fn set_last(&mut self) {
        self.is_last_block = true;
    }

    /// Is this the last block we are outputting?
    pub fn is_last_block(&self) -> bool {
        self.is_last_block
    }

    /// How many bytes of input the current block contains.
    pub fn current_block_input_bytes(&self) -> u64 {
        self.current_block_input_bytes
    }

    /// Sets the number of input bytes for the current block to 0.
    pub fn reset_input_bytes(&mut self) {
        self.current_block_input_bytes = 0;
    }

    /// Is there a buffered byte that has not been output yet?
    pub fn pending_byte(&self) -> bool {
        self.match_state.add
    }

    /// Returns 1 if pending_byte is true, 0 otherwise.
    pub fn pending_byte_as_num(&self) -> usize {
        // This could be implemented by using `as usize` as the documentation states this would give
        // the same result, but not sure if that should be relied upon.
        if self.match_state.add {
            1
        } else {
            0
        }
    }
}

const DEFAULT_WINDOW_SIZE: usize = 32768;

#[derive(Debug)]
/// Status after calling `process_chunk`.
pub enum ProcessStatus {
    /// All the input data was processed.
    Ok,
    /// The output buffer was full.
    ///
    /// The argument is the position of the next byte to be checked by `process_chunk`.
    BufferFull(usize),
}

#[derive(Debug)]
/// A struct to keep track of status between calls of `process_chunk_lazy`
///
/// This is needed as the output buffer might become full before having output all pending data.
pub struct ChunkState {
    /// Length of the last match that was found, if any.
    current_length: u16,
    /// Distance of the last match that was found, if any.
    current_distance: u16,
    /// The previous byte checked in process_chunk.
    prev_byte: u8,
    /// The current byte being checked in process_chunk.
    cur_byte: u8,
    /// Whether prev_byte still needs to be output.
    add: bool,
}

impl ChunkState {
    pub fn new() -> ChunkState {
        ChunkState {
            current_length: 0,
            current_distance: 0,
            prev_byte: 0,
            cur_byte: 0,
            add: false,
        }
    }
}

pub fn buffer_full(position: usize) -> ProcessStatus {
    ProcessStatus::BufferFull(position)
}

fn process_chunk(
    data: &[u8],
    iterated_data: &Range<usize>,
    mut match_state: &mut ChunkState,
    hash_table: &mut ChainedHashTable,
    writer: &mut DynamicWriter,
    max_hash_checks: u16,
    lazy_if_less_than: usize,
    matching_type: MatchingType,
) -> (usize, ProcessStatus) {
    let avoid_rle = if cfg!(test) {
        // Avoid RLE if lazy_if_less than is a specific value.
        // This is used in some tests, ideally we should probably do this in a less clunky way,
        // but we use a value here that is higher than the maximum sensible one anyhow, and will
        // be truncated by deflate_state for calls from outside the library.
        lazy_if_less_than == NO_RLE as usize
    } else {
        false
    };
    match matching_type {
        MatchingType::Greedy => {
            process_chunk_greedy(data, iterated_data, hash_table, writer, max_hash_checks)
        }
        MatchingType::Lazy => {
            if max_hash_checks > 0 || avoid_rle {
                process_chunk_lazy(
                    data,
                    iterated_data,
                    &mut match_state,
                    hash_table,
                    writer,
                    max_hash_checks,
                    lazy_if_less_than,
                )
            } else {
                // Use the RLE method if max_hash_checks is set to 0.
                process_chunk_greedy_rle(data, iterated_data, writer)
            }
        }
    }
}

/// Add the specified number of bytes to the hash table from the iterators
/// adding `start` to the position supplied to the hash table.
fn add_to_hash_table(
    bytes_to_add: usize,
    pos_of_first_byte: usize,
    insert_it: &mut iter::Zip<RangeFrom<usize>, Iter<u8>>, //Enumerate<Iter<u8>>,
    hash_it: &mut Iter<u8>,
    hash_table: &mut ChainedHashTable,
) {
    let taker = insert_it.by_ref().take(bytes_to_add).enumerate();
    let mut hash_taker = hash_it.by_ref().take(bytes_to_add);
    // Advance the iterators and add the bytes we jump over to the hash table and
    // checksum
    for (ipos, _) in taker {
        if let Some(&i_hash_byte) = hash_taker.next() {
            hash_table.add_hash_value(ipos + pos_of_first_byte, i_hash_byte);
        }
    }
}

/// Write the specified literal `byte` to the writer `w`, and return
/// `ProcessStatus::BufferFull($pos)` if the buffer is full after writing.
///
/// `pos` should indicate the byte to start at in the next call to `process_chunk`,
/// `is_hashed` should be set to true of the byte at pos has been added to the hash chain.
macro_rules! write_literal{
    ($w:ident, $byte:expr, $pos:expr) => {
        let b_status = $w.write_literal($byte);

        if let BufferStatus::Full = b_status {
            return (0, buffer_full($pos));
        }
    };
}

