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/*
* Copyright 2011 Rackspace
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
var cache = {};
// Do any others need escaping?
var TO_ESCAPE = {
'\'': '\\\'',
'\n': '\\n'
};
function populate(formatter) {
var i, type,
key = formatter,
prev = 0,
arg = 1,
builder = 'return \'';
for (i = 0; i < formatter.length; i++) {
if (formatter[i] === '%') {
type = formatter[i + 1];
switch (type) {
case 's':
builder += formatter.slice(prev, i) + '\' + arguments[' + arg + '] + \'';
prev = i + 2;
arg++;
break;
case 'j':
builder += formatter.slice(prev, i) + '\' + JSON.stringify(arguments[' + arg + ']) + \'';
prev = i + 2;
arg++;
break;
case '%':
builder += formatter.slice(prev, i + 1);
prev = i + 2;
i++;
break;
}
} else if (TO_ESCAPE[formatter[i]]) {
builder += formatter.slice(prev, i) + TO_ESCAPE[formatter[i]];
prev = i + 1;
}
}
builder += formatter.slice(prev) + '\';';
cache[key] = new Function(builder);
}
/**
* A fast version of sprintf(), which currently only supports the %s and %j.
* This caches a formatting function for each format string that is used, so
* you should only use this sprintf() will be called many times with a single
* format string and a limited number of format strings will ever be used (in
* general this means that format strings should be string literals).
*
* @param {String} formatter A format string.
* @param {...String} var_args Values that will be formatted by %s and %j.
* @return {String} The formatted output.
*/
exports.sprintf = function(formatter, var_args) {
if (!cache[formatter]) {
populate(formatter);
}
return cache[formatter].apply(null, arguments);
};
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