HRESULT CInArchive::TryEcd64(UInt64 offset, CCdInfo &cdInfo)
{
if (offset >= ((UInt64)1 << 63))
return S_FALSE;
RINOK(Seek(offset));
Byte buf[kEcd64_FullSize];
RINOK(ReadStream_FALSE(Stream, buf, kEcd64_FullSize));
if (Get32(buf) != NSignature::kEcd64)
return S_FALSE;
UInt64 mainSize = Get64(buf + 4);
if (mainSize < kEcd64_MainSize || mainSize > ((UInt64)1 << 32))
return S_FALSE;
cdInfo.ParseEcd64(buf);
return S_OK;
}
HRESULT CInArchive::FindCd(CCdInfo &cdInfo)
{
UInt64 endPosition;
RINOK(Stream->Seek(0, STREAM_SEEK_END, &endPosition));
const UInt32 kBufSizeMax = ((UInt32)1 << 16) + kEcdSize + kEcd64Locator_Size + kEcd64_FullSize;
UInt32 bufSize = (endPosition < kBufSizeMax) ? (UInt32)endPosition : kBufSizeMax;
if (bufSize < kEcdSize)
return S_FALSE;
CByteArr byteBuffer(bufSize);
UInt64 startPosition = endPosition - bufSize;
RINOK(Stream->Seek(startPosition, STREAM_SEEK_SET, &m_Position));
if (m_Position != startPosition)
return S_FALSE;
RINOK(ReadStream_FALSE(Stream, byteBuffer, bufSize));
const Byte *buf = byteBuffer;
for (UInt32 i = bufSize - kEcdSize;; i--)
{
if (buf[i] != 0x50)
{
if (i == 0) return S_FALSE;
i--;
if (buf[i] != 0x50)
{
if (i == 0) return S_FALSE;
continue;
}
}
if (Get32(buf + i) == NSignature::kEcd)
{
if (i >= kEcd64_FullSize + kEcd64Locator_Size)
{
const Byte *locator = buf + i - kEcd64Locator_Size;
if (Get32(locator) == NSignature::kEcd64Locator &&
Get32(locator + 4) == 0) // number of the disk with the start of the zip64 ECD
{
// Most of the zip64 use fixed size Zip64 ECD
UInt64 ecd64Offset = Get64(locator + 8);
UInt64 absEcd64 = endPosition - bufSize + i - (kEcd64Locator_Size + kEcd64_FullSize);
{
const Byte *ecd64 = locator - kEcd64_FullSize;
if (Get32(ecd64) == NSignature::kEcd64 &&
Get64(ecd64 + 4) == kEcd64_MainSize)
{
cdInfo.ParseEcd64(ecd64);
ArcInfo.Base = absEcd64 - ecd64Offset;
return S_OK;
}
}
// some zip64 use variable size Zip64 ECD.
// we try to find it
if (absEcd64 != ecd64Offset)
{
if (TryEcd64(ecd64Offset, cdInfo) == S_OK)
{
ArcInfo.Base = 0;
return S_OK;
}
}
if (ArcInfo.MarkerPos != 0 &&
ArcInfo.MarkerPos + ecd64Offset != absEcd64)
{
if (TryEcd64(ArcInfo.MarkerPos + ecd64Offset, cdInfo) == S_OK)
{
ArcInfo.Base = ArcInfo.MarkerPos;
return S_OK;
}
}
}
}
if (Get32(buf + i + 4) == 0) // ThisDiskNumber, StartCentralDirectoryDiskNumber;
{
cdInfo.ParseEcd(buf + i);
UInt64 absEcdPos = endPosition - bufSize + i;
UInt64 cdEnd = cdInfo.Size + cdInfo.Offset;
ArcInfo.Base = 0;
if (absEcdPos != cdEnd)
{
/*
if (cdInfo.Offset <= 16 && cdInfo.Size != 0)
{
// here we support some rare ZIP files with Central directory at the start
ArcInfo.Base = 0;
}
else
*/
ArcInfo.Base = absEcdPos - cdEnd;
}
return S_OK;
}
}
if (i == 0)
return S_FALSE;
}
}