/// If the match is only 3 bytes long and the distance is more than 8 * 1024, it's likely to take
/// up more space than it would save.
#[inline]
fn match_too_far(match_len: usize, match_dist: usize) -> bool {
    const TOO_FAR: usize = 8 * 1024;
    match_len == MIN_MATCH && match_dist > TOO_FAR
}

///Create the iterators used when processing through a chunk of data.
fn create_iterators<'a>(
    data: &'a [u8],
    iterated_data: &Range<usize>,
) -> (
    usize,
    iter::Zip<RangeFrom<usize>, Iter<'a, u8>>,
    Iter<'a, u8>,
) {
    let end = cmp::min(data.len(), iterated_data.end);
    let start = iterated_data.start;
    let current_chunk = &data[start..end];

    let insert_it = (start..).zip(current_chunk.iter());
    let hash_it = {
        let hash_start = if data.len() - start > 2 {
            start + 2
        } else {
            data.len()
        };
        (&data[hash_start..]).iter()
    };
    (end, insert_it, hash_it)
}

fn process_chunk_lazy(
    data: &[u8],
    iterated_data: &Range<usize>,
    state: &mut ChunkState,
    mut hash_table: &mut ChainedHashTable,
    writer: &mut DynamicWriter,
    max_hash_checks: u16,
    lazy_if_less_than: usize,
) -> (usize, ProcessStatus) {

    let (end, mut insert_it, mut hash_it) = create_iterators(data, iterated_data);

    const NO_LENGTH: u16 = 0;

    // The previous match length, if any.
    let mut prev_length = state.current_length;
    // The distance of the previous match if any.
    let mut prev_distance = state.current_distance;

    state.current_length = 0;
    state.current_distance = 0;

    // The number of bytes past end that was added due to finding a match that extends into
    // the lookahead window.
    let mut overlap = 0;


    // Set to true if we found a match that is equal to or longer than `lazy_if_less_than`,
    // indicating that we won't lazy match (check for a better match at the next byte).
    // If we had a good match, carry this over from the previous call.
    let mut ignore_next = prev_length as usize >= lazy_if_less_than;

    // This is to output the correct byte in case there is one pending to be output
    // from the previous call.
    state.prev_byte = state.cur_byte;

    // Iterate through the slice, adding literals or length/distance pairs
    while let Some((position, &b)) = insert_it.next() {
        state.cur_byte = b;
        if let Some(&hash_byte) = hash_it.next() {
            hash_table.add_hash_value(position, hash_byte);

            // Only lazy match if we have a match shorter than a set value
            // TODO: This should be cleaned up a bit
            if !ignore_next {
                let (mut match_len, match_dist) = {
                    // If there already was a decent match at the previous byte
                    // and we are lazy matching, do less match checks in this step.
                    let max_hash_checks = if prev_length >= 32 {
                        max_hash_checks >> 2
                    } else {
                        max_hash_checks
                    };

                    // Check if we can find a better match here than the one we had at
                    // the previous byte.
                    longest_match(
                        data,
                        hash_table,
                        position,
                        prev_length as usize,
                        max_hash_checks,
                    )
                };

                // If the match is only 3 bytes long and very far back, it's probably not worth
                // outputting.
                if match_too_far(match_len, match_dist) {
                    match_len = NO_LENGTH as usize;
                };

                if match_len >= lazy_if_less_than {
                    // We found a decent match, so we won't check for a better one at the next byte.
                    ignore_next = true;
                }
                state.current_length = match_len as u16;
                state.current_distance = match_dist as u16;
            } else {
                // We already had a decent match, so we don't bother checking for another one.
                state.current_length = NO_LENGTH;
                state.current_distance = 0;
                // Make sure we check again next time.
                ignore_next = false;
            };

            if prev_length >= state.current_length && prev_length >= MIN_MATCH as u16 {
                // The previous match was better so we add it.
                // Casting note: length and distance is already bounded by the longest match
                // function. Usize is just used for convenience.
                let b_status =
                    writer.write_length_distance(prev_length as u16, prev_distance as u16);

                // We add the bytes to the hash table and checksum.
                // Since we've already added two of them, we need to add two less than
                // the length.
                let bytes_to_add = prev_length - 2;

                add_to_hash_table(
                    bytes_to_add as usize,
                    position + 1,
                    &mut insert_it,
                    &mut hash_it,
                    &mut hash_table,
                );

                // If the match is longer than the current window, we have note how many
                // bytes we overlap, since we don't need to do any matching on these bytes
                // in the next call of this function.
                // We don't have to worry about setting overlap to 0 if this is false, as the
                // function will stop after this condition is true, and overlap is not altered
                // elsewhere.
                if position + prev_length as usize > end {
                    // We need to subtract 1 since the byte at pos is also included.
                    overlap = position + prev_length as usize - end - 1;
                };

                state.add = false;

