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Scanning identifiers

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This includes code that is likely not necessary.  The escape sequence scanning will likely not be used in our case, but I'm committing it here so it can be brought back if needed later.
This commit is contained in:
Tim Schaub
2013-06-07 11:52:34 -06:00
parent a748665646
commit 0844df8cc2
2 changed files with 279 additions and 3 deletions
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191
src/ol/expression/lexer.js
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@@ -9,6 +9,7 @@ goog.require('goog.asserts');
*/
ol.expression.Char = {
AMPERSAND: 38,
BACKSLASH: 92,
BANG: 33, // !
CARRIAGE_RETURN: 13,
COMMA: 44,
@@ -28,6 +29,7 @@ ol.expression.Char = {
LOWER_A: 97,
LOWER_E: 101,
LOWER_F: 102,
LOWER_U: 117,
LOWER_X: 120,
LOWER_Z: 122,
MINUS: 45,
@@ -249,6 +251,47 @@ ol.expression.Lexer.prototype.isIdentifierStart_ = function(code) {
};
/**
* Determine if the given identifier is an ECMAScript keyword. These cannot
* be used as identifiers in programs. There is no real reason these could not
* be used in ol expressions - so it might be worth allowing them.
*
* http://www.ecma-international.org/ecma-262/5.1/#sec-7.6.1.1
* @param {string} id Identifier.
* @return {boolean} The identifier is a keyword.
* @private
*/
ol.expression.Lexer.prototype.isKeyword_ = function(id) {
return (
id === 'break' ||
id === 'case' ||
id === 'catch' ||
id === 'continue' ||
id === 'debugger' ||
id === 'default' ||
id === 'delete' ||
id === 'do' ||
id === 'else' ||
id === 'finally' ||
id === 'for' ||
id === 'function' ||
id === 'if' ||
id === 'in' ||
id === 'instanceof' ||
id === 'new' ||
id === 'return' ||
id === 'switch' ||
id === 'this' ||
id === 'throw' ||
id === 'try' ||
id === 'typeof' ||
id === 'var' ||
id === 'void' ||
id === 'while' ||
id === 'with');
};
/**
* http://www.ecma-international.org/ecma-262/5.1/#sec-7.3
*
@@ -331,6 +374,129 @@ ol.expression.Lexer.prototype.getCurrentCharCode_ = function() {
};
/**
* Get an identifier that includes escape sequences.
*
* @return {string} The identifier.
* @private
*/
ol.expression.Lexer.prototype.getEscapedIdentifier_ = function() {
var code = this.getCurrentCharCode_();
var id = String.fromCharCode(code);
this.increment_(1);
// the \u sequence denotes an escaped character
if (code === ol.expression.Char.BACKSLASH) {
if (this.getCurrentCharCode_() !== ol.expression.Char.LOWER_U) {
throw new Error('Unexpected token at index ' + this.index_ +
': ' + this.getCurrentChar_());
}
this.increment_(1);
code = this.scanEscapeSequence_(ol.expression.Char.LOWER_U);
if (!code || code === ol.expression.Char.BACKSLASH ||
!this.isIdentifierStart_(code)) {
throw new Error('Unexpected token at index ' + this.index_ +
': ' + this.getCurrentChar_());
}
id = String.fromCharCode(code);
}
while (this.index_ < this.length_) {
code = this.getCurrentCharCode_();
if (!this.isIdentifierPart_(code)) {
break;
}
this.increment_(1);
id += String.fromCharCode(code);
// the \u sequence denotes an escaped character
if (code === ol.expression.Char.BACKSLASH) {
if (this.getCurrentCharCode_() !== ol.expression.Char.LOWER_U) {
throw new Error('Unexpected token at index ' + this.index_ +
': ' + this.getCurrentChar_());
}
id = id.substr(0, id.length - 1);
this.increment_(1);
code = this.scanEscapeSequence_(ol.expression.Char.LOWER_U);
if (!code || code === ol.expression.Char.BACKSLASH ||
!this.isIdentifierStart_(code)) {
throw new Error('Unexpected token at index ' + this.index_ +
': ' + this.getCurrentChar_());
}
id += String.fromCharCode(code);
}
}
return id;
};
/**
* Get an identifier. This assumes we've encountered an identifier that doesn't
* start with an escape sequence. If an escape sequence is encountered during
* the scan, we switch to the `getEscapedIdentifier_` method.
*
* @return {string} The identifier.
* @private
*/
ol.expression.Lexer.prototype.getIdentifier_ = function() {
goog.asserts.assert(
this.getCurrentCharCode_() !== ol.expression.Char.BACKSLASH,
'Must not be called with first char a backslash');
var start = this.index_;
this.increment_(1);
var code;
while (this.index_ < this.length_) {
code = this.getCurrentCharCode_();
if (code === ol.expression.Char.BACKSLASH) {
// reset cursor and start over scanning escaped identifier
this.index_ = start;
return this.getEscapedIdentifier_();
}
if (this.isIdentifierPart_(code)) {
this.increment_(1);
} else {
break;
}
}
return this.source_.slice(start, this.index_);
};
/**
* Scan an escape sequence of characters prefixed by the given character
* code. This works for both unicode escape sequences (e.g. \u0123) and
* hex escape sequences (e.g. \x12).
* http://www.ecma-international.org/ecma-262/5.1/#sec-7.8.4
*
* @param {number} prefix The character code of the escape prefix.
* @return {number} The unicode of the string resulting from the escape
* sequence. For invalid escape sequences, 0 is returned.
* @private
*/
ol.expression.Lexer.prototype.scanEscapeSequence_ = function(prefix) {
var code = 0;
var len = (prefix === ol.expression.Char.LOWER_U) ? 4 : 2;
var ch;
for (var i = 0; i < len; ++i) {
if (this.index_ < this.length_ &&
this.isHexDigit_(this.getCurrentCharCode_())) {
ch = this.getCurrentChar_();
code = (code * 16) + parseInt(ch, 16);
this.increment_(1);
} else {
return 0;
}
}
return code;
};
/**
* Scan hex literal as numeric token.
*
@@ -376,7 +542,30 @@ ol.expression.Lexer.prototype.scanHexLiteral_ = function() {
* @private
*/
ol.expression.Lexer.prototype.scanIdentifier_ = function() {
throw new Error('Not yet implemented');
var code = this.getCurrentCharCode_();
goog.asserts.assert(this.isIdentifierStart_(code),
'Must be called with a valid identifier');
var id = (code === ol.expression.Char.BACKSLASH) ?
this.getEscapedIdentifier_() : this.getIdentifier_();
var type;
if (id.length === 1) {
type = ol.expression.TokenType.IDENTIFIER;
} else if (this.isKeyword_(id)) {
type = ol.expression.TokenType.KEYWORD;
} else if (id === 'null') {
type = ol.expression.TokenType.NULL_LITERAL;
} else if (id === 'true' || id === 'false') {
type = ol.expression.TokenType.BOOLEAN_LITERAL;
} else {
type = ol.expression.TokenType.IDENTIFIER;
}
return {
type: type,
value: id
};
};