FCompression压缩解压

FCompression是一个用来对内存数据进行压缩解压的结构体（类），提供了几个静态方法，底层基于zlib库，支持zlib和gzib格式的压缩解压（gzib部分支持）。另外还有个Oodle格式，不过引擎没有集成。

FCompression 主要有三个方法，CompressMemoryBound用来预估压缩需要的缓存空间，CompressMemory用来压缩，UncompressMemory用来解压。在压缩期间，需要的缓存大小可以提前确定，但是解压所需的缓存无法确定。 UncompressMemory 需要一个解压缓存的大小UncompressedSize ，而这个大小要是解压后即数据未压缩之前的大小，如果传入的size和解压后的size不一样，会打印警告并返回错误，但是实际上数据已经解压成功了。所以使用这个函数最好在数据头里面将数据的原始尺寸写进去。

/**
 * Thread-safe abstract compression routine to query memory requirements for a compression operation.
 *
 * @param	Flags						Flags to control what method to use and optionally control memory vs speed
 * @param	UncompressedSize			Size of uncompressed data in bytes
 * @param	BitWindow					Bit window to use in compression
 * @return The maximum possible bytes needed for compression of data buffer of size UncompressedSize
 */
CORE_API static int32 CompressMemoryBound(FName FormatName, int32 UncompressedSize, ECompressionFlags Flags=COMPRESS_NoFlags, int32 CompressionData=0);

/**
 * Thread-safe abstract compression routine. Compresses memory from uncompressed buffer and writes it to compressed
 * buffer. Updates CompressedSize with size of compressed data. Compression controlled by the passed in flags.
 *
 * @param	Flags						Flags to control what method to use and optionally control memory vs speed
 * @param	CompressedBuffer			Buffer compressed data is going to be written to
 * @param	CompressedSize	[in/out]	Size of CompressedBuffer, at exit will be size of compressed data
 * @param	UncompressedBuffer			Buffer containing uncompressed data
 * @param	UncompressedSize			Size of uncompressed data in bytes
 * @param	BitWindow					Bit window to use in compression
 * @return true if compression succeeds, false if it fails because CompressedBuffer was too small or other reasons
 */
CORE_API static bool CompressMemory(FName FormatName, void* CompressedBuffer, int32& CompressedSize, const void* UncompressedBuffer, int32 UncompressedSize, ECompressionFlags Flags=COMPRESS_NoFlags, int32 CompressionData=0);

/**
 * Thread-safe abstract decompression routine. Uncompresses memory from compressed buffer and writes it to uncompressed
 * buffer. UncompressedSize is expected to be the exact size of the data after decompression.
 *
 * @param	Flags						Flags to control what method to use to decompress
 * @param	UncompressedBuffer			Buffer containing uncompressed data
 * @param	UncompressedSize			Size of uncompressed data in bytes
 * @param	CompressedBuffer			Buffer compressed data is going to be read from
 * @param	CompressedSize				Size of CompressedBuffer data in bytes
 * @param	bIsSourcePadded		Whether the source memory is padded with a full cache line at the end
 * @return true if compression succeeds, false if it fails because CompressedBuffer was too small or other reasons
 */
CORE_API static bool UncompressMemory(FName FormatName, void* UncompressedBuffer, int32 UncompressedSize, const void* CompressedBuffer, int32 CompressedSize, ECompressionFlags Flags=COMPRESS_NoFlags, int32 CompressionData=0);

示例代码

char* source = "FCompression Compress Test....................................................";
int srcLen = strlen(source) + 1;

int compressBufferLen = FCompression::CompressMemoryBound(NAME_Zlib, srcLen);
void* compressBuffer = FMemory::Malloc(compressBufferLen);
bool success = FCompression::CompressMemory(NAME_Zlib, compressBuffer, compressBufferLen, source, srcLen);

void* uncompressBuffer = FMemory::Malloc(1024);
FMemory::Memzero(uncompressBuffer, 1024);
success = FCompression::UncompressMemory(NAME_Zlib, uncompressBuffer, srcLen, compressBuffer, compressBufferLen);

FMemory::Free(uncompressBuffer);
FMemory::Free(compressBuffer);

转载于:https://www.cnblogs.com/haisong1991/p/11311891.html