                // Note that there is no current match.
                state.current_length = 0;
                state.current_distance = 0;

                if let BufferStatus::Full = b_status {
                    // MATCH(lazy)
                    return (overlap, buffer_full(position + prev_length as usize - 1));
                }

                ignore_next = false;

            } else if state.add {
                // We found a better match (or there was no previous match)
                // so output the previous byte.
                // BETTER OR NO MATCH
                write_literal!(writer, state.prev_byte, position + 1);
            } else {
                state.add = true
            }

            prev_length = state.current_length;
            prev_distance = state.current_distance;
            state.prev_byte = b;
        } else {
            // If there is a match at this point, it will not have been added, so we need to add it.
            if prev_length >= MIN_MATCH as u16 {
                let b_status =
                    writer.write_length_distance(prev_length as u16, prev_distance as u16);

                state.current_length = 0;
                state.current_distance = 0;
                state.add = false;

                // As this will be a 3-length match at the end of the input data, there can't be any
                // overlap.
                // TODO: Not sure if we need to signal that the buffer is full here.
                // It's only needed in the case of syncing.
                if let BufferStatus::Full = b_status {
                    // TODO: These bytes should be hashed when doing a sync flush.
                    // This can't be done here as the new input data does not exist yet.
                    return (0, buffer_full(end));
                } else {
                    return (0, ProcessStatus::Ok);
                }
            };

            if state.add {
                // We may still have a leftover byte at this point, so we add it here if needed.
                state.add = false;

                // ADD
                write_literal!(writer, state.prev_byte, position + 1);

            };

            // We are at the last two bytes we want to add, so there is no point
            // searching for matches here.

            // AFTER ADD
            write_literal!(writer, b, position + 1);
        }
    }
    (overlap, ProcessStatus::Ok)
}

fn process_chunk_greedy(
    data: &[u8],
    iterated_data: &Range<usize>,
    mut hash_table: &mut ChainedHashTable,
    writer: &mut DynamicWriter,
    max_hash_checks: u16,
) -> (usize, ProcessStatus) {

    let (end, mut insert_it, mut hash_it) = create_iterators(data, iterated_data);

    const NO_LENGTH: usize = 0;

    // The number of bytes past end that was added due to finding a match that extends into
    // the lookahead window.
    let mut overlap = 0;

    // Iterate through the slice, adding literals or length/distance pairs.
    while let Some((position, &b)) = insert_it.next() {
        if let Some(&hash_byte) = hash_it.next() {
            hash_table.add_hash_value(position, hash_byte);

            // TODO: This should be cleaned up a bit.
            let (match_len, match_dist) =
                { longest_match(data, hash_table, position, NO_LENGTH, max_hash_checks) };

            if match_len >= MIN_MATCH as usize && !match_too_far(match_len, match_dist) {
                // Casting note: length and distance is already bounded by the longest match
                // function. Usize is just used for convenience.
                let b_status = writer.write_length_distance(match_len as u16, match_dist as u16);

                // We add the bytes to the hash table and checksum.
                // Since we've already added one of them, we need to add one less than
                // the length.
                let bytes_to_add = match_len - 1;
                add_to_hash_table(
                    bytes_to_add,
                    position + 1,
                    &mut insert_it,
                    &mut hash_it,
                    &mut hash_table,
                );

                // If the match is longer than the current window, we have note how many
                // bytes we overlap, since we don't need to do any matching on these bytes
                // in the next call of this function.
                if position + match_len > end {
                    // We need to subtract 1 since the byte at pos is also included.
                    overlap = position + match_len - end;
                };

                if let BufferStatus::Full = b_status {
                    // MATCH
                    return (overlap, buffer_full(position + match_len));
                }

            } else {
                // NO MATCH
                write_literal!(writer, b, position + 1);
            }
        } else {
            // We are at the last two bytes we want to add, so there is no point
            // searching for matches here.
            // END
            write_literal!(writer, b, position + 1);
        }
    }
    (overlap, ProcessStatus::Ok)
}


#[derive(Eq, PartialEq, Clone, Copy, Debug)]
pub enum LZ77Status {
    /// Waiting for more input before doing any processing
    NeedInput,
    /// The output buffer is full, so the current block needs to be ended so the
    /// buffer can be flushed.
    EndBlock,
    /// All pending data has been processed.
    Finished,
}

#[cfg(test)]
pub fn lz77_compress_block_finish(
    data: &[u8],
    state: &mut LZ77State,
    buffer: &mut InputBuffer,
    mut writer: &mut DynamicWriter,
) -> (usize, LZ77Status) {
    let (consumed, status, _) =
        lz77_compress_block(data, state, buffer, &mut writer, Flush::Finish);
    (consumed, status)
}

