extsprintf.js

/*
 * extsprintf.js: extended POSIX-style sprintf
 */

var mod_assert = require('assert');
var mod_util = require('util');

/*
 * Public interface
 */
exports.sprintf = jsSprintf;
exports.printf = jsPrintf;
exports.fprintf = jsFprintf;

/*
 * Stripped down version of s[n]printf(3c).  We make a best effort to throw an
 * exception when given a format string we don't understand, rather than
 * ignoring it, so that we won't break existing programs if/when we go implement
 * the rest of this.
 *
 * This implementation currently supports specifying
 *	- field alignment ('-' flag),
 * 	- zero-pad ('0' flag)
 *	- always show numeric sign ('+' flag),
 *	- field width
 *	- conversions for strings, decimal integers, and floats (numbers).
 *	- argument size specifiers.  These are all accepted but ignored, since
 *	  Javascript has no notion of the physical size of an argument.
 *
 * Everything else is currently unsupported, most notably precision, unsigned
 * numbers, non-decimal numbers, and characters.
 */
function jsSprintf(fmt)
{
	var regex = [
	    '([^%]*)',				/* normal text */
	    '%',				/* start of format */
	    '([\'\\-+ #0]*?)',			/* flags (optional) */
	    '([1-9]\\d*)?',			/* width (optional) */
	    '(\\.([1-9]\\d*))?',		/* precision (optional) */
	    '[lhjztL]*?',			/* length mods (ignored) */
	    '([diouxXfFeEgGaAcCsSp%jr])'	/* conversion */
	].join('');

	var re = new RegExp(regex);
	var args = Array.prototype.slice.call(arguments, 1);
	var flags, width, precision, conversion;
	var left, pad, sign, arg, match;
	var ret = '';
	var argn = 1;

	mod_assert.equal('string', typeof (fmt));

	while ((match = re.exec(fmt)) !== null) {
		ret += match[1];
		fmt = fmt.substring(match[0].length);

		flags = match[2] || '';
		width = match[3] || 0;
		precision = match[4] || '';
		conversion = match[6];
		left = false;
		sign = false;
		pad = ' ';

		if (conversion == '%') {
			ret += '%';
			continue;
		}

		if (args.length === 0)
			throw (new Error('too few args to sprintf'));

		arg = args.shift();
		argn++;

		if (flags.match(/[\' #]/))
			throw (new Error(
			    'unsupported flags: ' + flags));

		if (precision.length > 0)
			throw (new Error(
			    'non-zero precision not supported'));

		if (flags.match(/-/))
			left = true;

		if (flags.match(/0/))
			pad = '0';

		if (flags.match(/\+/))
			sign = true;

		switch (conversion) {
		case 's':
			if (arg === undefined || arg === null)
				throw (new Error('argument ' + argn +
				    ': attempted to print undefined or null ' +
				    'as a string'));
			ret += doPad(pad, width, left, arg.toString());
			break;

		case 'd':
			arg = Math.floor(arg);
			/*jsl:fallthru*/
		case 'f':
			sign = sign && arg > 0 ? '+' : '';
			ret += sign + doPad(pad, width, left,
			    arg.toString());
			break;

		case 'x':
			ret += doPad(pad, width, left, arg.toString(16));
			break;

		case 'j': /* non-standard */
			if (width === 0)
				width = 10;
			ret += mod_util.inspect(arg, false, width);
			break;

		case 'r': /* non-standard */
			ret += dumpException(arg);
			break;

		default:
			throw (new Error('unsupported conversion: ' +
			    conversion));
		}
	}

	ret += fmt;
	return (ret);
}

function jsPrintf() {
	var args = Array.prototype.slice.call(arguments);
	args.unshift(process.stdout);
	jsFprintf.apply(null, args);
}

function jsFprintf(stream) {
	var args = Array.prototype.slice.call(arguments, 1);
	return (stream.write(jsSprintf.apply(this, args)));
}

function doPad(chr, width, left, str)
{
	var ret = str;

	while (ret.length < width) {
		if (left)
			ret += chr;
		else
			ret = chr + ret;
	}

	return (ret);
}

/*
 * This function dumps long stack traces for exceptions having a cause() method.
 * See node-verror for an example.
 */
function dumpException(ex)
{
	var ret;

	if (!(ex instanceof Error))
		throw (new Error(jsSprintf('invalid type for %%r: %j', ex)));

	/* Note that V8 prepends "ex.stack" with ex.toString(). */
	ret = 'EXCEPTION: ' + ex.constructor.name + ': ' + ex.stack;

	if (ex.cause && typeof (ex.cause) === 'function') {
		var cex = ex.cause();
		if (cex) {
			ret += '\nCaused by: ' + dumpException(cex);
		}
	}

	return (ret);
}