chevrotain
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Chevrotain is a high performance fault tolerant javascript parsing DSL for building recursive decent parsers
106 lines • 6.89 kB
JavaScript
import { buildAlternativesLookAheadFunc, buildLookaheadFuncForOptionalProd, buildLookaheadFuncForOr, buildSingleAlternativeLookaheadFunction, PROD_TYPE } from "../../grammar/lookahead";
import { forEach, has, isES2015MapSupported } from "../../../utils/utils";
import { DEFAULT_PARSER_CONFIG } from "../parser";
import { AT_LEAST_ONE_IDX, AT_LEAST_ONE_SEP_IDX, getKeyForAutomaticLookahead, MANY_IDX, MANY_SEP_IDX, OPTION_IDX, OR_IDX } from "../../grammar/keys";
import { collectMethods, getProductionDslName } from "../../grammar/gast/gast";
/**
* Trait responsible for the lookahead related utilities and optimizations.
*/
var LooksAhead = /** @class */ (function () {
function LooksAhead() {
}
LooksAhead.prototype.initLooksAhead = function (config) {
this.dynamicTokensEnabled = has(config, "dynamicTokensEnabled")
? config.dynamicTokensEnabled
: DEFAULT_PARSER_CONFIG.dynamicTokensEnabled;
this.maxLookahead = has(config, "maxLookahead")
? config.maxLookahead
: DEFAULT_PARSER_CONFIG.maxLookahead;
/* istanbul ignore next - Using plain array as dictionary will be tested on older node.js versions and IE11 */
this.lookAheadFuncsCache = isES2015MapSupported() ? new Map() : [];
// Performance optimization on newer engines that support ES6 Map
// For larger Maps this is slightly faster than using a plain object (array in our case).
/* istanbul ignore else - The else branch will be tested on older node.js versions and IE11 */
if (isES2015MapSupported()) {
this.getLaFuncFromCache = this.getLaFuncFromMap;
this.setLaFuncCache = this.setLaFuncCacheUsingMap;
}
else {
this.getLaFuncFromCache = this.getLaFuncFromObj;
this.setLaFuncCache = this.setLaFuncUsingObj;
}
};
LooksAhead.prototype.preComputeLookaheadFunctions = function (rules) {
var _this = this;
forEach(rules, function (currRule) {
_this.TRACE_INIT(currRule.name + " Rule Lookahead", function () {
var _a = collectMethods(currRule), alternation = _a.alternation, repetition = _a.repetition, option = _a.option, repetitionMandatory = _a.repetitionMandatory, repetitionMandatoryWithSeparator = _a.repetitionMandatoryWithSeparator, repetitionWithSeparator = _a.repetitionWithSeparator;
forEach(alternation, function (currProd) {
var prodIdx = currProd.idx === 0 ? "" : currProd.idx;
_this.TRACE_INIT("" + getProductionDslName(currProd) + prodIdx, function () {
var laFunc = buildLookaheadFuncForOr(currProd.idx, currRule, currProd.maxLookahead || _this.maxLookahead, currProd.hasPredicates, _this.dynamicTokensEnabled, _this.lookAheadBuilderForAlternatives);
var key = getKeyForAutomaticLookahead(_this.fullRuleNameToShort[currRule.name], OR_IDX, currProd.idx);
_this.setLaFuncCache(key, laFunc);
});
});
forEach(repetition, function (currProd) {
_this.computeLookaheadFunc(currRule, currProd.idx, MANY_IDX, PROD_TYPE.REPETITION, currProd.maxLookahead, getProductionDslName(currProd));
});
forEach(option, function (currProd) {
_this.computeLookaheadFunc(currRule, currProd.idx, OPTION_IDX, PROD_TYPE.OPTION, currProd.maxLookahead, getProductionDslName(currProd));
});
forEach(repetitionMandatory, function (currProd) {
_this.computeLookaheadFunc(currRule, currProd.idx, AT_LEAST_ONE_IDX, PROD_TYPE.REPETITION_MANDATORY, currProd.maxLookahead, getProductionDslName(currProd));
});
forEach(repetitionMandatoryWithSeparator, function (currProd) {
_this.computeLookaheadFunc(currRule, currProd.idx, AT_LEAST_ONE_SEP_IDX, PROD_TYPE.REPETITION_MANDATORY_WITH_SEPARATOR, currProd.maxLookahead, getProductionDslName(currProd));
});
forEach(repetitionWithSeparator, function (currProd) {
_this.computeLookaheadFunc(currRule, currProd.idx, MANY_SEP_IDX, PROD_TYPE.REPETITION_WITH_SEPARATOR, currProd.maxLookahead, getProductionDslName(currProd));
});
});
});
};
LooksAhead.prototype.computeLookaheadFunc = function (rule, prodOccurrence, prodKey, prodType, prodMaxLookahead, dslMethodName) {
var _this = this;
this.TRACE_INIT("" + dslMethodName + (prodOccurrence === 0 ? "" : prodOccurrence), function () {
var laFunc = buildLookaheadFuncForOptionalProd(prodOccurrence, rule, prodMaxLookahead || _this.maxLookahead, _this.dynamicTokensEnabled, prodType, _this.lookAheadBuilderForOptional);
var key = getKeyForAutomaticLookahead(_this.fullRuleNameToShort[rule.name], prodKey, prodOccurrence);
_this.setLaFuncCache(key, laFunc);
});
};
LooksAhead.prototype.lookAheadBuilderForOptional = function (alt, tokenMatcher, dynamicTokensEnabled) {
return buildSingleAlternativeLookaheadFunction(alt, tokenMatcher, dynamicTokensEnabled);
};
LooksAhead.prototype.lookAheadBuilderForAlternatives = function (alts, hasPredicates, tokenMatcher, dynamicTokensEnabled) {
return buildAlternativesLookAheadFunc(alts, hasPredicates, tokenMatcher, dynamicTokensEnabled);
};
// this actually returns a number, but it is always used as a string (object prop key)
LooksAhead.prototype.getKeyForAutomaticLookahead = function (dslMethodIdx, occurrence) {
var currRuleShortName = this.getLastExplicitRuleShortName();
return getKeyForAutomaticLookahead(currRuleShortName, dslMethodIdx, occurrence);
};
/* istanbul ignore next */
LooksAhead.prototype.getLaFuncFromCache = function (key) {
return undefined;
};
LooksAhead.prototype.getLaFuncFromMap = function (key) {
return this.lookAheadFuncsCache.get(key);
};
/* istanbul ignore next - Using plain array as dictionary will be tested on older node.js versions and IE11 */
LooksAhead.prototype.getLaFuncFromObj = function (key) {
return this.lookAheadFuncsCache[key];
};
/* istanbul ignore next */
LooksAhead.prototype.setLaFuncCache = function (key, value) { };
LooksAhead.prototype.setLaFuncCacheUsingMap = function (key, value) {
this.lookAheadFuncsCache.set(key, value);
};
/* istanbul ignore next - Using plain array as dictionary will be tested on older node.js versions and IE11 */
LooksAhead.prototype.setLaFuncUsingObj = function (key, value) {
this.lookAheadFuncsCache[key] = value;
};
return LooksAhead;
}());
export { LooksAhead };
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