/// Compress a slice with lz77 compression.
///
/// This function processes one window at a time, and returns when there is no input left,
/// or it determines it's time to end a block.
///
/// Returns the number of bytes of the input that were consumed, a status describing
/// whether there is no input, it's time to finish, or it's time to end the block, and the position
/// of the first byte in the input buffer that has not been output (but may have been checked for
/// matches).
pub fn lz77_compress_block(
    data: &[u8],
    state: &mut LZ77State,
    buffer: &mut InputBuffer,
    mut writer: &mut DynamicWriter,
    flush: Flush,
) -> (usize, LZ77Status, usize) {
    // Currently we only support the maximum window size
    let window_size = DEFAULT_WINDOW_SIZE;

    // Indicates whether we should try to process all the data including the lookahead, or if we
    // should wait until we have at least one window size of data before doing anything.
    let finish = flush == Flush::Finish || flush == Flush::Sync;
    let sync = flush == Flush::Sync;

    let mut current_position = 0;

    // The current status of the encoding.
    let mut status = LZ77Status::EndBlock;

    // Whether warm up the hash chain with the two first values.
    let mut add_initial = true;

    // If we have synced, add the two first bytes to the hash as they couldn't be added before.
    if state.was_synced {
        if buffer.current_end() > 2 {
            let pos_add = buffer.current_end() - 2;
            for (n, &b) in data.iter().take(2).enumerate() {
                state.hash_table.add_hash_value(n + pos_add, b);
            }
            add_initial = false;
        }
        state.was_synced = false;
    }

    // Add data to the input buffer and keep a reference to the slice of data not added yet.
    let mut remaining_data = buffer.add_data(data);

    loop {
        // Note if there is a pending byte from the previous call to process_chunk,
        // so we get the block input size right.
        let pending_previous = state.pending_byte_as_num();

        assert!(writer.buffer_length() <= (window_size * 2));
        // The process is a bit different for the first 32k bytes.
        // TODO: There is a lot of duplicate code between the two branches here, we should be able
        // to simplify this.
        if state.is_first_window {
            // Don't do anything until we are either flushing, or we have at least one window of
            // data.
            if buffer.current_end() >= (window_size * 2) + MAX_MATCH || finish {

                if buffer.get_buffer().len() >= 2 && add_initial &&
                    state.current_block_input_bytes == 0
                {
                    let b = buffer.get_buffer();
                    // Warm up the hash with the two first values, so we can find  matches at
                    // index 0.
                    state.hash_table.add_initial_hash_values(b[0], b[1]);
                    add_initial = false;
                }

                let first_chunk_end = cmp::min(window_size, buffer.current_end());

                let start = state.overlap;

                let (overlap, p_status) = process_chunk(
                    buffer.get_buffer(),
                    &(start..first_chunk_end),
                    &mut state.match_state,
                    &mut state.hash_table,
                    &mut writer,
                    state.max_hash_checks,
                    state.lazy_if_less_than as usize,
                    state.matching_type,
                );

                state.overlap = overlap;
                state.bytes_to_hash = overlap;

                // If the buffer is full, we want to end the block.
                if let ProcessStatus::BufferFull(written) = p_status {
                    state.overlap = if overlap > 0 { overlap } else { written };
                    status = LZ77Status::EndBlock;
                    current_position = written - state.pending_byte_as_num();
                    state.current_block_input_bytes +=
                        (written - start + overlap + pending_previous -
                             state.pending_byte_as_num()) as u64;
                    break;
                }


                // Update the length of how many input bytes the current block is representing,
                // taking into account pending bytes.
                state.current_block_input_bytes +=
                    (first_chunk_end - start + overlap + pending_previous -
                         state.pending_byte_as_num()) as u64;

                // We are at the first window so we don't need to slide the hash table yet.
                // If finishing or syncing, we stop here.
                if first_chunk_end >= buffer.current_end() && finish {
                    current_position = first_chunk_end - state.pending_byte_as_num();
                    if !sync {
                        state.set_last();
                        state.is_first_window = false;
                    } else {
                        state.overlap = first_chunk_end;
                        state.was_synced = true;
                    }
                    debug_assert!(
                        !state.pending_byte(),
                        "Bug! Ended compression wit a pending byte!"
                    );
                    status = LZ77Status::Finished;
                    break;
                }
                // Otherwise, continue.
                state.is_first_window = false;
            } else {
                status = LZ77Status::NeedInput;
                break;
            }
        } else if buffer.current_end() >= (window_size * 2) + MAX_MATCH || finish {
            if buffer.current_end() >= window_size + 2 {
                for (n, &h) in buffer.get_buffer()[window_size + 2..]
                    .iter()
                    .enumerate()
                    .take(state.bytes_to_hash)
                {
                    state.hash_table.add_hash_value(window_size + n, h);
                }
                state.bytes_to_hash = 0;
            }
            // This isn't the first chunk, so we start reading at one window in in the
            // buffer plus any additional overlap from earlier.
            let start = window_size + state.overlap;

