7
Network Working Group P. Deutsch
8
Request for Comments: 1951 Aladdin Enterprises
9
Category: Informational May 1996
12
DEFLATE Compressed Data Format Specification version 1.3
16
This memo provides information for the Internet community. This memo
17
does not specify an Internet standard of any kind. Distribution of
18
this memo is unlimited.
22
The IESG takes no position on the validity of any Intellectual
23
Property Rights statements contained in this document.
27
Copyright (c) 1996 L. Peter Deutsch
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Permission is granted to copy and distribute this document for any
30
purpose and without charge, including translations into other
31
languages and incorporation into compilations, provided that the
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copyright notice and this notice are preserved, and that any
33
substantive changes or deletions from the original are clearly
36
A pointer to the latest version of this and related documentation in
37
HTML format can be found at the URL
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<ftp://ftp.uu.net/graphics/png/documents/zlib/zdoc-index.html>.
42
This specification defines a lossless compressed data format that
43
compresses data using a combination of the LZ77 algorithm and Huffman
44
coding, with efficiency comparable to the best currently available
45
general-purpose compression methods. The data can be produced or
46
consumed, even for an arbitrarily long sequentially presented input
47
data stream, using only an a priori bounded amount of intermediate
48
storage. The format can be implemented readily in a manner not
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Deutsch Informational [Page 1]
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RFC 1951 DEFLATE Compressed Data Format Specification May 1996
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1. Introduction ................................................... 2
66
1.1. Purpose ................................................... 2
67
1.2. Intended audience ......................................... 3
68
1.3. Scope ..................................................... 3
69
1.4. Compliance ................................................ 3
70
1.5. Definitions of terms and conventions used ................ 3
71
1.6. Changes from previous versions ............................ 4
72
2. Compressed representation overview ............................. 4
73
3. Detailed specification ......................................... 5
74
3.1. Overall conventions ....................................... 5
75
3.1.1. Packing into bytes .................................. 5
76
3.2. Compressed block format ................................... 6
77
3.2.1. Synopsis of prefix and Huffman coding ............... 6
78
3.2.2. Use of Huffman coding in the "deflate" format ....... 7
79
3.2.3. Details of block format ............................. 9
80
3.2.4. Non-compressed blocks (BTYPE=00) ................... 11
81
3.2.5. Compressed blocks (length and distance codes) ...... 11
82
3.2.6. Compression with fixed Huffman codes (BTYPE=01) .... 12
83
3.2.7. Compression with dynamic Huffman codes (BTYPE=10) .. 13
84
3.3. Compliance ............................................... 14
85
4. Compression algorithm details ................................. 14
86
5. References .................................................... 16
87
6. Security Considerations ....................................... 16
88
7. Source code ................................................... 16
89
8. Acknowledgements .............................................. 16
90
9. Author's Address .............................................. 17
96
The purpose of this specification is to define a lossless
97
compressed data format that:
98
* Is independent of CPU type, operating system, file system,
99
and character set, and hence can be used for interchange;
100
* Can be produced or consumed, even for an arbitrarily long
101
sequentially presented input data stream, using only an a
102
priori bounded amount of intermediate storage, and hence
103
can be used in data communications or similar structures
104
such as Unix filters;
105
* Compresses data with efficiency comparable to the best
106
currently available general-purpose compression methods,
107
and in particular considerably better than the "compress"
109
* Can be implemented readily in a manner not covered by
110
patents, and hence can be practiced freely;
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RFC 1951 DEFLATE Compressed Data Format Specification May 1996
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* Is compatible with the file format produced by the current
120
widely used gzip utility, in that conforming decompressors
121
will be able to read data produced by the existing gzip
124
The data format defined by this specification does not attempt to:
126
* Allow random access to compressed data;
127
* Compress specialized data (e.g., raster graphics) as well
128
as the best currently available specialized algorithms.
130
A simple counting argument shows that no lossless compression
131
algorithm can compress every possible input data set. For the
132
format defined here, the worst case expansion is 5 bytes per 32K-
133
byte block, i.e., a size increase of 0.015% for large data sets.
134
English text usually compresses by a factor of 2.5 to 3;
135
executable files usually compress somewhat less; graphical data
136
such as raster images may compress much more.
138
1.2. Intended audience
140
This specification is intended for use by implementors of software
141
to compress data into "deflate" format and/or decompress data from
144
The text of the specification assumes a basic background in
145
programming at the level of bits and other primitive data
146
representations. Familiarity with the technique of Huffman coding
147
is helpful but not required.
