String Compression

Visual FoxPro example to compress and decompress a string. This example demonstrates string-to-string compression. It is only worth doing if the input string is long enough and compresses well enough. The output of any compression algorithm is binary. To convert binary data to a printable string, some sort of encoding must be applied -- and this alway expands the size. For example, hex encoding produces a string that is 2 character for each byte (i.e. it doubles the size). Base64 encoding is a better choice because the output is 4 characters for every 3 bytes encoded.

Download Chilkat Crypt ActiveX

LOCAL loCrypt
LOCAL lnSuccess
LOCAL s
LOCAL lcCompressed
LOCAL lcDecompressed


*  The Crypt component has the BZip2 compression
*  and decompression features, combined with encoding/decoding,
*  that is required for string-to-string compression.
loCrypt = CreateObject('Chilkat.Crypt2')

*  Any string argument automatically begins the 30-day trial.

lnSuccess = loCrypt.UnlockComponent("30-day trial")
IF (lnSuccess <> 1) THEN
    =MESSAGEBOX("Crypt component unlock failed")
    QUIT
ENDIF

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"

*  Make this string a bit bigger...
s = s + s
s = s + s
s = s + s

loCrypt.CryptAlgorithm = "none"
loCrypt.EncodingMode = "base64"

lcCompressed = loCrypt.CompressStringENC(s)

? lcCompressed

lcDecompressed = loCrypt.InflateStringENC(lcCompressed)

? lcDecompressed