ZipDeflate Class Reference

The deflater for the file compressor and decompressor. Allows the CCDiskFile to offer compression of files. At present just used to compress the native file format. More...

#include <zdeflate.h>

List of all members.

Public Member Functions
	ZipDeflate ()
	ZipDeflate constructor.
	~ZipDeflate ()
	ZipDeflate destructor.
INT32	Init (z_stream *strm, INT32 level)
	Initializes the internal stream state for compression. The fields zalloc, zfree and opaque must be initialized before by the caller. If zalloc and zfree are set to Z_NULL, deflateInit updates them to use default allocation functions.
INT32	deflate (z_stream *strm, INT32 flush)
	Actually go and deflate the stream.
INT32	End (z_stream *strm)
	End the deflation on this stream.
INT32	Init (z_stream *strm, INT32 level, INT32 method, INT32 windowBits, INT32 memLevel, INT32 strategy)
	This is another version of deflate Init with more compression options. The fields next_in, zalloc and zfree must be initialized before by the caller.
INT32	Reset (z_stream *strm)
	This function is equivalent to deflate End followed by deflateInit, but does not free and reallocate all the internal compression state. The stream will keep the same compression level and any other attributes that may have been set by deflate Init.
INT32	SetDictionary (z_stream *strm, const Bytef *dictionary, uInt dictLength)
	Initializes the compression dictionary (history buffer) from the given byte sequence without producing any compressed output. This function must be called immediately after deflateInit or deflateInit2, before any call of deflate. The compressor and decompressor must use exactly the same dictionary (see inflateSetDictionary). The dictionary should consist of strings (byte sequences) that are likely to be encountered later in the data to be compressed, with the most commonly used strings preferably put towards the end of the dictionary. Using a dictionary is most useful when the data to be compressed is short and can be predicted with good accuracy; the data can then be compressed better than with the default empty dictionary. In this version of the library, only the last 32K bytes of the dictionary are used. Upon return of this function, strm->adler is set to the Adler32 value of the dictionary; the decompressor may later use this value to determine which dictionary has been used by the compressor. (The Adler32 value applies to the whole dictionary even if only a subset of the dictionary is actually used by the compressor.).
INT32	Params (z_stream *strm, INT32 level, INT32 strategy)
	New for version 0.99 Dynamically update the compression level and compression strategy. This can be used to switch between compression and straight copy of the input data, or to switch to a different kind of input data requiring a different strategy. If the compression level is changed, the input available so far is compressed with the old level (and may be flushed); the new level will take effect only at the next call of deflate().
Protected Member Functions
void	ct_init (DeflateState *s)
INT32	ct_tally (DeflateState *s, INT32 dist, INT32 lc)
ulg	ct_flush_block (DeflateState *s, char *buf, ulg stored_len, INT32 eof)
void	ct_stored_block (DeflateState *s, char *buf, ulg stored_len, INT32 eof)
void	_tr_init (DeflateState *s)
	Initialize the tree data structures for a new zlib stream.
INT32	_tr_tally (DeflateState *s, unsigned dist, unsigned lc)
	Save the match info and tally the frequency counts. Return true if the current block must be flushed.
ulg	_tr_flush_block (DeflateState *s, charf *buf, ulg stored_len, INT32 eof)
void	_tr_align (DeflateState *s)
void	_tr_stored_block (DeflateState *s, charf *buf, ulg stored_len, INT32 eof)
Private Member Functions
	CC_DECLARE_MEMDUMP (ZipDeflate)
INT32	deflate_stored (DeflateState *s, INT32 flush)
	Copy without compression as much as possible from the input stream, return true if processing was terminated prematurely (no more input or output space). This function does not insert new strings in the dictionary since uncompressible data is probably not useful. This function is used only for the level=0 compression option. NOTE: this function should be optimized to avoid extra copying.
INT32	deflate_fast (DeflateState *s, INT32 flush)
	Compress as much as possible from the input stream, return true if processing was terminated prematurely (no more input or output space). This function does not perform lazy evaluationof matches and inserts new strings in the dictionary only for unmatched strings or for short matches. It is used only for the fast compression options.
INT32	deflate_slow (DeflateState *s, INT32 flush)
	Same as above, but achieves better compression. We use a lazy evaluation for matches: a match is finally adopted only if there is no better match at the next window position.
void	fill_window (DeflateState *s)
	Fill the window when the lookahead becomes insufficient. Updates strstart and lookahead.
void	lm_init (DeflateState *s)
	Initialize the "longest match" routines for a new zlib stream.
uInt	longest_match (DeflateState *s, IPos cur_match)
	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.
void	putShortMSB (DeflateState *s, uInt b)
	Put a short the pending_out buffer. The 16-bit value is put in MSB order. IN assertion: the stream state is correct and there is enough room in the pending_out buffer.
void	flush_pending (z_stream *strm)
	Flush as much pending output as possible. All deflate() output goes through this function so some applications may wish to modify it to avoid allocating a large strm->next_out buffer and copying into it. (See also read_buf()).
INT32	read_buf (z_stream *strm, charf *buf, unsigned size)
	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()).
void	tr_static_init (void)
	Initialize the various 'constant' tables. To do: do this at compile time.
void	init_block (DeflateState *s)
	Initialize a new block.
void	pqdownheap (DeflateState *s, ct_data *tree, INT32 k)
	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).
void	gen_bitlen (DeflateState *s, tree_desc *desc)
	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.
void	gen_codes (ct_data *tree, INT32 max_code, ushf bl_count[])
	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.
void	build_tree (DeflateState *s, tree_desc *desc)
	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.
void	scan_tree (DeflateState *s, ct_data *tree, INT32 max_code)
	Scan a literal or distance tree to determine the frequencies of the codes in the bit length tree.
void	send_tree (DeflateState *s, ct_data *tree, INT32 max_code)
	Send a literal or distance tree in compressed form, using the codes in bl_tree.
INT32	build_bl_tree (DeflateState *s)
	Construct the Huffman tree for the bit lengths and return the index in bl_order of the last bit length code to send.
void	send_all_trees (DeflateState *s, INT32 lcodes, INT32 dcodes, INT32 blcodes)
	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.
void	compress_block (DeflateState *s, ct_data *ltree, ct_data *dtree)
	Send the block data compressed using the given Huffman trees.
void	set_data_type (DeflateState *s)
	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 INT32 on 16 bit machines).
unsigned	bi_reverse (unsigned value, INT32 length)
	Send a value on a given number of bits. IN assertion: length <= 16 and value fits in length bits.Reverse the first len bits of a code, using straightforward code (a faster method would use a table) IN assertion: 1 <= len <= 15.
void	bi_windup (DeflateState *s)
	Write out any remaining bits in an incomplete byte. Flush the bit buffer and align the output on a byte boundary.
void	bi_flush (DeflateState *s)
	Flush the bit buffer, keeping at most 7 bits in it. New Version 0.99.
void	copy_block (DeflateState *s, char *buf, unsigned len, INT32 header)
	Copy a stored block, storing first the length and its one's complement if requested.

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Detailed Description

The deflater for the file compressor and decompressor. Allows the CCDiskFile to offer compression of files. At present just used to compress the native file format.

Author:

Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Humprhys

Date:

23/5/95

Definition at line 409 of file zdeflate.h.

