dom/base/XPathGenerator.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
   5  * You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "XPathGenerator.h"
   8
   9 #include "nsGkAtoms.h"
  10 #include "Element.h"
  11 #include "nsTArray.h"
  12
  13 /**
  14  * Check whether a character is a non-word character. A non-word character is a
  15  * character that isn't in ('a'..'z') or in ('A'..'Z') or a number or an
  16  * underscore.
  17  * */
  18 bool IsNonWordCharacter(const char16_t& aChar) {
  19   if (((char16_t('A') <= aChar) && (aChar <= char16_t('Z'))) ||
  20       ((char16_t('a') <= aChar) && (aChar <= char16_t('z'))) ||
  21       ((char16_t('0') <= aChar) && (aChar <= char16_t('9'))) ||
  22       (aChar == char16_t('_'))) {
  23     return false;
  24   } else {
  25     return true;
  26   }
  27 }
  28
  29 /**
  30  * Check whether a string contains a non-word character.
  31  * */
  32 bool ContainNonWordCharacter(const nsAString& aStr) {
  33   const char16_t* cur = aStr.BeginReading();
  34   const char16_t* end = aStr.EndReading();
  35   for (; cur < end; ++cur) {
  36     if (IsNonWordCharacter(*cur)) {
  37       return true;
  38     }
  39   }
  40   return false;
  41 }
  42
  43 /**
  44  * Get the prefix according to the given namespace and assign the result to
  45  * aResult.
  46  * */
  47 void GetPrefix(const nsINode* aNode, nsAString& aResult) {
  48   if (aNode->IsXULElement()) {
  49     aResult.AssignLiteral(u"xul");
  50   } else if (aNode->IsHTMLElement()) {
  51     aResult.AssignLiteral(u"xhtml");
  52   }
  53 }
  54
  55 void GetNameAttribute(const nsINode* aNode, nsAString& aResult) {
  56   if (aNode->HasName()) {
  57     const mozilla::dom::Element* elem = aNode->AsElement();
  58     elem->GetAttr(kNameSpaceID_None, nsGkAtoms::name, aResult);
  59   }
  60 }
  61
  62 /**
  63  * Put all sequences of ' in a string in between '," and ",' . And then put
  64  * the result string in between concat(' and ').
  65  *
  66  * For example, a string 'a'' will return result concat('',"'",'a',"''",'')
  67  * */
  68 void GenerateConcatExpression(const nsAString& aStr, nsAString& aResult) {
  69   const char16_t* cur = aStr.BeginReading();
  70   const char16_t* end = aStr.EndReading();
  71
  72   // Put all sequences of ' in between '," and ",'
  73   nsAutoString result;
  74   const char16_t* nonQuoteBeginPtr = nullptr;
  75   const char16_t* quoteBeginPtr = nullptr;
  76   for (; cur < end; ++cur) {
  77     if (char16_t('\'') == *cur) {
  78       if (nonQuoteBeginPtr) {
  79         result.Append(nonQuoteBeginPtr, cur - nonQuoteBeginPtr);
  80         nonQuoteBeginPtr = nullptr;
  81       }
  82       if (!quoteBeginPtr) {
  83         result.AppendLiteral(u"\',\"");
  84         quoteBeginPtr = cur;
  85       }
  86     } else {
  87       if (!nonQuoteBeginPtr) {
  88         nonQuoteBeginPtr = cur;
  89       }
  90       if (quoteBeginPtr) {
  91         result.Append(quoteBeginPtr, cur - quoteBeginPtr);
  92         result.AppendLiteral(u"\",\'");
  93         quoteBeginPtr = nullptr;
  94       }
  95     }
  96   }
  97
  98   if (quoteBeginPtr) {
  99     result.Append(quoteBeginPtr, cur - quoteBeginPtr);
 100     result.AppendLiteral(u"\",\'");
 101   } else if (nonQuoteBeginPtr) {
 102     result.Append(nonQuoteBeginPtr, cur - nonQuoteBeginPtr);
 103   }
 104
 105   // Prepend concat(' and append ').
