PPMD Streaming String Compression

Demonstrates streaming string compression using PPMD. Data may be compressed in chunks by initially calling one of the BeginCompress* methods, followed by 0 or more calls to a MoreCompress* method, and terminating with a call to an EndCompress* method.

Likewise, data may be decompressed by calling a BeginDecompress* method, followed by 0 or more MoreDecompress* calls, and ending with an EndDecompress* method call.

This example demonstrates string-to-string compression and decompression in chunks.

Download the Chilkat Compression ActiveX here: ChilkatCompression.zip
Unzip and register the DLL with regsvr32. (This is a pre-release)

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body>
<%
set compress = Server.CreateObject("Chilkat.Compression")

'  Any string argument automatically begins a 30-day trial.
success = compress.UnlockComponent("30-day trial")
If (success <> 1) Then
    Response.Write "Compression component unlock failed" & "<br>"

End If

compress.Algorithm = "ppmd"
compress.Charset = "ansi"
compress.EncodingMode = "base64"

'  Create a long string to compress.
strData = "abcdefg1122334455667788"
strData = strData & vbCrLf

'  Note: BeginCompressStringENC may return a zero-length
'  string.  This is normal if the input is buffered and no
'  compressed data is yet available.
'  However, a null reference indicates an error -- which is
'  generally only possible if the component was never unlocked.
strCompressed = compress.BeginCompressStringENC(strData)
If (strCompressed = vbNullString ) Then
    Response.Write compress.LastErrorText & "<br>"

End If

'  Compress 100 more chunks of data.  Each call to
'  MoreCompressStringENC may or may not produce additional
'  compressed output.
For i = 0 To 99
    strData = "abcdefg1122334455667788"
    strData = strData & vbCrLf

    strCompressed = strCompressed & compress.MoreCompressStringENC(strData)
Next

'  Finalize the compression with a single call to EndCompressStringENC:
strCompressed = strCompressed & compress.EndCompressStringENC()

'  Display the compressed string.
'  The result will be:
'  ec8YZ5vk9za18d0plwuV7R65em9OZge9gJXht/QAAAAAAAAAABNOZQAAKw==

Response.Write Server.HTMLEncode( strCompressed) & "<br>"

'  Decompress back to the original in a single call.

strOriginal = compress.DecompressStringENC(strCompressed)

'  Display the uncompressed original:
Response.Write Server.HTMLEncode( "--- Original ---") & "<br>"
Response.Write Server.HTMLEncode( strOriginal) & "<br>"

'  Decompress in multiple calls.  It doesn't matter how the
'  compressed data is split -- it could be fed to the decompressor
'  one char at a time if desired.
chunk1 = "ec8YZ5vk9za1"
chunk2 = "8d0p"
chunk3 = "lwuV7R65em9OZge9gJXht/QAAAA"
chunk4 = "AAAAAABNOZQAAKw=="

strOriginal = ""
strOriginal = compress.BeginDecompressStringENC(chunk1)
strOriginal = strOriginal & compress.MoreDecompressStringENC(chunk2)
strOriginal = strOriginal & compress.MoreDecompressStringENC(chunk3)
strOriginal = strOriginal & compress.MoreDecompressStringENC(chunk4)
strOriginal = strOriginal & compress.EndDecompressStringENC()

'  Display the uncompressed original after decompressing in chunks:
Response.Write Server.HTMLEncode( "--- Original after Decompressing from Chunks ---") & "<br>"
Response.Write Server.HTMLEncode( strOriginal) & "<br>"
%>
</body>
</html>

Need a specific example? Send a request to support@chilkatsoft.com