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Constructor & Destructor Documentation

ZipDeflate::ZipDeflate (   )

ZipDeflate constructor. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 34/05/95 Definition at line 259 of file zdeflate.cpp. { }

ZipDeflate::~ZipDeflate (   )

ZipDeflate destructor. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 34/05/95 Definition at line 273 of file zdeflate.cpp. { }

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Member Function Documentation

void ZipDeflate::_tr_align (  DeflateState *  s  )  [protected]

Definition at line 988 of file zdftrees.cpp. { send_bits(s, STATIC_TREES<<1, 3); send_code(s, END_BLOCK, static_ltree); s->compressed_len += 10L; /* 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) { send_bits(s, STATIC_TREES<<1, 3); send_code(s, END_BLOCK, static_ltree); s->compressed_len += 10L; bi_flush(s); } s->last_eob_len = 7; }

ulg ZipDeflate::_tr_flush_block (  DeflateState *  s, charf *  buf, ulg  stored_len, INT32  eof )  [protected]

void ZipDeflate::_tr_init (  DeflateState *  s  )  [protected]

Initialize the tree data structures for a new zlib stream. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Definition at line 405 of file zdftrees.cpp. { tr_static_init(); s->compressed_len = 0L; s->l_desc.dyn_tree = s->dyn_ltree; s->l_desc.stat_desc = &static_l_desc; s->d_desc.dyn_tree = s->dyn_dtree; s->d_desc.stat_desc = &static_d_desc; s->bl_desc.dyn_tree = 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 DEBUG s->bits_sent = 0L; #endif /* Initialize the first block of the first file: */ init_block(s); }

void ZipDeflate::_tr_stored_block (  DeflateState *  s, charf *  buf, ulg  stored_len, INT32  eof )  [protected]

INT32 ZipDeflate::_tr_tally (  DeflateState *  s, unsigned  dist, unsigned  lc )  [protected]

Save the match info and tally the frequency counts. Return true if the current block must be flushed. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Parameters: s  the current deflate state [INPUTS] dist distance of matched string lc match length-MIN_MATCH or unmatched char (if dist==0) Definition at line 1143 of file zdftrees.cpp. { s->d_buf[s->last_lit] = (ush)dist; s->l_buf[s->last_lit++] = (uch)lc; if (dist == 0) { /* lc is the unmatched char */ s->dyn_ltree[lc].Freq++; } else { s->matches++; /* Here, lc is the match length - MIN_MATCH */ dist--; /* dist = match distance - 1 */ Assert((ush)dist < (ush)MAX_DIST(s) && (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) && (ush)d_code(dist) < (ush)D_CODES, "_tr_tally: bad match"); s->dyn_ltree[length_code[lc]+LITERALS+1].Freq++; s->dyn_dtree[d_code(dist)].Freq++; } /* Try to guess if it is profitable to stop the current block here */ if (s->level > 2 && (s->last_lit & 0xfff) == 0) { /* Compute an upper bound for the compressed length */ ulg out_length = (ulg)s->last_lit*8L; ulg in_length = (ulg)((INT32)s->strstart - s->block_start); INT32 dcode; for (dcode = 0; dcode < D_CODES; dcode++) { out_length += (ulg)s->dyn_dtree[dcode].Freq * (5L+extra_dbits[dcode]); } out_length >>= 3; Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ", s->last_lit, in_length, out_length, 100L - out_length*100L/in_length)); if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1; } return (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. */ }

void ZipDeflate::bi_flush (  DeflateState *  s  )  [private]

Flush the bit buffer, keeping at most 7 bits in it. New Version 0.99. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Parameters: s  the current deflate state [INPUTS] Definition at line 1340 of file zdftrees.cpp. { if (s->bi_valid == 16) { put_short(s, s->bi_buf); s->bi_buf = 0; s->bi_valid = 0; } else if (s->bi_valid >= 8) { put_byte(s, (Byte)s->bi_buf); s->bi_buf >>= 8; s->bi_valid -= 8; } }

unsigned ZipDeflate::bi_reverse (  unsigned  code, INT32  len )  [private]

Send a value on a given number of bits. IN assertion: length <= 16 and value fits in length bits.Reverse the first len bits of a code, using straightforward code (a faster method would use a table) IN assertion: 1 <= len <= 15. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Parameters: code  the value to invert [INPUTS] len its bit length Definition at line 1318 of file zdftrees.cpp. { register unsigned res = 0; do { res |= code & 1; code >>= 1, res <<= 1; } while (--len > 0); return res >> 1; }

void ZipDeflate::bi_windup (  DeflateState *  s  )  [private]

Write out any remaining bits in an incomplete byte. Flush the bit buffer and align the output on a byte boundary. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Parameters: s  the current deflate state [INPUTS] Definition at line 1365 of file zdftrees.cpp. { if (s->bi_valid > 8) { put_short(s, s->bi_buf); } else if (s->bi_valid > 0) { put_byte(s, (Byte)s->bi_buf); } s->bi_buf = 0; s->bi_valid = 0; #ifdef DEBUG s->bits_sent = (s->bits_sent+7) & ~7; #endif }

INT32 ZipDeflate::build_bl_tree (  DeflateState *  s  )  [private]

Construct the Huffman tree for the bit lengths and return the index in bl_order of the last bit length code to send. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Parameters: s  the current deflate state [INPUTS] Definition at line 886 of file zdftrees.cpp. { INT32 max_blindex; /* index of last bit length code of non zero freq */ /* Determine the bit length frequencies for literal and distance trees */ scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code); scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code); /* Build the bit length tree: */ build_tree(s, (tree_desc *)(&(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; max_blindex >= 3; max_blindex--) { if (s->bl_tree[bl_order[max_blindex]].Len != 0) break; } /* Update opt_len to include the bit length tree and counts */ s->opt_len += 3*(max_blindex+1) + 5+5+4; Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld", s->opt_len, s->static_len)); return max_blindex; }

void ZipDeflate::build_tree (  DeflateState *  s, tree_desc *  desc )  [private]

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. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Parameters: s  current deflate state [INPUTS] desc the tree descriptor Definition at line 682 of file zdftrees.cpp. { ct_data *tree = desc->dyn_tree; ct_data *stree = desc->stat_desc->static_tree; INT32 elems = desc->stat_desc->elems; INT32 n, m; /* iterate over heap elements */ INT32 max_code = -1; /* largest code with non zero frequency */ INT32 node; /* new node being created */ /* 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; n < elems; n++) { if (tree[n].Freq != 0) { s->heap[++(s->heap_len)] = max_code = n; s->depth[n] = 0; } else { tree[n].Len = 0; } } /* 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) { node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0); tree[node].Freq = 1; s->depth[node] = 0; s->opt_len--; if (stree) s->static_len -= stree[node].Len; /* node is 0 or 1 so it does not have extra bits */ } 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/2; n >= 1; n--) pqdownheap(s, tree, n); /* Construct the Huffman tree by repeatedly combining the least two * frequent nodes. */ node = elems; /* next internal node of the tree */ do { pqremove(s, tree, n); /* n = node of least frequency */ m = s->heap[SMALLEST]; /* m = node of next least frequency */ s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */ s->heap[--(s->heap_max)] = m; /* Create a new node father of n and m */ tree[node].Freq = tree[n].Freq + tree[m].Freq; s->depth[node] = (uch) (MAX(s->depth[n], s->depth[m]) + 1); tree[n].Dad = tree[m].Dad = (ush)node; #ifdef DUMP_BL_TREE if (tree == s->bl_tree) { _ftprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)", node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq); } #endif /* and insert the new node in the heap */ s->heap[SMALLEST] = node++; pqdownheap(s, tree, SMALLEST); } while (s->heap_len >= 2); 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, (tree_desc *)desc); /* The field len is now set, we can generate the bit codes */ gen_codes ((ct_data *)tree, max_code, s->bl_count); }

ZipDeflate::CC_DECLARE_MEMDUMP (  ZipDeflate   )  [private]

void ZipDeflate::compress_block (  DeflateState *  s, ct_data *  ltree, ct_data *  dtree )  [private]

Send the block data compressed using the given Huffman trees. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Parameters: s  the current deflate state [INPUTS] ltree literal tree dtree distance tree Definition at line 1198 of file zdftrees.cpp. { unsigned dist; /* distance of matched string */ INT32 lc; /* match length or unmatched char (if dist == 0) */ UINT32 lx = 0; /* running index in l_buf */ unsigned code; /* the code to send */ INT32 extra; /* number of extra bits to send */ if (s->last_lit != 0) do { dist = s->d_buf[lx]; lc = s->l_buf[lx++]; if (dist == 0) { send_code(s, lc, ltree); /* send a literal byte */ Tracecv(_istgraph(lc), (stderr," '%c' ", lc)); } else { /* Here, lc is the match length - MIN_MATCH */ code = length_code[lc]; send_code(s, code+LITERALS+1, ltree); /* send the length code */ extra = extra_lbits[code]; if (extra != 0) { lc -= base_length[code]; send_bits(s, lc, extra); /* send the extra length bits */ } dist--; /* dist is now the match distance - 1 */ code = d_code(dist); Assert (code < D_CODES, "bad d_code"); send_code(s, code, dtree); /* send the distance code */ extra = extra_dbits[code]; if (extra != 0) { dist -= base_dist[code]; send_bits(s, dist, extra); /* send the extra distance bits */ } } /* literal or match pair ? */ /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */ Assert(s->pending < ( INT32 ) ( s->lit_bufsize + ( 2 * lx ) ), "pendingBuf overflow"); } while (lx < s->last_lit); send_code(s, END_BLOCK, ltree); s->last_eob_len = ltree[END_BLOCK].Len; }

void ZipDeflate::copy_block (  DeflateState *  s, char *  buf, unsigned  len, INT32  header )  [private]

