paszlib/src/trees.pas

unit Trees;

{$T-}
{$define ORG_DEBUG}
{
  trees.c -- output deflated data using Huffman coding
  Copyright (C) 1995-1998 Jean-loup Gailly

  Pascal tranlastion
  Copyright (C) 1998 by Jacques Nomssi Nzali
  For conditions of distribution and use, see copyright notice in readme.txt
}

{
 *  ALGORITHM
 *
 *      The "deflation" process uses several Huffman trees. The more
 *      common source values are represented by shorter bit sequences.
 *
 *      Each code tree is stored in a compressed form which is itself
 * a Huffman encoding of the lengths of all the code strings (in
 * ascending order by source values).  The actual code strings are
 * reconstructed from the lengths in the inflate process, as described
 * in the deflate specification.
 *
 *  REFERENCES
 *
 *      Deutsch, L.P.,"'Deflate' Compressed Data Format Specification".
 *      Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc
 *
 *      Storer, James A.
 *          Data Compression:  Methods and Theory, pp. 49-50.
 *          Computer Science Press, 1988.  ISBN 0-7167-8156-5.
 *
 *      Sedgewick, R.
 *          Algorithms, p290.
 *          Addison-Wesley, 1983. ISBN 0-201-06672-6.
 }

interface

{$I zconf.inc}

uses
  {$ifdef ZLIB_DEBUG}
  sysutils,
  {$endif}
  zbase
  ;

{ ===========================================================================
  Internal compression state. }

const
  LENGTH_CODES = 29;
{ number of length codes, not counting the special END_BLOCK code }

  LITERALS = 256;
{ number of literal bytes 0..255 }

  L_CODES = (LITERALS+1+LENGTH_CODES);
{ number of Literal or Length codes, including the END_BLOCK code }

  D_CODES = 30;
{ number of distance codes }

  BL_CODES = 19;
{ number of codes used to transfer the bit lengths }

  HEAP_SIZE = (2*L_CODES+1);
{ maximum heap size }

  MAX_BITS = 15;
{ All codes must not exceed MAX_BITS bits }

const
  INIT_STATE =  42;
  BUSY_STATE =  113;
  FINISH_STATE = 666;
{ Stream status }


{ Data structure describing a single value and its code string. }
type
  ct_data_ptr = ^ct_data;
  ct_data = record
    fc : record
      case byte of
      0:(freq : word);       { frequency count }
      1:(code : word);       { bit string }
    end;
    dl : record
      case byte of
      0:(dad : word);        { father node in Huffman tree }
      1:(len : word);        { length of bit string }
    end;
  end;

{ Freq = fc.freq
 Code = fc.code
 Dad = dl.dad
 Len = dl.len }

type
  ltree_type = array[0..HEAP_SIZE-1] of ct_data;    { literal and length tree }
  dtree_type = array[0..2*D_CODES+1-1] of ct_data;  { distance tree }
  htree_type = array[0..2*BL_CODES+1-1] of ct_data;  { Huffman tree for bit lengths }
  { generic tree type }
  tree_type = array[0..(maxzbaseint div SizeOf(ct_data))-1] of ct_data;

  tree_ptr = ^ct_data;
  ltree_ptr = ^ltree_type;
  dtree_ptr = ^dtree_type;
  htree_ptr = ^htree_type;


type
  static_tree_desc_ptr = ^static_tree_desc;
  static_tree_desc =
         record
    {const} static_tree : tree_ptr;     { static tree or NIL }
    {const} extra_bits : pinteger;   { extra bits for each code or NIL }
            extra_base : integer;           { base index for extra_bits }
            elems : integer;                { max number of elements in the tree }
            max_length : integer;           { max bit length for the codes }
          end;

  tree_desc_ptr = ^tree_desc;
  tree_desc = record
    dyn_tree : tree_ptr;    { the dynamic tree }
    max_code : integer;            { largest code with non zero frequency }
    stat_desc : static_tree_desc_ptr; { the corresponding static tree }
  end;

type
  Pos = word;
  Posf = Pos; {FAR}
  IPos = cardinal;

  pPosf = ^Posf;

  zPosfArray = array[0..(maxzbaseint div SizeOf(Posf))-1] of Posf;
  pzPosfArray = ^zPosfArray;

{ A Pos is an index in the character window. We use short instead of integer to
  save space in the various tables. IPos is used only for parameter passing.}

type
  deflate_state_ptr = ^deflate_state;
  deflate_state = record
    strm : z_streamp;          { pointer back to this zlib stream }
    status : integer;              { as the name implies }
    pending_buf : Pbytearray; { output still pending }
    pending_buf_size : longint;    { size of pending_buf }
    pending_out : Pbyte;      { next pending byte to output to the stream }
    pending : longint;             { nb of bytes in the pending buffer }
    noheader : integer;            { suppress zlib header and adler32 }
    data_type : Byte;          { UNKNOWN, BINARY or ASCII }
    method : Byte;             { STORED (for zip only) or DEFLATED }
    last_flush : integer;          { value of flush param for previous deflate call }

                { used by deflate.pas: }

    w_size : cardinal;             { LZ77 window size (32K by default) }
    w_bits : cardinal;             { log2(w_size)  (8..16) }
    w_mask : cardinal;             { w_size - 1 }

    window : Pbytearray;
    { Sliding window. Input bytes are read into the second half of the window,
      and move to the first half later to keep a dictionary of at least wSize
      bytes. With this organization, matches are limited to a distance of
      wSize-MAX_MATCH bytes, but this ensures that IO is always
      performed with a length multiple of the block size. Also, it limits
      the window size to 64K, which is quite useful on MSDOS.
      To do: use the user input buffer as sliding window. }

    window_size : longint;
    { Actual size of window: 2*wSize, except when the user input buffer
      is directly used as sliding window. }

    prev : pzPosfArray;
    { Link to older string with same hash index. To limit the size of this
      array to 64K, this link is maintained only for the last 32K strings.
      An index in this array is thus a window index modulo 32K. }

    head : pzPosfArray;    { Heads of the hash chains or NIL. }

    ins_h : cardinal;          { hash index of string to be inserted }
    hash_size : cardinal;      { number of elements in hash table }
    hash_bits : cardinal;      { log2(hash_size) }
    hash_mask : cardinal;      { hash_size-1 }

    hash_shift : cardinal;
    { Number of bits by which ins_h must be shifted at each input
      step. It must be such that after MIN_MATCH steps, the oldest
      byte no longer takes part in the hash key, that is:
        hash_shift * MIN_MATCH >= hash_bits     }

    block_start : longint;
    { Window position at the beginning of the current output block. Gets
      negative when the window is moved backwards. }

    match_length : cardinal;           { length of best match }
    prev_match : IPos;             { previous match }
    match_available : boolean;     { set if previous match exists }
    strstart : cardinal;               { start of string to insert }
    match_start : cardinal;            { start of matching string }
    lookahead : cardinal;              { number of valid bytes ahead in window }

    prev_length : cardinal;
    { Length of the best match at previous step. Matches not greater than this
      are discarded. This is used in the lazy match evaluation. }

    max_chain_length : cardinal;
    { To speed up deflation, hash chains are never searched beyond this
      length.  A higher limit improves compression ratio but degrades the
      speed. }

    { moved to the end because Borland Pascal won't accept the following:
    max_lazy_match : cardinal;
    max_insert_length : cardinal absolute max_lazy_match;
    }

    level : integer;    { compression level (1..9) }
    strategy : integer; { favor or force Huffman coding}

    good_match : cardinal;
    { Use a faster search when the previous match is longer than this }

    nice_match : integer; { Stop searching when current match exceeds this }

                { used by trees.pas: }
    { Didn't use ct_data typedef below to supress compiler warning }
    dyn_ltree : ltree_type;    { literal and length tree }
    dyn_dtree : dtree_type;  { distance tree }
    bl_tree : htree_type;   { Huffman tree for bit lengths }

    l_desc : tree_desc;                { desc. for literal tree }
    d_desc : tree_desc;                { desc. for distance tree }
    bl_desc : tree_desc;               { desc. for bit length tree }

    bl_count : array[0..MAX_BITS+1-1] of word;
    { number of codes at each bit length for an optimal tree }

    heap : array[0..2*L_CODES+1-1] of integer; { heap used to build the Huffman trees }
    heap_len : integer;                   { number of elements in the heap }
    heap_max : integer;                   { element of largest frequency }
    { The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
      The same heap array is used to build all trees. }

    depth : array[0..2*L_CODES+1-1] of byte;
    { Depth of each subtree used as tie breaker for trees of equal frequency }


    l_buf : Pbytearray;       { buffer for literals or lengths }

    lit_bufsize : cardinal;
    { Size of match buffer for literals/lengths.  There are 4 reasons for
      limiting lit_bufsize to 64K:
        - frequencies can be kept in 16 bit counters
        - if compression is not successful for the first block, all input
          data is still in the window so we can still emit a stored block even
          when input comes from standard input.  (This can also be done for
          all blocks if lit_bufsize is not greater than 32K.)
        - if compression is not successful for a file smaller than 64K, we can
          even emit a stored file instead of a stored block (saving 5 bytes).
          This is applicable only for zip (not gzip or zlib).
        - creating new Huffman trees less frequently may not provide fast
          adaptation to changes in the input data statistics. (Take for
          example a binary file with poorly compressible code followed by
          a highly compressible string table.) Smaller buffer sizes give
          fast adaptation but have of course the overhead of transmitting
          trees more frequently.
        - I can't count above 4 }


    last_lit : cardinal;      { running index in l_buf }

    d_buf : Pwordarray;
    { Buffer for distances. To simplify the code, d_buf and l_buf have
      the same number of elements. To use different lengths, an extra flag
      array would be necessary. }

    opt_len : longint;        { bit length of current block with optimal trees }
    static_len : longint;     { bit length of current block with static trees }
    compressed_len : longint; { total bit length of compressed file }
    matches : cardinal;       { number of string matches in current block }
    last_eob_len : integer;   { bit length of EOB code for last block }

{$ifdef ZLIB_DEBUG}
    bits_sent : longint;    { bit length of the compressed data }
{$endif}

    bi_buf : word;
    { Output buffer. bits are inserted starting at the bottom (least
      significant bits). }

    bi_valid : integer;
    { Number of valid bits in bi_buf.  All bits above the last valid bit
      are always zero. }

    case byte of
    0:(max_lazy_match : cardinal);
    { Attempt to find a better match only when the current match is strictly
      smaller than this value. This mechanism is used only for compression
      levels >= 4. }