            // Determine where we have to stop iterating to slide the buffer and hash,
            // or stop because we are at the end of the input data.
            let end = cmp::min(window_size * 2, buffer.current_end());

            let (overlap, p_status) = process_chunk(
                buffer.get_buffer(),
                &(start..end),
                &mut state.match_state,
                &mut state.hash_table,
                &mut writer,
                state.max_hash_checks,
                state.lazy_if_less_than as usize,
                state.matching_type,
            );

            state.bytes_to_hash = overlap;


            if let ProcessStatus::BufferFull(written) = p_status {
                state.current_block_input_bytes +=
                    (written - start + pending_previous - state.pending_byte_as_num()) as u64;

                // If the buffer is full, return and end the block.
                // If overlap is non-zero, the buffer was full after outputting the last byte,
                // otherwise we have to skip to the point in the buffer where we stopped in the
                // next call.
                state.overlap = if overlap > 0 {
                    // If we are at the end of the window, make sure we slide the buffer and the
                    // hash table.
                    if state.max_hash_checks > 0 {
                        state.hash_table.slide(window_size);
                    }
                    remaining_data = buffer.slide(remaining_data.unwrap_or(&[]));
                    overlap
                } else {
                    written - window_size
                };

                current_position = written - state.pending_byte_as_num();


                // Status is already EndBlock at this point.
                // status = LZ77Status::EndBlock;
                break;
            }

            state.current_block_input_bytes +=
                (end - start + overlap + pending_previous - state.pending_byte_as_num()) as u64;

            // The buffer is not full, but we still need to note if there is any overlap into the
            // next window.
            state.overlap = overlap;

            if remaining_data.is_none() && finish && end == buffer.current_end() {
                current_position = buffer.current_end();
                debug_assert!(
                    !state.pending_byte(),
                    "Bug! Ended compression wit a pending byte!"
                );

                // We stopped before or at the window size, so we are at the end.
                if !sync {
                    // If we are finishing and not syncing, we simply indicate that we are done.
                    state.set_last();
                } else {
                    // For sync flushing we need to slide the buffer and the hash chains so that the
                    // next call to this function starts at the right place.

                    // There won't be any overlap, since when syncing, we process to the end of the.
                    // pending data.
                    state.overlap = buffer.current_end() - window_size;
                    state.was_synced = true;
                }
                status = LZ77Status::Finished;
                break;
            } else {
                // We are not at the end, so slide and continue.
                // We slide the hash table back to make space for new hash values
                // We only need to remember 2^15 bytes back (the maximum distance allowed by the
                // deflate spec).
                if state.max_hash_checks > 0 {
                    state.hash_table.slide(window_size);
                }

                // Also slide the buffer, discarding data we no longer need and adding new data.
                remaining_data = buffer.slide(remaining_data.unwrap_or(&[]));
            }
        } else {
            // The caller has not indicated that they want to finish or flush, and there is less
            // than a window + lookahead of new data, so we wait for more.
            status = LZ77Status::NeedInput;
            break;
        }

    }

    (
        data.len() - remaining_data.unwrap_or(&[]).len(),
        status,
        current_position,
    )
}

#[cfg(test)]
pub fn decompress_lz77(input: &[LZValue]) -> Vec<u8> {
    decompress_lz77_with_backbuffer(input, &[])
}

#[cfg(test)]
pub fn decompress_lz77_with_backbuffer(input: &[LZValue], back_buffer: &[u8]) -> Vec<u8> {
    let mut output = Vec::new();
    for p in input {
        match p.value() {
            LZType::Literal(l) => output.push(l),
            LZType::StoredLengthDistance(l, d) => {
                // We found a match, so we have to get the data that the match refers to.
                let d = d as usize;
                let prev_output_len = output.len();
                // Get match data from the back buffer if the match extends that far.
                let consumed = if d > output.len() {
                    let into_back_buffer = d - output.len();

                    assert!(
                        into_back_buffer <= back_buffer.len(),
                        "ERROR: Attempted to refer to a match in non-existing data!\
                         into_back_buffer: {}, back_buffer len {}, d {}, l {:?}",
                        into_back_buffer,
                        back_buffer.len(),
                        d,
                        l
                    );
                    let start = back_buffer.len() - into_back_buffer;
                    let end = cmp::min(back_buffer.len(), start + l.actual_length() as usize);
                    output.extend_from_slice(&back_buffer[start..end]);

                    end - start
                } else {
                    0
                };

                // Get match data from the currently decompressed data.
                let start = prev_output_len.saturating_sub(d);
                let mut n = 0;
                while n < (l.actual_length() as usize).saturating_sub(consumed) {
                    let b = output[start + n];
                    output.push(b);
                    n += 1;
                }
            }
        }
    }
    output
}