Copy a stored block, storing first the length and its one's complement if requested. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Parameters: s  the current deflate state [INPUTS] buf the input data len its length header true if block header must be written Definition at line 1394 of file zdftrees.cpp. { bi_windup(s); /* align on byte boundary */ s->last_eob_len = 8; /* enough lookahead for inflate */ if (header) { put_short(s, (ush)len); put_short(s, (ush)~len); #ifdef DEBUG s->bits_sent += 2*16; #endif } #ifdef DEBUG s->bits_sent += (ulg)len<<3; #endif while (len--) { put_byte(s, *buf++); } }

ulg ZipDeflate::ct_flush_block (  DeflateState *  s, char *  buf, ulg  stored_len, INT32  eof )  [protected]

void ZipDeflate::ct_init (  DeflateState *  s  )  [protected]

void ZipDeflate::ct_stored_block (  DeflateState *  s, char *  buf, ulg  stored_len, INT32  eof )  [protected]

INT32 ZipDeflate::ct_tally (  DeflateState *  s, INT32  dist, INT32  lc )  [protected]

INT32 ZipDeflate::deflate (  z_stream *  strm, INT32  flush )

Actually go and deflate the stream. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Performs one or both of the following actions: Compress more input starting at next_in and update next_in and avail_in accordingly. If not all input can be processed (because there is not enough room in the output buffer), next_in and avail_in are updated and processing will resume at this point for the next call of deflate(). Provide more output starting at next_out and update next_out and avail_out accordingly. This action is forced if the parameter flush is non zero. Forcing flush frequently degrades the compression ratio, so this parameter should be set only when necessary (in interactive applications). Some output may be provided even if flush is not set. Before the call of deflate(), the application should ensure that at least one of the actions is possible, by providing more input and/or consuming more output, and updating avail_in or avail_out accordingly; avail_out should never be zero before the call. The application can consume the compressed output when it wants, for example when the output buffer is full (avail_out == 0), or after each call of deflate(). If deflate returns Z_OK and with zero avail_out, it must be called again after making room in the output buffer because there might be more output pending. If the parameter flush is set to Z_PARTIAL_FLUSH, the current compression block is terminated and flushed to the output buffer so that the decompressor can get all input data available so far. For method 9, a future variant on method 8, the current block will be flushed but not terminated. If flush is set to Z_FULL_FLUSH, the compression block is terminated, a special marker is output and the compression dictionary is discarded; this is useful to allow the decompressor to synchronize if one compressed block has been damaged (see inflateSync below). Flushing degrades compression and so should be used only when necessary. Using Z_FULL_FLUSH too often can seriously degrade the compression. If the parameter flush is set to Z_FINISH, all pending input is processed, all pending output is flushed and deflate returns with ZStream_END if there was enough output space; if deflate returns with Z_OK, this function must be called again with Z_FINISH and more output space (updated avail_out) but no more input data, until it returns with ZStream_END or an error. After deflate has returned ZStream_END, the only possible operations on the stream are deflateReset or deflateEnd. Z_FINISH can be used immediately after deflateInit if all the compression is to be done in a single step. In this case, avail_out must be at least 0.1% larger than avail_in plus 12 bytes. If deflate does not return ZStream_END, then it must be called again as described above. deflate() may update data_type if it can make a good guess about the input data type (Z_ASCII or Z_BINARY). In doubt, the data is considered binary. This field is only for information purposes and does not affect the compression algorithm in any manner. deflate() returns Z_OK if some progress has been made (more input processed or more output produced), ZStream_END if all input has been consumed and all output has been produced (only when flush is set to Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example if next_in or next_out was NULL), Z_BUF_ERROR if no progress is possible. Definition at line 779 of file zdeflate.cpp. { INT32 old_flush; /* value of flush param for previous deflate call */ DeflateState *s; if (strm == Z_NULL || strm->De_state == Z_NULL || flush > Z_FINISH || flush < 0) { return Z_STREAM_ERROR; } s = strm->De_state; if (strm->next_out == Z_NULL || (strm->next_in == Z_NULL && strm->avail_in != 0) || (s->status == FINISH_STATE && flush != Z_FINISH)) { ERR_RETURN(strm, Z_STREAM_ERROR); } if (strm->avail_out == 0) ERR_RETURN(strm, Z_BUF_ERROR); strm->De_state->strm = strm; /* just in case */ old_flush = s->last_flush; s->last_flush = flush; /* Write the zlib header */ if (s->status == INIT_STATE) { uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8; uInt level_flags = (s->level-1) >> 1; if (level_flags > 3) level_flags = 3; header |= (level_flags << 6); if (s->strstart != 0) header |= PRESET_DICT; header += 31 - (header % 31); s->status = BUSY_STATE; putShortMSB(s, header); /* Save the adler32 of the preset dictionary: */ if (s->strstart != 0) { putShortMSB(s, (uInt)(strm->adler >> 16)); putShortMSB(s, (uInt)(strm->adler & 0xffff)); } strm->adler = 1L; } /* Flush as much pending output as possible */ if (s->pending != 0) { flush_pending(strm); if (strm->avail_out == 0) { /* Since avail_out is 0, deflate will be called again with * more output space, but possibly with both pending and * avail_in equal to zero. There won't be anything to do, * but this is not an error situation so make sure we * return OK instead of BUF_ERROR at next call of deflate: */ s->last_flush = -1; return Z_OK; } /* Make sure there is something to do and avoid duplicate consecutive * flushes. For repeated and useless calls with Z_FINISH, we keep * returning Z_STREAM_END instead of Z_BUFF_ERROR. */ } else if (strm->avail_in == 0 && flush <= old_flush && flush != Z_FINISH) { ERR_RETURN(strm, Z_BUF_ERROR); } /* User must not provide more input after the first FINISH: */ if (s->status == FINISH_STATE && strm->avail_in != 0) { ERR_RETURN(strm, Z_BUF_ERROR); } /* Start a new block or continue the current one. */ if (strm->avail_in != 0 || s->lookahead != 0 || (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) { INT32 quit; if (flush == Z_FINISH) { s->status = FINISH_STATE; } //quit = (*(configuration_table[s->level].func))(s, flush); switch (configuration_table[s->level].func) { case Z_deflate_stored : quit = deflate_stored(s, flush); break; case Z_deflate_fast : quit = deflate_fast(s, flush); break; case Z_deflate_slow : quit = deflate_slow(s, flush); break; default: // We have a type we don't understand so error return Z_STREAM_ERROR; } if (strm->avail_out == 0) { s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */ } if (quit || strm->avail_out == 0) return Z_OK; /* If flush != Z_NO_FLUSH && avail_out == 0, the next call * of deflate should use the same flush parameter to make sure * that the flush is complete. So we don't have to output an * empty block here, this will be done at next call. This also * ensures that for a very small output buffer, we emit at most * one empty block. */ if (flush != Z_NO_FLUSH && flush != Z_FINISH) { if (flush == Z_PARTIAL_FLUSH) { _tr_align(s); } else { /* FULL_FLUSH or SYNC_FLUSH */ _tr_stored_block(s, (char*)0, 0L, 0); /* For a full flush, this empty block will be recognized * as a special marker by inflate_sync(). */ if (flush == Z_FULL_FLUSH) { CLEAR_HASH(s); /* forget history */ } } flush_pending(strm); if (strm->avail_out == 0) { s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */ return Z_OK; } } } Assert(strm->avail_out > 0, "bug2"); if (flush != Z_FINISH) return Z_OK; if (s->noheader) return Z_STREAM_END; /* Write the zlib trailer (adler32) */ putShortMSB(s, (uInt)(strm->adler >> 16)); putShortMSB(s, (uInt)(strm->adler & 0xffff)); flush_pending(strm); /* If avail_out is zero, the application will call deflate again * to flush the rest. */ s->noheader = -1; /* write the trailer only once! */ return s->pending != 0 ? Z_OK : Z_STREAM_END; }

