dolphin/Source/Core/DiscIO/CompressedBlob.h

// Copyright 2008 Dolphin Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later

// WARNING Code not big-endian safe.

// To create new compressed BLOBs, use CompressFileToBlob.

// File format
// * Header
// * [Block Pointers interleaved with block hashes (hash of decompressed data)]
// * [Data]

#pragma once

#include <memory>
#include <string>
#include <vector>

#include "Common/CommonTypes.h"
#include "Common/IOFile.h"
#include "DiscIO/Blob.h"

namespace DiscIO
{
static constexpr u32 GCZ_MAGIC = 0xB10BC001;

// GCZ file structure:
// BlobHeader
// u64 offsetsToBlocks[n], top bit specifies whether the block is compressed, or not.
// compressed data

// Blocks that won't compress to less than 97% of the original size are stored as-is.
struct CompressedBlobHeader  // 32 bytes
{
  u32 magic_cookie;  // 0xB10BB10B
  u32 sub_type;      // GC image, whatever
  u64 compressed_data_size;
  u64 data_size;
  u32 block_size;
  u32 num_blocks;
};

class CompressedBlobReader : public SectorReader
{
public:
  static std::unique_ptr<CompressedBlobReader> Create(File::IOFile file,
                                                      const std::string& filename);
  ~CompressedBlobReader();

  const CompressedBlobHeader& GetHeader() const { return m_header; }

  BlobType GetBlobType() const override { return BlobType::GCZ; }
  std::unique_ptr<BlobReader> CopyReader() const override;

  u64 GetRawSize() const override { return m_file_size; }
  u64 GetDataSize() const override { return m_header.data_size; }
  DataSizeType GetDataSizeType() const override { return DataSizeType::Accurate; }

  u64 GetBlockSize() const override { return m_header.block_size; }
  bool HasFastRandomAccessInBlock() const override { return false; }
  std::string GetCompressionMethod() const override { return "Deflate"; }
  std::optional<int> GetCompressionLevel() const override { return std::nullopt; }

  u64 GetBlockCompressedSize(u64 block_num) const;
  bool GetBlock(u64 block_num, u8* out_ptr) override;

private:
  CompressedBlobReader(File::IOFile file, const std::string& filename);

  CompressedBlobHeader m_header;
  std::vector<u64> m_block_pointers;
  std::vector<u32> m_hashes;
  int m_data_offset;
  File::IOFile m_file;
  u64 m_file_size;
  std::vector<u8> m_zlib_buffer;
  std::string m_file_name;
};

}  // namespace DiscIO