1 files changed, 170 insertions, 0 deletions
diff --git a/zenserver/frontend/zipfs.cpp b/zenserver/frontend/zipfs.cpp
new file mode 100644
index 000000000..5fb9d0177
--- /dev/null
+++ b/zenserver/frontend/zipfs.cpp
@@ -0,0 +1,170 @@
+// 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