#[cfg(test)]
pub struct TestStruct {
    state: LZ77State,
    buffer: InputBuffer,
    writer: DynamicWriter,
}

#[cfg(test)]
impl TestStruct {
    fn new() -> TestStruct {
        TestStruct::with_config(
            HIGH_MAX_HASH_CHECKS,
            HIGH_LAZY_IF_LESS_THAN,
            MatchingType::Lazy,
        )
    }

    fn with_config(
        max_hash_checks: u16,
        lazy_if_less_than: u16,
        matching_type: MatchingType,
    ) -> TestStruct {
        TestStruct {
            state: LZ77State::new(max_hash_checks, lazy_if_less_than, matching_type),
            buffer: InputBuffer::empty(),
            writer: DynamicWriter::new(),
        }
    }

    fn compress_block(&mut self, data: &[u8], flush: bool) -> (usize, LZ77Status, usize) {
        lz77_compress_block(
            data,
            &mut self.state,
            &mut self.buffer,
            &mut self.writer,
            if flush { Flush::Finish } else { Flush::None },
        )
    }
}

#[cfg(test)]
pub fn lz77_compress(data: &[u8]) -> Option<Vec<LZValue>> {
    lz77_compress_conf(
        data,
        HIGH_MAX_HASH_CHECKS,
        HIGH_LAZY_IF_LESS_THAN,
        MatchingType::Lazy,
    )
}

/// Compress a slice, not storing frequency information
///
/// This is a convenience function for compression with fixed huffman values
/// Only used in tests for now
#[cfg(test)]
pub fn lz77_compress_conf(
    data: &[u8],
    max_hash_checks: u16,
    lazy_if_less_than: u16,
    matching_type: MatchingType,
) -> Option<Vec<LZValue>> {
    let mut test_boxed = Box::new(TestStruct::with_config(
        max_hash_checks,
        lazy_if_less_than,
        matching_type,
    ));
    let mut out = Vec::<LZValue>::with_capacity(data.len() / 3);
    {
        let mut test = test_boxed.as_mut();
        let mut slice = data;

        while !test.state.is_last_block {
            let bytes_written = lz77_compress_block_finish(
                slice,
                &mut test.state,
                &mut test.buffer,
                &mut test.writer,
            ).0;
            slice = &slice[bytes_written..];
            out.extend(test.writer.get_buffer());
            test.writer.clear();
        }

    }

    Some(out)
}

#[cfg(test)]
mod test {
    use super::*;

    use lzvalue::{LZValue, LZType, lit, ld};
    use chained_hash_table::WINDOW_SIZE;
    use compression_options::DEFAULT_LAZY_IF_LESS_THAN;
    use test_utils::get_test_data;
    use output_writer::MAX_BUFFER_LENGTH;

    /// Helper function to print the output from the lz77 compression function
    fn print_output(input: &[LZValue]) {
        let mut output = vec![];
        for l in input {
            match l.value() {
                LZType::Literal(l) => output.push(l),
                LZType::StoredLengthDistance(l, d) => {
                    output.extend(format!("<L {}>", l.actual_length()).into_bytes());
                    output.extend(format!("<D {}>", d).into_bytes())
                }
            }
        }

        println!("\"{}\"", String::from_utf8(output).unwrap());
    }

    /// Test that a short string from an example on SO compresses correctly
    #[test]
    fn compress_short() {
        use std::str;

        let test_bytes = String::from("Deflate late").into_bytes();
        let res = lz77_compress(&test_bytes).unwrap();

        let decompressed = decompress_lz77(&res);

        assert_eq!(test_bytes, decompressed);
        assert_eq!(*res.last().unwrap(), LZValue::length_distance(4, 5));
    }

    /// Test that compression is working for a longer file
    #[test]
    fn compress_long() {
        use std::str;
        let input = get_test_data();
        let compressed = lz77_compress(&input).unwrap();
        assert!(compressed.len() < input.len());

        let decompressed = decompress_lz77(&compressed);
        println!("compress_long length: {}", input.len());

        // This is to check where the compression fails, if it were to
        for (n, (&a, &b)) in input.iter().zip(decompressed.iter()).enumerate() {
            if a != b {
                println!("First difference at {}, input: {}, output: {}", n, a, b);
                break;
            }
        }
        assert_eq!(input.len(), decompressed.len());
        assert!(&decompressed == &input);
    }

    /// Check that lazy matching is working as intended
    #[test]
    fn lazy() {
        // We want to match on `badger` rather than `nba` as it is longer
        // let data = b" nba nbadg badger nbadger";
        let data = b"nba badger nbadger";
        let compressed = lz77_compress(data).unwrap();
        let test = compressed[compressed.len() - 1];
        if let LZType::StoredLengthDistance(l, _) = test.value() {
            assert_eq!(l.actual_length(), 6);
        } else {
            print_output(&compressed);
            panic!();
        }
    }

    fn roundtrip(data: &[u8]) {
        let compressed = super::lz77_compress(&data).unwrap();
        let decompressed = decompress_lz77(&compressed);
        assert!(decompressed == data);
    }

