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// Copyright Epic Games, Inc. All Rights Reserved.
#include "zipfs.h"
namespace zen {
//////////////////////////////////////////////////////////////////////////
namespace {
#if ZEN_COMPILER_MSC
# pragma warning(push)
# pragma warning(disable : 4200)
#endif
using ZipInt16 = uint16_t;
struct ZipInt32
{
operator uint32_t () const { return *(uint32_t*)Parts; }
uint16_t Parts[2];
};
struct EocdRecord
{
enum : uint32_t {
Magic = 0x0605'4b50,
};
ZipInt32 Signature;
ZipInt16 ThisDiskIndex;
ZipInt16 CdStartDiskIndex;
ZipInt16 CdRecordThisDiskCount;
ZipInt16 CdRecordCount;
ZipInt32 CdSize;
ZipInt32 CdOffset;
ZipInt16 CommentSize;
char Comment[];
};
struct CentralDirectoryRecord
{
enum : uint32_t {
Magic = 0x0201'4b50,
};
ZipInt32 Signature;
ZipInt16 VersionMadeBy;
ZipInt16 VersionRequired;
ZipInt16 Flags;
ZipInt16 CompressionMethod;
ZipInt16 LastModTime;
ZipInt16 LastModDate;
ZipInt32 Crc32;
ZipInt32 CompressedSize;
ZipInt32 OriginalSize;
ZipInt16 FileNameLength;
ZipInt16 ExtraFieldLength;
ZipInt16 CommentLength;
ZipInt16 DiskIndex;
ZipInt16 InternalFileAttr;
ZipInt32 ExternalFileAttr;
ZipInt32 Offset;
char FileName[];
};
struct LocalFileHeader
{
enum : uint32_t {
Magic = 0x0304'4b50,
};
ZipInt32 Signature;
ZipInt16 VersionRequired;
ZipInt16 Flags;
ZipInt16 CompressionMethod;
ZipInt16 LastModTime;
ZipInt16 LastModDate;
ZipInt32 Crc32;
ZipInt32 CompressedSize;
ZipInt32 OriginalSize;
ZipInt16 FileNameLength;
ZipInt16 ExtraFieldLength;
char FileName[];
};
#if ZEN_COMPILER_MSC
# pragma warning(pop)
#endif
} // namespace
//////////////////////////////////////////////////////////////////////////
ZipFs::ZipFs(IoBuffer&& Buffer)
{
MemoryView View = Buffer.GetView();
uint8_t* Cursor = (uint8_t*)(View.GetData()) + View.GetSize();
if (View.GetSize() < sizeof(EocdRecord))
{
return;
}
const auto* EocdCursor = (EocdRecord*)(Cursor - sizeof(EocdRecord));
// It is more correct to search backwards for EocdRecord::Magic as the
// comment can be of a variable length. But here we're not going to support
// zip files with comments.
if (EocdCursor->Signature != EocdRecord::Magic)
{
return;
}
// Zip64 isn't supported either
if (EocdCursor->ThisDiskIndex == 0xffff)
{
return;
}
Cursor -= View.GetSize();
const auto* CdCursor = (CentralDirectoryRecord*)(Cursor + EocdCursor->CdOffset);
for (int i = 0, n = EocdCursor->CdRecordCount; i < n; ++i)
{
const CentralDirectoryRecord& Cd = *CdCursor;
bool Acceptable = true;
Acceptable &= (Cd.OriginalSize > 0); // has some content
Acceptable &= (Cd.CompressionMethod == 0); // is stored uncomrpessed
if (Acceptable)
{
const uint8_t* Lfh = Cursor + Cd.Offset;
if (uintptr_t(Lfh - Cursor) < View.GetSize())
{
std::string_view FileName(Cd.FileName, Cd.FileNameLength);
m_Files.insert(std::make_pair(FileName, FileItem{Lfh, size_t(0)}));
}
}
uint32_t ExtraBytes = Cd.FileNameLength + Cd.ExtraFieldLength + Cd.CommentLength;
CdCursor = (CentralDirectoryRecord*)(Cd.FileName + ExtraBytes);
}
m_Buffer = std::move(Buffer);
}
//////////////////////////////////////////////////////////////////////////
IoBuffer ZipFs::GetFile(const std::string_view& FileName) const
{
FileMap::iterator Iter = m_Files.find(FileName);
if (Iter == m_Files.end())
{
return{};
}
FileItem& Item = Iter->second;
if (Item.GetSize() > 0)
{
return IoBuffer(IoBuffer::Wrap, Item.GetData(), Item.GetSize());
}
const auto* Lfh = (LocalFileHeader*)(Item.GetData());
Item = MemoryView(
Lfh->FileName + Lfh->FileNameLength + Lfh->ExtraFieldLength,
Lfh->OriginalSize
);
return IoBuffer(IoBuffer::Wrap, Item.GetData(), Item.GetSize());
}
} // namespace zen
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