Using the Compression API in buffer mode
The following samples demonstrate using the Compression API in buffer mode. Buffer mode was developed for ease of use and automatically splits up the input buffer into blocks of a size that is appropriate for the selected compression algorithm. Buffer mode automatically formats and stores the uncompressed buffer size in the compressed buffer where it is available to the decompressor. The size of the compressed buffer is not automatically saved, and the application needs to save this for decompression. Do not include the COMPRESS_RAW flag when calling CreateCompressor or CreateDecompressor if you want to use the Compression API in buffer mode.
Buffer mode is recommended for most cases. For more information about how to use block mode, see Using the Compression API in block mode
Applications using buffer or block mode have the option to specify a custom memory allocation routine when calling CreateCompressor or CreateDecompressor. See the Using the Compression API in block mode section for an example of a simple customized allocation routine.
Windows 8 and Windows Server 2012: To use the following example code, you must be running Windows 8 or Windows Server 2012 and have "compressapi.h" and "cabinet.dll" and link to the "Cabinet.lib".
The following code snippet demonstrates file compression with the XPRESS compression algorithm and Huffman encoding using the Compression API in buffer mode. The application accepts a file, compresses its contents and generates a compressed file. First the application calls CreateCompressor with COMPRESS_ALGORITHM_XPRESS_HUFF to generate a compressor. Then it calls Compress, with CompressedBufferSize set to 0, to query for the required size of the compressed buffer. It allocates an output buffer to the CompressedBufferSize value. The application calls Compress a second time to perform the actual compression. Finally, the application writes the compressed data to the output file.
#include <Windows.h>
#include <stdio.h>
#include <compressapi.h>
void wmain(_In_ int argc, _In_ WCHAR *argv[])
{
COMPRESSOR_HANDLE Compressor = NULL;
PBYTE CompressedBuffer = NULL;
PBYTE InputBuffer = NULL;
HANDLE InputFile = INVALID_HANDLE_VALUE;
HANDLE CompressedFile = INVALID_HANDLE_VALUE;
BOOL DeleteTargetFile = TRUE;
BOOL Success;
SIZE_T CompressedDataSize, CompressedBufferSize;
DWORD InputFileSize, ByteRead, ByteWritten;
LARGE_INTEGER FileSize;
ULONGLONG StartTime, EndTime;
double TimeDuration;
if (argc != 3)
{
wprintf(L"Usage:\n\t%s <input_file_name> <compressd_file_name>\n", argv[0]);
return;
}
// Open input file for reading, existing file only.
InputFile = CreateFile(
argv[1], // Input file name
GENERIC_READ, // Open for reading
FILE_SHARE_READ, // Share for read
NULL, // Default security
OPEN_EXISTING, // Existing file only
FILE_ATTRIBUTE_NORMAL, // Normal file
NULL); // No attr. template
if (InputFile == INVALID_HANDLE_VALUE)
{
wprintf(L"Cannot open \t%s\n", argv[1]);
goto done;
}
// Get input file size.
Success = GetFileSizeEx(InputFile, &FileSize);
if ((!Success)||(FileSize.QuadPart > 0xFFFFFFFF))
{
wprintf(L"Cannot get input file size or file is larger than 4GB.\n");
goto done;
}
InputFileSize = FileSize.LowPart;
// Allocate memory for file content.
InputBuffer = (PBYTE)malloc(InputFileSize);
if (!InputBuffer)
{
wprintf(L"Cannot allocate memory for uncompressed buffer.\n");
goto done;
}
// Read input file.
Success = ReadFile(InputFile, InputBuffer, InputFileSize, &ByteRead, NULL);
if ((!Success)||(ByteRead != InputFileSize))
{
wprintf(L"Cannot read from \t%s\n", argv[1]);
goto done;
}
// Open an empty file for writing, if exist, overwrite it.
CompressedFile = CreateFile(
argv[2], // Compressed file name
GENERIC_WRITE|DELETE, // Open for writing; delete if cannot compress
0, // Do not share
NULL, // Default security
CREATE_ALWAYS, // Create a new file; if exist, overwrite it
FILE_ATTRIBUTE_NORMAL, // Normal file
NULL); // No template
if (CompressedFile == INVALID_HANDLE_VALUE)
{
wprintf(L"Cannot create file \t%s\n", argv[2]);
goto done;
}
// Create an XpressHuff compressor.
Success = CreateCompressor(
COMPRESS_ALGORITHM_XPRESS_HUFF, // Compression Algorithm
NULL, // Optional allocation routine
&Compressor); // Handle
if (!Success)
{
wprintf(L"Cannot create a compressor %d.\n", GetLastError());
goto done;
}
// Query compressed buffer size.
