//===- llvm/Support/Compressor.h --------------------------------*- C++ -*-===// // // The LLVM Compiler Infrastructure // // This file was developed by Reid Spencer and is distributed under the // University of Illinois Open Source License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file declares the llvm::Compressor class. // //===----------------------------------------------------------------------===// #ifndef LLVM_SUPPORT_COMPRESSOR_H #define LLVM_SUPPORT_COMPRESSOR_H #include "llvm/Support/DataTypes.h" #include namespace llvm { /// This class provides an abstraction for compression and decompression of /// a block of memory. The algorithm used here is currently bzip2 but that /// may change without notice. Should newer algorithms prove to compress /// bytecode better than bzip2, that newer algorithm will be added, but won't /// replace bzip2. This interface allows us to abstract the notion of /// compression and deal with alternate compression schemes over time. /// The type of compression used can be determined by inspecting the /// first byte of the compressed output. Currently value '0' means no /// compression was used (for very small files) and value '2' means bzip2 /// compression was used. The Compressor is intended for use with memory /// mapped files where the entire data block to be compressed or decompressed /// is available in memory. However, output can be gathered in repeated calls /// to a callback. Utilities for sending compressed or decompressed output /// to a stream or directly to a memory block are also provided. /// @since 1.4 /// @brief An abstraction for memory to memory data (de)compression class Compressor { /// @name High Level Interface /// @{ public: /// This method compresses a block of memory pointed to by \p in with /// size \p size to a block of memory, \p out, that is allocated with /// malloc. It is the caller's responsibility to free \p out. The \p hint /// indicates which type of compression the caller would *prefer*. /// @throws std::string explaining error if a compression error occurs /// @returns The size of the output buffer \p out. /// @brief Compress memory to a new memory buffer. static size_t compressToNewBuffer( const char* in, ///< The buffer to be compressed size_t size, ///< The size of the buffer to be compressed char*&out ///< The returned output buffer ); /// This method compresses a block of memory pointed to by \p in with /// size \p size to a stream. The stream \p out must be open and ready for /// writing when this method is called. The stream will not be closed by /// this method. The \p hint argument indicates which type of /// compression the caller would *prefer*. /// @returns The amount of data written to \p out. /// @brief Compress memory to a file. static size_t compressToStream( const char*in, ///< The buffer to be compressed size_t size, ///< The size of the buffer to be compressed std::ostream& out ///< The output stream to write data on ); /// This method decompresses a block of memory pointed to by \p in with /// size \p size to a new block of memory, \p out, \p that was allocated /// by malloc. It is the caller's responsibility to free \p out. /// @returns The size of the output buffer \p out. /// @brief Decompress memory to a new memory buffer. static size_t decompressToNewBuffer( const char *in, ///< The buffer to be decompressed size_t size, ///< Size of the buffer to be decompressed char*&out ///< The returned output buffer ); /// This method decompresses a block of memory pointed to by \p in with /// size \p size to a stream. The stream \p out must be open and ready for /// writing when this method is called. The stream will not be closed by /// this method. /// @returns The amount of data written to \p out. /// @brief Decompress memory to a stream. static size_t decompressToStream( const char *in, ///< The buffer to be decompressed size_t size, ///< Size of the buffer to be decompressed std::ostream& out ///< The stream to write write data on ); /// @} /// @name Low Level Interface /// @{ public: /// A callback function type used by the Compressor's low level interface /// to get the next chunk of data to which (de)compressed output will be /// written. This callback completely abstracts the notion of how to /// handle the output data of compression or decompression. The callback /// is responsible for determining both the storage location and the size /// of the output. The callback may also do other things with the data /// such as write it, transmit it, etc. Note that providing very small /// values for \p size will make the compression run very inefficiently. /// It is recommended that \p size be chosen based on the some multiple or /// fraction of the object being decompressed or compressed, respetively. /// @returns 0 for success, 1 for failure /// @throws nothing /// @brief Output callback function type typedef size_t (OutputDataCallback)(char*& buffer, size_t& size, void* context); /// This function does the compression work. The block of memory starting /// at \p in and extending for \p size bytes is compressed. The compressed /// output is written to memory blocks returned by the \p cb callback. The /// caller must provide an implementation of the OutputDataCallback /// function type and provide its address as \p cb. Note that the callback /// function will be called as many times as necessary to complete the /// compression of the \p in block but that the total size will generally /// be less than \p size. It is a good idea to provide as large a value to /// the callback's \p size parameter as possible so that fewer calls to /// the callback are made. The \p hint parameter tells the function which /// kind of compression to start with. However, if its not available on /// the platform, the algorithm "falls back" from bzip2 -> zlib -> simple. /// @throws std::string if an error occurs /// @returns the total size of the compressed data /// @brief Compress a block of memory. static size_t compress( const char* in, ///< The buffer to be compressed size_t size, ///< The size of the buffer to be compressed OutputDataCallback* cb, ///< Call back for memory allocation void* context = 0 ///< Context for callback ); /// This function does the decompression work. The block of memory /// starting at \p in and extending for \p size bytes is decompressed. The /// decompressed output is written to memory blocks returned by the \p cb /// callback. The caller must provide an implementation of the /// OutputDataCallback function type and provide its address as \p cb. /// Note that the callback function will be called as many times as /// necessary to complete the compression of the \p in block but that the /// total size will generally be greater than \p size. It is a good idea /// to provide as large a value to the callback's \p size parameter as /// possible so that fewer calls to the callback are made. /// @throws std::string if an error occurs /// @returns the total size of the decompressed data /// @brief Decompress a block of memory. static size_t decompress( const char *in, ///< The buffer to be decompressed size_t size, ///< Size of the buffer to be decompressed OutputDataCallback* cb, ///< Call back for memory allocation void* context = 0 ///< Context for callback ); /// @} }; } // vim: sw=2 ai #endif