INT32 ZipDeflate::deflate_fast (  DeflateState *  s, INT32  flush )  [private]

Compress as much as possible from the input stream, return true if processing was terminated prematurely (no more input or output space). This function does not perform lazy evaluationof matches and inserts new strings in the dictionary only for unmatched strings or for short matches. It is used only for the fast compression options. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Definition at line 1494 of file zdeflate.cpp. { IPos hash_head = NIL; /* head of the hash chain */ INT32 bflush; /* set if current block must be flushed */ for (;;) { /* Make sure that we always have enough lookahead, except * at the end of the input file. We need MAX_MATCH bytes * for the next match, plus MIN_MATCH bytes to insert the * string following the next match. */ if (s->lookahead < MIN_LOOKAHEAD) { fill_window(s); if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) return 1; if (s->lookahead == 0) break; /* flush the current block */ } /* Insert the string window[strstart .. strstart+2] in the * dictionary, and set hash_head to the head of the hash chain: */ if (s->lookahead >= MIN_MATCH) { INSERT_STRING(s, s->strstart, hash_head); } /* Find the longest match, discarding those <= prev_length. * At this point we have always match_length < MIN_MATCH */ if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) { /* To simplify the code, we prevent matches with the string * of window index 0 (in particular we have to avoid a match * of the string with itself at the start of the input file). */ if (s->strategy != Z_HUFFMAN_ONLY) { s->match_length = longest_match (s, hash_head); } /* longest_match() sets match_start */ } if (s->match_length >= MIN_MATCH) { check_match(s, s->strstart, s->match_start, s->match_length); bflush = _tr_tally(s, s->strstart - s->match_start, s->match_length - MIN_MATCH); s->lookahead -= s->match_length; /* Insert new strings in the hash table only if the match length * is not too large. This saves time but degrades compression. */ if (s->match_length <= s->max_insert_length && s->lookahead >= MIN_MATCH) { s->match_length--; /* string at strstart already in hash table */ do { s->strstart++; INSERT_STRING(s, s->strstart, hash_head); /* strstart never exceeds WSIZE-MAX_MATCH, so there are * always MIN_MATCH bytes ahead. */ } while (--s->match_length != 0); s->strstart++; } else { s->strstart += s->match_length; s->match_length = 0; s->ins_h = s->window[s->strstart]; UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]); #if MIN_MATCH != 3 Call UPDATE_HASH() MIN_MATCH-3 more times #endif /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not * matter since it will be recomputed at next deflate call. */ } } else { /* No match, output a literal byte */ Tracevv((stderr,"%c", s->window[s->strstart])); bflush = _tr_tally (s, 0, s->window[s->strstart]); s->lookahead--; s->strstart++; } if (bflush) FLUSH_BLOCK(s, 0); } FLUSH_BLOCK(s, flush == Z_FINISH); return 0; /* normal exit */ }

INT32 ZipDeflate::deflate_slow (  DeflateState *  s, INT32  flush )  [private]

Same as above, but achieves better compression. We use a lazy evaluation for matches: a match is finally adopted only if there is no better match at the next window position. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Definition at line 1591 of file zdeflate.cpp. { IPos hash_head = NIL; /* head of hash chain */ INT32 bflush; /* set if current block must be flushed */ /* Process the input block. */ for (;;) { /* Make sure that we always have enough lookahead, except * at the end of the input file. We need MAX_MATCH bytes * for the next match, plus MIN_MATCH bytes to insert the * string following the next match. */ if (s->lookahead < MIN_LOOKAHEAD) { fill_window(s); if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) return 1; if (s->lookahead == 0) break; /* flush the current block */ } /* Insert the string window[strstart .. strstart+2] in the * dictionary, and set hash_head to the head of the hash chain: */ if (s->lookahead >= MIN_MATCH) { INSERT_STRING(s, s->strstart, hash_head); } /* Find the longest match, discarding those <= prev_length. */ s->prev_length = s->match_length, s->prev_match = s->match_start; s->match_length = MIN_MATCH-1; if (hash_head != NIL && s->prev_length < s->max_lazy_match && s->strstart - hash_head <= MAX_DIST(s)) { /* To simplify the code, we prevent matches with the string * of window index 0 (in particular we have to avoid a match * of the string with itself at the start of the input file). */ if (s->strategy != Z_HUFFMAN_ONLY) { s->match_length = longest_match (s, hash_head); } /* longest_match() sets match_start */ if (s->match_length <= 5 && (s->strategy == Z_FILTERED || (s->match_length == MIN_MATCH && s->strstart - s->match_start > TOO_FAR))) { /* If prev_match is also MIN_MATCH, match_start is garbage * but we will ignore the current match anyway. */ s->match_length = MIN_MATCH-1; } } /* If there was a match at the previous step and the current * match is not better, output the previous match: */ if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) { uInt max_insert = s->strstart + s->lookahead - MIN_MATCH; /* Do not insert strings in hash table beyond this. */ check_match(s, s->strstart-1, s->prev_match, s->prev_length); bflush = _tr_tally(s, s->strstart -1 - s->prev_match, s->prev_length - MIN_MATCH); /* Insert in hash table all strings up to the end of the match. * strstart-1 and strstart are already inserted. If there is not * enough lookahead, the last two strings are not inserted in * the hash table. */ s->lookahead -= s->prev_length-1; s->prev_length -= 2; do { if (++s->strstart <= max_insert) { INSERT_STRING(s, s->strstart, hash_head); } } while (--s->prev_length != 0); s->match_available = 0; s->match_length = MIN_MATCH-1; s->strstart++; if (bflush) FLUSH_BLOCK(s, 0); } else if (s->match_available) { /* If there was no match at the previous position, output a * single literal. If there was a match but the current match * is longer, truncate the previous match to a single literal. */ Tracevv((stderr,"%c", s->window[s->strstart-1])); if (_tr_tally (s, 0, s->window[s->strstart-1])) { FLUSH_BLOCK_ONLY(s, 0); } s->strstart++; s->lookahead--; if (s->strm->avail_out == 0) return 1; } else { /* There is no previous match to compare with, wait for * the next step to decide. */ s->match_available = 1; s->strstart++; s->lookahead--; } } Assert (flush != Z_NO_FLUSH, "no flush?"); if (s->match_available) { Tracevv((stderr,"%c", s->window[s->strstart-1])); _tr_tally (s, 0, s->window[s->strstart-1]); s->match_available = 0; } FLUSH_BLOCK(s, flush == Z_FINISH); return 0; }

INT32 ZipDeflate::deflate_stored (  DeflateState *  s, INT32  flush )  [private]

Copy without compression as much as possible from the input stream, return true if processing was terminated prematurely (no more input or output space). This function does not insert new strings in the dictionary since uncompressible data is probably not useful. This function is used only for the level=0 compression option. NOTE: this function should be optimized to avoid extra copying. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Definition at line 1445 of file zdeflate.cpp. { for (;;) { /* Fill the window as much as possible: */ if (s->lookahead <= 1) { Assert(s->strstart < s->w_size+MAX_DIST(s) || s->block_start >= (INT32)s->w_size, "slide too late"); fill_window(s); if (s->lookahead == 0 && flush == Z_NO_FLUSH) return 1; if (s->lookahead == 0) break; /* flush the current block */ } Assert(s->block_start >= 0L, "block gone"); s->strstart += s->lookahead; s->lookahead = 0; /* Stored blocks are limited to 0xffff bytes: */ if (s->strstart == 0 || s->strstart > 0xfffe) { /* strstart == 0 is possible when wraparound on 16-bit machine */ s->lookahead = s->strstart - 0xffff; s->strstart = 0xffff; } /* Emit a stored block if it is large enough: */ if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) { FLUSH_BLOCK(s, 0); } } FLUSH_BLOCK(s, flush == Z_FINISH); return 0; /* normal exit */ }

