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// gzip.cpp - written and placed in the public domain by Wei Dai
#include "pch.h"
#include "gzip.h"
NAMESPACE_BEGIN(CryptoPP)
void Gzip::WritePrestreamHeader()
{
m_totalLen = 0;
m_crc.Restart();
AttachedTransformation()->Put(MAGIC1);
AttachedTransformation()->Put(MAGIC2);
AttachedTransformation()->Put(DEFLATED);
AttachedTransformation()->Put(0); // general flag
AttachedTransformation()->PutWord32(0); // time stamp
byte extra = (GetDeflateLevel() == 1) ? FAST : ((GetDeflateLevel() == 9) ? SLOW : 0);
AttachedTransformation()->Put(extra);
AttachedTransformation()->Put(GZIP_OS_CODE);
}
void Gzip::ProcessUncompressedData(const byte *inString, size_t length)
{
m_crc.Update(inString, length);
m_totalLen += (word32)length;
}
void Gzip::WritePoststreamTail()
{
SecByteBlock crc(4);
m_crc.Final(crc);
AttachedTransformation()->Put(crc, 4);
AttachedTransformation()->PutWord32(m_totalLen, LITTLE_ENDIAN_ORDER);
}
// *************************************************************
Gunzip::Gunzip(BufferedTransformation *attachment, bool repeat, int propagation)
: Inflator(attachment, repeat, propagation)
{
}
void Gunzip::ProcessPrestreamHeader()
{
m_length = 0;
m_crc.Restart();
byte buf[6];
byte b, flags;
if (m_inQueue.Get(buf, 2)!=2) throw HeaderErr();
if (buf[0] != MAGIC1 || buf[1] != MAGIC2) throw HeaderErr();
if (!m_inQueue.Skip(1)) throw HeaderErr(); // skip extra flags
if (!m_inQueue.Get(flags)) throw HeaderErr();
if (flags & (ENCRYPTED | CONTINUED)) throw HeaderErr();
if (m_inQueue.Skip(6)!=6) throw HeaderErr(); // Skip file time, extra flags and OS type
if (flags & EXTRA_FIELDS) // skip extra fields
{
word16 length;
if (m_inQueue.GetWord16(length, LITTLE_ENDIAN_ORDER) != 2) throw HeaderErr();
if (m_inQueue.Skip(length)!=length) throw HeaderErr();
}
if (flags & FILENAME) // skip filename
do
if (!m_inQueue.Get(b)) throw HeaderErr();
while (b);
if (flags & COMMENTS) // skip comments
do
if (!m_inQueue.Get(b)) throw HeaderErr();
while (b);
}
void Gunzip::ProcessDecompressedData(const byte *inString, size_t length)
{
AttachedTransformation()->Put(inString, length);
m_crc.Update(inString, length);
m_length += (word32)length;
}
void Gunzip::ProcessPoststreamTail()
{
SecByteBlock crc(4);
if (m_inQueue.Get(crc, 4) != 4)
throw TailErr();
if (!m_crc.Verify(crc))
throw CrcErr();
word32 lengthCheck;
if (m_inQueue.GetWord32(lengthCheck, LITTLE_ENDIAN_ORDER) != 4)
throw TailErr();
if (lengthCheck != m_length)
throw LengthErr();
}
NAMESPACE_END
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