CFLib.org – Common Function Library Project

Description:
Pads a string with null bytes, to a multiple of the given block size. Useful for encryption compatibility.

Return Values:
The supplied string padded with null bytes.

Example:

<cfscript>
    // Note: Verify using string length (null bytes are not visible when displayed with writeOutput)
    originalText = "Four";
    writeOutput("<br>Original Text  Length = "& len(originalText));
    paddedText = nullPad(originalText, 8);
    writeOutput("<br>Padded Text Length = "& len(paddedText));
</cfscript>

Parameters:

Full UDF Source:

string function nullPad( string plainText, numeric blockSize, string encoding="UTF-8")
{
    if (arguments.blockSize <= 0) {
        throw("Block size must be greater than 0");
    }
    local.newText = arguments.plainText;
    local.bytes = charsetDecode(arguments.plainText, arguments.encoding);
    local.remain = arrayLen( local.bytes ) % arguments.blockSize;

    if (local.remain != 0) 
    {
        local.padSize = arguments.blockSize - local.remain;
        local.newText &= repeatString( urlDecode("%00"), local.padSize );
    }

    return local.newText;
}