INT32 ZipDeflate::End (  z_stream *  strm  )

End the deflation on this stream. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 All dynamically allocated data structures for this stream are freed. This function discards any unprocessed input and does not flush any pending output. deflate End returns Z_OK if success, Z_STREAM_ERROR if the stream state was inconsistent. In the error case, msg may be set but then points to a static string (which must not be deallocated). Definition at line 970 of file zdeflate.cpp. { if (strm == NULL || strm->De_state == NULL) return Z_STREAM_ERROR; INT32 status; /* Deallocate in reverse order of allocations: */ TRY_FREE(strm, strm->De_state->pending_buf); TRY_FREE(strm, strm->De_state->head); TRY_FREE(strm, strm->De_state->prev); TRY_FREE(strm, strm->De_state->window); status = strm->De_state->status; delete strm->De_state; strm->De_state = NULL; return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK; }

void ZipDeflate::fill_window (  DeflateState *  s  )  [private]

Fill the window when the lookahead becomes insufficient. Updates strstart and lookahead. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 IN assertion: lookahead < MIN_LOOKAHEAD OUT assertions: strstart <= window_size-MIN_LOOKAHEAD At least one byte has been read, or avail_in == 0; reads are performed for at least two bytes (required for the zip translate_eol option -- not supported here). Definition at line 1314 of file zdeflate.cpp. { register unsigned n, m; register Posf *p; unsigned more; /* Amount of free space at the end of the window. */ uInt wsize = s->w_size; do { more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart); /* Deal with !@#$% 64K limit: */ if (more == 0 && s->strstart == 0 && s->lookahead == 0) { more = wsize; } else if (more == (unsigned)(-1)) { /* Very unlikely, but possible on 16 bit machine if strstart == 0 * and lookahead == 1 (input done one byte at time) */ more--; /* If the window is almost full and there is insufficient lookahead, * move the upper half to the lower one to make room in the upper half. */ } else if (s->strstart >= wsize+MAX_DIST(s)) { zmemcpy((charf *)s->window, (charf *)s->window+wsize, (unsigned)wsize); s->match_start -= wsize; s->strstart -= wsize; /* we now have strstart >= MAX_DIST */ s->block_start -= (INT32) wsize; /* Slide the hash table (could be avoided with 32 bit values at the expense of memory usage): */ n = s->hash_size; p = &s->head[n]; do { m = *--p; *p = (Pos)(m >= wsize ? m-wsize : NIL); } while (--n); n = wsize; p = &s->prev[n]; do { m = *--p; *p = (Pos)(m >= wsize ? m-wsize : NIL); /* If n is not on any hash chain, prev[n] is garbage but * its value will never be used. */ } while (--n); more += wsize; } if (s->strm->avail_in == 0) return; /* If there was no sliding: * strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 && * more == window_size - lookahead - strstart * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1) * => more >= window_size - 2*WSIZE + 2 * In the BIG_MEM or MMAP case (not yet supported), * window_size == input_size + MIN_LOOKAHEAD && * strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD. * Otherwise, window_size == 2*WSIZE so more >= 2. * If there was sliding, more >= WSIZE. So in all cases, more >= 2. */ Assert(more >= 2, "more < 2"); n = read_buf(s->strm, (charf *)s->window + s->strstart + s->lookahead, more); s->lookahead += n; /* Initialize the hash value now that we have some input: */ if (s->lookahead >= MIN_MATCH) { s->ins_h = s->window[s->strstart]; UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]); #if MIN_MATCH != 3 Call UPDATE_HASH() MIN_MATCH-3 more times #endif } /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage, * but this is not important since only literal bytes will be emitted. */ } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0); }

void ZipDeflate::flush_pending (  z_stream *  strm  )  [private]

Flush as much pending output as possible. All deflate() output goes through this function so some applications may wish to modify it to avoid allocating a large strm->next_out buffer and copying into it. (See also read_buf()). Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Definition at line 692 of file zdeflate.cpp. { unsigned len = strm->De_state->pending; if (len > strm->avail_out) len = strm->avail_out; if (len == 0) return; zmemcpy(strm->next_out, strm->De_state->pending_out, len); strm->next_out += len; strm->De_state->pending_out += len; strm->total_out += len; strm->avail_out -= len; strm->De_state->pending -= len; if (strm->De_state->pending == 0) { strm->De_state->pending_out = strm->De_state->pending_buf; } }

void ZipDeflate::gen_bitlen (  DeflateState *  s, tree_desc *  desc )  [private]

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. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Parameters: s  current deflate state [INPUTS] desc the tree descriptor Definition at line 540 of file zdftrees.cpp. { ct_data *tree = desc->dyn_tree; INT32 max_code = desc->max_code; ct_data *stree = desc->stat_desc->static_tree; intf *extra = desc->stat_desc->extra_bits; INT32 base = desc->stat_desc->extra_base; INT32 max_length = desc->stat_desc->max_length; INT32 h; /* heap index */ INT32 n, m; /* iterate over the tree elements */ INT32 bits; /* bit length */ INT32 xbits; /* extra bits */ ush f; /* frequency */ INT32 overflow = 0; /* number of elements with bit length too large */ for (bits = 0; bits <= MAX_BITS; bits++) 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]].Len = 0; /* root of the heap */ for (h = s->heap_max+1; h < HEAP_SIZE; h++) { n = s->heap[h]; bits = tree[tree[n].Dad].Len + 1; if (bits > max_length) bits = max_length, overflow++; tree[n].Len = (ush)bits; /* We overwrite tree[n].Dad which is no longer needed */ if (n > max_code) continue; /* not a leaf node */ s->bl_count[bits]++; xbits = 0; if (n >= base) xbits = extra[n-base]; f = tree[n].Freq; s->opt_len += (ulg)f * (bits + xbits); if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits); } if (overflow == 0) return; Trace((stderr,"\nbit length overflow\n")); /* This happens for example on obj2 and pic of the Calgary corpus */ /* Find the first bit length which could increase: */ do { bits = max_length-1; while (s->bl_count[bits] == 0) bits--; s->bl_count[bits]--; /* move one leaf down the tree */ s->bl_count[bits+1] += 2; /* move one overflow item as its brother */ 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] */ overflow -= 2; } while (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.) */ for (bits = max_length; bits != 0; bits--) { n = s->bl_count[bits]; while (n != 0) { m = s->heap[--h]; if (m > max_code) continue; if (tree[m].Len != (unsigned) bits) { Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits)); s->opt_len += ((INT32)bits - (INT32)tree[m].Len) *(INT32)tree[m].Freq; tree[m].Len = (ush)bits; } n--; } } }

void ZipDeflate::gen_codes (  ct_data *  tree, INT32  max_code, ushf  bl_count[] )  [private]

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. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Parameters: tree  the tree to decorate [INPUTS] max_code largest code with non zero frequency bl_count[] number of codes at each bit length Definition at line 634 of file zdftrees.cpp. { ush next_code[MAX_BITS+1]; /* next code value for each bit length */ ush code = 0; /* running code value */ INT32 bits; /* bit index */ INT32 n; /* code index */ /* The distribution counts are first used to generate the code values * without bit reversal. */ for (bits = 1; bits <= MAX_BITS; bits++) { next_code[bits] = code = (code + bl_count[bits-1]) << 1; } /* Check that the bit counts in bl_count are consistent. The last code * must be all ones. */ Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1, "inconsistent bit counts"); Tracev((stderr,"\ngen_codes: max_code %d ", max_code)); for (n = 0; n <= max_code; n++) { INT32 len = tree[n].Len; if (len == 0) continue; /* Now reverse the bits */ tree[n].Code = bi_reverse(next_code[len]++, len); Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ", n, (_istgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1)); } }

INT32 ZipDeflate::Init (  z_stream *  strm, INT32  level, INT32  method, INT32  windowBits, INT32  memLevel, INT32  strategy )

