Xojo Plugin

Decompress Large Binary File in Blocks

See more Compression Examples

Decompresses a large binary file in blocks. Xojo Plugin

Dim success As Boolean
success = False

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

Dim facSrc As New Chilkat.FileAccess
Dim facDest As New Chilkat.FileAccess

// 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) Then
    System.DebugLog(facSrc.LastErrorText)
    Return
End If

// If we compress in 32K chunks, find out how many blocks there will be.
Dim blockSize As Int32
blockSize = 32768
Dim numBlocks As Int32
numBlocks = facSrc.GetNumBlocks(blockSize)

// Open an output file for the decompressed data.
success = facDest.OpenForWrite("c:/temp/qa_output/decompressed.bmp")
If (success = False) Then
    System.DebugLog(facDest.LastErrorText)
    Return
End If

Dim compress As New Chilkat.Compression
compress.Algorithm = "deflate"

Dim decompressedBytes As MemoryBlock
Dim compressedBytes As MemoryBlock

// Assuming numBlocks > 1
compress.FirstChunk = True
compress.LastChunk = False

Dim i As Int32
i = 0
While i < numBlocks
    compressedBytes = facSrc.ReadBlock(i,blockSize)

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

    i = i + 1

    compress.FirstChunk = False
    If (i = (numBlocks - 1)) Then
        compress.LastChunk = True
    End If

Wend

facSrc.FileClose 
facDest.FileClose 

System.DebugLog("Finished decompressing file.")