    1:(max_insert_length : cardinal);
    { Insert new strings in the hash table only if the match length is not
      greater than this length. This saves time but degrades compression.
      max_insert_length is used only for compression levels <= 3. }
  end;

procedure _tr_init (var s : deflate_state);

function _tr_tally (var s : deflate_state;
                    dist : cardinal;
                    lc : cardinal) : boolean;

function _tr_flush_block (var s : deflate_state;
                          buf : Pbyte;
                          stored_len : longint;
			  eof : boolean) : longint;

procedure _tr_align(var s : deflate_state);

procedure _tr_stored_block(var s : deflate_state;
                           buf : Pbyte;
                           stored_len : longint;
                           eof : boolean);

implementation

{ #define GEN_TREES_H }

{$ifndef GEN_TREES_H}
{ header created automatically with -DGEN_TREES_H }

const
  DIST_CODE_LEN = 512; { see definition of array dist_code below }

{ The static literal tree. Since the bit lengths are imposed, there is no
  need for the L_CODES extra codes used during heap construction. However
  The codes 286 and 287 are needed to build a canonical tree (see _tr_init
  below). }
const
  static_ltree : array[0..L_CODES+2-1] of ct_data = (
{ fc:(freq, code) dl:(dad,len) }
(fc:(freq: 12);dl:(len: 8)), (fc:(freq:140);dl:(len: 8)), (fc:(freq: 76);dl:(len: 8)),
(fc:(freq:204);dl:(len: 8)), (fc:(freq: 44);dl:(len: 8)), (fc:(freq:172);dl:(len: 8)),
(fc:(freq:108);dl:(len: 8)), (fc:(freq:236);dl:(len: 8)), (fc:(freq: 28);dl:(len: 8)),
(fc:(freq:156);dl:(len: 8)), (fc:(freq: 92);dl:(len: 8)), (fc:(freq:220);dl:(len: 8)),
(fc:(freq: 60);dl:(len: 8)), (fc:(freq:188);dl:(len: 8)), (fc:(freq:124);dl:(len: 8)),
(fc:(freq:252);dl:(len: 8)), (fc:(freq:  2);dl:(len: 8)), (fc:(freq:130);dl:(len: 8)),
(fc:(freq: 66);dl:(len: 8)), (fc:(freq:194);dl:(len: 8)), (fc:(freq: 34);dl:(len: 8)),
(fc:(freq:162);dl:(len: 8)), (fc:(freq: 98);dl:(len: 8)), (fc:(freq:226);dl:(len: 8)),
(fc:(freq: 18);dl:(len: 8)), (fc:(freq:146);dl:(len: 8)), (fc:(freq: 82);dl:(len: 8)),
(fc:(freq:210);dl:(len: 8)), (fc:(freq: 50);dl:(len: 8)), (fc:(freq:178);dl:(len: 8)),
(fc:(freq:114);dl:(len: 8)), (fc:(freq:242);dl:(len: 8)), (fc:(freq: 10);dl:(len: 8)),
(fc:(freq:138);dl:(len: 8)), (fc:(freq: 74);dl:(len: 8)), (fc:(freq:202);dl:(len: 8)),
(fc:(freq: 42);dl:(len: 8)), (fc:(freq:170);dl:(len: 8)), (fc:(freq:106);dl:(len: 8)),
(fc:(freq:234);dl:(len: 8)), (fc:(freq: 26);dl:(len: 8)), (fc:(freq:154);dl:(len: 8)),
(fc:(freq: 90);dl:(len: 8)), (fc:(freq:218);dl:(len: 8)), (fc:(freq: 58);dl:(len: 8)),
(fc:(freq:186);dl:(len: 8)), (fc:(freq:122);dl:(len: 8)), (fc:(freq:250);dl:(len: 8)),
(fc:(freq:  6);dl:(len: 8)), (fc:(freq:134);dl:(len: 8)), (fc:(freq: 70);dl:(len: 8)),
(fc:(freq:198);dl:(len: 8)), (fc:(freq: 38);dl:(len: 8)), (fc:(freq:166);dl:(len: 8)),
(fc:(freq:102);dl:(len: 8)), (fc:(freq:230);dl:(len: 8)), (fc:(freq: 22);dl:(len: 8)),
(fc:(freq:150);dl:(len: 8)), (fc:(freq: 86);dl:(len: 8)), (fc:(freq:214);dl:(len: 8)),
(fc:(freq: 54);dl:(len: 8)), (fc:(freq:182);dl:(len: 8)), (fc:(freq:118);dl:(len: 8)),
(fc:(freq:246);dl:(len: 8)), (fc:(freq: 14);dl:(len: 8)), (fc:(freq:142);dl:(len: 8)),
(fc:(freq: 78);dl:(len: 8)), (fc:(freq:206);dl:(len: 8)), (fc:(freq: 46);dl:(len: 8)),
(fc:(freq:174);dl:(len: 8)), (fc:(freq:110);dl:(len: 8)), (fc:(freq:238);dl:(len: 8)),
(fc:(freq: 30);dl:(len: 8)), (fc:(freq:158);dl:(len: 8)), (fc:(freq: 94);dl:(len: 8)),
(fc:(freq:222);dl:(len: 8)), (fc:(freq: 62);dl:(len: 8)), (fc:(freq:190);dl:(len: 8)),
(fc:(freq:126);dl:(len: 8)), (fc:(freq:254);dl:(len: 8)), (fc:(freq:  1);dl:(len: 8)),
(fc:(freq:129);dl:(len: 8)), (fc:(freq: 65);dl:(len: 8)), (fc:(freq:193);dl:(len: 8)),
(fc:(freq: 33);dl:(len: 8)), (fc:(freq:161);dl:(len: 8)), (fc:(freq: 97);dl:(len: 8)),
(fc:(freq:225);dl:(len: 8)), (fc:(freq: 17);dl:(len: 8)), (fc:(freq:145);dl:(len: 8)),
(fc:(freq: 81);dl:(len: 8)), (fc:(freq:209);dl:(len: 8)), (fc:(freq: 49);dl:(len: 8)),
(fc:(freq:177);dl:(len: 8)), (fc:(freq:113);dl:(len: 8)), (fc:(freq:241);dl:(len: 8)),
(fc:(freq:  9);dl:(len: 8)), (fc:(freq:137);dl:(len: 8)), (fc:(freq: 73);dl:(len: 8)),
(fc:(freq:201);dl:(len: 8)), (fc:(freq: 41);dl:(len: 8)), (fc:(freq:169);dl:(len: 8)),
(fc:(freq:105);dl:(len: 8)), (fc:(freq:233);dl:(len: 8)), (fc:(freq: 25);dl:(len: 8)),
(fc:(freq:153);dl:(len: 8)), (fc:(freq: 89);dl:(len: 8)), (fc:(freq:217);dl:(len: 8)),
(fc:(freq: 57);dl:(len: 8)), (fc:(freq:185);dl:(len: 8)), (fc:(freq:121);dl:(len: 8)),
(fc:(freq:249);dl:(len: 8)), (fc:(freq:  5);dl:(len: 8)), (fc:(freq:133);dl:(len: 8)),
(fc:(freq: 69);dl:(len: 8)), (fc:(freq:197);dl:(len: 8)), (fc:(freq: 37);dl:(len: 8)),
(fc:(freq:165);dl:(len: 8)), (fc:(freq:101);dl:(len: 8)), (fc:(freq:229);dl:(len: 8)),
(fc:(freq: 21);dl:(len: 8)), (fc:(freq:149);dl:(len: 8)), (fc:(freq: 85);dl:(len: 8)),
(fc:(freq:213);dl:(len: 8)), (fc:(freq: 53);dl:(len: 8)), (fc:(freq:181);dl:(len: 8)),
(fc:(freq:117);dl:(len: 8)), (fc:(freq:245);dl:(len: 8)), (fc:(freq: 13);dl:(len: 8)),
(fc:(freq:141);dl:(len: 8)), (fc:(freq: 77);dl:(len: 8)), (fc:(freq:205);dl:(len: 8)),
(fc:(freq: 45);dl:(len: 8)), (fc:(freq:173);dl:(len: 8)), (fc:(freq:109);dl:(len: 8)),
(fc:(freq:237);dl:(len: 8)), (fc:(freq: 29);dl:(len: 8)), (fc:(freq:157);dl:(len: 8)),
(fc:(freq: 93);dl:(len: 8)), (fc:(freq:221);dl:(len: 8)), (fc:(freq: 61);dl:(len: 8)),
(fc:(freq:189);dl:(len: 8)), (fc:(freq:125);dl:(len: 8)), (fc:(freq:253);dl:(len: 8)),
(fc:(freq: 19);dl:(len: 9)), (fc:(freq:275);dl:(len: 9)), (fc:(freq:147);dl:(len: 9)),
(fc:(freq:403);dl:(len: 9)), (fc:(freq: 83);dl:(len: 9)), (fc:(freq:339);dl:(len: 9)),
(fc:(freq:211);dl:(len: 9)), (fc:(freq:467);dl:(len: 9)), (fc:(freq: 51);dl:(len: 9)),
(fc:(freq:307);dl:(len: 9)), (fc:(freq:179);dl:(len: 9)), (fc:(freq:435);dl:(len: 9)),
(fc:(freq:115);dl:(len: 9)), (fc:(freq:371);dl:(len: 9)), (fc:(freq:243);dl:(len: 9)),
(fc:(freq:499);dl:(len: 9)), (fc:(freq: 11);dl:(len: 9)), (fc:(freq:267);dl:(len: 9)),
(fc:(freq:139);dl:(len: 9)), (fc:(freq:395);dl:(len: 9)), (fc:(freq: 75);dl:(len: 9)),
(fc:(freq:331);dl:(len: 9)), (fc:(freq:203);dl:(len: 9)), (fc:(freq:459);dl:(len: 9)),
(fc:(freq: 43);dl:(len: 9)), (fc:(freq:299);dl:(len: 9)), (fc:(freq:171);dl:(len: 9)),
(fc:(freq:427);dl:(len: 9)), (fc:(freq:107);dl:(len: 9)), (fc:(freq:363);dl:(len: 9)),
(fc:(freq:235);dl:(len: 9)), (fc:(freq:491);dl:(len: 9)), (fc:(freq: 27);dl:(len: 9)),
(fc:(freq:283);dl:(len: 9)), (fc:(freq:155);dl:(len: 9)), (fc:(freq:411);dl:(len: 9)),
(fc:(freq: 91);dl:(len: 9)), (fc:(freq:347);dl:(len: 9)), (fc:(freq:219);dl:(len: 9)),
(fc:(freq:475);dl:(len: 9)), (fc:(freq: 59);dl:(len: 9)), (fc:(freq:315);dl:(len: 9)),
(fc:(freq:187);dl:(len: 9)), (fc:(freq:443);dl:(len: 9)), (fc:(freq:123);dl:(len: 9)),
(fc:(freq:379);dl:(len: 9)), (fc:(freq:251);dl:(len: 9)), (fc:(freq:507);dl:(len: 9)),
(fc:(freq:  7);dl:(len: 9)), (fc:(freq:263);dl:(len: 9)), (fc:(freq:135);dl:(len: 9)),
(fc:(freq:391);dl:(len: 9)), (fc:(freq: 71);dl:(len: 9)), (fc:(freq:327);dl:(len: 9)),
(fc:(freq:199);dl:(len: 9)), (fc:(freq:455);dl:(len: 9)), (fc:(freq: 39);dl:(len: 9)),
(fc:(freq:295);dl:(len: 9)), (fc:(freq:167);dl:(len: 9)), (fc:(freq:423);dl:(len: 9)),
(fc:(freq:103);dl:(len: 9)), (fc:(freq:359);dl:(len: 9)), (fc:(freq:231);dl:(len: 9)),
(fc:(freq:487);dl:(len: 9)), (fc:(freq: 23);dl:(len: 9)), (fc:(freq:279);dl:(len: 9)),
(fc:(freq:151);dl:(len: 9)), (fc:(freq:407);dl:(len: 9)), (fc:(freq: 87);dl:(len: 9)),
(fc:(freq:343);dl:(len: 9)), (fc:(freq:215);dl:(len: 9)), (fc:(freq:471);dl:(len: 9)),
(fc:(freq: 55);dl:(len: 9)), (fc:(freq:311);dl:(len: 9)), (fc:(freq:183);dl:(len: 9)),
(fc:(freq:439);dl:(len: 9)), (fc:(freq:119);dl:(len: 9)), (fc:(freq:375);dl:(len: 9)),
(fc:(freq:247);dl:(len: 9)), (fc:(freq:503);dl:(len: 9)), (fc:(freq: 15);dl:(len: 9)),
(fc:(freq:271);dl:(len: 9)), (fc:(freq:143);dl:(len: 9)), (fc:(freq:399);dl:(len: 9)),
(fc:(freq: 79);dl:(len: 9)), (fc:(freq:335);dl:(len: 9)), (fc:(freq:207);dl:(len: 9)),
(fc:(freq:463);dl:(len: 9)), (fc:(freq: 47);dl:(len: 9)), (fc:(freq:303);dl:(len: 9)),
(fc:(freq:175);dl:(len: 9)), (fc:(freq:431);dl:(len: 9)), (fc:(freq:111);dl:(len: 9)),
(fc:(freq:367);dl:(len: 9)), (fc:(freq:239);dl:(len: 9)), (fc:(freq:495);dl:(len: 9)),
(fc:(freq: 31);dl:(len: 9)), (fc:(freq:287);dl:(len: 9)), (fc:(freq:159);dl:(len: 9)),
(fc:(freq:415);dl:(len: 9)), (fc:(freq: 95);dl:(len: 9)), (fc:(freq:351);dl:(len: 9)),
(fc:(freq:223);dl:(len: 9)), (fc:(freq:479);dl:(len: 9)), (fc:(freq: 63);dl:(len: 9)),
(fc:(freq:319);dl:(len: 9)), (fc:(freq:191);dl:(len: 9)), (fc:(freq:447);dl:(len: 9)),
(fc:(freq:127);dl:(len: 9)), (fc:(freq:383);dl:(len: 9)), (fc:(freq:255);dl:(len: 9)),
(fc:(freq:511);dl:(len: 9)), (fc:(freq:  0);dl:(len: 7)), (fc:(freq: 64);dl:(len: 7)),
(fc:(freq: 32);dl:(len: 7)), (fc:(freq: 96);dl:(len: 7)), (fc:(freq: 16);dl:(len: 7)),
(fc:(freq: 80);dl:(len: 7)), (fc:(freq: 48);dl:(len: 7)), (fc:(freq:112);dl:(len: 7)),
(fc:(freq:  8);dl:(len: 7)), (fc:(freq: 72);dl:(len: 7)), (fc:(freq: 40);dl:(len: 7)),
(fc:(freq:104);dl:(len: 7)), (fc:(freq: 24);dl:(len: 7)), (fc:(freq: 88);dl:(len: 7)),
(fc:(freq: 56);dl:(len: 7)), (fc:(freq:120);dl:(len: 7)), (fc:(freq:  4);dl:(len: 7)),
(fc:(freq: 68);dl:(len: 7)), (fc:(freq: 36);dl:(len: 7)), (fc:(freq:100);dl:(len: 7)),
(fc:(freq: 20);dl:(len: 7)), (fc:(freq: 84);dl:(len: 7)), (fc:(freq: 52);dl:(len: 7)),
(fc:(freq:116);dl:(len: 7)), (fc:(freq:  3);dl:(len: 8)), (fc:(freq:131);dl:(len: 8)),
(fc:(freq: 67);dl:(len: 8)), (fc:(freq:195);dl:(len: 8)), (fc:(freq: 35);dl:(len: 8)),
(fc:(freq:163);dl:(len: 8)), (fc:(freq: 99);dl:(len: 8)), (fc:(freq:227);dl:(len: 8))
);


