31 lines
841 B
JavaScript
31 lines
841 B
JavaScript
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'use strict';
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module.exports = TokenStream;
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function TokenStream(tokens) {
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if (!Array.isArray(tokens)) {
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throw new TypeError('tokens must be passed to TokenStream as an array.');
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}
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this._tokens = tokens;
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}
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TokenStream.prototype.lookahead = function (index) {
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if (this._tokens.length <= index) {
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throw new Error('Cannot read past the end of a stream');
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}
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return this._tokens[index];
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};
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TokenStream.prototype.peek = function () {
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if (this._tokens.length === 0) {
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throw new Error('Cannot read past the end of a stream');
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}
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return this._tokens[0];
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};
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TokenStream.prototype.advance = function () {
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if (this._tokens.length === 0) {
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throw new Error('Cannot read past the end of a stream');
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}
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return this._tokens.shift();
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};
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TokenStream.prototype.defer = function (token) {
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this._tokens.unshift(token);
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};
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