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sprintf.js
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sprintf.js
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/**
* JavaScript printf/sprintf functions.
*
* This code is unrestricted: you are free to use it however you like.
*
* The functions should work as expected, performing left or right alignment,
* truncating strings, outputting numbers with a required precision etc.
*
* For complex cases, these functions follow the Perl implementations of
* (s)printf, allowing arguments to be passed out-of-order, and to set the
* precision or length of the output based on arguments instead of fixed
* numbers.
*
* See http://perldoc.perl.org/functions/sprintf.html for more information.
*
* Implemented:
* - zero and space-padding
* - right and left-alignment,
* - base X prefix (binary, octal and hex)
* - positive number prefix
* - (minimum) width
* - precision / truncation / maximum width
* - out of order arguments
*
* Not implemented (yet):
* - vector flag
* - size (bytes, words, long-words etc.)
*
* Will not implement:
* - %n or %p (no pass-by-reference in JavaScript)
*
* @version 2007.04.27
* @author Ash Searle
*/
function sprintf() {
function pad(str, len, chr, leftJustify)
{
var padding = (str.length >= len) ? '' : Array(1 + len - str.length >>> 0).join(chr);
return leftJustify ? str + padding : padding + str;
}
function justify(value, prefix, leftJustify, minWidth, zeroPad) {
var diff = minWidth - value.length;
if (diff > 0) {
if (leftJustify || !zeroPad) {
value = pad(value, minWidth, ' ', leftJustify);
} else {
value = value.slice(0, prefix.length) + pad('', diff, '0', true) + value.slice(prefix.length);
}
}
return value;
}
function formatBaseX(value, base, prefix, leftJustify, minWidth, precision, zeroPad) {
// Note: casts negative numbers to positive ones
var number = value >>> 0;
prefix = prefix && number && {'2': '0b', '8': '0', '16': '0x'}[base] || '';
value = prefix + pad(number.toString(base), precision || 0, '0', false);
return justify(value, prefix, leftJustify, minWidth, zeroPad);
}
function formatString(value, leftJustify, minWidth, precision, zeroPad) {
if (precision != null) {
value = value.slice(0, precision);
}
return justify(value, '', leftJustify, minWidth, zeroPad);
}
var a = arguments, i = 0, format = a[i++];
return format.replace(sprintf.regex, function(substring, valueIndex, flags, minWidth, _, precision, type) {
if (substring == '%%') return '%';
// parse flags
var leftJustify = false, positivePrefix = '', zeroPad = false, prefixBaseX = false;
for (var j = 0; flags && j < flags.length; j++) switch (flags.charAt(j)) {
case ' ': positivePrefix = ' '; break;
case '+': positivePrefix = '+'; break;
case '-': leftJustify = true; break;
case '0': zeroPad = true; break;
case '#': prefixBaseX = true; break;
}
// parameters may be null, undefined, empty-string or real valued
// we want to ignore null, undefined and empty-string values
if (!minWidth) {
minWidth = 0;
} else if (minWidth == '*') {
minWidth = +a[i++];
} else if (minWidth.charAt(0) == '*') {
minWidth = +a[minWidth.slice(1, -1)];
} else {
minWidth = +minWidth;
}
// Note: undocumented perl feature:
if (minWidth < 0) {
minWidth = -minWidth;
leftJustify = true;
}
if (!isFinite(minWidth)) {
throw new Error('sprintf: (minimum-)width must be finite');
}
if (!precision) {
precision = 'fFeE'.indexOf(type) > -1 ? 6 : (type == 'd') ? 0 : void(0);
} else if (precision == '*') {
precision = +a[i++];
} else if (precision.charAt(0) == '*') {
precision = +a[precision.slice(1, -1)];
} else {
precision = +precision;
}
// grab value using valueIndex if required?
var value = valueIndex ? a[valueIndex.slice(0, -1)] : a[i++];
switch (type) {
case 's': return formatString(String(value), leftJustify, minWidth, precision, zeroPad);
case 'c': return formatString(String.fromCharCode(+value), leftJustify, minWidth, precision, zeroPad);
case 'b': return formatBaseX(value, 2, prefixBaseX, leftJustify, minWidth, precision, zeroPad);
case 'o': return formatBaseX(value, 8, prefixBaseX, leftJustify, minWidth, precision, zeroPad);
case 'x': return formatBaseX(value, 16, prefixBaseX, leftJustify, minWidth, precision, zeroPad);
case 'X': return formatBaseX(value, 16, prefixBaseX, leftJustify, minWidth, precision, zeroPad).toUpperCase();
case 'u': return formatBaseX(value, 10, prefixBaseX, leftJustify, minWidth, precision, zeroPad);
case 'i':
case 'd': {
var number = parseInt(+value);
var prefix = number < 0 ? '-' : positivePrefix;
value = prefix + pad(String(Math.abs(number)), precision, '0', false);
return justify(value, prefix, leftJustify, minWidth, zeroPad);
}
case 'e':
case 'E':
case 'f':
case 'F':
case 'g':
case 'G':
{
var number = +value;
var prefix = number < 0 ? '-' : positivePrefix;
var method = ['toExponential', 'toFixed', 'toPrecision']['efg'.indexOf(type.toLowerCase())];
var textTransform = ['toString', 'toUpperCase']['eEfFgG'.indexOf(type) % 2];
value = prefix + Math.abs(number)[method](precision);
return justify(value, prefix, leftJustify, minWidth, zeroPad)[textTransform]();
}
default: return substring;
}
});
}
sprintf.regex = /%%|%(\d+\$)?([-+#0 ]*)(\*\d+\$|\*|\d+)?(\.(\*\d+\$|\*|\d+))?([scboxXuidfegEG])/g;