(Xojo Plugin) Decompress Large Text File in Blocks

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

Chilkat Xojo Plugin Download Xojo Plugin for Windows, Linux, Mac OS X, and ARM, ARM64

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

Dim success As Boolean
success = compress.CompressFile("qa_data/hamlet.xml","qa_data/hamlet_compressed.dat")
If (success <> True) Then
    System.DebugLog(compress.LastErrorText)
    Return
End If

Dim fac As New Chilkat.FileAccess

// Examine the uncompressed and compressed sizes:
Dim originalPath As String
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.
System.DebugLog("uncompressed size: " + Str(fac.FileSize(originalPath)))
System.DebugLog("compressed size: " + Str(fac.FileSize("qa_data/hamlet_compressed.dat")))

// Decompress in blocks..
Dim facSrc As New Chilkat.FileAccess
Dim facDest As New Chilkat.FileAccess

success = facSrc.OpenForRead("qa_data/hamlet_compressed.dat")

// 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.
Dim restoredPath As String
restoredPath = "qa_output/hamlet_restored.xml"
success = facDest.OpenForWrite(restoredPath)
If (success <> True) Then
    System.DebugLog(facDest.LastErrorText)
    Return
End If

Dim decompressedStr As String
Dim compressedBytes As MemoryBlock

Dim i As Int32
i = 0
While i < numBlocks
    compressedBytes = facSrc.ReadBlock(i,blockSize)
    If (i = 0) Then
        decompressedStr = compress.BeginDecompressString(compressedBytes)
    Else
        decompressedStr = compress.MoreDecompressString(compressedBytes)
    End If

    success = facDest.AppendText(decompressedStr,"utf-8")

    i = i + 1
Wend

// At the very end, flush any remaining content, if any.
decompressedStr = compress.EndDecompressString()
success = facDest.AppendText(decompressedStr,"utf-8")

facSrc.FileClose 
facDest.FileClose 

// Examine the size of the restored file.
System.DebugLog("restored size: " + Str(fac.FileSize(restoredPath)))

// Compare the contents of the original with the restored.
Dim bEqualContents As Boolean
bEqualContents = fac.FileContentsEqual(restoredPath,originalPath)
System.DebugLog("Contents Equal: " + Str(bEqualContents))