{ The static distance tree. (Actually a trivial tree since all lens use
  5 bits.) }
  static_dtree : array[0..D_CODES-1] of ct_data = (
(fc:(freq: 0); dl:(len:5)), (fc:(freq:16); dl:(len:5)), (fc:(freq: 8); dl:(len:5)),
(fc:(freq:24); dl:(len:5)), (fc:(freq: 4); dl:(len:5)), (fc:(freq:20); dl:(len:5)),
(fc:(freq:12); dl:(len:5)), (fc:(freq:28); dl:(len:5)), (fc:(freq: 2); dl:(len:5)),
(fc:(freq:18); dl:(len:5)), (fc:(freq:10); dl:(len:5)), (fc:(freq:26); dl:(len:5)),
(fc:(freq: 6); dl:(len:5)), (fc:(freq:22); dl:(len:5)), (fc:(freq:14); dl:(len:5)),
(fc:(freq:30); dl:(len:5)), (fc:(freq: 1); dl:(len:5)), (fc:(freq:17); dl:(len:5)),
(fc:(freq: 9); dl:(len:5)), (fc:(freq:25); dl:(len:5)), (fc:(freq: 5); dl:(len:5)),
(fc:(freq:21); dl:(len:5)), (fc:(freq:13); dl:(len:5)), (fc:(freq:29); dl:(len:5)),
(fc:(freq: 3); dl:(len:5)), (fc:(freq:19); dl:(len:5)), (fc:(freq:11); dl:(len:5)),
(fc:(freq:27); dl:(len:5)), (fc:(freq: 7); dl:(len:5)), (fc:(freq:23); dl:(len:5))
);

{ Distance codes. The first 256 values correspond to the distances
  3 .. 258, the last 256 values correspond to the top 8 bits of
  the 15 bit distances. }
  _dist_code : array[0..DIST_CODE_LEN-1] of byte = (
 0,  1,  2,  3,  4,  4,  5,  5,  6,  6,  6,  6,  7,  7,  7,  7,  8,  8,  8,  8,
 8,  8,  8,  8,  9,  9,  9,  9,  9,  9,  9,  9, 10, 10, 10, 10, 10, 10, 10, 10,
10, 10, 10, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11, 11, 11, 11, 11, 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, 13, 13, 13, 13,
13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13,
13, 13, 13, 13, 13, 13, 13, 13, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14,
14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14,
14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14,
14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 15, 15, 15, 15, 15, 15, 15, 15,
15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15,
15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15,
15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15,  0,  0, 16, 17,
18, 18, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21, 22, 22, 22, 22, 22, 22, 22, 22,
23, 23, 23, 23, 23, 23, 23, 23, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
24, 24, 24, 24, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26,
26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 27, 27, 27, 27, 27, 27, 27, 27,
27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27,
27, 27, 27, 27, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28,
28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28,
28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28,
28, 28, 28, 28, 28, 28, 28, 28, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29,
29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29,
29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29,
29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29
);

{ length code for each normalized match length (0 == MIN_MATCH) }
  _length_code : array[0..MAX_MATCH-MIN_MATCH+1-1] of byte = (
 0,  1,  2,  3,  4,  5,  6,  7,  8,  8,  9,  9, 10, 10, 11, 11, 12, 12, 12, 12,
13, 13, 13, 13, 14, 14, 14, 14, 15, 15, 15, 15, 16, 16, 16, 16, 16, 16, 16, 16,
17, 17, 17, 17, 17, 17, 17, 17, 18, 18, 18, 18, 18, 18, 18, 18, 19, 19, 19, 19,
19, 19, 19, 19, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20,
21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 22, 22, 22, 22,
22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 23, 23, 23, 23, 23, 23, 23, 23,
23, 23, 23, 23, 23, 23, 23, 23, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 26, 26, 26, 26, 26, 26, 26, 26,
26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26,
26, 26, 26, 26, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27,
27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 28
);


{ First normalized length for each code (0 = MIN_MATCH) }
  base_length : array[0..LENGTH_CODES-1] of integer = (
0, 1, 2, 3, 4, 5, 6, 7, 8, 10, 12, 14, 16, 20, 24, 28, 32, 40, 48, 56,
64, 80, 96, 112, 128, 160, 192, 224, 0
);


{ First normalized distance for each code (0 = distance of 1) }
  base_dist : array[0..D_CODES-1] of integer = (
    0,     1,     2,     3,     4,     6,     8,    12,    16,    24,
   32,    48,    64,    96,   128,   192,   256,   384,   512,   768,
 1024,  1536,  2048,  3072,  4096,  6144,  8192, 12288, 16384, 24576
);
{$endif}

{ Output a byte on the stream.
  IN assertion: there is enough room in pending_buf.
macro put_byte(s, c)
begin
  s^.pending_buf^[s^.pending] := (c);
  inc(s^.pending);
end
}

const
  MIN_LOOKAHEAD = (MAX_MATCH+MIN_MATCH+1);
{ Minimum amount of lookahead, except at the end of the input file.
  See deflate.c for comments about the MIN_MATCH+1. }

{macro d_code(dist)
   if (dist) < 256 then
     := _dist_code[dist]
   else
     := _dist_code[256+((dist) shr 7)]);
  Mapping from a distance to a distance code. dist is the distance - 1 and
  must not have side effects. _dist_code[256] and _dist_code[257] are never
  used. }

{$ifndef ORG_DEBUG}
{ Inline versions of _tr_tally for speed: }

#if defined(GEN_TREES_H) || !defined(STDC)
  extern byte _length_code[];
  extern byte _dist_code[];
#else
  extern const byte _length_code[];
  extern const byte _dist_code[];
#endif

macro _tr_tally_lit(s, c, flush)
var
  cc : byte;
begin
    cc := (c);
    s^.d_buf[s^.last_lit] := 0;
    s^.l_buf[s^.last_lit] := cc;
    inc(s^.last_lit);
    inc(s^.dyn_ltree[cc].fc.Freq);
    flush := (s^.last_lit = s^.lit_bufsize-1);
end;

macro _tr_tally_dist(s, distance, length, flush) \
var
  len : byte;
  dist : word;
begin
    len := (length);
    dist := (distance);
    s^.d_buf[s^.last_lit] := dist;
    s^.l_buf[s^.last_lit] = len;
    inc(s^.last_lit);
    dec(dist);
    inc(s^.dyn_ltree[_length_code[len]+LITERALS+1].fc.Freq);
    inc(s^.dyn_dtree[d_code(dist)].Freq);
    flush := (s^.last_lit = s^.lit_bufsize-1);
end;