This is another version of deflate Init with more compression options. The fields next_in, zalloc and zfree must be initialized before by the caller. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Parameters: strm  the zip stream to use [INPUTS] level usually Z_DEFAULT_COMPRESSION, or between 1 and 9. 1 best speed 9 best compression method always DEFLATED at present (For future expansion) windowBits the base two logarithm of the window size, range 8..15 memLevel memory to allocate for the internal compression state 1..9 (8 default) strategy used to tune the compressor to the current type of data The method parameter is the compression method. It must be 8 in this version of the library. (Method 9 will allow a 64K history buffer and partial block flushes.) The windowBits parameter is the base two logarithm of the window size (the size of the history buffer). It should be in the range 8..15 for this version of the library (the value 16 will be allowed for method 9). Larger values of this parameter result in better compression at the expense of memory usage. The default value is 15 if deflateInit is used instead. The memLevel parameter specifies how much memory should be allocated for the internal compression state. memLevel=1 uses minimum memory but is slow and reduces compression ratio; memLevel=9 uses maximum memory for optimal speed. The default value is 8. See zconf.h for total memory usage as a function of windowBits and memLevel. The strategy parameter is used to tune the compression algorithm. Use the value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data produced by a filter (or predictor), or Z_HUFFMAN_ONLY to force Huffman encoding only (no string match). Filtered data consists mostly of small values with a somewhat random distribution. In this case, the compression algorithm is tuned to compress them better. The strategy parameter only affects the compression ratio but not the correctness of the compressed output even if it is not set appropriately. If next_in is not null, the library will use this buffer to hold also some history information; the buffer must either hold the entire input data, or have at least 1<<(windowBits+1) bytes and be writable. If next_in is null, the library will allocate its own history buffer (and leave next_in null). next_out need not be provided here but must be provided by the application for the next call of deflate(). If the history buffer is provided by the application, next_in must must never be changed by the application since the compressor maintains information inside this buffer from call to call; the application must provide more input only by increasing avail_in. next_in is always reset by the library in this case. This deflate Init returns Z_OK if success, Z_MEM_ERROR if there was not enough memory, Z_STREAM_ERROR if a parameter is invalid (such as an invalid method). msg is set to null if there is no error message. This deflate Init does not perform any compression: this will be done by deflate(). Definition at line 375 of file zdeflate.cpp. { ushf *overlay; /* We overlay pending_buf and d_buf+l_buf. This works since the average * output size for (length,distance) codes is <= 24 bits. */ // First, check if the stream passed in is valid or not //if (version == Z_NULL || version[0] != ZLIB_VERSION[0] || stream_size != sizeof(ZStream)) //{ // return Z_VERSION_ERROR; //} if (strm == NULL) return Z_STREAM_ERROR; DeflateState *s = NULL; INT32 noheader = 0; strm->msg = NULL; if (strm->zalloc == NULL) { strm->zalloc = GZipFile::zcalloc; strm->opaque = 0; // (voidpf)0; } if (strm->zfree == NULL) strm->zfree = GZipFile::zcfree; if (level == Z_DEFAULT_COMPRESSION) level = 6; if (windowBits < 0) { /* undocumented feature: suppress zlib header */ noheader = 1; windowBits = -windowBits; } if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED || windowBits < 8 || windowBits > 15 || level < 0 || level > 9 || strategy < 0 || strategy > Z_HUFFMAN_ONLY) { return Z_STREAM_ERROR; } //s = ( DeflateState *) ZALLOC(strm, 1, sizeof( DeflateState)); s = new DeflateState; if (s == NULL) return Z_MEM_ERROR; strm->De_state = s; s->strm = strm; s->noheader = noheader; s->w_bits = windowBits; s->w_size = 1 << (s->w_bits); s->w_mask = s->w_size - 1; s->hash_bits = memLevel + 7; s->hash_size = 1 << (s->hash_bits); s->hash_mask = s->hash_size - 1; s->hash_shift = ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH); s->window = (Byte*) ZALLOC(strm, s->w_size, 2*sizeof(Byte)); s->prev = (Pos*) ZALLOC(strm, s->w_size, sizeof(Pos)); s->head = (Pos*) ZALLOC(strm, s->hash_size, sizeof(Pos)); s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */ overlay = (ushf *) ZALLOC(strm, s->lit_bufsize, sizeof(ush)+2); s->pending_buf = (uchf *) overlay; if (s->window == NULL || s->prev == NULL || s->head == NULL || s->pending_buf == NULL) { //strm->msg = ERR_MSG(Z_MEM_ERROR); End(strm); return Z_MEM_ERROR; } s->d_buf = overlay + s->lit_bufsize/sizeof(ush); s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize; s->level = level; s->strategy = strategy; s->method = (Byte)method; return Reset(strm); }

INT32 ZipDeflate::Init (  z_stream *  strm, INT32  level )

Initializes the internal stream state for compression. The fields zalloc, zfree and opaque must be initialized before by the caller. If zalloc and zfree are set to Z_NULL, deflateInit updates them to use default allocation functions. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Parameters: s  the zip stream to use [INPUTS] level usually Z_DEFAULT_COMPRESSION, or between 1 and 9. 1 best speed 9 best compression The compression level must be Z_DEFAULT_COMPRESSION, or between 1 and 9: 1 gives best speed, 9 gives best compression. Z_DEFAULT_COMPRESSION requests a default compromise between speed and compression (currently equivalent to level 6). deflate Init returns Z_OK if success, Z_MEM_ERROR if there was not enough memory, Z_STREAM_ERROR if level is not a valid compression level. msg is set to null if there is no error message. deflateInit does not perform any compression: this will be done by deflate(). Definition at line 304 of file zdeflate.cpp. { // Just call the main init with default parameters return Init(strm, level, Z_DEFLATED, MAX_WBITS, DEF_MEM_LEVEL, Z_DEFAULT_STRATEGY); //version, stream_size); /* To do: ignore strm->next_in if we use it as window */ }

void ZipDeflate::init_block (  DeflateState *  s  )  [private]

Initialize a new block. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Definition at line 441 of file zdftrees.cpp. { INT32 n; /* iterates over tree elements */ /* Initialize the trees. */ for (n = 0; n < L_CODES; n++) s->dyn_ltree[n].Freq = 0; for (n = 0; n < D_CODES; n++) s->dyn_dtree[n].Freq = 0; for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0; s->dyn_ltree[END_BLOCK].Freq = 1; s->opt_len = s->static_len = 0L; s->last_lit = s->matches = 0; }

void ZipDeflate::lm_init (  DeflateState *  s  )  [private]

Initialize the "longest match" routines for a new zlib stream. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Definition at line 1084 of file zdeflate.cpp. { s->window_size = (ulg)2L*s->w_size; CLEAR_HASH(s); /* 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 = 0L; s->lookahead = 0; s->match_length = s->prev_length = MIN_MATCH-1; s->match_available = 0; s->ins_h = 0; #ifdef ASMV match_init(); /* initialize the asm code */ #endif }

uInt ZipDeflate::longest_match (  DeflateState *  s, IPos  cur_match )  [private]

