Utilisation de l’API Compression en mode tampon
Les exemples suivants illustrent l’utilisation de l’API Compression en mode tampon. Le mode tampon a été développé pour faciliter l’utilisation et fractionne automatiquement la mémoire tampon d’entrée en blocs d’une taille appropriée pour l’algorithme de compression sélectionné. Le mode mémoire tampon met en forme et stocke automatiquement la taille de la mémoire tampon non compressée dans la mémoire tampon compressée où elle est disponible pour le décompresseur. La taille de la mémoire tampon compressée n’est pas enregistrée automatiquement, et l’application doit l’enregistrer pour la décompression. N’incluez pas l’indicateur COMPRESS_RAW lors de l’appel de CreateCompressor ou CreateDecompressor si vous souhaitez utiliser l’API De compression en mode mémoire tampon.
Le mode tampon est recommandé dans la plupart des cas. Pour plus d’informations sur l’utilisation du mode bloc, consultez Utilisation de l’API Compression en mode bloc
Les applications utilisant le mode tampon ou bloc ont la possibilité de spécifier une routine d’allocation de mémoire personnalisée lors de l’appel de CreateCompressor ou CreateDecompressor. Pour obtenir un exemple de routine d’allocation personnalisée simple, consultez la section Utilisation de l’API compression en mode bloc .
Windows 8 et Windows Server 2012 : pour utiliser l’exemple de code suivant, vous devez exécuter Windows 8 ou Windows Server 2012 et disposer de « compressapi.h » et « cabinet.dll » et d’un lien vers « Cabinet.lib ».
L’extrait de code suivant illustre la compression de fichiers avec l’algorithme de compression XPRESS et l’encodage Huffman à l’aide de l’API compression en mode tampon. L’application accepte un fichier, compresse son contenu et génère un fichier compressé. Tout d’abord, l’application appelle CreateCompressor avec COMPRESS_ALGORITHM_XPRESS_HUFF pour générer un compresseur. Ensuite, il appelle Compress, avec CompressedBufferSize défini sur 0, pour interroger la taille requise de la mémoire tampon compressée. Il alloue une mémoire tampon de sortie à la valeur CompressedBufferSize . L’application appelle Compresser une deuxième fois pour effectuer la compression réelle. Enfin, l’application écrit les données compressées dans le fichier de sortie.
#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);
}
}
L’extrait de code suivant illustre la décompression des fichiers à l’aide de l’API Compression en mode tampon.
#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);
}
}