{$endif}

{ ===========================================================================
  Constants }

const
  MAX_BL_BITS = 7;
{ Bit length codes must not exceed MAX_BL_BITS bits }

const
  END_BLOCK = 256;
{ end of block literal code }

const
  REP_3_6 = 16;
{ repeat previous bit length 3-6 times (2 bits of repeat count) }

const
  REPZ_3_10 = 17;
{ repeat a zero length 3-10 times  (3 bits of repeat count) }

const
  REPZ_11_138 = 18;
{ repeat a zero length 11-138 times  (7 bits of repeat count) }

{local}
const
  extra_lbits : array[0..LENGTH_CODES-1] of integer
    { extra bits for each length code }
   = (0,0,0,0,0,0,0,0,1,1,1,1,2,2,2,2,3,3,3,3,4,4,4,4,5,5,5,5,0);

{local}
const
  extra_dbits : array[0..D_CODES-1] of integer
    { extra bits for each distance code }
   = (0,0,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13);

{local}
const
  extra_blbits : array[0..BL_CODES-1] of integer { extra bits for each bit length code }
   = (0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7);

{local}
const
  bl_order : array[0..BL_CODES-1] of byte
   = (16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15);
{ The lengths of the bit length codes are sent in order of decreasing
  probability, to avoid transmitting the lengths for unused bit length codes.
 }

const
  Buf_size = (8 * 2*sizeof(char));
{ Number of bits used within bi_buf. (bi_buf might be implemented on
  more than 16 bits on some systems.) }

{ ===========================================================================
  Local data. These are initialized only once. }


{$ifdef GEN_TREES_H)}
{ non ANSI compilers may not accept trees.h }

const
  DIST_CODE_LEN = 512; { see definition of array dist_code below }

{local}
var
  static_ltree : array[0..L_CODES+2-1] of ct_data;
{ The static literal tree. Since the bit lengths are imposed, there is no
  need for the L_CODES extra codes used during heap construction. However
  The codes 286 and 287 are needed to build a canonical tree (see _tr_init
  below). }

{local}
  static_dtree : array[0..D_CODES-1] of ct_data;
{ The static distance tree. (Actually a trivial tree since all codes use
  5 bits.) }

  _dist_code : array[0..DIST_CODE_LEN-1] of byte;
{ Distance codes. The first 256 values correspond to the distances
  3 .. 258, the last 256 values correspond to the top 8 bits of
  the 15 bit distances. }

  _length_code : array[0..MAX_MATCH-MIN_MATCH+1-1] of byte;
{ length code for each normalized match length (0 == MIN_MATCH) }

{local}
  base_length : array[0..LENGTH_CODES-1] of integer;
{ First normalized length for each code (0 = MIN_MATCH) }

{local}
  base_dist : array[0..D_CODES-1] of integer;
{ First normalized distance for each code (0 = distance of 1) }

{$endif} { GEN_TREES_H }

{local}
const
  static_l_desc :  static_tree_desc  =
      (static_tree: {tree_ptr}@static_ltree[0];  { pointer to array of ct_data }
       extra_bits: {pzIntfArray}@extra_lbits[0]; { pointer to array of integer }
       extra_base: LITERALS+1;
       elems: L_CODES;
       max_length: MAX_BITS);

{local}
const
  static_d_desc : static_tree_desc  =
      (static_tree: {tree_ptr}@static_dtree[0];
       extra_bits: {pzIntfArray}@extra_dbits[0];
       extra_base : 0;
       elems: D_CODES;
       max_length: MAX_BITS);

{local}
const
  static_bl_desc : static_tree_desc =
      (static_tree: {tree_ptr}(NIL);
       extra_bits: {pzIntfArray}@extra_blbits[0];
       extra_base : 0;
       elems: BL_CODES;
       max_length: MAX_BL_BITS);

{$ifdef GEN_TREES_H}
{local}
procedure gen_trees_header;
{$endif}

(*
{ ===========================================================================
  Output a short LSB first on the stream.
  IN assertion: there is enough room in pendingBuf. }

macro put_short(s, w)
begin
    {put_byte(s, (byte)((w) & 0xff));}
    s.pending_buf^[s.pending] := byte((w) and $ff);
    inc(s.pending);

    {put_byte(s, (byte)((word)(w) >> 8));}
    s.pending_buf^[s.pending] := byte(word(w) shr 8);;
    inc(s.pending);
end
*)

{ ===========================================================================
  Send a value on a given number of bits.
  IN assertion: length <= 16 and value fits in length bits. }

{$ifdef ORG_DEBUG}

{local}
procedure send_bits(var s : deflate_state;
                    value : integer;   { value to send }
                    length : integer); { number of bits }
begin
  {$ifdef ZLIB_DEBUG}
  Tracevv(' l '+IntToStr(length)+ ' v '+IntToStr(value));
  Assert((length > 0) and (length <= 15), 'invalid length');
  inc(s.bits_sent, longint(length));
  {$ENDIF}

  { If not enough room in bi_buf, use (valid) bits from bi_buf and
    (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
    unused bits in value. }
  {$PUSH}
  {$Q-}
  {$R-}
  if (s.bi_valid > integer(Buf_size) - length) then
  begin
    s.bi_buf := s.bi_buf or integer(value shl s.bi_valid);
    {put_short(s, s.bi_buf);}
    s.pending_buf^[s.pending] := byte(s.bi_buf and $ff);
    inc(s.pending);
    s.pending_buf^[s.pending] := byte(word(s.bi_buf) shr 8);;
    inc(s.pending);

    s.bi_buf := word(value) shr (Buf_size - s.bi_valid);
    inc(s.bi_valid, length - Buf_size);
  end
  else
  begin
    s.bi_buf := s.bi_buf or integer(value shl s.bi_valid);
    inc(s.bi_valid, length);
  end;
  {$POP}
end;

{$else} { !ZLIB_DEBUG }


macro send_code(s, c, tree)
begin
  send_bits(s, tree[c].Code, tree[c].Len);
  { Send a code of the given tree. c and tree must not have side effects }
end

macro send_bits(s, value, length) \
begin integer len := length;\
  if (s^.bi_valid > (integer)Buf_size - len) begin\
    integer val := value;\
    s^.bi_buf |= (val << s^.bi_valid);\
    {put_short(s, s.bi_buf);}
    s.pending_buf^[s.pending] := byte(s.bi_buf and $ff);
    inc(s.pending);
    s.pending_buf^[s.pending] := byte(word(s.bi_buf) shr 8);;
    inc(s.pending);

    s^.bi_buf := (word)val >> (Buf_size - s^.bi_valid);\
    s^.bi_valid += len - Buf_size;\
  end else begin\
    s^.bi_buf |= (value) << s^.bi_valid;\
    s^.bi_valid += len;\
  end\
end;
{$endif} { ZLIB_DEBUG }

{ ===========================================================================
  Reverse the first len bits of a code, using straightforward code (a faster
  method would use a table)
  IN assertion: 1 <= len <= 15 }

{local}
function bi_reverse(code : cardinal;         { the value to invert }
                    len : integer) : cardinal;   { its bit length }

var
  res : cardinal; {register}
begin
  res := 0;
  repeat
    res := res or (code and 1);
    code := code shr 1;
    res := res shl 1;
    dec(len);
  until (len <= 0);
  bi_reverse := res shr 1;
end;

{ ===========================================================================
  Generate the codes for a given tree and bit counts (which need not be
  optimal).
  IN assertion: the array bl_count contains the bit length statistics for
  the given tree and the field len is set for all tree elements.
  OUT assertion: the field code is set for all tree elements of non
      zero code length. }

{local}
procedure gen_codes(tree : tree_ptr;  { the tree to decorate }
                    max_code : integer;   { largest code with non zero frequency }
                    var bl_count : array of word);  { number of codes at each bit length }

var
  next_code : array[0..MAX_BITS+1-1] of word; { next code value for each bit length }
  code : word;              { running code value }
  bits : integer;                  { bit index }
  n : integer;                     { code index }
var
  len : integer;
begin
  code := 0;

  { The distribution counts are first used to generate the code values
    without bit reversal. }

  for bits := 1 to MAX_BITS do
  begin
    code := ((code + bl_count[bits-1]) shl 1);
    next_code[bits] := code;
  end;
  { Check that the bit counts in bl_count are consistent. The last code
    must be all ones. }

  {$IFDEF ZLIB_DEBUG}
  Assert (code + bl_count[MAX_BITS]-1 = (1 shl MAX_BITS)-1,
          'inconsistent bit counts');
  Tracev(#13'gen_codes: max_code '+IntToStr(max_code));
  {$ENDIF}

  for n := 0 to max_code do
  begin
    len := tree[n].dl.Len;
    if (len = 0) then
      continue;
    { Now reverse the bits }
    tree[n].fc.Code := bi_reverse(next_code[len], len);
    inc(next_code[len]);
    {$ifdef ZLIB_DEBUG}
    if (n>31) and (n<128) then
      Tracecv(tree <> tree_ptr(@static_ltree),
       (^M'n #'+IntToStr(n)+' '+char(n)+' l '+IntToStr(len)+' c '+
         IntToStr(tree[n].fc.Code)+' ('+IntToStr(next_code[len]-1)+')'))
    else
      Tracecv(tree <> tree_ptr(@static_ltree),
      (^M'n #'+IntToStr(n)+'   l '+IntToStr(len)+' c '+
         IntToStr(tree[n].fc.Code)+' ('+IntToStr(next_code[len]-1)+')'));
    {$ENDIF}
  end;
end;

{ ===========================================================================
  Genererate the file trees.h describing the static trees. }
{$ifdef GEN_TREES_H}

macro SEPARATOR(i, last, width)
  if (i) = (last) then
    ( ^M');'^M^M
  else    \
    if (i) mod (width) = (width)-1 then
       ','^M
     else
       ', '

procedure gen_trees_header;
var
  header : system.text;
  i : integer;
begin
  system.assign(header, 'trees.inc');
  {$push}{$I-}
  ReWrite(header);
  {$pop}
  Assert (IOresult <> 0, 'Can''t open trees.h');
  WriteLn(header,
    '{ header created automatically with -DGEN_TREES_H }'^M);

  WriteLn(header, 'local const ct_data static_ltree[L_CODES+2] := (');
  for i := 0 to L_CODES+2-1 do
  begin
    WriteLn(header, '((%3u),(%3u))%s', static_ltree[i].Code,
		static_ltree[i].Len, SEPARATOR(i, L_CODES+1, 5));
  end;