 106   aResult.Assign(u"concat(\'"_ns + result + u"\')"_ns);
 107 }
 108
 109 void XPathGenerator::QuoteArgument(const nsAString& aArg, nsAString& aResult) {
 110   if (!aArg.Contains('\'')) {
 111     aResult.Assign(u"\'"_ns + aArg + u"\'"_ns);
 112   } else if (!aArg.Contains('\"')) {
 113     aResult.Assign(u"\""_ns + aArg + u"\""_ns);
 114   } else {
 115     GenerateConcatExpression(aArg, aResult);
 116   }
 117 }
 118
 119 void XPathGenerator::EscapeName(const nsAString& aName, nsAString& aResult) {
 120   if (ContainNonWordCharacter(aName)) {
 121     nsAutoString quotedArg;
 122     QuoteArgument(aName, quotedArg);
 123     aResult.Assign(u"*[local-name()="_ns + quotedArg + u"]"_ns);
 124   } else {
 125     aResult.Assign(aName);
 126   }
 127 }
 128
 129 void XPathGenerator::Generate(const nsINode* aNode, nsAString& aResult) {
 130   if (!aNode->GetParentNode()) {
 131     aResult.Truncate();
 132     return;
 133   }
 134
 135   nsAutoString nodeNamespaceURI;
 136   aNode->GetNamespaceURI(nodeNamespaceURI);
 137   const nsString& nodeLocalName = aNode->LocalName();
 138
 139   nsAutoString prefix;
 140   nsAutoString tag;
 141   nsAutoString nodeEscapeName;
 142   GetPrefix(aNode, prefix);
 143   EscapeName(nodeLocalName, nodeEscapeName);
 144   if (prefix.IsEmpty()) {
 145     tag.Assign(nodeEscapeName);
 146   } else {
 147     tag.Assign(prefix + u":"_ns + nodeEscapeName);
 148   }
 149
 150   if (aNode->HasID()) {
 151     // this must be an element
 152     const mozilla::dom::Element* elem = aNode->AsElement();
 153     nsAutoString elemId;
 154     nsAutoString quotedArgument;
 155     elem->GetId(elemId);
 156     QuoteArgument(elemId, quotedArgument);
 157     aResult.Assign(u"//"_ns + tag + u"[@id="_ns + quotedArgument + u"]"_ns);
 158     return;
 159   }
 160
 161   int32_t count = 1;
 162   nsAutoString nodeNameAttribute;
 163   GetNameAttribute(aNode, nodeNameAttribute);
 164   for (const mozilla::dom::Element* e = aNode->GetPreviousElementSibling(); e;
 165        e = e->GetPreviousElementSibling()) {
 166     nsAutoString elementNamespaceURI;
 167     e->GetNamespaceURI(elementNamespaceURI);
 168     nsAutoString elementNameAttribute;
 169     GetNameAttribute(e, elementNameAttribute);
 170     if (e->LocalName().Equals(nodeLocalName) &&
 171         elementNamespaceURI.Equals(nodeNamespaceURI) &&
 172         (nodeNameAttribute.IsEmpty() ||
 173          elementNameAttribute.Equals(nodeNameAttribute))) {
 174       ++count;
 175     }
 176   }
 177
 178   nsAutoString namePart;
 179   nsAutoString countPart;
 180   if (!nodeNameAttribute.IsEmpty()) {
 181     nsAutoString quotedArgument;
 182     QuoteArgument(nodeNameAttribute, quotedArgument);
 183     namePart.Assign(u"[@name="_ns + quotedArgument + u"]"_ns);
 184   }
 185   if (count != 1) {
 186     countPart.AssignLiteral(u"[");
 187     countPart.AppendInt(count);
 188     countPart.AppendLiteral(u"]");
 189   }
 190   Generate(aNode->GetParentNode(), aResult);
 191   aResult.Append(u"/"_ns + tag + namePart + countPart);
 192 }