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. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 For 80x86 and 680x0, an optimized version will be provided in match.asm or match.S. The code will be functionally equivalent. Definition at line 1127 of file zdeflate.cpp. { unsigned chain_length = s->max_chain_length;/* max hash chain length */ register Bytef *scan = s->window + s->strstart; /* current string */ register Bytef *match; /* matched string */ register INT32 len; /* length of current match */ INT32 best_len = s->prev_length; /* best match length so far */ INT32 nice_match = s->nice_match; /* stop if match long enough */ IPos limit = s->strstart > (IPos)MAX_DIST(s) ? s->strstart - (IPos)MAX_DIST(s) : NIL; /* Stop when cur_match becomes <= limit. To simplify the code, * we prevent matches with the string of window index 0. */ Posf *prev = s->prev; uInt 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. */ register Bytef *strend = s->window + s->strstart + MAX_MATCH - 1; register ush scan_start = *(ushf*)scan; register ush scan_end = *(ushf*)(scan+best_len-1); #else register Bytef *strend = s->window + s->strstart + MAX_MATCH; register Byte scan_end1 = scan[best_len-1]; register Byte scan_end = 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. */ Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever"); /* Do not waste too much time if we already have a good match: */ if (s->prev_length >= s->good_match) { chain_length >>= 2; } /* Do not look for matches beyond the end of the input. This is necessary * to make deflate deterministic. */ if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead; Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead"); do { Assert(cur_match < s->strstart, "no future"); match = s->window + cur_match; /* Skip to next match if the match length cannot increase * or if the match length is less than 2: */ #if (defined(UNALIGNED_OK) && MAX_MATCH == 258) /* This code assumes sizeof(unsigned short) == 2. Do not use * UNALIGNED_OK if your compiler uses a different size. */ if (*(ushf*)(match+best_len-1) != scan_end || *(ushf*)match != scan_start) continue; /* 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. */ Assert(scan[2] == match[2], "scan[2]?"); scan++, match++; do { } while (*(ushf*)(scan+=2) == *(ushf*)(match+=2) && *(ushf*)(scan+=2) == *(ushf*)(match+=2) && *(ushf*)(scan+=2) == *(ushf*)(match+=2) && *(ushf*)(scan+=2) == *(ushf*)(match+=2) && scan < strend); /* The funny "do {}" generates better code on most compilers */ /* Here, scan <= window+strstart+257 */ Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan"); if (*scan == *match) scan++; len = (MAX_MATCH - 1) - (INT32)(strend-scan); scan = strend - (MAX_MATCH-1); #else /* UNALIGNED_OK */ if (match[best_len] != scan_end || match[best_len-1] != scan_end1 || *match != *scan || *++match != scan[1]) 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. */ scan += 2, match++; Assert(*scan == *match, "match[2]?"); /* We check for insufficient lookahead only every 8th comparison; * the 256th check will be made at strstart+258. */ do { } while (*++scan == *++match && *++scan == *++match && *++scan == *++match && *++scan == *++match && *++scan == *++match && *++scan == *++match && *++scan == *++match && *++scan == *++match && scan < strend); Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan"); len = MAX_MATCH - (INT32)(strend - scan); scan = strend - MAX_MATCH; #endif /* UNALIGNED_OK */ if (len > best_len) { s->match_start = cur_match; best_len = len; if (len >= nice_match) break; #ifdef UNALIGNED_OK scan_end = *(ushf*)(scan+best_len-1); #else scan_end1 = scan[best_len-1]; scan_end = scan[best_len]; #endif } } while ((cur_match = prev[cur_match & wmask]) > limit && --chain_length != 0); if ((uInt)best_len <= s->lookahead) return best_len; return s->lookahead; }

INT32 ZipDeflate::Params (  z_stream *  strm, INT32  level, INT32  strategy )

New for version 0.99 Dynamically update the compression level and compression strategy. This can be used to switch between compression and straight copy of the input data, or to switch to a different kind of input data requiring a different strategy. If the compression level is changed, the input available so far is compressed with the old level (and may be flushed); the new level will take effect only at the next call of deflate(). Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 03/05/95 Parameters: [INPUTS]  Returns: returns Z_OK if success, Z_STREAM_ERROR if the source stream state was inconsistent Before the call of deflateParams, the stream state must be set as for a call of deflate(), since the currently available input may have to be compressed and flushed. In particular, strm->avail_out must be non-zero. deflateParams returns Z_OK if success, Z_STREAM_ERROR if the source stream state was inconsistent or if a parameter was invalid, Z_BUF_ERROR if strm->avail_out was zero. Definition at line 620 of file zdeflate.cpp. { DeflateState *s; compress_func func; INT32 err = Z_OK; if (strm == Z_NULL || strm->De_state == Z_NULL) return Z_STREAM_ERROR; s = strm->De_state; if (level == Z_DEFAULT_COMPRESSION) { level = 6; } if (level < 0 || level > 9 || strategy < 0 || strategy > Z_HUFFMAN_ONLY) { return Z_STREAM_ERROR; } func = configuration_table[s->level].func; if (func != configuration_table[level].func && strm->total_in != 0) { /* Flush the last buffer: */ err = deflate(strm, Z_PARTIAL_FLUSH); } if (s->level != level) { s->level = level; s->max_lazy_match = configuration_table[level].max_lazy; s->good_match = configuration_table[level].good_length; s->nice_match = configuration_table[level].nice_length; s->max_chain_length = configuration_table[level].max_chain; } s->strategy = strategy; return err; }

void ZipDeflate::pqdownheap (  DeflateState *  s, ct_data *  tree, INT32  k )  [private]

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). Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Parameters: s  current deflate state [INPUTS] tree the tree to restore k node to move down Definition at line 498 of file zdftrees.cpp. { INT32 v = s->heap[k]; INT32 j = k << 1; /* left son of k */ while (j <= s->heap_len) { /* Set j to the smallest of the two sons: */ if (j < s->heap_len && smaller(tree, s->heap[j+1], s->heap[j], s->depth)) { j++; } /* Exit if v is smaller than both sons */ if (smaller(tree, v, s->heap[j], s->depth)) 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 <<= 1; } s->heap[k] = v; }

void ZipDeflate::putShortMSB (  DeflateState *  s, uInt  b )  [private]

Put a short the pending_out buffer. The 16-bit value is put in MSB order. IN assertion: the stream state is correct and there is enough room in the pending_out buffer. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Definition at line 673 of file zdeflate.cpp. { put_byte(s, (Byte)(b >> 8)); put_byte(s, (Byte)(b & 0xff)); }

INT32 ZipDeflate::read_buf (  z_stream *  strm, charf *  buf, unsigned  size )  [private]

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()). Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Definition at line 1054 of file zdeflate.cpp. { unsigned len = strm->avail_in; if (len > size) len = size; if (len == 0) return 0; strm->avail_in -= len; if (!strm->De_state->noheader) { strm->adler = GZipFile::adler32(strm->adler, strm->next_in, len); } zmemcpy(buf, strm->next_in, len); strm->next_in += len; strm->total_in += len; return (INT32)len; }

INT32 ZipDeflate::Reset (  z_stream *  strm  )

This function is equivalent to deflate End followed by deflateInit, but does not free and reallocate all the internal compression state. The stream will keep the same compression level and any other attributes that may have been set by deflate Init. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Parameters: s  the zip stream to use [INPUTS] Returns: returns Z_OK if success, Z_STREAM_ERROR if the source stream state was inconsistent deflate Reset returns Z_OK if success, or Z_STREAM_ERROR if the source stream state was inconsistent (such as zalloc or state being NULL). Definition at line 564 of file zdeflate.cpp. { DeflateState *s; if (strm == Z_NULL || strm->De_state == Z_NULL || strm->zalloc == Z_NULL || strm->zfree == Z_NULL) return Z_STREAM_ERROR; strm->total_in = strm->total_out = 0; strm->msg = NULL; /* use zfree if we ever allocate msg dynamically */ strm->data_type = Z_UNKNOWN; s = strm->De_state; s->pending = 0; s->pending_out = s->pending_buf; if (s->noheader < 0) { s->noheader = 0; /* was set to -1 by deflate(..., Z_FINISH); */ } s->status = s->noheader ? BUSY_STATE : INIT_STATE; strm->adler = 1; s->last_flush = Z_NO_FLUSH; _tr_init(s); lm_init(s); return Z_OK; }

void ZipDeflate::scan_tree (  DeflateState *  s, ct_data *  tree, INT32  max_code )  [private]

Scan a literal or distance tree to determine the frequencies of the codes in the bit length tree. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Parameters: s  the current deflate state [INPUTS] tree the tree to be scanned max_code and its largest code of non zero frequency Definition at line 778 of file zdftrees.cpp. { INT32 n; /* iterates over all tree elements */ INT32 prevlen = -1; /* last emitted length */ INT32 curlen; /* length of current code */ INT32 nextlen = tree[0].Len; /* length of next code */ INT32 count = 0; /* repeat count of the current code */ INT32 max_count = 7; /* max repeat count */ INT32 min_count = 4; /* min repeat count */ if (nextlen == 0) max_count = 138, min_count = 3; tree[max_code+1].Len = (ush)0xffff; /* guard */ for (n = 0; n <= max_code; n++) { curlen = nextlen; nextlen = tree[n+1].Len; if (++count < max_count && curlen == nextlen) { continue; } else if (count < min_count) { s->bl_tree[curlen].Freq += count; } else if (curlen != 0) { if (curlen != prevlen) s->bl_tree[curlen].Freq++; s->bl_tree[REP_3_6].Freq++; } else if (count <= 10) { s->bl_tree[REPZ_3_10].Freq++; } else { s->bl_tree[REPZ_11_138].Freq++; } count = 0; prevlen = curlen; if (nextlen == 0) { max_count = 138, min_count = 3; } else if (curlen == nextlen) { max_count = 6, min_count = 3; } else { max_count = 7, min_count = 4; } } }

void ZipDeflate::send_all_trees (  DeflateState *  s, INT32  lcodes, INT32  dcodes, INT32  blcodes )  [private]