  WriteLn(header, 'local const ct_data static_dtree[D_CODES] := (');
  for i := 0 to D_CODES-1 do
  begin
    WriteLn(header, '((%2u),(%2u))%s', static_dtree[i].Code,
		static_dtree[i].Len, SEPARATOR(i, D_CODES-1, 5));
  end;

  WriteLn(header, 'const byte _dist_code[DIST_CODE_LEN] := (');
  for i := 0 to DIST_CODE_LEN-1 do
  begin
    WriteLn(header, '%2u%s', _dist_code[i],
		SEPARATOR(i, DIST_CODE_LEN-1, 20));
  end;

  WriteLn(header, 'const byte _length_code[MAX_MATCH-MIN_MATCH+1]= (');
  for i := 0 to MAX_MATCH-MIN_MATCH+1-1 do
  begin
    WriteLn(header, '%2u%s', _length_code[i],
		SEPARATOR(i, MAX_MATCH-MIN_MATCH, 20));
  end;

  WriteLn(header, 'local const integer base_length[LENGTH_CODES] := (');
  for i := 0 to LENGTH_CODES-1 do
  begin
    WriteLn(header, '%1u%s', base_length[i],
		SEPARATOR(i, LENGTH_CODES-1, 20));
  end;

  WriteLn(header, 'local const integer base_dist[D_CODES] := (');
  for i := 0 to D_CODES-1 do
  begin
    WriteLn(header, '%5u%s', base_dist[i],
		SEPARATOR(i, D_CODES-1, 10));
  end;

  close(header);
end;
{$endif} { GEN_TREES_H }


{ ===========================================================================
  Initialize the various 'constant' tables. }

{local}
procedure tr_static_init;

{$ifdef GEN_TREES_H}
const
  static_init_done : boolean = FALSE;
var
  n : integer;        { iterates over tree elements }
  bits : integer;     { bit counter }
  length : integer;   { length value }
  code : integer;     { code value }
  dist : integer;     { distance index }
  bl_count : array[0..MAX_BITS+1-1] of word;
    { number of codes at each bit length for an optimal tree }
begin
    if (static_init_done) then
      exit;

    { Initialize the mapping length (0..255) -> length code (0..28) }
    length := 0;
    for code := 0 to LENGTH_CODES-1-1 do
    begin
      base_length[code] := length;
      for n := 0 to (1 shl extra_lbits[code])-1 do
      begin
        _length_code[length] := byte(code);
        inc(length);
      end;
    end;
    Assert (length = 256, 'tr_static_init: length <> 256');
    { Note that the length 255 (match length 258) can be represented
      in two different ways: code 284 + 5 bits or code 285, so we
      overwrite length_code[255] to use the best encoding: }

    _length_code[length-1] := byte(code);

    { Initialize the mapping dist (0..32K) -> dist code (0..29) }
    dist := 0;
    for code := 0 to 16-1 do
    begin
      base_dist[code] := dist;
      for n := 0 to (1 shl extra_dbits[code])-1 do
      begin
        _dist_code[dist] := byte(code);
        inc(dist);
      end;
    end;
    Assert (dist = 256, 'tr_static_init: dist <> 256');
    dist := dist shr 7; { from now on, all distances are divided by 128 }
    for code := 16 to D_CODES-1 do
    begin
      base_dist[code] := dist shl 7;
      for n := 0 to (1 shl (extra_dbits[code]-7))-1 do
      begin
        _dist_code[256 + dist] := byte(code);
        inc(dist);
      end;
    end;
    Assert (dist = 256, 'tr_static_init: 256+dist <> 512');

    { Construct the codes of the static literal tree }
    for bits := 0 to MAX_BITS do
      bl_count[bits] := 0;
    n := 0;
    while (n <= 143) do
    begin
      static_ltree[n].dl.Len := 8;
      inc(n);
      inc(bl_count[8]);
    end;
    while (n <= 255) do
    begin
      static_ltree[n].dl.Len := 9;
      inc(n);
      inc(bl_count[9]);
    end;
    while (n <= 279) do
    begin
      static_ltree[n].dl.Len := 7;
      inc(n);
      inc(bl_count[7]);
    end;
    while (n <= 287) do
    begin
      static_ltree[n].dl.Len := 8;
      inc(n);
      inc(bl_count[8]);
    end;

    { Codes 286 and 287 do not exist, but we must include them in the
      tree construction to get a canonical Huffman tree (longest code
      all ones)  }

    gen_codes(tree_ptr(@static_ltree), L_CODES+1, bl_count);

    { The static distance tree is trivial: }
    for n := 0 to D_CODES-1 do
    begin
      static_dtree[n].dl.Len := 5;
      static_dtree[n].fc.Code := bi_reverse(cardinal(n), 5);
    end;
    static_init_done := TRUE;

    gen_trees_header;  { save to include file }
{$else}
begin
{$endif} { GEN_TREES_H) }
end;

{ ===========================================================================
  Initialize a new block. }
{local}

procedure init_block(var s : deflate_state);
var
  n : integer; { iterates over tree elements }
begin
  { Initialize the trees. }
  for n := 0 to L_CODES-1 do
    s.dyn_ltree[n].fc.Freq := 0;
  for n := 0 to D_CODES-1 do
    s.dyn_dtree[n].fc.Freq := 0;
  for n := 0 to BL_CODES-1 do
    s.bl_tree[n].fc.Freq := 0;

  s.dyn_ltree[END_BLOCK].fc.Freq := 1;
  s.static_len := 0;
  s.opt_len := 0;
  s.matches := 0;
  s.last_lit := 0;
end;

const
  SMALLEST = 1;
{ Index within the heap array of least frequent node in the Huffman tree }

{ ===========================================================================
  Initialize the tree data structures for a new zlib stream. }
procedure _tr_init(var s : deflate_state);
begin
  tr_static_init;

  s.compressed_len := 0;

  s.l_desc.dyn_tree := tree_ptr(@s.dyn_ltree);
  s.l_desc.stat_desc := @static_l_desc;

  s.d_desc.dyn_tree := tree_ptr(@s.dyn_dtree);
  s.d_desc.stat_desc := @static_d_desc;

  s.bl_desc.dyn_tree := tree_ptr(@s.bl_tree);
  s.bl_desc.stat_desc := @static_bl_desc;

  s.bi_buf := 0;
  s.bi_valid := 0;
  s.last_eob_len := 8; { enough lookahead for inflate }
{$ifdef ZLIB_DEBUG}
  s.bits_sent := 0;
{$endif}

  { Initialize the first block of the first file: }
  init_block(s);
end;

{ ===========================================================================
  Remove the smallest element from the heap and recreate the heap with
  one less element. Updates heap and heap_len.

macro pqremove(s, tree, top)
begin
    top := s.heap[SMALLEST];
    s.heap[SMALLEST] := s.heap[s.heap_len];
    dec(s.heap_len);
    pqdownheap(s, tree, SMALLEST);
end
}

{ ===========================================================================
  Compares to subtrees, using the tree depth as tie breaker when
  the subtrees have equal frequency. This minimizes the worst case length.

macro smaller(tree, n, m, depth)
   ( (tree[n].Freq < tree[m].Freq) or
     ((tree[n].Freq = tree[m].Freq) and (depth[n] <= depth[m])) )
}

{ ===========================================================================
  Restore the heap property by moving down the tree starting at node k,
  exchanging a node with the smallest of its two sons if necessary, stopping
  when the heap property is re-established (each father smaller than its
  two sons). }
{local}

procedure pqdownheap(var s : deflate_state;
                     tree : tree_ptr;   { the tree to restore }
                     k : integer);          { node to move down }
var
  v : integer;
  j : integer;
begin
  v := s.heap[k];
  j := k shl 1;  { left son of k }
  while (j <= s.heap_len) do
  begin
    { Set j to the smallest of the two sons: }
    if (j < s.heap_len) and
       {smaller(tree, s.heap[j+1], s.heap[j], s.depth)}
      ( (tree[s.heap[j+1]].fc.Freq < tree[s.heap[j]].fc.Freq) or
        ((tree[s.heap[j+1]].fc.Freq = tree[s.heap[j]].fc.Freq) and
         (s.depth[s.heap[j+1]] <= s.depth[s.heap[j]])) ) then
    begin
      inc(j);
    end;
    { Exit if v is smaller than both sons }
    if {(smaller(tree, v, s.heap[j], s.depth))}
     ( (tree[v].fc.Freq < tree[s.heap[j]].fc.Freq) or
       ((tree[v].fc.Freq = tree[s.heap[j]].fc.Freq) and
        (s.depth[v] <= s.depth[s.heap[j]])) ) then
      break;
    { Exchange v with the smallest son }
    s.heap[k] := s.heap[j];
    k := j;

    { And continue down the tree, setting j to the left son of k }
    j := j shl 1;
  end;
  s.heap[k] := v;
end;

{ ===========================================================================
  Compute the optimal bit lengths for a tree and update the total bit length
  for the current block.
  IN assertion: the fields freq and dad are set, heap[heap_max] and
     above are the tree nodes sorted by increasing frequency.
  OUT assertions: the field len is set to the optimal bit length, the
      array bl_count contains the frequencies for each bit length.
      The length opt_len is updated; static_len is also updated if stree is
      not null. }

{local}
procedure gen_bitlen(var s : deflate_state;
                     var desc : tree_desc);   { the tree descriptor }
var
  tree : tree_ptr;
  max_code : integer;
  stree : tree_ptr; {const}
  extra : pinteger; {const}
  base : integer;
  max_length : integer;
  h : integer;              { heap index }
  n, m : integer;           { iterate over the tree elements }
  bits : integer;           { bit length }
  xbits : integer;          { extra bits }
  f : word;              { frequency }
  overflow : integer;   { number of elements with bit length too large }
begin
  tree := desc.dyn_tree;
  max_code := desc.max_code;
  stree := desc.stat_desc^.static_tree;
  extra := desc.stat_desc^.extra_bits;
  base := desc.stat_desc^.extra_base;
  max_length := desc.stat_desc^.max_length;
  overflow := 0;

  for bits := 0 to MAX_BITS do
    s.bl_count[bits] := 0;

