Uso de la API de compresión en modo de búfer
En los ejemplos siguientes se muestra cómo usar compression API en modo de búfer. El modo de búfer se desarrolló para facilitar el uso y divide automáticamente el búfer de entrada en bloques de un tamaño adecuado para el algoritmo de compresión seleccionado. El modo de búfer da formato automáticamente y almacena el tamaño del búfer sin comprimir en el búfer comprimido donde está disponible para el descomprimidor. El tamaño del búfer comprimido no se guarda automáticamente y la aplicación debe guardarlo para la descompresión. No incluya la marca COMPRESS_RAW al llamar a CreateCompressor o CreateDecompressor si desea usar compression API en modo de búfer.
Se recomienda el modo de búfer para la mayoría de los casos. Para obtener más información sobre cómo usar el modo de bloqueo, consulte Using the Compression API in block mode (Uso de la API de compresión en modo de bloqueo).
Las aplicaciones que usan el modo de búfer o bloque tienen la opción de especificar una rutina de asignación de memoria personalizada al llamar a CreateCompressor o CreateDecompressor. Consulte la sección Using the Compression API in block mode (Uso de la API de compresión en modo de bloque ) para obtener un ejemplo de una rutina de asignación personalizada sencilla.
Windows 8 y Windows Server 2012: para usar el código de ejemplo siguiente, debe ejecutar Windows 8 o Windows Server 2012 y tener "compressapi.h" y "cabinet.dll" y vincular a "Cabinet.lib".
En el fragmento de código siguiente se muestra la compresión de archivos con el algoritmo de compresión XPRESS y la codificación Huffman mediante compression API en modo de búfer. La aplicación acepta un archivo, comprime su contenido y genera un archivo comprimido. En primer lugar, la aplicación llama a CreateCompressor con COMPRESS_ALGORITHM_XPRESS_HUFF para generar un compresor. A continuación, llama a Compress, con CompressedBufferSize establecido en 0, para consultar el tamaño necesario del búfer comprimido. Asigna un búfer de salida al valor CompressedBufferSize . La aplicación llama a Compress una segunda vez para realizar la compresión real. Por último, la aplicación escribe los datos comprimidos en el archivo de salida.
#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);
}
}
En el siguiente fragmento de código se muestra la descompresión de archivos mediante compression API en modo de búfer.
#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);
}
}