    // Check that data with the exact window size is working properly
    #[test]
    #[allow(unused)]
    fn exact_window_size() {
        use std::io::Write;
        let mut data = vec![0; WINDOW_SIZE];
        roundtrip(&data);
        {
            data.write(&[22; WINDOW_SIZE]);
        }
        roundtrip(&data);
        {
            data.write(&[55; WINDOW_SIZE]);
        }
        roundtrip(&data);
    }

    /// Test that matches at the window border are working correctly
    #[test]
    fn border() {
        use chained_hash_table::WINDOW_SIZE;
        let mut data = vec![35; WINDOW_SIZE];
        data.extend(b"Test");
        let compressed = super::lz77_compress(&data).unwrap();
        assert!(compressed.len() < data.len());
        let decompressed = decompress_lz77(&compressed);

        assert_eq!(decompressed.len(), data.len());
        assert!(decompressed == data);
    }

    #[test]
    fn border_multiple_blocks() {
        use chained_hash_table::WINDOW_SIZE;
        let mut data = vec![0; (WINDOW_SIZE * 2) + 50];
        data.push(1);
        let compressed = super::lz77_compress(&data).unwrap();
        assert!(compressed.len() < data.len());
        let decompressed = decompress_lz77(&compressed);
        assert_eq!(decompressed.len(), data.len());
        assert!(decompressed == data);
    }

    #[test]
    fn compress_block_status() {
        use input_buffer::InputBuffer;

        let data = b"Test data data";
        let mut writer = DynamicWriter::new();

        let mut buffer = InputBuffer::empty();
        let mut state = LZ77State::new(4096, DEFAULT_LAZY_IF_LESS_THAN, MatchingType::Lazy);
        let status = lz77_compress_block_finish(data, &mut state, &mut buffer, &mut writer);
        assert_eq!(status.1, LZ77Status::Finished);
        assert!(&buffer.get_buffer()[..data.len()] == data);
        assert_eq!(buffer.current_end(), data.len());
    }

    #[test]
    fn compress_block_multiple_windows() {
        use input_buffer::InputBuffer;
        use output_writer::DynamicWriter;

        let data = get_test_data();
        assert!(data.len() > (WINDOW_SIZE * 2) + super::MAX_MATCH);
        let mut writer = DynamicWriter::new();

        let mut buffer = InputBuffer::empty();
        let mut state = LZ77State::new(0, DEFAULT_LAZY_IF_LESS_THAN, MatchingType::Lazy);
        let (bytes_consumed, status) =
            lz77_compress_block_finish(&data, &mut state, &mut buffer, &mut writer);
        assert_eq!(
            buffer.get_buffer().len(),
            (WINDOW_SIZE * 2) + super::MAX_MATCH
        );
        assert_eq!(status, LZ77Status::EndBlock);
        let buf_len = buffer.get_buffer().len();
        assert!(buffer.get_buffer()[..] == data[..buf_len]);

        writer.clear();
        let (_, status) = lz77_compress_block_finish(
            &data[bytes_consumed..],
            &mut state,
            &mut buffer,
            &mut writer,
        );
        assert_eq!(status, LZ77Status::EndBlock);

    }

    #[test]
    fn multiple_inputs() {
        let data = b"Badger badger bababa test data 25 asfgestghresjkgh";
        let comp1 = lz77_compress(data).unwrap();
        let comp2 = {
            const SPLIT: usize = 25;
            let first_part = &data[..SPLIT];
            let second_part = &data[SPLIT..];
            let mut state = TestStruct::new();
            let (bytes_written, status, _) = state.compress_block(first_part, false);
            assert_eq!(bytes_written, first_part.len());
            assert_eq!(status, LZ77Status::NeedInput);
            let (bytes_written, status, _) = state.compress_block(second_part, true);
            assert_eq!(bytes_written, second_part.len());
            assert_eq!(status, LZ77Status::Finished);
            Vec::from(state.writer.get_buffer())
        };
        assert!(comp1 == comp2);
    }


    #[test]
    /// Test that the exit from process_chunk when buffer is full is working correctly.
    fn buffer_fill() {
        let data = get_test_data();
        // The comments above these calls refers the positions with the
        // corersponding comments in process_chunk_{greedy/lazy}.
        // POS BETTER OR NO MATCH
        buffer_test_literals(&data);
        // POS END
        // POS NO MATCH
        buffer_test_last_bytes(MatchingType::Greedy, &data);
        // POS ADD
        // POS AFTER ADD
        buffer_test_last_bytes(MatchingType::Lazy, &data);

        // POS MATCH
        buffer_test_match(MatchingType::Greedy);
        // POS MATCH(lazy)
        buffer_test_match(MatchingType::Lazy);

