C

Decompress Large Text File in Blocks

See more Compression Examples

Decompresses a large text file in blocks, and compares the restored (decompressed) file with the original to make sure it's correct. C

#include <C_CkCompression.h>
#include <C_CkFileAccess.h>
#include <C_CkByteData.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkCompression compress;
    HCkFileAccess fac;
    const char *originalPath;
    HCkFileAccess facSrc;
    HCkFileAccess facDest;
    int blockSize;
    int numBlocks;
    const char *restoredPath;
    const char *decompressedStr;
    HCkByteData compressedBytes;
    int i;
    BOOL bEqualContents;

    success = FALSE;

    //  This example requires the Chilkat API to have been previously unlocked.
    //  See Global Unlock Sample for sample code.

    //  First, let's compress a text file.
    //  We'll then decompress in blocks, and compare the decompressed with the original file.

    //  Compress a text file:
    compress = CkCompression_Create();
    CkCompression_putAlgorithm(compress,"deflate");

    success = CkCompression_CompressFile(compress,"qa_data/hamlet.xml","qa_data/hamlet_compressed.dat");
    if (success == FALSE) {
        printf("%s\n",CkCompression_lastErrorText(compress));
        CkCompression_Dispose(compress);
        return;
    }

    fac = CkFileAccess_Create();

    //  Examine the uncompressed and compressed sizes:
    originalPath = "qa_data/hamlet.xml";
    //  Note: The FileSize method returns a signed 32-bit integer.  If the file is potentially larger than 2GB, call FileSizeStr instead to return
    //  the size of the file as a string, then convert to an integer value.
    printf("uncompressed size: %d\n",CkFileAccess_FileSize(fac,originalPath));
    printf("compressed size: %d\n",CkFileAccess_FileSize(fac,"qa_data/hamlet_compressed.dat"));

    //  Decompress in blocks..
    facSrc = CkFileAccess_Create();
    facDest = CkFileAccess_Create();

    CkFileAccess_OpenForRead(facSrc,"qa_data/hamlet_compressed.dat");

    //  If we compress in 32K chunks, find out how many blocks there will be.
    blockSize = 32768;
    numBlocks = CkFileAccess_GetNumBlocks(facSrc,blockSize);

    //  Open an output file for the decompressed data.
    restoredPath = "qa_output/hamlet_restored.xml";
    success = CkFileAccess_OpenForWrite(facDest,restoredPath);
    if (success == FALSE) {
        printf("%s\n",CkFileAccess_lastErrorText(facDest));
        CkCompression_Dispose(compress);
        CkFileAccess_Dispose(fac);
        CkFileAccess_Dispose(facSrc);
        CkFileAccess_Dispose(facDest);
        return;
    }

    compressedBytes = CkByteData_Create();

    //  Assuming numBlocks > 1
    CkCompression_putFirstChunk(compress,TRUE);
    CkCompression_putLastChunk(compress,FALSE);

    i = 0;
    while (i < numBlocks) {
        success = CkFileAccess_ReadBlock(facSrc,i,blockSize,compressedBytes);
        decompressedStr = CkCompression_decompressString(compress,compressedBytes);

        CkFileAccess_AppendText(facDest,decompressedStr,"utf-8");

        i = i + 1;

        CkCompression_putFirstChunk(compress,FALSE);
        if (i == (numBlocks - 1)) {
            CkCompression_putLastChunk(compress,TRUE);
        }

    }

    CkFileAccess_FileClose(facSrc);
    CkFileAccess_FileClose(facDest);

    //  Examine the size of the restored file.
    printf("restored size: %d\n",CkFileAccess_FileSize(fac,restoredPath));

    //  Compare the contents of the original with the restored.
    bEqualContents = CkFileAccess_FileContentsEqual(fac,restoredPath,originalPath);
    printf("Contents Equal: %d\n",bEqualContents);


    CkCompression_Dispose(compress);
    CkFileAccess_Dispose(fac);
    CkFileAccess_Dispose(facSrc);
    CkFileAccess_Dispose(facDest);
    CkByteData_Dispose(compressedBytes);

    }