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/* String streams are the things fed to parsers (which can feed them
* to a tokenizer if they want). They provide peek and next methods
* for looking at the current character (next 'consumes' this
* character, peek does not), and a get method for retrieving all the
* text that was consumed since the last time get was called.
*
* An easy mistake to make is to let a StopIteration exception finish
* the token stream while there are still characters pending in the
* string stream (hitting the end of the buffer while parsing a
* token). To make it easier to detect such errors, the strings throw
* an exception when this happens.
*/
// Make a string stream out of an iterator that returns strings. This
// is applied to the result of traverseDOM (see codemirror.js), and
// the resulting stream is fed to the parser.
window.stringStream = function(source){
// String that's currently being iterated over.
var current = "";
// Position in that string.
var pos = 0;
// Accumulator for strings that have been iterated over but not
// get()-ed yet.
var accum = "";
// Make sure there are more characters ready, or throw
// StopIteration.
function ensureChars() {
while (pos == current.length) {
accum += current;
current = ""; // In case source.next() throws
pos = 0;
try {current = source.next();}
catch (e) {
if (e != StopIteration) throw e;
else return false;
}
}
return true;
}
return {
// Return the next character in the stream.
peek: function() {
if (!ensureChars()) return null;
return current.charAt(pos);
},
// Get the next character, throw StopIteration if at end, check
// for unused content.
next: function() {
if (!ensureChars()) {
if (accum.length > 0)
throw "End of stringstream reached without emptying buffer ('" + accum + "').";
else
throw StopIteration;
}
return current.charAt(pos++);
},
// Return the characters iterated over since the last call to
// .get().
get: function() {
var temp = accum;
accum = "";
if (pos > 0){
temp += current.slice(0, pos);
current = current.slice(pos);
pos = 0;
}
return temp;
},
// Push a string back into the stream.
push: function(str) {
current = current.slice(0, pos) + str + current.slice(pos);
},
lookAhead: function(str, consume, skipSpaces, caseInsensitive) {
function cased(str) {return caseInsensitive ? str.toLowerCase() : str;}
str = cased(str);
var found = false;
var _accum = accum, _pos = pos;
if (skipSpaces) this.nextWhileMatches(/[\s\u00a0]/);
while (true) {
var end = pos + str.length, left = current.length - pos;
if (end <= current.length) {
found = str == cased(current.slice(pos, end));
pos = end;
break;
}
else if (str.slice(0, left) == cased(current.slice(pos))) {
accum += current; current = "";
try {current = source.next();}
catch (e) {break;}
pos = 0;
str = str.slice(left);
}
else {
break;
}
}
if (!(found && consume)) {
current = accum.slice(_accum.length) + current;
pos = _pos;
accum = _accum;
}
return found;
},
// Utils built on top of the above
more: function() {
return this.peek() !== null;
},
applies: function(test) {
var next = this.peek();
return (next !== null && test(next));
},
nextWhile: function(test) {
var next;
while ((next = this.peek()) !== null && test(next))
this.next();
},
matches: function(re) {
var next = this.peek();
return (next !== null && re.test(next));
},
nextWhileMatches: function(re) {
var next;
while ((next = this.peek()) !== null && re.test(next))
this.next();
},
equals: function(ch) {
return ch === this.peek();
},
endOfLine: function() {
var next = this.peek();
return next == null || next == "\n";
}
};
};
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