  { In a first pass, compute the optimal bit lengths (which may
    overflow in the case of the bit length tree). }

  tree[s.heap[s.heap_max]].dl.Len := 0; { root of the heap }

  for h := s.heap_max+1 to HEAP_SIZE-1 do
  begin
    n := s.heap[h];
    bits := tree[tree[n].dl.Dad].dl.Len + 1;
    if (bits > max_length) then
    begin
      bits := max_length;
      inc(overflow);
    end;
    tree[n].dl.Len := word(bits);
    { We overwrite tree[n].dl.Dad which is no longer needed }

    if (n > max_code) then
      continue; { not a leaf node }

    inc(s.bl_count[bits]);
    xbits := 0;
    if (n >= base) then
      xbits := extra[n-base];
    f := tree[n].fc.Freq;
    inc(s.opt_len, longint(f) * (bits + xbits));
    if (stree <> NIL) then
      inc(s.static_len, longint(f) * (stree[n].dl.Len + xbits));
  end;
  if (overflow = 0) then
    exit;
  {$ifdef ZLIB_DEBUG}
  Tracev(^M'bit length overflow');
  {$endif}
  { This happens for example on obj2 and pic of the Calgary corpus }

  { Find the first bit length which could increase: }
  repeat
    bits := max_length-1;
    while (s.bl_count[bits] = 0) do
      dec(bits);
    dec(s.bl_count[bits]);      { move one leaf down the tree }
    inc(s.bl_count[bits+1], 2); { move one overflow item as its brother }
    dec(s.bl_count[max_length]);
    { The brother of the overflow item also moves one step up,
      but this does not affect bl_count[max_length] }

    dec(overflow, 2);
  until (overflow <= 0);

  { Now recompute all bit lengths, scanning in increasing frequency.
    h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
    lengths instead of fixing only the wrong ones. This idea is taken
    from 'ar' written by Haruhiko Okumura.) }
  h := HEAP_SIZE;  { Delphi3: compiler warning w/o this }
  for bits := max_length downto 1 do
  begin
    n := s.bl_count[bits];
    while (n <> 0) do
    begin
      dec(h);
      m := s.heap[h];
      if (m > max_code) then
        continue;
      if (tree[m].dl.Len <> cardinal(bits)) then
      begin
        {$ifdef ZLIB_DEBUG}
        Trace('code '+IntToStr(m)+' bits '+IntToStr(tree[m].dl.Len)
              +'.'+IntToStr(bits));
        {$ENDIF}
        inc(s.opt_len, (cardinal(bits) - cardinal(tree[m].dl.Len))
                        * cardinal(tree[m].fc.Freq) );
        tree[m].dl.Len := word(bits);
      end;
      dec(n);
    end;
  end;
end;

{ ===========================================================================
  Construct one Huffman tree and assigns the code bit strings and lengths.
  Update the total bit length for the current block.
  IN assertion: the field freq is set for all tree elements.
  OUT assertions: the fields len and code are set to the optimal bit length
      and corresponding code. The length opt_len is updated; static_len is
      also updated if stree is not null. The field max_code is set. }

{local}
procedure build_tree(var s : deflate_state;
                     var desc : tree_desc); { the tree descriptor }

var
  tree : tree_ptr;
  stree : tree_ptr; {const}
  elems : integer;
  n, m : integer;          { iterate over heap elements }
  max_code : integer;      { largest code with non zero frequency }
  node : integer;          { new node being created }
begin
  tree := desc.dyn_tree;
  stree := desc.stat_desc^.static_tree;
  elems := desc.stat_desc^.elems;
  max_code := -1;

  { Construct the initial heap, with least frequent element in
    heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
    heap[0] is not used. }
  s.heap_len := 0;
  s.heap_max := HEAP_SIZE;

  for n := 0 to elems-1 do
  begin
    if (tree[n].fc.Freq <> 0) then
    begin
      max_code := n;
      inc(s.heap_len);
      s.heap[s.heap_len] := n;
      s.depth[n] := 0;
    end
    else
    begin
      tree[n].dl.Len := 0;
    end;
  end;

  { The pkzip format requires that at least one distance code exists,
    and that at least one bit should be sent even if there is only one
    possible code. So to avoid special checks later on we force at least
    two codes of non zero frequency. }

  while (s.heap_len < 2) do
  begin
    inc(s.heap_len);
    if (max_code < 2) then
    begin
      inc(max_code);
      s.heap[s.heap_len] := max_code;
      node := max_code;
    end
    else
    begin
      s.heap[s.heap_len] := 0;
      node := 0;
    end;
    tree[node].fc.Freq := 1;
    s.depth[node] := 0;
    dec(s.opt_len);
    if (stree <> NIL) then
      dec(s.static_len, stree[node].dl.Len);
    { node is 0 or 1 so it does not have extra bits }
  end;
  desc.max_code := max_code;

  { The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
    establish sub-heaps of increasing lengths: }

  for n := s.heap_len div 2 downto 1 do
    pqdownheap(s, tree, n);

  { Construct the Huffman tree by repeatedly combining the least two
    frequent nodes. }

  node := elems;              { next internal node of the tree }
  repeat
    {pqremove(s, tree, n);}  { n := node of least frequency }
    n := s.heap[SMALLEST];
    s.heap[SMALLEST] := s.heap[s.heap_len];
    dec(s.heap_len);
    pqdownheap(s, tree, SMALLEST);

    m := s.heap[SMALLEST]; { m := node of next least frequency }

    dec(s.heap_max);
    s.heap[s.heap_max] := n; { keep the nodes sorted by frequency }
    dec(s.heap_max);
    s.heap[s.heap_max] := m;

    { Create a new node father of n and m }
    tree[node].fc.Freq := tree[n].fc.Freq + tree[m].fc.Freq;
    { maximum }
    if (s.depth[n] >= s.depth[m]) then
      s.depth[node] := byte (s.depth[n] + 1)
    else
      s.depth[node] := byte (s.depth[m] + 1);

    tree[m].dl.Dad := word(node);
    tree[n].dl.Dad := word(node);
{$ifdef DUMP_BL_TREE}
    if (tree = tree_ptr(@s.bl_tree)) then
    begin
      WriteLn(#13'node ',node,'(',tree[node].fc.Freq,') sons ',n,
              '(',tree[n].fc.Freq,') ', m, '(',tree[m].fc.Freq,')');
    end;
{$endif}
    { and insert the new node in the heap }
    s.heap[SMALLEST] := node;
    inc(node);
    pqdownheap(s, tree, SMALLEST);

  until (s.heap_len < 2);

  dec(s.heap_max);
  s.heap[s.heap_max] := s.heap[SMALLEST];

  { At this point, the fields freq and dad are set. We can now
    generate the bit lengths. }

  gen_bitlen(s, desc);

  { The field len is now set, we can generate the bit codes }
  gen_codes (tree, max_code, s.bl_count);
end;

{ ===========================================================================
  Scan a literal or distance tree to determine the frequencies of the codes
  in the bit length tree. }

{local}
procedure scan_tree(var s : deflate_state;
                    var tree : array of ct_data;    { the tree to be scanned }
                    max_code : integer);    { and its largest code of non zero frequency }
var
  n : integer;                 { iterates over all tree elements }
  prevlen : integer;           { last emitted length }
  curlen : integer;            { length of current code }
  nextlen : integer;           { length of next code }
  count : integer;             { repeat count of the current code }
  max_count : integer;         { max repeat count }
  min_count : integer;         { min repeat count }
begin
  prevlen := -1;
  nextlen := tree[0].dl.Len;
  count := 0;
  max_count := 7;
  min_count := 4;

  if (nextlen = 0) then
  begin
    max_count := 138;
    min_count := 3;
  end;
  tree[max_code+1].dl.Len := word($ffff); { guard }

  for n := 0 to max_code do
  begin
    curlen := nextlen;
{$push}{$R-}
    nextlen := tree[n+1].dl.Len;
{$pop}
    inc(count);
    if (count < max_count) and (curlen = nextlen) then
      continue
    else
      if (count < min_count) then
        inc(s.bl_tree[curlen].fc.Freq, count)
      else
        if (curlen <> 0) then
        begin
          if (curlen <> prevlen) then
            inc(s.bl_tree[curlen].fc.Freq);
          inc(s.bl_tree[REP_3_6].fc.Freq);
        end
        else
          if (count <= 10) then
            inc(s.bl_tree[REPZ_3_10].fc.Freq)
          else
            inc(s.bl_tree[REPZ_11_138].fc.Freq);

    count := 0;
    prevlen := curlen;
    if (nextlen = 0) then
    begin
      max_count := 138;
      min_count := 3;
    end
    else
      if (curlen = nextlen) then
      begin
        max_count := 6;
        min_count := 3;
      end
      else
      begin
        max_count := 7;
        min_count := 4;
      end;
  end;
end;

{ ===========================================================================
  Send a literal or distance tree in compressed form, using the codes in
  bl_tree. }

{local}
procedure send_tree(var s : deflate_state;
                    var tree : array of ct_data;    { the tree to be scanned }
                    max_code : integer);    { and its largest code of non zero frequency }

var
  n : integer;                { iterates over all tree elements }
  prevlen : integer;          { last emitted length }
  curlen : integer;           { length of current code }
  nextlen : integer;          { length of next code }
  count : integer;            { repeat count of the current code }
  max_count : integer;        { max repeat count }
  min_count : integer;        { min repeat count }
begin
  prevlen := -1;
  nextlen := tree[0].dl.Len;
  count := 0;
  max_count := 7;
  min_count := 4;

  { tree[max_code+1].dl.Len := -1; }  { guard already set }
  if (nextlen = 0) then
  begin
    max_count := 138;
    min_count := 3;
  end;

  for n := 0 to max_code do
  begin
    curlen := nextlen;
    nextlen := tree[n+1].dl.Len;
    inc(count);
    if (count < max_count) and (curlen = nextlen) then
      continue
    else
      if (count < min_count) then
      begin
        repeat
          {$ifdef ZLIB_DEBUG}
          Tracevvv(#13'cd '+IntToStr(curlen));
          {$ENDIF}
          send_bits(s, s.bl_tree[curlen].fc.Code, s.bl_tree[curlen].dl.Len);
          dec(count);
        until (count = 0);
      end
      else
        if (curlen <> 0) then
        begin
          if (curlen <> prevlen) then
          begin
            {$ifdef ZLIB_DEBUG}
            Tracevvv(#13'cd '+IntToStr(curlen));
            {$ENDIF}
            send_bits(s, s.bl_tree[curlen].fc.Code, s.bl_tree[curlen].dl.Len);
            dec(count);
          end;
          {$IFDEF ZLIB_DEBUG}
          Assert((count >= 3) and (count <= 6), ' 3_6?');
          {$ENDIF}
          {$ifdef ZLIB_DEBUG}
          Tracevvv(#13'cd '+IntToStr(REP_3_6));
          {$ENDIF}
          send_bits(s, s.bl_tree[REP_3_6].fc.Code, s.bl_tree[REP_3_6].dl.Len);
          send_bits(s, count-3, 2);
        end
        else
          if (count <= 10) then
          begin
            {$ifdef ZLIB_DEBUG}
            Tracevvv(#13'cd '+IntToStr(REPZ_3_10));
            {$ENDIF}
            send_bits(s, s.bl_tree[REPZ_3_10].fc.Code, s.bl_tree[REPZ_3_10].dl.Len);
            send_bits(s, count-3, 3);
          end
          else
          begin
            {$ifdef ZLIB_DEBUG}
            Tracevvv(#13'cd '+IntToStr(REPZ_11_138));
            {$ENDIF}
            send_bits(s, s.bl_tree[REPZ_11_138].fc.Code, s.bl_tree[REPZ_11_138].dl.Len);
            send_bits(s, count-11, 7);
          end;
    count := 0;
    prevlen := curlen;
    if (nextlen = 0) then
    begin
      max_count := 138;
      min_count := 3;
    end
    else
      if (curlen = nextlen) then
      begin
        max_count := 6;
        min_count := 3;
      end
      else
      begin
        max_count := 7;
        min_count := 4;
      end;
  end;
end;

