zdeflate.pas

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  dest^.state := pInternal_state(ds);
  ds^ := ss^;
  ds^.strm := dest;

  ds^.window := pzByteArray ( ZALLOC(dest^, ds^.w_size, 2*sizeof(Byte)) );
  ds^.prev   := pzPosfArray ( ZALLOC(dest^, ds^.w_size, sizeof(Pos)) );
  ds^.head   := pzPosfArray ( ZALLOC(dest^, ds^.hash_size, sizeof(Pos)) );
  overlay := pushfArray ( ZALLOC(dest^, ds^.lit_bufsize, sizeof(ush)+2) );
  ds^.pending_buf := pzByteArray ( overlay );

  if (ds^.window = Z_NULL) or (ds^.prev = Z_NULL) or (ds^.head = Z_NULL)
     or (ds^.pending_buf = Z_NULL) then
  begin
    deflateEnd (dest^);
    deflateCopy := Z_MEM_ERROR;
    exit;
  end;
  { following zmemcpy do not work for 16-bit MSDOS }
  zmemcpy(pBytef(ds^.window), pBytef(ss^.window), ds^.w_size * 2 * sizeof(Byte));
  zmemcpy(pBytef(ds^.prev), pBytef(ss^.prev), ds^.w_size * sizeof(Pos));
  zmemcpy(pBytef(ds^.head), pBytef(ss^.head), ds^.hash_size * sizeof(Pos));
  zmemcpy(pBytef(ds^.pending_buf), pBytef(ss^.pending_buf), uInt(ds^.pending_buf_size));

  ds^.pending_out := @ds^.pending_buf^[ptr2int(ss^.pending_out) - ptr2int(ss^.pending_buf)];
  ds^.d_buf := pushfArray (@overlay^[ds^.lit_bufsize div sizeof(ush)] );
  ds^.l_buf := puchfArray (@ds^.pending_buf^[(1+sizeof(ush))*ds^.lit_bufsize]);

  ds^.l_desc.dyn_tree := tree_ptr(@ds^.dyn_ltree);
  ds^.d_desc.dyn_tree := tree_ptr(@ds^.dyn_dtree);
  ds^.bl_desc.dyn_tree := tree_ptr(@ds^.bl_tree);

  deflateCopy := Z_OK;
{$endif}
end;


{ ===========================================================================
  Read a new buffer from the current input stream, update the adler32
  and total number of bytes read.  All deflate() input goes through
  this function so some applications may wish to modify it to avoid
  allocating a large strm^.next_in buffer and copying from it.
  (See also flush_pending()). }

{local}
function read_buf(strm : z_streamp; buf : pBytef; size : unsigned) : int;
var
  len : unsigned;
begin
  len := strm^.avail_in;

  if (len > size) then
    len := size;
  if (len = 0) then
  begin
    read_buf := 0;
    exit;
  end;

  Dec(strm^.avail_in, len);

  if deflate_state_ptr(strm^.state)^.noheader = 0 then
  begin
    strm^.adler := adler32(strm^.adler, strm^.next_in, len);
  end;
  zmemcpy(buf, strm^.next_in, len);
  Inc(strm^.next_in, len);
  Inc(strm^.total_in, len);

  read_buf := int(len);
end;

{ ===========================================================================
  Initialize the "longest match" routines for a new zlib stream }

{local}
procedure lm_init (var s : deflate_state);
begin
  s.window_size := ulg( uLong(2)*s.w_size);

  {macro CLEAR_HASH(s);}
  s.head^[s.hash_size-1] := ZNIL;
  zmemzero(pBytef(s.head), unsigned(s.hash_size-1)*sizeof(s.head^[0]));

  { Set the default configuration parameters: }

  s.max_lazy_match   := configuration_table[s.level].max_lazy;
  s.good_match       := configuration_table[s.level].good_length;
  s.nice_match       := configuration_table[s.level].nice_length;
  s.max_chain_length := configuration_table[s.level].max_chain;

  s.strstart := 0;
  s.block_start := long(0);
  s.lookahead := 0;
  s.prev_length := MIN_MATCH-1;
  s.match_length := MIN_MATCH-1;
  s.match_available := FALSE;
  s.ins_h := 0;
{$ifdef ASMV}
  match_init; { initialize the asm code }
{$endif}
end;

{ ===========================================================================
  Set match_start to the longest match starting at the given string and
  return its length. Matches shorter or equal to prev_length are discarded,
  in which case the result is equal to prev_length and match_start is
  garbage.
  IN assertions: cur_match is the head of the hash chain for the current
    string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
  OUT assertion: the match length is not greater than s^.lookahead. }


{$ifndef ASMV}
{ For 80x86 and 680x0, an optimized version will be provided in match.asm or
  match.S. The code will be functionally equivalent. }