        // POS END
        buffer_test_add_end(&data);
    }

    /// Test buffer fill when a byte is added due to no match being found.
    fn buffer_test_literals(data: &[u8]) {
        let mut state = TestStruct::with_config(0, NO_RLE, MatchingType::Lazy);
        let (bytes_consumed, status, position) = state.compress_block(&data, false);

        // There should be enough data for the block to have ended.
        assert_eq!(status, LZ77Status::EndBlock);
        assert!(bytes_consumed <= (WINDOW_SIZE * 2) + MAX_MATCH);

        // The buffer should be full.
        assert_eq!(state.writer.get_buffer().len(), MAX_BUFFER_LENGTH);
        assert_eq!(position, state.writer.get_buffer().len());
        // Since all literals have been input, the block should have the exact number of litlens
        // as there were input bytes.
        assert_eq!(
            state.state.current_block_input_bytes() as usize,
            MAX_BUFFER_LENGTH
        );
        state.state.reset_input_bytes();

        let mut out = decompress_lz77(state.writer.get_buffer());

        state.writer.clear();
        // The buffer should now be cleared.
        assert_eq!(state.writer.get_buffer().len(), 0);

        assert!(data[..out.len()] == out[..]);

        let _ = state.compress_block(&data[bytes_consumed..], false);
        // We should have some new data in the buffer at this point.
        assert!(state.writer.get_buffer().len() > 0);
        assert_eq!(
            state.state.current_block_input_bytes() as usize,
            MAX_BUFFER_LENGTH
        );

        out.extend_from_slice(&decompress_lz77(state.writer.get_buffer()));
        assert!(data[..out.len()] == out[..]);
    }

    /// Test buffer fill at the last two bytes that are not hashed.
    fn buffer_test_last_bytes(matching_type: MatchingType, data: &[u8]) {
        const BYTES_USED: usize = MAX_BUFFER_LENGTH;
        assert!(
            &data[..BYTES_USED] ==
                &decompress_lz77(&lz77_compress_conf(
                    &data[..BYTES_USED],
                    0,
                    NO_RLE,
                    matching_type,
                ).unwrap())
                    [..]
        );
        assert!(
            &data[..BYTES_USED + 1] ==
                &decompress_lz77(&lz77_compress_conf(
                    &data[..BYTES_USED + 1],
                    0,
                    NO_RLE,
                    matching_type,
                ).unwrap())
                    [..]
        );
    }

    /// Test buffer fill when buffer is full at a match.
    fn buffer_test_match(matching_type: MatchingType) {
        // TODO: Also test this for the second block to make sure
        // buffer is slid.
        let mut state = TestStruct::with_config(1, 0, matching_type);
        for _ in 0..MAX_BUFFER_LENGTH - 4 {
            assert!(state.writer.write_literal(0) == BufferStatus::NotFull);
        }
        state.compress_block(&[1, 2, 3, 1, 2, 3, 4], true);
        assert!(*state.writer.get_buffer().last().unwrap() == LZValue::length_distance(3, 3));

    }

    /// Test buffer fill for the lazy match algorithm when adding a pending byte at the end.
    fn buffer_test_add_end(_data: &[u8]) {
        // This is disabled while the buffer size has not been stabilized.
        /*
        let mut state = TestStruct::with_config(DEFAULT_MAX_HASH_CHECKS,
                                                DEFAULT_LAZY_IF_LESS_THAN,
                                                MatchingType::Lazy);
        // For the test file, this is how much data needs to be added to get the buffer
        // full at the right spot to test that this buffer full exit is workong correctly.
        for i in 0..31743 {
            assert!(state.writer.write_literal(0) == BufferStatus::NotFull, "Buffer pos: {}", i);
        }

        let dec = decompress_lz77(&state.writer.get_buffer()[pos..]);
        assert!(dec.len() > 0);
        assert!(dec[..] == data[..dec.len()]);
         */
    }

    /// Check that decompressing lz77-data that refers to the back-buffer works.
    #[test]
    fn test_decompress_with_backbuffer() {
        let bb = vec![5; WINDOW_SIZE];
        let lz_compressed = [lit(2), lit(4), ld(4, 20), lit(1), lit(1), ld(5, 10)];
        let dec = decompress_lz77_with_backbuffer(&lz_compressed, &bb);

        // ------------l2 l4  <-ld4,20-> l1 l1  <---ld5,10-->
        assert!(dec == [2, 4, 5, 5, 5, 5, 1, 1, 5, 5, 2, 4, 5]);
    }

}

#[cfg(all(test, feature = "benchmarks"))]
mod bench {
    use test_std::Bencher;
    use test_utils::get_test_data;
    use super::lz77_compress;
    #[bench]
    fn test_file_zlib_lz77_only(b: &mut Bencher) {
        let test_data = get_test_data();
        b.iter(|| lz77_compress(&test_data));
    }
}