{ ===========================================================================
  Construct the Huffman tree for the bit lengths and return the index in
  bl_order of the last bit length code to send. }

{local}
function build_bl_tree(var s : deflate_state) : integer;
var
  max_blindex : integer;  { index of last bit length code of non zero freq }
begin
  { Determine the bit length frequencies for literal and distance trees }
  scan_tree(s, s.dyn_ltree, s.l_desc.max_code);
  scan_tree(s, s.dyn_dtree, s.d_desc.max_code);

  { Build the bit length tree: }
  build_tree(s, s.bl_desc);
  { opt_len now includes the length of the tree representations, except
    the lengths of the bit lengths codes and the 5+5+4 bits for the counts. }

  { Determine the number of bit length codes to send. The pkzip format
    requires that at least 4 bit length codes be sent. (appnote.txt says
    3 but the actual value used is 4.) }

  for max_blindex := BL_CODES-1 downto 3 do
  begin
    if (s.bl_tree[bl_order[max_blindex]].dl.Len <> 0) then
      break;
  end;
  { Update opt_len to include the bit length tree and counts }
  inc(s.opt_len, 3*(max_blindex+1) + 5+5+4);
  {$ifdef ZLIB_DEBUG}
  Tracev(^M'dyn trees: dyn %ld, stat %ld {s.opt_len, s.static_len}');
  {$ENDIF}

  build_bl_tree := max_blindex;
end;

{ ===========================================================================
  Send the header for a block using dynamic Huffman trees: the counts, the
  lengths of the bit length codes, the literal tree and the distance tree.
  IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4. }

{local}
procedure send_all_trees(var s : deflate_state;
                         lcodes : integer;
                         dcodes : integer;
                         blcodes : integer); { number of codes for each tree }
var
  rank : integer;                    { index in bl_order }
begin
  {$IFDEF ZLIB_DEBUG}
  Assert ((lcodes >= 257) and (dcodes >= 1) and (blcodes >= 4),
          'not enough codes');
  Assert ((lcodes <= L_CODES) and (dcodes <= D_CODES)
          and (blcodes <= BL_CODES), 'too many codes');
  Tracev(^M'bl counts: ');
  {$ENDIF}
  send_bits(s, lcodes-257, 5); { not +255 as stated in appnote.txt }
  send_bits(s, dcodes-1,   5);
  send_bits(s, blcodes-4,  4); { not -3 as stated in appnote.txt }
  for rank := 0 to blcodes-1 do
  begin
    {$ifdef ZLIB_DEBUG}
    Tracev(^M'bl code '+IntToStr(bl_order[rank]));
    {$ENDIF}
    send_bits(s, s.bl_tree[bl_order[rank]].dl.Len, 3);
  end;
  {$ifdef ZLIB_DEBUG}
  Tracev(^M'bl tree: sent '+IntToStr(s.bits_sent));
  {$ENDIF}

  send_tree(s, s.dyn_ltree, lcodes-1); { literal tree }
  {$ifdef ZLIB_DEBUG}
  Tracev(^M'lit tree: sent '+IntToStr(s.bits_sent));
  {$ENDIF}

  send_tree(s, s.dyn_dtree, dcodes-1); { distance tree }
  {$ifdef ZLIB_DEBUG}
  Tracev(^M'dist tree: sent '+IntToStr(s.bits_sent));
  {$ENDIF}
end;

{ ===========================================================================
  Flush the bit buffer and align the output on a byte boundary }

{local}
procedure bi_windup(var s : deflate_state);
begin
  if (s.bi_valid > 8) then
  begin
    {put_short(s, s.bi_buf);}
    s.pending_buf^[s.pending] := byte(s.bi_buf and $ff);
    inc(s.pending);
    s.pending_buf^[s.pending] := byte(word(s.bi_buf) shr 8);;
    inc(s.pending);
  end
  else
    if (s.bi_valid > 0) then
    begin
      {put_byte(s, (Byte)s^.bi_buf);}
      s.pending_buf^[s.pending] := Byte(s.bi_buf);
      inc(s.pending);
    end;
  s.bi_buf := 0;
  s.bi_valid := 0;
{$ifdef ZLIB_DEBUG}
  s.bits_sent := (s.bits_sent+7) and (not 7);
{$endif}
end;

{ ===========================================================================
  Copy a stored block, storing first the length and its
  one's complement if requested. }

{local}
procedure copy_block(var s : deflate_state;
                     buf : Pbyte;       { the input data }
                     len : word;        { its length }
                     header : boolean); { true if block header must be written }
begin
  bi_windup(s);        { align on byte boundary }
  s.last_eob_len := 8; { enough lookahead for inflate }

  if (header) then
  begin
    {put_short(s, (word)len);}
    s.pending_buf^[s.pending] := byte(len and $ff);
    inc(s.pending);
    s.pending_buf^[s.pending] := byte(len shr 8);;
    inc(s.pending);
    {put_short(s, (word)~len);}
    s.pending_buf^[s.pending] := byte((not len) and $ff);
    inc(s.pending);
    s.pending_buf^[s.pending] := byte((not len) shr 8);;
    inc(s.pending);

{$ifdef ZLIB_DEBUG}
    inc(s.bits_sent, 2*16);
{$endif}
  end;
{$ifdef ZLIB_DEBUG}
  inc(s.bits_sent, len shl 3);
{$endif}
  move(buf^,s.pending_buf^[s.pending],len);
  inc(s.pending,len);
end;


{ ===========================================================================
  Send a stored block }

procedure _tr_stored_block(var s : deflate_state;
                           buf : Pbyte;     { input block }
                           stored_len : longint; { length of input block }
                           eof : boolean);   { true if this is the last block for a file }

begin
  send_bits(s, (STORED_BLOCK shl 1)+ord(eof), 3);  { send block type }
  s.compressed_len := (s.compressed_len + 3 + 7) and longint(not cardinal(7));
  inc(s.compressed_len, (stored_len + 4) shl 3);

  copy_block(s, buf, cardinal(stored_len), TRUE); { with header }
end;

{ ===========================================================================
  Flush the bit buffer, keeping at most 7 bits in it. }

{local}
procedure bi_flush(var s : deflate_state);
begin
  if (s.bi_valid = 16) then
  begin
    {put_short(s, s.bi_buf);}
    s.pending_buf^[s.pending] := byte(s.bi_buf and $ff);
    inc(s.pending);
    s.pending_buf^[s.pending] := byte(word(s.bi_buf) shr 8);;
    inc(s.pending);

    s.bi_buf := 0;
    s.bi_valid := 0;
  end
  else
   if (s.bi_valid >= 8) then
   begin
     {put_byte(s, (Byte)s^.bi_buf);}
     s.pending_buf^[s.pending] := Byte(s.bi_buf);
     inc(s.pending);

     s.bi_buf := s.bi_buf shr 8;
     dec(s.bi_valid, 8);
   end;
end;


{ ===========================================================================
  Send one empty static block to give enough lookahead for inflate.
  This takes 10 bits, of which 7 may remain in the bit buffer.
  The current inflate code requires 9 bits of lookahead. If the
  last two codes for the previous block (real code plus EOB) were coded
  on 5 bits or less, inflate may have only 5+3 bits of lookahead to decode
  the last real code. In this case we send two empty static blocks instead
  of one. (There are no problems if the previous block is stored or fixed.)
  To simplify the code, we assume the worst case of last real code encoded
  on one bit only. }

procedure _tr_align(var s : deflate_state);
begin
  send_bits(s, STATIC_TREES shl 1, 3);
  {$ifdef ZLIB_DEBUG}
  Tracevvv(#13'cd '+IntToStr(END_BLOCK));
  {$ENDIF}
  send_bits(s, static_ltree[END_BLOCK].fc.Code, static_ltree[END_BLOCK].dl.Len);
  inc(s.compressed_len, cardinal(10)); { 3 for block type, 7 for EOB }
  bi_flush(s);
  { Of the 10 bits for the empty block, we have already sent
    (10 - bi_valid) bits. The lookahead for the last real code (before
    the EOB of the previous block) was thus at least one plus the length
    of the EOB plus what we have just sent of the empty static block. }
  if (1 + s.last_eob_len + 10 - s.bi_valid < 9) then
  begin
    send_bits(s, STATIC_TREES shl 1, 3);
    {$ifdef ZLIB_DEBUG}
    Tracevvv(#13'cd '+IntToStr(END_BLOCK));
    {$ENDIF}
    send_bits(s, static_ltree[END_BLOCK].fc.Code, static_ltree[END_BLOCK].dl.Len);
    inc(s.compressed_len, cardinal(10));
    bi_flush(s);
  end;
  s.last_eob_len := 7;
end;

{ ===========================================================================
  Set the data type to ASCII or BINARY, using a crude approximation:
  binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise.
  IN assertion: the fields freq of dyn_ltree are set and the total of all
  frequencies does not exceed 64K (to fit in an integer on 16 bit machines). }

{local}
procedure set_data_type(var s : deflate_state);
var
  n : integer;
  ascii_freq : cardinal;
  bin_freq : cardinal;
begin
  n := 0;
  ascii_freq := 0;
  bin_freq := 0;

  while (n < 7) do
  begin
    inc(bin_freq, s.dyn_ltree[n].fc.Freq);
    inc(n);
  end;
  while (n < 128) do
  begin
    inc(ascii_freq, s.dyn_ltree[n].fc.Freq);
    inc(n);
  end;
  while (n < LITERALS) do
  begin
    inc(bin_freq, s.dyn_ltree[n].fc.Freq);
    inc(n);
  end;
  if (bin_freq > (ascii_freq shr 2)) then
    s.data_type := Byte(Z_BINARY)
  else
    s.data_type := Byte(Z_ASCII);
end;

{ ===========================================================================
  Send the block data compressed using the given Huffman trees }