151
The specification specifies a method for representing a sequence
152
of bytes as a (usually shorter) sequence of bits, and a method for
153
packing the latter bit sequence into bytes.
157
Unless otherwise indicated below, a compliant decompressor must be
158
able to accept and decompress any data set that conforms to all
159
the specifications presented here; a compliant compressor must
160
produce data sets that conform to all the specifications presented
163
1.5. Definitions of terms and conventions used
165
Byte: 8 bits stored or transmitted as a unit (same as an octet).
166
For this specification, a byte is exactly 8 bits, even on machines
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RFC 1951 DEFLATE Compressed Data Format Specification May 1996
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which store a character on a number of bits different from eight.
176
See below, for the numbering of bits within a byte.
178
String: a sequence of arbitrary bytes.
180
1.6. Changes from previous versions
182
There have been no technical changes to the deflate format since
183
version 1.1 of this specification. In version 1.2, some
184
terminology was changed. Version 1.3 is a conversion of the
185
specification to RFC style.
187
2. Compressed representation overview
189
A compressed data set consists of a series of blocks, corresponding
190
to successive blocks of input data. The block sizes are arbitrary,
191
except that non-compressible blocks are limited to 65,535 bytes.
193
Each block is compressed using a combination of the LZ77 algorithm
194
and Huffman coding. The Huffman trees for each block are independent
195
of those for previous or subsequent blocks; the LZ77 algorithm may
196
use a reference to a duplicated string occurring in a previous block,
197
up to 32K input bytes before.
199
Each block consists of two parts: a pair of Huffman code trees that
200
describe the representation of the compressed data part, and a
201
compressed data part. (The Huffman trees themselves are compressed
202
using Huffman encoding.) The compressed data consists of a series of
203
elements of two types: literal bytes (of strings that have not been
204
detected as duplicated within the previous 32K input bytes), and
205
pointers to duplicated strings, where a pointer is represented as a
206
pair <length, backward distance>. The representation used in the
207
"deflate" format limits distances to 32K bytes and lengths to 258
208
bytes, but does not limit the size of a block, except for
209
uncompressible blocks, which are limited as noted above.
211
Each type of value (literals, distances, and lengths) in the
212
compressed data is represented using a Huffman code, using one code
213
tree for literals and lengths and a separate code tree for distances.
214
The code trees for each block appear in a compact form just before
215
the compressed data for that block.
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RFC 1951 DEFLATE Compressed Data Format Specification May 1996
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3. Detailed specification
233
3.1. Overall conventions In the diagrams below, a box like this:
236
| | <-- the vertical bars might be missing
239
represents one byte; a box like this:
245
represents a variable number of bytes.
247
Bytes stored within a computer do not have a "bit order", since
248
they are always treated as a unit. However, a byte considered as
249
an integer between 0 and 255 does have a most- and least-
250
significant bit, and since we write numbers with the most-
251
significant digit on the left, we also write bytes with the most-
252
significant bit on the left. In the diagrams below, we number the
253
bits of a byte so that bit 0 is the least-significant bit, i.e.,
254
the bits are numbered:
260
Within a computer, a number may occupy multiple bytes. All
261
multi-byte numbers in the format described here are stored with
262
the least-significant byte first (at the lower memory address).
263
For example, the decimal number 520 is stored as:
271
| + more significant byte = 2 x 256
272
+ less significant byte = 8
274
3.1.1. Packing into bytes
276
This document does not address the issue of the order in which
277
bits of a byte are transmitted on a bit-sequential medium,
278
since the final data format described here is byte- rather than
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RFC 1951 DEFLATE Compressed Data Format Specification May 1996
287
bit-oriented. However, we describe the compressed block format
288
in below, as a sequence of data elements of various bit
289
lengths, not a sequence of bytes. We must therefore specify
290
how to pack these data elements into bytes to form the final
291
compressed byte sequence:
293
* Data elements are packed into bytes in order of
294
increasing bit number within the byte, i.e., starting
295
with the least-significant bit of the byte.
296
* Data elements other than Huffman codes are packed
297
starting with the least-significant bit of the data
299
* Huffman codes are packed starting with the most-
300
significant bit of the code.
