mirror of
https://github.com/classilla/tenfourfox.git
synced 2024-09-10 11:54:40 +00:00
283 lines
8.9 KiB
C++
283 lines
8.9 KiB
C++
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "mozilla/Assertions.h"
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#include "txXPathOptimizer.h"
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#include "txExprResult.h"
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#include "nsIAtom.h"
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#include "nsGkAtoms.h"
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#include "txXPathNode.h"
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#include "txExpr.h"
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#include "txIXPathContext.h"
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class txEarlyEvalContext : public txIEvalContext
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{
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public:
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explicit txEarlyEvalContext(txResultRecycler* aRecycler)
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: mRecycler(aRecycler)
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{
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}
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// txIEvalContext
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nsresult getVariable(int32_t aNamespace, nsIAtom* aLName,
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txAExprResult*& aResult)
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{
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MOZ_CRASH("shouldn't depend on this context");
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}
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bool isStripSpaceAllowed(const txXPathNode& aNode)
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{
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MOZ_CRASH("shouldn't depend on this context");
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}
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void* getPrivateContext()
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{
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MOZ_CRASH("shouldn't depend on this context");
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}
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txResultRecycler* recycler()
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{
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return mRecycler;
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}
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void receiveError(const nsAString& aMsg, nsresult aRes)
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{
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}
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const txXPathNode& getContextNode()
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{
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MOZ_CRASH("shouldn't depend on this context");
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}
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uint32_t size()
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{
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MOZ_CRASH("shouldn't depend on this context");
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}
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uint32_t position()
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{
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MOZ_CRASH("shouldn't depend on this context");
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}
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private:
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txResultRecycler* mRecycler;
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};
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nsresult
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txXPathOptimizer::optimize(Expr* aInExpr, Expr** aOutExpr)
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{
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*aOutExpr = nullptr;
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nsresult rv = NS_OK;
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// First check if the expression will produce the same result
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// under any context.
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Expr::ExprType exprType = aInExpr->getType();
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if (exprType != Expr::LITERAL_EXPR &&
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!aInExpr->isSensitiveTo(Expr::ANY_CONTEXT)) {
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RefPtr<txResultRecycler> recycler = new txResultRecycler;
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txEarlyEvalContext context(recycler);
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RefPtr<txAExprResult> exprRes;
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// Don't throw if this fails since it could be that the expression
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// is or contains an error-expression.
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rv = aInExpr->evaluate(&context, getter_AddRefs(exprRes));
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if (NS_SUCCEEDED(rv)) {
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*aOutExpr = new txLiteralExpr(exprRes);
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}
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return NS_OK;
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}
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// Then optimize sub expressions
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uint32_t i = 0;
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Expr* subExpr;
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while ((subExpr = aInExpr->getSubExprAt(i))) {
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Expr* newExpr = nullptr;
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rv = optimize(subExpr, &newExpr);
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NS_ENSURE_SUCCESS(rv, rv);
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if (newExpr) {
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delete subExpr;
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aInExpr->setSubExprAt(i, newExpr);
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}
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++i;
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}
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// Finally see if current expression can be optimized
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switch (exprType) {
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case Expr::LOCATIONSTEP_EXPR:
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return optimizeStep(aInExpr, aOutExpr);
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case Expr::PATH_EXPR:
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return optimizePath(aInExpr, aOutExpr);
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case Expr::UNION_EXPR:
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return optimizeUnion(aInExpr, aOutExpr);
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default:
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break;
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}
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return NS_OK;
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}
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nsresult
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txXPathOptimizer::optimizeStep(Expr* aInExpr, Expr** aOutExpr)
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{
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LocationStep* step = static_cast<LocationStep*>(aInExpr);
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if (step->getAxisIdentifier() == LocationStep::ATTRIBUTE_AXIS) {
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// Test for @foo type steps.
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txNameTest* nameTest = nullptr;
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if (!step->getSubExprAt(0) &&
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step->getNodeTest()->getType() == txNameTest::NAME_TEST &&
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(nameTest = static_cast<txNameTest*>(step->getNodeTest()))->
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mLocalName != nsGkAtoms::_asterisk) {
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*aOutExpr = new txNamedAttributeStep(nameTest->mNamespace,
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nameTest->mPrefix,
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nameTest->mLocalName);
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return NS_OK; // return since we no longer have a step-object.
