From 5f8de423f190bbb79a62f804151bc24824fa32d8 Mon Sep 17 00:00:00 2001 From: "Matt A. Tobin" Date: Fri, 2 Feb 2018 04:16:08 -0500 Subject: Add m-esr52 at 52.6.0 --- dom/xslt/xpath/txXPathOptimizer.cpp | 282 ++++++++++++++++++++++++++++++++++++ 1 file changed, 282 insertions(+) create mode 100644 dom/xslt/xpath/txXPathOptimizer.cpp (limited to 'dom/xslt/xpath/txXPathOptimizer.cpp') diff --git a/dom/xslt/xpath/txXPathOptimizer.cpp b/dom/xslt/xpath/txXPathOptimizer.cpp new file mode 100644 index 000000000..756dd253d --- /dev/null +++ b/dom/xslt/xpath/txXPathOptimizer.cpp @@ -0,0 +1,282 @@ +/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#include "mozilla/Assertions.h" +#include "txXPathOptimizer.h" +#include "txExprResult.h" +#include "nsIAtom.h" +#include "nsGkAtoms.h" +#include "txXPathNode.h" +#include "txExpr.h" +#include "txIXPathContext.h" + +class txEarlyEvalContext : public txIEvalContext +{ +public: + explicit txEarlyEvalContext(txResultRecycler* aRecycler) + : mRecycler(aRecycler) + { + } + + // txIEvalContext + nsresult getVariable(int32_t aNamespace, nsIAtom* aLName, + txAExprResult*& aResult) + { + MOZ_CRASH("shouldn't depend on this context"); + } + bool isStripSpaceAllowed(const txXPathNode& aNode) + { + MOZ_CRASH("shouldn't depend on this context"); + } + void* getPrivateContext() + { + MOZ_CRASH("shouldn't depend on this context"); + } + txResultRecycler* recycler() + { + return mRecycler; + } + void receiveError(const nsAString& aMsg, nsresult aRes) + { + } + const txXPathNode& getContextNode() + { + MOZ_CRASH("shouldn't depend on this context"); + } + uint32_t size() + { + MOZ_CRASH("shouldn't depend on this context"); + } + uint32_t position() + { + MOZ_CRASH("shouldn't depend on this context"); + } + +private: + txResultRecycler* mRecycler; +}; + + +nsresult +txXPathOptimizer::optimize(Expr* aInExpr, Expr** aOutExpr) +{ + *aOutExpr = nullptr; + nsresult rv = NS_OK; + + // First check if the expression will produce the same result + // under any context. + Expr::ExprType exprType = aInExpr->getType(); + if (exprType != Expr::LITERAL_EXPR && + !aInExpr->isSensitiveTo(Expr::ANY_CONTEXT)) { + RefPtr recycler = new txResultRecycler; + txEarlyEvalContext context(recycler); + RefPtr exprRes; + + // Don't throw if this fails since it could be that the expression + // is or contains an error-expression. + rv = aInExpr->evaluate(&context, getter_AddRefs(exprRes)); + if (NS_SUCCEEDED(rv)) { + *aOutExpr = new txLiteralExpr(exprRes); + } + + return NS_OK; + } + + // Then optimize sub expressions + uint32_t i = 0; + Expr* subExpr; + while ((subExpr = aInExpr->getSubExprAt(i))) { + Expr* newExpr = nullptr; + rv = optimize(subExpr, &newExpr); + NS_ENSURE_SUCCESS(rv, rv); + if (newExpr) { + delete subExpr; + aInExpr->setSubExprAt(i, newExpr); + } + + ++i; + } + + // Finally see if current expression can be optimized + switch (exprType) { + case Expr::LOCATIONSTEP_EXPR: + return optimizeStep(aInExpr, aOutExpr); + + case Expr::PATH_EXPR: + return optimizePath(aInExpr, aOutExpr); + + case Expr::UNION_EXPR: + return optimizeUnion(aInExpr, aOutExpr); + + default: + break; + } + + return NS_OK; +} + +nsresult +txXPathOptimizer::optimizeStep(Expr* aInExpr, Expr** aOutExpr) +{ + LocationStep* step = static_cast(aInExpr); + + if (step->getAxisIdentifier() == LocationStep::ATTRIBUTE_AXIS) { + // Test for @foo type steps. + txNameTest* nameTest = nullptr; + if (!step->getSubExprAt(0) && + step->getNodeTest()->getType() == txNameTest::NAME_TEST && + (nameTest = static_cast(step->getNodeTest()))-> + mLocalName != nsGkAtoms::_asterisk) { + + *aOutExpr = new txNamedAttributeStep(nameTest->mNamespace, + nameTest->mPrefix, + nameTest->mLocalName); + return NS_OK; // return since we no longer have a step-object. + } + } + + // Test for predicates that can be combined into the nodetest + Expr* pred; + while ((pred = step->getSubExprAt(0)) && + !pred->canReturnType(Expr::NUMBER_RESULT) && + !pred->isSensitiveTo(Expr::NODESET_CONTEXT)) { + txNodeTest* predTest = new txPredicatedNodeTest(step->getNodeTest(), pred); + step->dropFirst(); + step->setNodeTest(predTest); + } + + return NS_OK; +} + +nsresult +txXPathOptimizer::optimizePath(Expr* aInExpr, Expr** aOutExpr) +{ + PathExpr* path = static_cast(aInExpr); + + uint32_t i; + Expr* subExpr; + // look for steps like "//foo" that can be turned into "/descendant::foo" + // and "//." that can be turned into "/descendant-or-self::node()" + for (i = 0; (subExpr = path->getSubExprAt(i)); ++i) { + if (path->getPathOpAt(i) == PathExpr::DESCENDANT_OP && + subExpr->getType() == Expr::LOCATIONSTEP_EXPR && + !subExpr->getSubExprAt(0)) { + LocationStep* step = static_cast(subExpr); + if (step->getAxisIdentifier() == LocationStep::CHILD_AXIS) { + step->setAxisIdentifier(LocationStep::DESCENDANT_AXIS); + path->setPathOpAt(i, PathExpr::RELATIVE_OP); + } + else if (step->getAxisIdentifier() == LocationStep::SELF_AXIS) { + step->setAxisIdentifier(LocationStep::DESCENDANT_OR_SELF_AXIS); + path->setPathOpAt(i, PathExpr::RELATIVE_OP); + } + } + } + + // look for expressions that start with a "./" + subExpr = path->getSubExprAt(0); + LocationStep* step; + if (subExpr->getType() == Expr::LOCATIONSTEP_EXPR && + path->getSubExprAt(1) && + path->getPathOpAt(1) != PathExpr::DESCENDANT_OP) { + step = static_cast(subExpr); + if (step->getAxisIdentifier() == LocationStep::SELF_AXIS && + !step->getSubExprAt(0)) { + txNodeTest* test = step->getNodeTest(); + txNodeTypeTest* typeTest; + if (test->getType() == txNodeTest::NODETYPE_TEST && + (typeTest = static_cast(test))-> + getNodeTestType() == txNodeTypeTest::NODE_TYPE) { + // We have a '.' as first step followed by a single '/'. + + // Check if there are only two steps. If so, return the second + // as resulting expression. + if (!path->getSubExprAt(2)) { + *aOutExpr = path->getSubExprAt(1); + path->setSubExprAt(1, nullptr); + + return NS_OK; + } + + // Just delete the '.' step and leave the rest of the PathExpr + path->deleteExprAt(0); + } + } + } + + return NS_OK; +} + +nsresult +txXPathOptimizer::optimizeUnion(Expr* aInExpr, Expr** aOutExpr) +{ + UnionExpr* uni = static_cast(aInExpr); + + // Check for expressions like "foo | bar" and + // "descendant::foo | descendant::bar" + + nsresult rv; + uint32_t current; + Expr* subExpr; + for (current = 0; (subExpr = uni->getSubExprAt(current)); ++current) { + if (subExpr->getType() != Expr::LOCATIONSTEP_EXPR || + subExpr->getSubExprAt(0)) { + continue; + } + + LocationStep* currentStep = static_cast(subExpr); + LocationStep::LocationStepType axis = currentStep->getAxisIdentifier(); + + txUnionNodeTest* unionTest = nullptr; + + // Check if there are any other steps with the same axis and merge + // them with currentStep + uint32_t i; + for (i = current + 1; (subExpr = uni->getSubExprAt(i)); ++i) { + if (subExpr->getType() != Expr::LOCATIONSTEP_EXPR || + subExpr->getSubExprAt(0)) { + continue; + } + + LocationStep* step = static_cast(subExpr); + if (step->getAxisIdentifier() != axis) { + continue; + } + + // Create a txUnionNodeTest if needed + if (!unionTest) { + nsAutoPtr owner(unionTest = new txUnionNodeTest); + rv = unionTest->addNodeTest(currentStep->getNodeTest()); + NS_ENSURE_SUCCESS(rv, rv); + + currentStep->setNodeTest(unionTest); + owner.forget(); + } + + // Merge the nodetest into the union + rv = unionTest->addNodeTest(step->getNodeTest()); + NS_ENSURE_SUCCESS(rv, rv); + + step->setNodeTest(nullptr); + + // Remove the step from the UnionExpr + uni->deleteExprAt(i); + --i; + } + + // Check if all expressions were merged into a single step. If so, + // return the step as the new expression. + if (unionTest && current == 0 && !uni->getSubExprAt(1)) { + // Make sure the step doesn't get deleted when the UnionExpr is + uni->setSubExprAt(0, nullptr); + *aOutExpr = currentStep; + + // Return right away since we no longer have a union + return NS_OK; + } + } + + return NS_OK; +} -- cgit v1.2.3