302
In other words, if one were to print out the compressed data as
303
a sequence of bytes, starting with the first byte at the
304
*right* margin and proceeding to the *left*, with the most-
305
significant bit of each byte on the left as usual, one would be
306
able to parse the result from right to left, with fixed-width
307
elements in the correct MSB-to-LSB order and Huffman codes in
308
bit-reversed order (i.e., with the first bit of the code in the
309
relative LSB position).
311
3.2. Compressed block format
313
3.2.1. Synopsis of prefix and Huffman coding
315
Prefix coding represents symbols from an a priori known
316
alphabet by bit sequences (codes), one code for each symbol, in
317
a manner such that different symbols may be represented by bit
318
sequences of different lengths, but a parser can always parse
319
an encoded string unambiguously symbol-by-symbol.
321
We define a prefix code in terms of a binary tree in which the
322
two edges descending from each non-leaf node are labeled 0 and
323
1 and in which the leaf nodes correspond one-for-one with (are
324
labeled with) the symbols of the alphabet; then the code for a
325
symbol is the sequence of 0's and 1's on the edges leading from
326
the root to the leaf labeled with that symbol. For example:
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RFC 1951 DEFLATE Compressed Data Format Specification May 1996
354
A parser can decode the next symbol from an encoded input
355
stream by walking down the tree from the root, at each step
356
choosing the edge corresponding to the next input bit.
358
Given an alphabet with known symbol frequencies, the Huffman
359
algorithm allows the construction of an optimal prefix code
360
(one which represents strings with those symbol frequencies
361
using the fewest bits of any possible prefix codes for that
362
alphabet). Such a code is called a Huffman code. (See
363
reference [1] in Chapter 5, references for additional
364
information on Huffman codes.)
366
Note that in the "deflate" format, the Huffman codes for the
367
various alphabets must not exceed certain maximum code lengths.
368
This constraint complicates the algorithm for computing code
369
lengths from symbol frequencies. Again, see Chapter 5,
370
references for details.
372
3.2.2. Use of Huffman coding in the "deflate" format
374
The Huffman codes used for each alphabet in the "deflate"
375
format have two additional rules:
377
* All codes of a given bit length have lexicographically
378
consecutive values, in the same order as the symbols
381
* Shorter codes lexicographically precede longer codes.
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RFC 1951 DEFLATE Compressed Data Format Specification May 1996
399
We could recode the example above to follow this rule as
400
follows, assuming that the order of the alphabet is ABCD:
409
I.e., 0 precedes 10 which precedes 11x, and 110 and 111 are
410
lexicographically consecutive.
412
Given this rule, we can define the Huffman code for an alphabet
413
just by giving the bit lengths of the codes for each symbol of
414
the alphabet in order; this is sufficient to determine the
415
actual codes. In our example, the code is completely defined
416
by the sequence of bit lengths (2, 1, 3, 3). The following
417
algorithm generates the codes as integers, intended to be read
418
from most- to least-significant bit. The code lengths are
419
initially in tree[I].Len; the codes are produced in
422
1) Count the number of codes for each code length. Let
423
bl_count[N] be the number of codes of length N, N >= 1.
425
2) Find the numerical value of the smallest code for each
430
for (bits = 1; bits <= MAX_BITS; bits++) {
431
code = (code + bl_count[bits-1]) << 1;
432
next_code[bits] = code;
435
3) Assign numerical values to all codes, using consecutive
436
values for all codes of the same length with the base
437
values determined at step 2. Codes that are never used
438
(which have a bit length of zero) must not be assigned a
441
for (n = 0; n <= max_code; n++) {
444
tree[n].Code = next_code[len];
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RFC 1951 DEFLATE Compressed Data Format Specification May 1996
459
Consider the alphabet ABCDEFGH, with bit lengths (3, 3, 3, 3,
460
3, 2, 4, 4). After step 1, we have:
468
Step 2 computes the following next_code values:
477
Step 3 produces the following code values:
490
3.2.3. Details of block format
492
Each block of compressed data begins with 3 header bits
493
containing the following data:
498
Note that the header bits do not necessarily begin on a byte
499
boundary, since a block does not necessarily occupy an integral
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RFC 1951 DEFLATE Compressed Data Format Specification May 1996
511
BFINAL is set if and only if this is the last block of the data
514
BTYPE specifies how the data are compressed, as follows:
517
01 - compressed with fixed Huffman codes
518
10 - compressed with dynamic Huffman codes
519
11 - reserved (error)
521
The only difference between the two compressed cases is how the
522
Huffman codes for the literal/length and distance alphabets are
525
In all cases, the decoding algorithm for the actual data is as
529
read block header from input stream.
