gzip.cpp

各种加密算法的源代码

#include "gzip.h"
#include <assert.h>

Gzip::Gzip(int dlevel, BufferedTransformation *bt)
    : Deflator(dlevel, bt),
      totalLen(0)
{
    assert (dlevel >= 1 && dlevel <= 9);
    outQueue->Put(MAGIC1);
    outQueue->Put(MAGIC2);
    outQueue->Put(DEFLATED);
    outQueue->Put(0);       // general flag
    outQueue->PutLong(0);   // time stamp
    byte extra = (dlevel == 1) ? FAST : ((dlevel == 9) ? SLOW : 0);
    outQueue->Put(extra);
    outQueue->Put(GZIP_OS_CODE);
}

void Gzip::Put(byte inByte)
{
    Deflator::Put(inByte);
    crc.Update(&inByte, 1);
    ++totalLen;
}

void Gzip::Put(const byte *inString, unsigned int length)
{
    Deflator::Put(inString, length);
    crc.Update(inString, length);
    totalLen += length;
}

void Gzip::InputFinished()
{
    Deflator::InputFinished();
    outQueue->PutLong(crc.GetCrc(), FALSE);
    outQueue->PutLong(totalLen, FALSE);
}

Gunzip::Gunzip(BufferedTransformation *output,
               BufferedTransformation *bypassed)
    : Fork(2), inflater(new BodyProcesser(*this), new TailProcesser(*this))
{
    SelectOutPort(1);
    Attach(bypassed);
    SelectOutPort(0);
    Attach(output);

    state = PROCESS_HEADER;
    tailLen = 0;
}

void Gunzip::Put(const byte *inString, unsigned int length)
{
    switch (state)
    {
        case PROCESS_HEADER:
            inQueue.Put(inString, length);
            if (inQueue.CurrentSize()>=MAX_HEADERSIZE)
                ProcessHeader();
            break;
        case PROCESS_BODY:
            inflater.Put(inString, length);
            break;
        case AFTER_END:
            outPorts[1]->Put(inString, length);
            break;
    }
}

void Gunzip::InputFinished()
{
    if (state==PROCESS_HEADER)
        ProcessHeader();

    if (state!=AFTER_END)
        inflater.InputFinished();
}

void Gunzip::ProcessHeader()
{
    byte buf[6];
    byte b, flags;

    if (inQueue.Get(buf, 2)!=2) goto error;
    if (buf[0] != MAGIC1 || buf[1] != MAGIC2) goto error;
    if (!inQueue.Skip(1)) goto error;    // skip extra flags
    if (!inQueue.Get(flags)) goto error;
    if (flags & (ENCRYPTED | CONTINUED)) goto error;
    if (inQueue.Skip(6)!=6) goto error;    // Skip file time, extra flags and OS type

    if (flags & EXTRA_FIELDS)   // skip extra fields
    {
        word16 length;
        if(!inQueue.GetShort(length, FALSE)) goto error;
        if (inQueue.Skip(length)!=length) goto error;
    }

    if (flags & FILENAME)   // skip filename
        do
            if(!inQueue.Get(b)) goto error;
        while (b);

    if (flags & COMMENTS)   // skip comments
        do
            if(!inQueue.Get(b)) goto error;
        while (b);

    inQueue.TransferTo(inflater);
    state = PROCESS_BODY;
    return;
error:
#ifdef THROW_EXCEPTIONS
    throw Err();
#else
    assert(FALSE);
#endif
}

void Gunzip::ProcessTail()
{
    assert(tailLen == 8);

#ifdef THROW_EXCEPTIONS
    word32 calculatedCrc = crc.GetCrc();

    if ((((word32)tail[0]) | ((word32)tail[1] << 8) | ((word32)tail[2] << 16) | ((word32)tail[3] << 24)) != calculatedCrc)
        throw CrcErr();

    if ((((word32)tail[4]) | ((word32)tail[5] << 8) | ((word32)tail[6] << 16) | ((word32)tail[7] << 24)) != totalLen)
        throw LengthErr();
#endif

    tailLen = 9;    // signal TailProcesser to bypass everything from now on
}

Gunzip::BodyProcesser::BodyProcesser(Gunzip &parent)
    : parent(parent)
{
    parent.totalLen = 0;
}

void Gunzip::BodyProcesser::Put(const byte *inString, unsigned int length)
{
    parent.outPorts[0]->Put(inString, length);
    parent.crc.Update(inString, length);
    parent.totalLen += length;
}

Gunzip::TailProcesser::TailProcesser(Gunzip &parent)
    : parent(parent)
{
    parent.tailLen = 0;
}

void Gunzip::TailProcesser::Put(const byte *inString, unsigned int length)
{
    if (parent.tailLen < 8)
    {
        int l = min(8-parent.tailLen, length);
        memcpy(parent.tail+parent.tailLen, inString, l);
        inString += l;
        length -= l;
        parent.tailLen += l;
    }

    if (parent.tailLen == 8)
        parent.ProcessTail();

    if (length)
        parent.outPorts[1]->Put(inString, length);
}