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. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Parameters: s  the current deflate state [INPUTS] lcodes, dcodes, blcodes number of codes for each tree Definition at line 929 of file zdftrees.cpp. { INT32 rank; /* index in bl_order */ Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes"); Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES, "too many codes"); Tracev((stderr, "\nbl counts: ")); 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; rank < blcodes; rank++) { Tracev((stderr, "\nbl code %2d ", bl_order[rank])); send_bits(s, s->bl_tree[bl_order[rank]].Len, 3); } Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent)); send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */ Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent)); send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */ Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent)); }

void ZipDeflate::send_tree (  DeflateState *  s, ct_data *  tree, INT32  max_code )  [private]

Send a literal or distance tree in compressed form, using the codes in bl_tree. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Parameters: s  the current deflate state [INPUTS] tree the tree to be scanned max_code and its largest code of non zero frequency Definition at line 830 of file zdftrees.cpp. { INT32 n; /* iterates over all tree elements */ INT32 prevlen = -1; /* last emitted length */ INT32 curlen; /* length of current code */ INT32 nextlen = tree[0].Len; /* length of next code */ INT32 count = 0; /* repeat count of the current code */ INT32 max_count = 7; /* max repeat count */ INT32 min_count = 4; /* min repeat count */ /* tree[max_code+1].Len = -1; */ /* guard already set */ if (nextlen == 0) max_count = 138, min_count = 3; for (n = 0; n <= max_code; n++) { curlen = nextlen; nextlen = tree[n+1].Len; if (++count < max_count && curlen == nextlen) { continue; } else if (count < min_count) { do { send_code(s, curlen, s->bl_tree); } while (--count != 0); } else if (curlen != 0) { if (curlen != prevlen) { send_code(s, curlen, s->bl_tree); count--; } Assert(count >= 3 && count <= 6, " 3_6?"); send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2); } else if (count <= 10) { send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3); } else { send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7); } count = 0; prevlen = curlen; if (nextlen == 0) { max_count = 138, min_count = 3; } else if (curlen == nextlen) { max_count = 6, min_count = 3; } else { max_count = 7, min_count = 4; } } }

void ZipDeflate::set_data_type (  DeflateState *  s  )  [private]

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 INT32 on 16 bit machines). Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Parameters: s  the current deflate state [INPUTS] Definition at line 1256 of file zdftrees.cpp. { INT32 n = 0; unsigned ascii_freq = 0; unsigned bin_freq = 0; while (n < 7) bin_freq += s->dyn_ltree[n++].Freq; while (n < 128) ascii_freq += s->dyn_ltree[n++].Freq; while (n < LITERALS) bin_freq += s->dyn_ltree[n++].Freq; s->data_type = (Byte)(bin_freq > (ascii_freq >> 2) ? Z_BINARY : Z_ASCII); }

INT32 ZipDeflate::SetDictionary (  z_stream *  strm, const Bytef *  dictionary, uInt  dictLength )

Initializes the compression dictionary (history buffer) from the given byte sequence without producing any compressed output. This function must be called immediately after deflateInit or deflateInit2, before any call of deflate. The compressor and decompressor must use exactly the same dictionary (see inflateSetDictionary). The dictionary should consist of strings (byte sequences) that are likely to be encountered later in the data to be compressed, with the most commonly used strings preferably put towards the end of the dictionary. Using a dictionary is most useful when the data to be compressed is short and can be predicted with good accuracy; the data can then be compressed better than with the default empty dictionary. In this version of the library, only the last 32K bytes of the dictionary are used. Upon return of this function, strm->adler is set to the Adler32 value of the dictionary; the decompressor may later use this value to determine which dictionary has been used by the compressor. (The Adler32 value applies to the whole dictionary even if only a subset of the dictionary is actually used by the compressor.). Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 03/05/96 Parameters: s  the zip stream to use [INPUTS] dictionary pointer to the dictionary to use dictlength length of dictionary Returns: returns Z_OK if success, Z_STREAM_ERROR if the source stream state was inconsistent deflateSetDictionary returns Z_OK if success, or Z_STREAM_ERROR if a parameter is invalid (such as NULL dictionary) or the stream state is inconsistent (for example if deflate has already been called for this stream). deflateSetDictionary does not perform any compression: this will be done by deflate(). New for version 0.99 Definition at line 502 of file zdeflate.cpp. { DeflateState *s; uInt length = dictLength; uInt n; IPos hash_head = 0; if (strm == Z_NULL || strm->De_state == Z_NULL || dictionary == Z_NULL || strm->De_state->status != INIT_STATE) return Z_STREAM_ERROR; s = strm->De_state; strm->adler = GZipFile::adler32(strm->adler, dictionary, dictLength); if (length < MIN_MATCH) return Z_OK; if (length > MAX_DIST(s)) { length = MAX_DIST(s); dictionary += dictLength - length; } zmemcpy((charf *)s->window, dictionary, length); s->strstart = length; s->block_start = (INT32)length; /* Insert all strings in the hash table (except for the last two bytes). * s->lookahead stays null, so s->ins_h will be recomputed at the next * call of fill_window. */ s->ins_h = s->window[0]; UPDATE_HASH(s, s->ins_h, s->window[1]); for (n = 0; n <= length - MIN_MATCH; n++) { INSERT_STRING(s, n, hash_head); } if (hash_head) hash_head = 0; /* to make compiler happy */ return Z_OK; }

void ZipDeflate::tr_static_init (  void   )  [private]

Initialize the various 'constant' tables. To do: do this at compile time. Author: Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com> Date: 24/05/95 Definition at line 328 of file zdftrees.cpp. { static BOOL static_init_done = 0; INT32 n; /* iterates over tree elements */ INT32 bits; /* bit counter */ INT32 length; /* length value */ INT32 code; /* code value */ INT32 dist; /* distance index */ ush bl_count[MAX_BITS+1]; /* number of codes at each bit length for an optimal tree */ if (static_init_done) return; /* Initialize the mapping length (0..255) -> length code (0..28) */ length = 0; for (code = 0; code < LENGTH_CODES-1; code++) { base_length[code] = length; for (n = 0; n < (1<<extra_lbits[code]); n++) { length_code[length++] = (uch)code; } } 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] = (uch)code; /* Initialize the mapping dist (0..32K) -> dist code (0..29) */ dist = 0; for (code = 0 ; code < 16; code++) { base_dist[code] = dist; for (n = 0; n < (1<<extra_dbits[code]); n++) { dist_code[dist++] = (uch)code; } } Assert (dist == 256, "tr_static_init: dist != 256"); dist >>= 7; /* from now on, all distances are divided by 128 */ for ( ; code < D_CODES; code++) { base_dist[code] = dist << 7; for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) { dist_code[256 + dist++] = (uch)code; } } Assert (dist == 256, "tr_static_init: 256+dist != 512"); /* Construct the codes of the static literal tree */ for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0; n = 0; while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++; while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++; while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++; while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++; /* 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((ct_data *)static_ltree, L_CODES+1, bl_count); /* The static distance tree is trivial: */ for (n = 0; n < D_CODES; n++) { static_dtree[n].Len = 5; static_dtree[n].Code = bi_reverse((unsigned)n, 5); } static_init_done = 1; }

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The documentation for this class was generated from the following files:

• Kernel/zdeflate.h (r1785/r751)
• Kernel/zdeflate.cpp (r1785/r1282)
• Kernel/zdftrees.cpp (r1785/r817)

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