1// zlib.cpp - written and placed in the public domain by Wei Dai
2
3// "zlib" is the name of a well known C language compression library
4// (http://www.zlib.org) and also the name of a compression format
5// (RFC 1950) that the library implements. This file is part of a
6// complete reimplementation of the zlib compression format.
7
8#include "pch.h"
9#include "zlib.h"
10#include "zdeflate.h"
11#include "zinflate.h"
12
13NAMESPACE_BEGIN(CryptoPP)
14
15static const byte DEFLATE_METHOD = 8;
16static const byte FDICT_FLAG = 1 << 5;
17
18// *************************************************************
19
20void ZlibCompressor::WritePrestreamHeader()
21{
22	m_adler32.Restart();
23	byte cmf = DEFLATE_METHOD | ((GetLog2WindowSize()-8) << 4);
24	byte flags = GetCompressionLevel() << 6;
25	AttachedTransformation()->PutWord16(RoundUpToMultipleOf(cmf*256+flags, 31));
26}
27
28void ZlibCompressor::ProcessUncompressedData(const byte *inString, size_t length)
29{
30	m_adler32.Update(inString, length);
31}
32
33void ZlibCompressor::WritePoststreamTail()
34{
35	FixedSizeSecBlock<byte, 4> adler32;
36	m_adler32.Final(adler32);
37	AttachedTransformation()->Put(adler32, 4);
38}
39
40unsigned int ZlibCompressor::GetCompressionLevel() const
41{
42	static const unsigned int deflateToCompressionLevel[] = {0, 1, 1, 1, 2, 2, 2, 2, 2, 3};
43	return deflateToCompressionLevel[GetDeflateLevel()];
44}
45
46// *************************************************************
47
48ZlibDecompressor::ZlibDecompressor(BufferedTransformation *attachment, bool repeat, int propagation)
49	: Inflator(attachment, repeat, propagation)
50{
51}
52
53void ZlibDecompressor::ProcessPrestreamHeader()
54{
55	m_adler32.Restart();
56
57	byte cmf;
58	byte flags;
59
60	if (!m_inQueue.Get(cmf) || !m_inQueue.Get(flags))
61		throw HeaderErr();
62
63	if ((cmf*256+flags) % 31 != 0)
64		throw HeaderErr();	// if you hit this exception, you're probably trying to decompress invalid data
65
66	if ((cmf & 0xf) != DEFLATE_METHOD)
67		throw UnsupportedAlgorithm();
68
69	if (flags & FDICT_FLAG)
70		throw UnsupportedPresetDictionary();
71
72	m_log2WindowSize = 8 + (cmf >> 4);
73}
74
75void ZlibDecompressor::ProcessDecompressedData(const byte *inString, size_t length)
76{
77	AttachedTransformation()->Put(inString, length);
78	m_adler32.Update(inString, length);
79}
80
81void ZlibDecompressor::ProcessPoststreamTail()
82{
83	FixedSizeSecBlock<byte, 4> adler32;
84	if (m_inQueue.Get(adler32, 4) != 4)
85		throw Adler32Err();
86	if (!m_adler32.Verify(adler32))
87		throw Adler32Err();
88}
89
90NAMESPACE_END
91