Go

Decompress Large Binary File in Blocks

See more Compression Examples

Decompresses a large binary file in blocks. Go

    success := false

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

    facSrc := chilkat.NewFileAccess()
    facDest := chilkat.NewFileAccess()

    // Open a previously compressed file for decompressing.
    // See Compress Large File in Blocks

    success = facSrc.OpenForRead("c:/temp/qa_output/compressedBmp.dat")
    if success == false {
        fmt.Println(facSrc.LastErrorText())
        facSrc.DisposeFileAccess()
        facDest.DisposeFileAccess()
        return
    }

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

    // Open an output file for the decompressed data.
    success = facDest.OpenForWrite("c:/temp/qa_output/decompressed.bmp")
    if success == false {
        fmt.Println(facDest.LastErrorText())
        facSrc.DisposeFileAccess()
        facDest.DisposeFileAccess()
        return
    }

    compress := chilkat.NewCompression()
    compress.SetAlgorithm("deflate")

    var decompressedBytes []byte
    var compressedBytes []byte

    // Assuming numBlocks > 1
    compress.SetFirstChunk(true)
    compress.SetLastChunk(false)

    i := 0
    for i < numBlocks {
        compressedBytes = facSrc.ReadBlock(i,blockSize)

        decompressedBytes = compress.DecompressBytes(compressedBytes)
        facDest.FileWrite(decompressedBytes)

        i = i + 1

        compress.SetFirstChunk(false)
        if i == (numBlocks - 1) {
            compress.SetLastChunk(true)
        }

    }

    facSrc.FileClose()
    facDest.FileClose()

    fmt.Println("Finished decompressing file.")

    facSrc.DisposeFileAccess()
    facDest.DisposeFileAccess()
    compress.DisposeCompression()