Xojo Plugin

Compress Large Binary File in Blocks

See more Compression Examples

Compresses a large binary file in blocks. Xojo Plugin

Dim success As Boolean
success = False

// This example assumes 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 large binary file for reading.
success = facSrc.OpenForRead("qa_data/bmp/big.bmp")
If (success = False) Then
    System.DebugLog(facSrc.LastErrorText)
    Return
End If

// If we compress in 64K chunks, find out how many blocks there will be.
Dim blockSize As Int32
blockSize = 65536
Dim numBlocks As Int32
numBlocks = facSrc.GetNumBlocks(blockSize)

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

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

Dim fileBytes As MemoryBlock
Dim compressedBytes As MemoryBlock

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

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

    success = facDest.FileWrite(compressedBytes)

    i = i + 1

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

Wend

facSrc.FileClose 
facDest.FileClose 

System.DebugLog("Finished compressing file.")