{$ifndef FASTEST}

{local}
function longest_match(var s : deflate_state;
                       cur_match : IPos  { current match }
                       ) : uInt;
label
  nextstep;
var
  chain_length : unsigned;    { max hash chain length }
  {register} scan : pBytef;   { current string }
  {register} match : pBytef;  { matched string }
  {register} len : int;       { length of current match }
  best_len : int;             { best match length so far }
  nice_match : int;           { stop if match long enough }
  limit : IPos;

  prev : pzPosfArray;
  wmask : uInt;
{$ifdef UNALIGNED_OK}
  {register} strend : pBytef;
  {register} scan_start : ush;
  {register} scan_end : ush;
{$else}
  {register} strend : pBytef;
  {register} scan_end1 : Byte;
  {register} scan_end : Byte;
{$endif}
var
  MAX_DIST : uInt;
begin
  chain_length := s.max_chain_length; { max hash chain length }
  scan := @(s.window^[s.strstart]);
  best_len := s.prev_length;              { best match length so far }
  nice_match := s.nice_match;             { stop if match long enough }


  MAX_DIST := 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. }

  if s.strstart > IPos(MAX_DIST) then
    limit := s.strstart - IPos(MAX_DIST)
  else
    limit := ZNIL;
  { Stop when cur_match becomes <= limit. To simplify the code,
    we prevent matches with the string of window index 0. }

  prev := s.prev;
  wmask := s.w_mask;

{$ifdef UNALIGNED_OK}
  { Compare two bytes at a time. Note: this is not always beneficial.
    Try with and without -DUNALIGNED_OK to check. }

  strend := pBytef(@(s.window^[s.strstart + MAX_MATCH - 1]));
  scan_start := pushf(scan)^;
  scan_end   := pushfArray(scan)^[best_len-1];   { fix }
{$else}
  strend := pBytef(@(s.window^[s.strstart + MAX_MATCH]));
  {$IFOPT R+} {$R-} {$DEFINE NoRangeCheck} {$ENDIF}
  scan_end1  := pzByteArray(scan)^[best_len-1];
  {$IFDEF NoRangeCheck} {$R+} {$UNDEF NoRangeCheck} {$ENDIF}
  scan_end   := pzByteArray(scan)^[best_len];
{$endif}

    { The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
      It is easy to get rid of this optimization if necessary. }
    {$IFDEF DEBUG}
    Assert((s.hash_bits >= 8) and (MAX_MATCH = 258), 'Code too clever');
    {$ENDIF}
    { Do not waste too much time if we already have a good match: }
    if (s.prev_length >= s.good_match) then
    begin
      chain_length := chain_length shr 2;
    end;

    { Do not look for matches beyond the end of the input. This is necessary
      to make deflate deterministic. }

    if (uInt(nice_match) > s.lookahead) then
      nice_match := s.lookahead;
    {$IFDEF DEBUG}
    Assert(ulg(s.strstart) <= s.window_size-MIN_LOOKAHEAD, 'need lookahead');
    {$ENDIF}
    repeat
        {$IFDEF DEBUG}
        Assert(cur_match < s.strstart, 'no future');
        {$ENDIF}
        match := @(s.window^[cur_match]);

        { Skip to next match if the match length cannot increase
          or if the match length is less than 2: }

{$undef DO_UNALIGNED_OK}
{$ifdef UNALIGNED_OK}
  {$ifdef MAX_MATCH_IS_258}
    {$define DO_UNALIGNED_OK}
  {$endif}
{$endif}

{$ifdef DO_UNALIGNED_OK}
        { This code assumes sizeof(unsigned short) = 2. Do not use
          UNALIGNED_OK if your compiler uses a different size. }
  {$IFOPT R+} {$R-} {$DEFINE NoRangeCheck} {$ENDIF}
        if (pushfArray(match)^[best_len-1] <> scan_end) or
           (pushf(match)^ <> scan_start) then
          goto nextstep; {continue;}
  {$IFDEF NoRangeCheck} {$R+} {$UNDEF NoRangeCheck} {$ENDIF}

        { It is not necessary to compare scan[2] and match[2] since they are
          always equal when the other bytes match, given that the hash keys
          are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
          strstart+3, +5, ... up to strstart+257. We check for insufficient
          lookahead only every 4th comparison; the 128th check will be made
          at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
          necessary to put more guard bytes at the end of the window, or
          to check more often for insufficient lookahead. }
        {$IFDEF DEBUG}
        Assert(pzByteArray(scan)^[2] = pzByteArray(match)^[2], 'scan[2]?');
        {$ENDIF}
        Inc(scan);
        Inc(match);

        repeat
          Inc(scan,2); Inc(match,2); if (pushf(scan)^<>pushf(match)^) then break;
          Inc(scan,2); Inc(match,2); if (pushf(scan)^<>pushf(match)^) then break;
          Inc(scan,2); Inc(match,2); if (pushf(scan)^<>pushf(match)^) then break;
          Inc(scan,2); Inc(match,2); if (pushf(scan)^<>pushf(match)^) then break;
        until (ptr2int(scan) >= ptr2int(strend));
        { The funny "do while" generates better code on most compilers }

