GZip Compress String

Compress and uncompress strings using the deflate algorithm. The underlying compression algorithm used by GZip is the deflate compression algorithm, which is also the most common algorithm used in the Zip file format (.zip). This method compresses a string by first converting it to the specified charset. This is necessary for programming languages where strings are represented as 2-byte/char Unicode. By indicating a charset, the size is already "comrpessed" by 50% (if the characters are an iso-8859 or windows-125* charset).

After charset conversion, the bytes are deflated. Finally, the resultant binary data is encoded according to the specified encoding ("base64", "hex", "url", "quoted-printable", etc.) and returned as a printable string. The most efficient encoding is Base64, which encodes 3 binary bytes in 4 printable characters.

Note: it only makes sense to compress strings that are long enough such that the expansion caused by (base64) encoding is relatively small.

Download Chilkat Zip ActiveX

Dim gzip As New Gzip

Dim success As Long

'  Any string unlocks the component for the 1st 30-days.
success = gzip.UnlockComponent("Anything for 30-day trial")
If (success <> 1) Then
    MsgBox gzip.LastErrorText
    Exit Sub
End If

'  Create a string that is somewhat large.
Dim s As String
s = "A friend called me up the other day and talked about investing in a dot-com"
s = s & " that sells lobsters. Internet lobsters. Where will this end? --Donald Trump"
s = s + s
s = s + s

'  Deflate and print the compressed string.
Dim cs As String
cs = gzip.DeflateStringENC(s,"windows-1252","base64")
Text1.Text = Text1.Text & cs & vbCrLf

'  Inflate to restore the string:
Dim s2 As String
s2 = gzip.InflateStringENC(cs,"windows-1252","base64")
Text1.Text = Text1.Text & s2 & vbCrLf