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}
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}
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// Test for predicates that can be combined into the nodetest
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Expr* pred;
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while ((pred = step->getSubExprAt(0)) &&
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!pred->canReturnType(Expr::NUMBER_RESULT) &&
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!pred->isSensitiveTo(Expr::NODESET_CONTEXT)) {
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txNodeTest* predTest = new txPredicatedNodeTest(step->getNodeTest(), pred);
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step->dropFirst();
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step->setNodeTest(predTest);
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}
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return NS_OK;
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}
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nsresult
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txXPathOptimizer::optimizePath(Expr* aInExpr, Expr** aOutExpr)
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{
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PathExpr* path = static_cast<PathExpr*>(aInExpr);
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uint32_t i;
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Expr* subExpr;
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// look for steps like "//foo" that can be turned into "/descendant::foo"
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// and "//." that can be turned into "/descendant-or-self::node()"
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for (i = 0; (subExpr = path->getSubExprAt(i)); ++i) {
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if (path->getPathOpAt(i) == PathExpr::DESCENDANT_OP &&
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subExpr->getType() == Expr::LOCATIONSTEP_EXPR &&
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!subExpr->getSubExprAt(0)) {
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LocationStep* step = static_cast<LocationStep*>(subExpr);
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if (step->getAxisIdentifier() == LocationStep::CHILD_AXIS) {
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step->setAxisIdentifier(LocationStep::DESCENDANT_AXIS);
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path->setPathOpAt(i, PathExpr::RELATIVE_OP);
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}
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else if (step->getAxisIdentifier() == LocationStep::SELF_AXIS) {
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step->setAxisIdentifier(LocationStep::DESCENDANT_OR_SELF_AXIS);
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path->setPathOpAt(i, PathExpr::RELATIVE_OP);
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}
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}
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}
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// look for expressions that start with a "./"
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subExpr = path->getSubExprAt(0);
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LocationStep* step;
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if (subExpr->getType() == Expr::LOCATIONSTEP_EXPR &&
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path->getSubExprAt(1) &&
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path->getPathOpAt(1) != PathExpr::DESCENDANT_OP) {
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step = static_cast<LocationStep*>(subExpr);
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if (step->getAxisIdentifier() == LocationStep::SELF_AXIS &&
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!step->getSubExprAt(0)) {
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txNodeTest* test = step->getNodeTest();
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txNodeTypeTest* typeTest;
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if (test->getType() == txNodeTest::NODETYPE_TEST &&
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(typeTest = static_cast<txNodeTypeTest*>(test))->
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getNodeTestType() == txNodeTypeTest::NODE_TYPE) {
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// We have a '.' as first step followed by a single '/'.
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// Check if there are only two steps. If so, return the second
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// as resulting expression.
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if (!path->getSubExprAt(2)) {
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*aOutExpr = path->getSubExprAt(1);
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path->setSubExprAt(1, nullptr);
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return NS_OK;
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}
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// Just delete the '.' step and leave the rest of the PathExpr
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path->deleteExprAt(0);
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}
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}
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}
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return NS_OK;
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}
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nsresult
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txXPathOptimizer::optimizeUnion(Expr* aInExpr, Expr** aOutExpr)
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{
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UnionExpr* uni = static_cast<UnionExpr*>(aInExpr);
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// Check for expressions like "foo | bar" and
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// "descendant::foo | descendant::bar"
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nsresult rv;
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uint32_t current;
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Expr* subExpr;
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for (current = 0; (subExpr = uni->getSubExprAt(current)); ++current) {
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if (subExpr->getType() != Expr::LOCATIONSTEP_EXPR ||
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subExpr->getSubExprAt(0)) {
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continue;
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}
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LocationStep* currentStep = static_cast<LocationStep*>(subExpr);
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LocationStep::LocationStepType axis = currentStep->getAxisIdentifier();
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txUnionNodeTest* unionTest = nullptr;
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// Check if there are any other steps with the same axis and merge
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// them with currentStep
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uint32_t i;
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for (i = current + 1; (subExpr = uni->getSubExprAt(i)); ++i) {
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if (subExpr->getType() != Expr::LOCATIONSTEP_EXPR ||
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subExpr->getSubExprAt(0)) {
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continue;
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}
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LocationStep* step = static_cast<LocationStep*>(subExpr);
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if (step->getAxisIdentifier() != axis) {
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continue;
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}
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// Create a txUnionNodeTest if needed
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if (!unionTest) {
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nsAutoPtr<txNodeTest> owner(unionTest = new txUnionNodeTest);
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rv = unionTest->addNodeTest(currentStep->getNodeTest());
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NS_ENSURE_SUCCESS(rv, rv);
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currentStep->setNodeTest(unionTest);
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owner.forget();
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}
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// Merge the nodetest into the union
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rv = unionTest->addNodeTest(step->getNodeTest());
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NS_ENSURE_SUCCESS(rv, rv);
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step->setNodeTest(nullptr);
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// Remove the step from the UnionExpr
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uni->deleteExprAt(i);
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--i;
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}
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// Check if all expressions were merged into a single step. If so,
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// return the step as the new expression.
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if (unionTest && current == 0 && !uni->getSubExprAt(1)) {
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// Make sure the step doesn't get deleted when the UnionExpr is
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uni->setSubExprAt(0, nullptr);
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*aOutExpr = currentStep;
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// Return right away since we no longer have a union
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return NS_OK;
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}
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}
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return NS_OK;
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}
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