530
if stored with no compression
531
skip any remaining bits in current partially
533
read LEN and NLEN (see next section)
534
copy LEN bytes of data to output
536
if compressed with dynamic Huffman codes
537
read representation of code trees (see
539
loop (until end of block code recognized)
540
decode literal/length value from input stream
542
copy value (literal byte) to output stream
544
if value = end of block (256)
546
otherwise (value = 257..285)
547
decode distance from input stream
549
move backwards distance bytes in the output
550
stream, and copy length bytes from this
551
position to the output stream.
555
Note that a duplicated string reference may refer to a string
556
in a previous block; i.e., the backward distance may cross one
557
or more block boundaries. However a distance cannot refer past
558
the beginning of the output stream. (An application using a
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RFC 1951 DEFLATE Compressed Data Format Specification May 1996
567
preset dictionary might discard part of the output stream; a
568
distance can refer to that part of the output stream anyway)
569
Note also that the referenced string may overlap the current
570
position; for example, if the last 2 bytes decoded have values
571
X and Y, a string reference with <length = 5, distance = 2>
572
adds X,Y,X,Y,X to the output stream.
574
We now specify each compression method in turn.
576
3.2.4. Non-compressed blocks (BTYPE=00)
578
Any bits of input up to the next byte boundary are ignored.
579
The rest of the block consists of the following information:
582
+---+---+---+---+================================+
583
| LEN | NLEN |... LEN bytes of literal data...|
584
+---+---+---+---+================================+
586
LEN is the number of data bytes in the block. NLEN is the
587
one's complement of LEN.
589
3.2.5. Compressed blocks (length and distance codes)
591
As noted above, encoded data blocks in the "deflate" format
592
consist of sequences of symbols drawn from three conceptually
593
distinct alphabets: either literal bytes, from the alphabet of
594
byte values (0..255), or <length, backward distance> pairs,
595
where the length is drawn from (3..258) and the distance is
596
drawn from (1..32,768). In fact, the literal and length
597
alphabets are merged into a single alphabet (0..285), where
598
values 0..255 represent literal bytes, the value 256 indicates
599
end-of-block, and values 257..285 represent length codes
600
(possibly in conjunction with extra bits following the symbol
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RFC 1951 DEFLATE Compressed Data Format Specification May 1996
624
Code Bits Length(s) Code Bits Lengths Code Bits Length(s)
625
---- ---- ------ ---- ---- ------- ---- ---- -------
626
257 0 3 267 1 15,16 277 4 67-82
627
258 0 4 268 1 17,18 278 4 83-98
628
259 0 5 269 2 19-22 279 4 99-114
629
260 0 6 270 2 23-26 280 4 115-130
630
261 0 7 271 2 27-30 281 5 131-162
631
262 0 8 272 2 31-34 282 5 163-194
632
263 0 9 273 3 35-42 283 5 195-226
633
264 0 10 274 3 43-50 284 5 227-257
634
265 1 11,12 275 3 51-58 285 0 258
635
266 1 13,14 276 3 59-66
637
The extra bits should be interpreted as a machine integer
638
stored with the most-significant bit first, e.g., bits 1110
639
represent the value 14.
642
Code Bits Dist Code Bits Dist Code Bits Distance
643
---- ---- ---- ---- ---- ------ ---- ---- --------
644
0 0 1 10 4 33-48 20 9 1025-1536
645
1 0 2 11 4 49-64 21 9 1537-2048
646
2 0 3 12 5 65-96 22 10 2049-3072
647
3 0 4 13 5 97-128 23 10 3073-4096
648
4 1 5,6 14 6 129-192 24 11 4097-6144
649
5 1 7,8 15 6 193-256 25 11 6145-8192
650
6 2 9-12 16 7 257-384 26 12 8193-12288
651
7 2 13-16 17 7 385-512 27 12 12289-16384
652
8 3 17-24 18 8 513-768 28 13 16385-24576
653
9 3 25-32 19 8 769-1024 29 13 24577-32768
655
3.2.6. Compression with fixed Huffman codes (BTYPE=01)
657
The Huffman codes for the two alphabets are fixed, and are not
658
represented explicitly in the data. The Huffman code lengths
659
for the literal/length alphabet are:
663
0 - 143 8 00110000 through
665
144 - 255 9 110010000 through
667
256 - 279 7 0000000 through
669
280 - 287 8 11000000 through
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RFC 1951 DEFLATE Compressed Data Format Specification May 1996
679
The code lengths are sufficient to generate the actual codes,
680
as described above; we show the codes in the table for added
681
clarity. Literal/length values 286-287 will never actually
682
occur in the compressed data, but participate in the code
685
Distance codes 0-31 are represented by (fixed-length) 5-bit
686
codes, with possible additional bits as shown in the table
687
shown in Paragraph 3.2.5, above. Note that distance codes 30-
688
31 will never actually occur in the compressed data.
