Freemarker millisecond truncation code extracted out and turned into a Groovy script to verify it's correctness

FreemarkerMilliTrunc.groovy

import groovy.transform.Field
@Field def _ = [do: { body ->
    [while: { condition ->
        body()
        if (condition()) call(condition)
    }]
}]

String formatMillis(int x, int forcedDigits = 3, int dstIdx = 0) {
    if (x > 999 || x < 0) {
        // Shouldn't ever happen...
        throw new RuntimeException(
                "Calendar.MILLISECOND > 999");
    }
    String res = ''
    _.do {
        res += String.valueOf ((48 + (x / 100)) as char);
        forcedDigits--;
        x = x % 100 * 10;
    }.while { x != 0 || forcedDigits > 0 }
    res
}    

String formatMillis2(int x, int forcedDigits = 6, int dstIdx = 0) {
    String res = ''
    for (int i = forcedDigits - 1; i >= 0; --i) {
        int power = Math.pow(10, i)
        int place = x / power;
        res += String.valueOf((48 + place) as char);
        x = x - (place * power)
    }
    res
}    

(8000..9000).each { 
println "$it --> ${formatMillis2(it)}"
}