michael@0: /*
michael@0:     Copyright (c) 2006 Lawrence Oluyede <l.oluyede@gmail.com>
michael@0: 
michael@0:     Permission is hereby granted, free of charge, to any person obtaining a copy
michael@0:     of this software and associated documentation files (the "Software"), to deal
michael@0:     in the Software without restriction, including without limitation the rights
michael@0:     to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
michael@0:     copies of the Software, and to permit persons to whom the Software is
michael@0:     furnished to do so, subject to the following conditions:
michael@0: 
michael@0:     The above copyright notice and this permission notice shall be included in all
michael@0:     copies or substantial portions of the Software.
michael@0: 
michael@0:     THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
michael@0:     IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
michael@0:     FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
michael@0:     AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
michael@0:     LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
michael@0:     OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
michael@0:     SOFTWARE.
michael@0: */
michael@0: 
michael@0: /*
michael@0:  startsWith(str, prefix[, start[, end]]) -> bool
michael@0: 
michael@0:  Return true if str ends with the specified prefix, false otherwise.
michael@0:  With optional start, test str beginning at that position.
michael@0:  With optional end, stop comparing str at that position.
michael@0:  prefix can also be an array of strings to try.
michael@0: */
michael@0: 
michael@0: var EXPORTED_SYMBOLS = ['startsWith', 'endsWith'];
michael@0: 
michael@0: function startsWith(str, prefix, start, end) {
michael@0:     if (arguments.length < 2) {
michael@0:         throw new TypeError('startsWith() requires at least 2 arguments');
michael@0:     }
michael@0: 
michael@0:     // check if start and end are null/undefined or a 'number'
michael@0:     if ((start == null) || (isNaN(new Number(start)))) {
michael@0:         start = 0;
michael@0:     }
michael@0:     if ((end == null) || (isNaN(new Number(end)))) {
michael@0:         end = Number.MAX_VALUE;
michael@0:     }
michael@0: 
michael@0:     // if it's an array
michael@0:     if (typeof prefix == "object") {
michael@0:         for (var i = 0, j = prefix.length; i < j; i++) {
michael@0:             var res = _stringTailMatch(str, prefix[i], start, end, true);
michael@0:             if (res) {
michael@0:                 return true;
michael@0:             }
michael@0:         }
michael@0:         return false;
michael@0:     }
michael@0: 
michael@0:     return _stringTailMatch(str, prefix, start, end, true);
michael@0: }
michael@0: 
michael@0: /*
michael@0:  endsWith(str, suffix[, start[, end]]) -> bool
michael@0: 
michael@0:  Return true if str ends with the specified suffix, false otherwise.
michael@0:  With optional start, test str beginning at that position.
michael@0:  With optional end, stop comparing str at that position.
michael@0:  suffix can also be an array of strings to try.
michael@0: */
michael@0: function endsWith(str, suffix, start, end) {
michael@0:     if (arguments.length < 2) {
michael@0:         throw new TypeError('endsWith() requires at least 2 arguments');
michael@0:     }
michael@0: 
michael@0:     // check if start and end are null/undefined or a 'number'
michael@0:     if ((start == null) || (isNaN(new Number(start)))) {
michael@0:         start = 0;
michael@0:     }
michael@0:     if ((end == null) || (isNaN(new Number(end)))) {
michael@0:         end = Number.MAX_VALUE;
michael@0:     }
michael@0: 
michael@0:     // if it's an array
michael@0:     if (typeof suffix == "object") {
michael@0:         for (var i = 0, j = suffix.length; i < j; i++) {
michael@0:             var res = _stringTailMatch(str, suffix[i], start, end, false);
michael@0:             if (res) {
michael@0:                 return true;
michael@0:             }
michael@0:         }
michael@0:         return false;
michael@0:     }
michael@0: 
michael@0:     return _stringTailMatch(str, suffix, start, end, false);
michael@0: }
michael@0: 
michael@0: /*
michael@0:  Matches the end (direction == false) or start (direction == true) of str
michael@0:  against substr, using the start and end arguments. Returns false
michael@0:  if not found and true if found.
michael@0: */
michael@0: function _stringTailMatch(str, substr, start, end, fromStart) {
michael@0:     var len = str.length;
michael@0:     var slen = substr.length;
michael@0: 
michael@0:     var indices = _adjustIndices(start, end, len);
michael@0:     start = indices[0]; end = indices[1]; len = indices[2];
michael@0: 
michael@0:     if (fromStart) {
michael@0:         if (start + slen > len) {
michael@0:             return false;
michael@0:         }
michael@0:     } else {
michael@0:         if (end - start < slen || start > len) {
michael@0:             return false;
michael@0:         }
michael@0:         if (end - slen > start) {
michael@0:             start = end - slen;
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     if (end - start >= slen) {
michael@0:         return str.substr(start, slen) == substr;
michael@0:     }
michael@0:     return false;
michael@0: }
michael@0: 
michael@0: function _adjustIndices(start, end, len)
michael@0: {
michael@0: 	if (end > len) {
michael@0: 	    end = len;
michael@0: 	} else if (end < 0) {
michael@0: 	    end += len;
michael@0: 	}
michael@0: 
michael@0:     if (end < 0) {
michael@0:         end = 0;
michael@0:     }
michael@0: 	if (start < 0) {
michael@0: 	    start += len;
michael@0: 	}
michael@0: 	if (start < 0) {
michael@0: 		start = 0;
michael@0: 	}
michael@0: 	
michael@0: 	return [start, end, len];
michael@0: }