690
3.2.7. Compression with dynamic Huffman codes (BTYPE=10)
692
The Huffman codes for the two alphabets appear in the block
693
immediately after the header bits and before the actual
694
compressed data, first the literal/length code and then the
695
distance code. Each code is defined by a sequence of code
696
lengths, as discussed in Paragraph 3.2.2, above. For even
697
greater compactness, the code length sequences themselves are
698
compressed using a Huffman code. The alphabet for code lengths
701
0 - 15: Represent code lengths of 0 - 15
702
16: Copy the previous code length 3 - 6 times.
703
The next 2 bits indicate repeat length
705
Example: Codes 8, 16 (+2 bits 11),
706
16 (+2 bits 10) will expand to
707
12 code lengths of 8 (1 + 6 + 5)
708
17: Repeat a code length of 0 for 3 - 10 times.
710
18: Repeat a code length of 0 for 11 - 138 times
713
A code length of 0 indicates that the corresponding symbol in
714
the literal/length or distance alphabet will not occur in the
715
block, and should not participate in the Huffman code
716
construction algorithm given earlier. If only one distance
717
code is used, it is encoded using one bit, not zero bits; in
718
this case there is a single code length of one, with one unused
719
code. One distance code of zero bits means that there are no
720
distance codes used at all (the data is all literals).
722
We can now define the format of the block:
724
5 Bits: HLIT, # of Literal/Length codes - 257 (257 - 286)
725
5 Bits: HDIST, # of Distance codes - 1 (1 - 32)
726
4 Bits: HCLEN, # of Code Length codes - 4 (4 - 19)
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RFC 1951 DEFLATE Compressed Data Format Specification May 1996
735
(HCLEN + 4) x 3 bits: code lengths for the code length
736
alphabet given just above, in the order: 16, 17, 18,
737
0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15
739
These code lengths are interpreted as 3-bit integers
740
(0-7); as above, a code length of 0 means the
741
corresponding symbol (literal/length or distance code
744
HLIT + 257 code lengths for the literal/length alphabet,
745
encoded using the code length Huffman code
747
HDIST + 1 code lengths for the distance alphabet,
748
encoded using the code length Huffman code
750
The actual compressed data of the block,
751
encoded using the literal/length and distance Huffman
754
The literal/length symbol 256 (end of data),
755
encoded using the literal/length Huffman code
757
The code length repeat codes can cross from HLIT + 257 to the
758
HDIST + 1 code lengths. In other words, all code lengths form
759
a single sequence of HLIT + HDIST + 258 values.
763
A compressor may limit further the ranges of values specified in
764
the previous section and still be compliant; for example, it may
765
limit the range of backward pointers to some value smaller than
766
32K. Similarly, a compressor may limit the size of blocks so that
767
a compressible block fits in memory.
769
A compliant decompressor must accept the full range of possible
770
values defined in the previous section, and must accept blocks of
773
4. Compression algorithm details
775
While it is the intent of this document to define the "deflate"
776
compressed data format without reference to any particular
777
compression algorithm, the format is related to the compressed
778
formats produced by LZ77 (Lempel-Ziv 1977, see reference [2] below);
779
since many variations of LZ77 are patented, it is strongly
780
recommended that the implementor of a compressor follow the general
781
algorithm presented here, which is known not to be patented per se.
782
The material in this section is not part of the definition of the
786
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RFC 1951 DEFLATE Compressed Data Format Specification May 1996
791
specification per se, and a compressor need not follow it in order to
794
The compressor terminates a block when it determines that starting a
795
new block with fresh trees would be useful, or when the block size
796
fills up the compressor's block buffer.