Success = Compress(
Compressor, // Compressor Handle
InputBuffer, // Input buffer, Uncompressed data
InputFileSize, // Uncompressed data size
NULL, // Compressed Buffer
0, // Compressed Buffer size
&CompressedBufferSize); // Compressed Data size
// Allocate memory for compressed buffer.
if (!Success)
{
DWORD ErrorCode = GetLastError();
if (ErrorCode != ERROR_INSUFFICIENT_BUFFER)
{
wprintf(L"Cannot compress data: %d.\n", ErrorCode);
goto done;
}
CompressedBuffer = (PBYTE)malloc(CompressedBufferSize);
if (!CompressedBuffer)
{
wprintf(L"Cannot allocate memory for compressed buffer.\n");
goto done;
}
}
StartTime = GetTickCount64();
// Call Compress() again to do real compression and output the compressed
// data to CompressedBuffer.
Success = Compress(
Compressor, // Compressor Handle
InputBuffer, // Input buffer, Uncompressed data
InputFileSize, // Uncompressed data size
CompressedBuffer, // Compressed Buffer
CompressedBufferSize, // Compressed Buffer size
&CompressedDataSize); // Compressed Data size
if (!Success)
{
wprintf(L"Cannot compress data: %d\n", GetLastError());
goto done;
}
EndTime = GetTickCount64();
// Get compression time.
TimeDuration = (EndTime - StartTime)/1000.0;
// Write compressed data to output file.
Success = WriteFile(
CompressedFile, // File handle
CompressedBuffer, // Start of data to write
CompressedDataSize, // Number of byte to write
&ByteWritten, // Number of byte written
NULL); // No overlapping structure
if ((ByteWritten != CompressedDataSize) || (!Success))
{
wprintf(L"Cannot write compressed data to file: %d.\n", GetLastError());
goto done;
}
wprintf(
L"Input file size: %d; Compressed Size: %d\n",
InputFileSize,
CompressedDataSize);
wprintf(L"Compression Time(Exclude I/O): %.2f seconds\n", TimeDuration);
wprintf(L"File Compressed.\n");
DeleteTargetFile = FALSE;
done:
if (Compressor != NULL)
{
CloseCompressor(Compressor);
}
if (CompressedBuffer)
{
free(CompressedBuffer);
}
if (InputBuffer)
{
free(InputBuffer);
}
if (InputFile != INVALID_HANDLE_VALUE)
{
CloseHandle(InputFile);
}
if (CompressedFile != INVALID_HANDLE_VALUE)
{
// Compression fails, delete the compressed file.
if (DeleteTargetFile)
{
FILE_DISPOSITION_INFO fdi;
fdi.DeleteFile = TRUE; // Marking for deletion
Success = SetFileInformationByHandle(
CompressedFile,
FileDispositionInfo,
&fdi,
sizeof(FILE_DISPOSITION_INFO));
if (!Success) {
wprintf(L"Cannot delete corrupted compressed file.\n");
}
}
CloseHandle(CompressedFile);
}
}
The following code snippet demonstrates file decompression using the Compression API in buffer mode.
#include <Windows.h>
#include <stdio.h>
#include <compressapi.h>
void wmain(_In_ int argc, _In_ WCHAR *argv[])
{
DECOMPRESSOR_HANDLE Decompressor = NULL;
PBYTE CompressedBuffer = NULL;
PBYTE DecompressedBuffer = NULL;
HANDLE InputFile = INVALID_HANDLE_VALUE;
HANDLE DecompressedFile = INVALID_HANDLE_VALUE;
BOOL DeleteTargetFile = TRUE;
BOOL Success;
SIZE_T DecompressedBufferSize, DecompressedDataSize;
DWORD InputFileSize, ByteRead, ByteWritten;
ULONGLONG StartTime, EndTime;
LARGE_INTEGER FileSize;
double TimeDuration;
if (argc != 3)
{
wprintf(L"Usage:\n\t%s <compressed_file_name> <decompressed_file_name>\n", argv[0]);
return;
}
// Open input file for reading, existing file only.
InputFile = CreateFile(
argv[1], // Input file name, compressed file
GENERIC_READ, // Open for reading
FILE_SHARE_READ, // Share for read
NULL, // Default security
OPEN_EXISTING, // Existing file only
FILE_ATTRIBUTE_NORMAL, // Normal file
NULL); // No template
if (InputFile == INVALID_HANDLE_VALUE)
{
wprintf(L"Cannot open \t%s\n", argv[1]);
goto done;
}
// Get compressed file size.
Success = GetFileSizeEx(InputFile, &FileSize);
if ((!Success)||(FileSize.QuadPart > 0xFFFFFFFF))
{
wprintf(L"Cannot get input file size or file is larger than 4GB.\n");
goto done;
}
InputFileSize = FileSize.LowPart;
// Allocation memory for compressed content.