        { Here, scan <= window+strstart+257 }
        {$IFDEF DEBUG}
        Assert(ptr2int(scan) <=
               ptr2int(@(s.window^[unsigned(s.window_size-1)])),
               'wild scan');
        {$ENDIF}
        if (scan^ = match^) then
          Inc(scan);

        len := (MAX_MATCH - 1) - int(ptr2int(strend)-ptr2int(scan));
        scan := strend;
        Dec(scan, (MAX_MATCH-1));

{$else} { UNALIGNED_OK }

  {$IFOPT R+} {$R-} {$DEFINE NoRangeCheck} {$ENDIF}
        if (pzByteArray(match)^[best_len]   <> scan_end) or
           (pzByteArray(match)^[best_len-1] <> scan_end1) or
           (match^ <> scan^) then
          goto nextstep; {continue;}
  {$IFDEF NoRangeCheck} {$R+} {$UNDEF NoRangeCheck} {$ENDIF}
        Inc(match);
        if (match^ <> pzByteArray(scan)^[1]) then
          goto nextstep; {continue;}

        { The check at best_len-1 can be removed because it will be made
          again later. (This heuristic is not always a win.)
          It is not necessary to compare scan[2] and match[2] since they
          are always equal when the other bytes match, given that
          the hash keys are equal and that HASH_BITS >= 8. }

        Inc(scan, 2);
        Inc(match);
        {$IFDEF DEBUG}
        Assert( scan^ = match^, 'match[2]?');
        {$ENDIF}
        { We check for insufficient lookahead only every 8th comparison;
          the 256th check will be made at strstart+258. }

        repeat
          Inc(scan); Inc(match); if (scan^ <> match^) then break;
          Inc(scan); Inc(match); if (scan^ <> match^) then break;
          Inc(scan); Inc(match); if (scan^ <> match^) then break;
          Inc(scan); Inc(match); if (scan^ <> match^) then break;
          Inc(scan); Inc(match); if (scan^ <> match^) then break;
          Inc(scan); Inc(match); if (scan^ <> match^) then break;
          Inc(scan); Inc(match); if (scan^ <> match^) then break;
          Inc(scan); Inc(match); if (scan^ <> match^) then break;
        until (ptr2int(scan) >= ptr2int(strend));

        {$IFDEF DEBUG}
        Assert(ptr2int(scan) <=
               ptr2int(@(s.window^[unsigned(s.window_size-1)])),
               'wild scan');
        {$ENDIF}

        len := MAX_MATCH - int(ptr2int(strend) - ptr2int(scan));
        scan := strend;
        Dec(scan, MAX_MATCH);

{$endif} { UNALIGNED_OK }

        if (len > best_len) then
        begin
            s.match_start := cur_match;
            best_len := len;
            if (len >= nice_match) then
              break;
  {$IFOPT R+} {$R-} {$DEFINE NoRangeCheck} {$ENDIF}
{$ifdef UNALIGNED_OK}
            scan_end   := pzByteArray(scan)^[best_len-1];
{$else}
            scan_end1  := pzByteArray(scan)^[best_len-1];
            scan_end   := pzByteArray(scan)^[best_len];
{$endif}
  {$IFDEF NoRangeCheck} {$R+} {$UNDEF NoRangeCheck} {$ENDIF}
        end;
    nextstep:
      cur_match := prev^[cur_match and wmask];
      Dec(chain_length);
    until (cur_match <= limit) or (chain_length = 0);

    if (uInt(best_len) <= s.lookahead) then
      longest_match := uInt(best_len)
    else
      longest_match := s.lookahead;
end;
{$endif} { ASMV }

{$else} { FASTEST }
{ ---------------------------------------------------------------------------
  Optimized version for level = 1 only }

{local}
function longest_match(var s : deflate_state;
                       cur_match : IPos  { current match }
                       ) : uInt;
var
  {register} scan : pBytef;   { current string }
  {register} match : pBytef;  { matched string }
  {register} len : int;       { length of current match }
  {register} strend : pBytef;
begin
  scan := @s.window^[s.strstart];
  strend := @s.window^[s.strstart + MAX_MATCH];


    { The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
      It is easy to get rid of this optimization if necessary. }
    {$IFDEF DEBUG}
    Assert((s.hash_bits >= 8) and (MAX_MATCH = 258), 'Code too clever');

    Assert(ulg(s.strstart) <= s.window_size-MIN_LOOKAHEAD, 'need lookahead');

    Assert(cur_match < s.strstart, 'no future');
    {$ENDIF}
    match := s.window + cur_match;