798
The compressor uses a chained hash table to find duplicated strings,
799
using a hash function that operates on 3-byte sequences. At any
800
given point during compression, let XYZ be the next 3 input bytes to
801
be examined (not necessarily all different, of course). First, the
802
compressor examines the hash chain for XYZ. If the chain is empty,
803
the compressor simply writes out X as a literal byte and advances one
804
byte in the input. If the hash chain is not empty, indicating that
805
the sequence XYZ (or, if we are unlucky, some other 3 bytes with the
806
same hash function value) has occurred recently, the compressor
807
compares all strings on the XYZ hash chain with the actual input data
808
sequence starting at the current point, and selects the longest
811
The compressor searches the hash chains starting with the most recent
812
strings, to favor small distances and thus take advantage of the
813
Huffman encoding. The hash chains are singly linked. There are no
814
deletions from the hash chains; the algorithm simply discards matches
815
that are too old. To avoid a worst-case situation, very long hash
816
chains are arbitrarily truncated at a certain length, determined by a
819
To improve overall compression, the compressor optionally defers the
820
selection of matches ("lazy matching"): after a match of length N has
821
been found, the compressor searches for a longer match starting at
822
the next input byte. If it finds a longer match, it truncates the
823
previous match to a length of one (thus producing a single literal
824
byte) and then emits the longer match. Otherwise, it emits the
825
original match, and, as described above, advances N bytes before
828
Run-time parameters also control this "lazy match" procedure. If
829
compression ratio is most important, the compressor attempts a
830
complete second search regardless of the length of the first match.
831
In the normal case, if the current match is "long enough", the
832
compressor reduces the search for a longer match, thus speeding up
833
the process. If speed is most important, the compressor inserts new
834
strings in the hash table only when no match was found, or when the
835
match is not "too long". This degrades the compression ratio but
836
saves time since there are both fewer insertions and fewer searches.
842
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RFC 1951 DEFLATE Compressed Data Format Specification May 1996
849
[1] Huffman, D. A., "A Method for the Construction of Minimum
850
Redundancy Codes", Proceedings of the Institute of Radio
851
Engineers, September 1952, Volume 40, Number 9, pp. 1098-1101.
853
[2] Ziv J., Lempel A., "A Universal Algorithm for Sequential Data
854
Compression", IEEE Transactions on Information Theory, Vol. 23,
857
[3] Gailly, J.-L., and Adler, M., ZLIB documentation and sources,
858
available in ftp://ftp.uu.net/pub/archiving/zip/doc/
860
[4] Gailly, J.-L., and Adler, M., GZIP documentation and sources,
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available as gzip-*.tar in ftp://prep.ai.mit.edu/pub/gnu/
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[5] Schwartz, E. S., and Kallick, B. "Generating a canonical prefix
864
encoding." Comm. ACM, 7,3 (Mar. 1964), pp. 166-169.
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[6] Hirschberg and Lelewer, "Efficient decoding of prefix codes,"
867
Comm. ACM, 33,4, April 1990, pp. 449-459.
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6. Security Considerations
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Any data compression method involves the reduction of redundancy in
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the data. Consequently, any corruption of the data is likely to have
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severe effects and be difficult to correct. Uncompressed text, on
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the other hand, will probably still be readable despite the presence
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of some corrupted bytes.
877
It is recommended that systems using this data format provide some
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means of validating the integrity of the compressed data. See
879
reference [3], for example.
883
Source code for a C language implementation of a "deflate" compliant
884
compressor and decompressor is available within the zlib package at
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ftp://ftp.uu.net/pub/archiving/zip/zlib/.
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Trademarks cited in this document are the property of their
892
Phil Katz designed the deflate format. Jean-Loup Gailly and Mark
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Adler wrote the related software described in this specification.
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Glenn Randers-Pehrson converted this document to RFC and HTML format.
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Deutsch Informational [Page 16]
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RFC 1951 DEFLATE Compressed Data Format Specification May 1996
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203 Santa Margarita Ave.
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Phone: (415) 322-0103 (AM only)
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EMail: <ghost@aladdin.com>
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Questions about the technical content of this specification can be
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Jean-Loup Gailly <gzip@prep.ai.mit.edu> and
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Mark Adler <madler@alumni.caltech.edu>
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Editorial comments on this specification can be sent by email to:
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L. Peter Deutsch <ghost@aladdin.com> and
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Glenn Randers-Pehrson <randeg@alumni.rpi.edu>
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removed
win32/3rdparty/zlib/doc/rfc1951.txt