CompressedBuffer = (PBYTE)malloc(InputFileSize);
if (!CompressedBuffer)
{
wprintf(L"Cannot allocate memory for compressed buffer.\n");
goto done;
}
// Read compressed content into buffer.
Success = ReadFile(InputFile, CompressedBuffer, InputFileSize, &ByteRead, NULL);
if ((!Success) || (ByteRead != InputFileSize))
{
wprintf(L"Cannot read from \t%s\n", argv[1]);
goto done;
}
// Open an empty file for writing, if exist, destroy it.
DecompressedFile = CreateFile(
argv[2], // Decompressed file name
GENERIC_WRITE|DELETE, // Open for writing
0, // Do not share
NULL, // Default security
CREATE_ALWAYS, // Create a new file, if exists, overwrite it.
FILE_ATTRIBUTE_NORMAL, // Normal file
NULL); // No template
if (DecompressedFile == INVALID_HANDLE_VALUE)
{
wprintf(L"Cannot create file \t%s\n", argv[2]);
goto done;
}
// Create an XpressHuff decompressor.
Success = CreateDecompressor(
COMPRESS_ALGORITHM_XPRESS_HUFF, // Compression Algorithm
NULL, // Optional allocation routine
&Decompressor); // Handle
if (!Success)
{
wprintf(L"Cannot create a decompressor: %d.\n", GetLastError());
goto done;
}
// Query decompressed buffer size.
Success = Decompress(
Decompressor, // Compressor Handle
CompressedBuffer, // Compressed data
InputFileSize, // Compressed data size
NULL, // Buffer set to NULL
0, // Buffer size set to 0
&DecompressedBufferSize); // Decompressed Data size
// Allocate memory for decompressed buffer.
if (!Success)
{
DWORD ErrorCode = GetLastError();
// Note that the original size returned by the function is extracted
// from the buffer itself and should be treated as untrusted and tested
// against reasonable limits.
if (ErrorCode != ERROR_INSUFFICIENT_BUFFER)
{
wprintf(L"Cannot decompress data: %d.\n",ErrorCode);
goto done;
}
DecompressedBuffer = (PBYTE)malloc(DecompressedBufferSize);
if (!DecompressedBuffer)
{
wprintf(L"Cannot allocate memory for decompressed buffer.\n");
goto done;
}
}
StartTime = GetTickCount64();
// Decompress data and write data to DecompressedBuffer.
Success = Decompress(
Decompressor, // Decompressor handle
CompressedBuffer, // Compressed data
InputFileSize, // Compressed data size
DecompressedBuffer, // Decompressed buffer
DecompressedBufferSize, // Decompressed buffer size
&DecompressedDataSize); // Decompressed data size
if (!Success)
{
wprintf(L"Cannot decompress data: %d.\n", GetLastError());
goto done;
}
EndTime = GetTickCount64();
// Get decompression time.
TimeDuration = (EndTime - StartTime)/1000.0;
// Write decompressed data to output file.
Success = WriteFile(
DecompressedFile, // File handle
DecompressedBuffer, // Start of data to write
DecompressedDataSize, // Number of byte to write
&ByteWritten, // Number of byte written
NULL); // No overlapping structure
if ((ByteWritten != DecompressedDataSize) || (!Success))
{
wprintf(L"Cannot write decompressed data to file.\n");
goto done;
}
wprintf(
L"Compressed size: %d; Decompressed Size: %d\n",
InputFileSize,
DecompressedDataSize);
wprintf(L"Decompression Time(Exclude I/O): %.2f seconds\n", TimeDuration);
wprintf(L"File decompressed.\n");
DeleteTargetFile = FALSE;
done:
if (Decompressor != NULL)
{
CloseDecompressor(Decompressor);
}
if (CompressedBuffer)
{
free(CompressedBuffer);
}
if (DecompressedBuffer)
{
free(DecompressedBuffer);
}
if (InputFile != INVALID_HANDLE_VALUE)
{
CloseHandle(InputFile);
}
if (DecompressedFile != INVALID_HANDLE_VALUE)
{
// Compression fails, delete the compressed file.
if (DeleteTargetFile)
{
FILE_DISPOSITION_INFO fdi;
fdi.DeleteFile = TRUE; // Marking for deletion
Success = SetFileInformationByHandle(
DecompressedFile,
FileDispositionInfo,
&fdi,
sizeof(FILE_DISPOSITION_INFO));
if (!Success) {
wprintf(L"Cannot delete corrupted decompressed file.\n");
}
}
CloseHandle(DecompressedFile);
}
}
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