{local}
procedure compress_block(var s : deflate_state;
                         var ltree : array of ct_data;   { literal tree }
                         var dtree : array of ct_data);  { distance tree }
var
  dist : cardinal;      { distance of matched string }
  lc : integer;             { match length or unmatched char (if dist == 0) }
  lx : cardinal;        { running index in l_buf }
  code : cardinal;      { the code to send }
  extra : integer;          { number of extra bits to send }
begin
  lx := 0;
  if (s.last_lit <> 0) then
  repeat
    dist := s.d_buf^[lx];
    lc := s.l_buf^[lx];
    inc(lx);
    if (dist = 0) then
    begin
      { send a literal byte }
      {$ifdef ZLIB_DEBUG}
      Tracevvv(#13'cd '+IntToStr(lc));
      Tracecv((lc > 31) and (lc < 128), ' '+char(lc)+' ');
      {$ENDIF}
      send_bits(s, ltree[lc].fc.Code, ltree[lc].dl.Len);
    end
    else
    begin
      { Here, lc is the match length - MIN_MATCH }
      code := _length_code[lc];
      { send the length code }
      {$ifdef ZLIB_DEBUG}
      Tracevvv(#13'cd '+IntToStr(code+LITERALS+1));
      {$ENDIF}
      send_bits(s, ltree[code+LITERALS+1].fc.Code, ltree[code+LITERALS+1].dl.Len);
      extra := extra_lbits[code];
      if (extra <> 0) then
      begin
        dec(lc, base_length[code]);
        send_bits(s, lc, extra);       { send the extra length bits }
      end;
      dec(dist); { dist is now the match distance - 1 }
      {code := d_code(dist);}
      if (dist < 256) then
        code := _dist_code[dist]
      else
        code := _dist_code[256+(dist shr 7)];

      {$IFDEF ZLIB_DEBUG}
      Assert (code < D_CODES, 'bad d_code');
      {$ENDIF}

      { send the distance code }
      {$ifdef ZLIB_DEBUG}
      Tracevvv(#13'cd '+IntToStr(code));
      {$ENDIF}
      send_bits(s, dtree[code].fc.Code, dtree[code].dl.Len);
      extra := extra_dbits[code];
      if (extra <> 0) then
      begin
        dec(dist, base_dist[code]);
        send_bits(s, dist, extra);   { send the extra distance bits }
      end;
    end; { literal or match pair ? }

    { Check that the overlay between pending_buf and d_buf+l_buf is ok: }
    {$IFDEF ZLIB_DEBUG}
    Assert(s.pending < s.lit_bufsize + 2*lx, 'pendingBuf overflow');
    {$ENDIF}
  until (lx >= s.last_lit);

  {$ifdef ZLIB_DEBUG}
  Tracevvv(#13'cd '+IntToStr(END_BLOCK));
  {$ENDIF}
  send_bits(s, ltree[END_BLOCK].fc.Code, ltree[END_BLOCK].dl.Len);
  s.last_eob_len := ltree[END_BLOCK].dl.Len;
end;


{ ===========================================================================
  Determine the best encoding for the current block: dynamic trees, static
  trees or store, and output the encoded block to the zip file. This function
  returns the total compressed length for the file so far. }

function _tr_flush_block (var s : deflate_state;
         buf : Pbyte;         { input block, or NULL if too old }
         stored_len : longint;     { length of input block }
         eof : boolean) : longint; { true if this is the last block for a file }
var
  opt_lenb, static_lenb : longint; { opt_len and static_len in bytes }
  max_blindex : integer;  { index of last bit length code of non zero freq }
begin
  max_blindex := 0;

  { Build the Huffman trees unless a stored block is forced }
  if (s.level > 0) then
  begin
    { Check if the file is ascii or binary }
    if (s.data_type = Z_UNKNOWN) then
      set_data_type(s);

    { Construct the literal and distance trees }
    build_tree(s, s.l_desc);
    {$ifdef ZLIB_DEBUG}
    Tracev(^M'lit data: dyn %ld, stat %ld {s.opt_len, s.static_len}');
    {$ENDIF}

    build_tree(s, s.d_desc);
    {$ifdef ZLIB_DEBUG}
    Tracev(^M'dist data: dyn %ld, stat %ld {s.opt_len, s.static_len}');
    {$ENDIF}
    { At this point, opt_len and static_len are the total bit lengths of
      the compressed block data, excluding the tree representations. }

    { Build the bit length tree for the above two trees, and get the index
      in bl_order of the last bit length code to send. }
    max_blindex := build_bl_tree(s);

    { Determine the best encoding. Compute first the block length in bytes}
    opt_lenb := (s.opt_len+3+7) shr 3;
    static_lenb := (s.static_len+3+7) shr 3;

    {$ifdef ZLIB_DEBUG}
    Tracev(^M'opt %lu(%lu) stat %lu(%lu) stored %lu lit %u '+
	    '{opt_lenb, s.opt_len, static_lenb, s.static_len, stored_len,'+
	    's.last_lit}');
    {$ENDIF}

    if (static_lenb <= opt_lenb) then
      opt_lenb := static_lenb;

  end
  else
  begin
    {$IFDEF ZLIB_DEBUG}
    Assert(buf <> nil, 'lost buf');
    {$ENDIF}
    static_lenb := stored_len + 5;
    opt_lenb := static_lenb;        { force a stored block }
  end;

  { If compression failed and this is the first and last block,
    and if the .zip file can be seeked (to rewrite the local header),
    the whole file is transformed into a stored file:  }

{$ifdef STORED_FILE_OK}
{$ifdef FORCE_STORED_FILE}
  if eof and (s.compressed_len = 0) then
  begin { force stored file }
{$else}
  if (stored_len <= opt_lenb) and eof and (s.compressed_len=cardinal(0))
     and seekable()) do
  begin
{$endif}
    { Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: }
    if buf=nil then
      error ('block vanished');

    copy_block(buf, cardinal(stored_len), 0); { without header }
    s.compressed_len := stored_len shl 3;
    s.method := STORED;
  end
  else
{$endif} { STORED_FILE_OK }

{$ifdef FORCE_STORED}
  if buf<>nil then
  begin { force stored block }
{$else}
  if (stored_len+4 <= opt_lenb) and (buf <> nil) then
  begin
                     { 4: two words for the lengths }
{$endif}
    { The test buf <> NULL is only necessary if LIT_BUFSIZE > WSIZE.
      Otherwise we can't have processed more than WSIZE input bytes since
      the last block flush, because compression would have been
      successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
      transform a block into a stored block. }

    _tr_stored_block(s, buf, stored_len, eof);

{$ifdef FORCE_STATIC}
  end
  else
    if (static_lenb >= 0) then
    begin { force static trees }
{$else}
  end
  else
    if (static_lenb = opt_lenb) then
    begin
{$endif}
      send_bits(s, (STATIC_TREES shl 1)+ord(eof), 3);
      compress_block(s, static_ltree, static_dtree);
      inc(s.compressed_len, 3 + s.static_len);
    end
    else
    begin
      send_bits(s, (DYN_TREES shl 1)+ord(eof), 3);
      send_all_trees(s, s.l_desc.max_code+1, s.d_desc.max_code+1,
                     max_blindex+1);
      compress_block(s, s.dyn_ltree, s.dyn_dtree);
      inc(s.compressed_len, 3 + s.opt_len);
    end;
  {$ifdef ZLIB_DEBUG}
  Assert (s.compressed_len = s.bits_sent, 'bad compressed size');
  {$ENDIF}
  init_block(s);

  if (eof) then
  begin
    bi_windup(s);
    inc(s.compressed_len, 7);  { align on byte boundary }
  end;
  {$ifdef ZLIB_DEBUG}
  Tracev(#13'comprlen %lu(%lu) {s.compressed_len shr 3,'+
         's.compressed_len-7*ord(eof)}');
  {$ENDIF}

  _tr_flush_block := s.compressed_len shr 3;
end;


{ ===========================================================================
  Save the match info and tally the frequency counts. Return true if
  the current block must be flushed. }

function _tr_tally (var s : deflate_state;
   dist : cardinal;          { distance of matched string }
   lc : cardinal) : boolean; { match length-MIN_MATCH or unmatched char (if dist=0) }
var
  {$IFDEF ZLIB_DEBUG}
  MAX_DIST : word;
  {$ENDIF}
  code : word;
{$ifdef TRUNCATE_BLOCK}
var
  out_length : longint;
  in_length : longint;
  dcode : integer;
{$endif}
begin
  s.d_buf^[s.last_lit] := word(dist);
  s.l_buf^[s.last_lit] := byte(lc);
  inc(s.last_lit);
  if (dist = 0) then
  begin
    { lc is the unmatched char }
    inc(s.dyn_ltree[lc].fc.Freq);
  end
  else
  begin
    inc(s.matches);
    { Here, lc is the match length - MIN_MATCH }
    dec(dist);             { dist := match distance - 1 }

    {macro d_code(dist)}
    if (dist) < 256 then
      code := _dist_code[dist]
    else
      code := _dist_code[256+(dist shr 7)];
    {$IFDEF ZLIB_DEBUG}
{macro  MAX_DIST(s) <=> ((s)^.w_size-MIN_LOOKAHEAD)
   In order to simplify the code, particularly on 16 bit machines, match
   distances are limited to MAX_DIST instead of WSIZE. }
    MAX_DIST := word(s.w_size-MIN_LOOKAHEAD);
    Assert((dist < word(MAX_DIST)) and
           (word(lc) <= word(MAX_MATCH-MIN_MATCH)) and
           (word(code) < word(D_CODES)),  '_tr_tally: bad match');
    {$ENDIF}
    inc(s.dyn_ltree[_length_code[lc]+LITERALS+1].fc.Freq);
    {s.dyn_dtree[d_code(dist)].Freq++;}
    inc(s.dyn_dtree[code].fc.Freq);
  end;

{$ifdef TRUNCATE_BLOCK}
  { Try to guess if it is profitable to stop the current block here }
  if (s.last_lit and $1fff = 0) and (s.level > 2) then
  begin
    { Compute an upper bound for the compressed length }
    out_length := longint(s.last_lit)*cardinal(8);
    in_length := longint(cardinal(s.strstart) - s.block_start);
    for dcode := 0 to D_CODES-1 do
    begin
      inc(out_length, longint(s.dyn_dtree[dcode].fc.Freq *
            (cardinal(5)+extra_dbits[dcode])) );
    end;
    out_length := out_length shr 3;
    {$ifdef ZLIB_DEBUG}
    Tracev(^M'last_lit %u, in %ld, out ~%ld(%ld%%) ');
          { s.last_lit, in_length, out_length,
           cardinal(100) - out_length*100 div in_length)); }
    {$ENDIF}
    if (s.matches < s.last_lit div 2) and (out_length < in_length div 2) then
    begin
      _tr_tally := TRUE;
      exit;
    end;
  end;
{$endif}
  _tr_tally := (s.last_lit = s.lit_bufsize-1);
  { We avoid equality with lit_bufsize because of wraparound at 64K
    on 16 bit machines and because stored blocks are restricted to
    64K-1 bytes. }
end;

end.