Source/WTF/wtf/JSONValues.cpp - WebKit - Git at Google

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) 2014 University of Washington. All rights reserved.
  * Copyright (C) 2017-2019 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
  * copyright notice, this list of conditions and the following disclaimer
  * in the documentation and/or other materials provided with the
  * distribution.
  *     * Neither the name of Google Inc. nor the names of its
  * contributors may be used to endorse or promote products derived from
  * this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "config.h"
 #include <wtf/JSONValues.h>

 #include <wtf/text/StringBuilder.h>

 namespace WTF {
 namespace JSONImpl {

 namespace {

 static const int stackLimit = 1000;

 enum class Token {
     ObjectBegin,
     ObjectEnd,
     ArrayBegin,
     ArrayEnd,
     String,
     Number,
     BoolTrue,
     BoolFalse,
     Null,
     ListSeparator,
     ObjectPairSeparator,
     Invalid,
 };

 const char* const nullString = "null";
 const char* const trueString = "true";
 const char* const falseString = "false";

 bool parseConstToken(const UChar* start, const UChar* end, const UChar** tokenEnd, const char* token)
 {
     while (start < end && *token != '\0' && *start++ == *token++) { }

     if (*token != '\0')
         return false;

     *tokenEnd = start;
     return true;
 }

 bool readInt(const UChar* start, const UChar* end, const UChar** tokenEnd, bool canHaveLeadingZeros)
 {
     if (start == end)
         return false;

     bool haveLeadingZero = '0' == *start;
     int length = 0;
     while (start < end && '0' <= *start && *start <= '9') {
         ++start;
         ++length;
     }

     if (!length)
         return false;

     if (!canHaveLeadingZeros && length > 1 && haveLeadingZero)
         return false;

     *tokenEnd = start;
     return true;
 }

 bool parseNumberToken(const UChar* start, const UChar* end, const UChar** tokenEnd)
 {
     // We just grab the number here. We validate the size in DecodeNumber.
     // According to RFC 4627, a valid number is: [minus] int [frac] [exp]
     if (start == end)
         return false;

     UChar c = *start;
     if ('-' == c)
         ++start;

     if (!readInt(start, end, &start, false))
         return false;

     if (start == end) {
         *tokenEnd = start;
         return true;
     }

     // Optional fraction part.
     c = *start;
     if ('.' == c) {
         ++start;
         if (!readInt(start, end, &start, true))
             return false;
         if (start == end) {
             *tokenEnd = start;
             return true;
         }
         c = *start;
     }

     // Optional exponent part.
     if ('e' == c || 'E' == c) {
         ++start;
         if (start == end)
             return false;
         c = *start;
         if ('-' == c || '+' == c) {
             ++start;
             if (start == end)
                 return false;
         }
         if (!readInt(start, end, &start, true))
             return false;
     }

     *tokenEnd = start;
     return true;
 }

 bool readHexDigits(const UChar* start, const UChar* end, const UChar** tokenEnd, int digits)
 {
     if (end - start < digits)
         return false;

     for (int i = 0; i < digits; ++i) {
         if (!isASCIIHexDigit(*start++))
             return false;
     }

     *tokenEnd = start;
     return true;
 }

 bool parseStringToken(const UChar* start, const UChar* end, const UChar** tokenEnd)
 {
     while (start < end) {
         UChar c = *start++;
         if ('\\' == c && start < end) {
             c = *start++;
             // Make sure the escaped char is valid.
             switch (c) {
             case 'x':
                 if (!readHexDigits(start, end, &start, 2))
                     return false;
                 break;
             case 'u':
                 if (!readHexDigits(start, end, &start, 4))
                     return false;
                 break;
             case '\\':
             case '/':
             case 'b':
             case 'f':
             case 'n':
             case 'r':
             case 't':
             case 'v':
             case '"':
                 break;
             default:
                 return false;
             }
         } else if ('"' == c) {
             *tokenEnd = start;
             return true;
         }
     }

     return false;
 }

 Token parseToken(const UChar* start, const UChar* end, const UChar** tokenStart, const UChar** tokenEnd)
 {
     while (start < end && isSpaceOrNewline(*start))
         ++start;

     if (start == end)
         return Token::Invalid;

     *tokenStart = start;

     switch (*start) {
     case 'n':
         if (parseConstToken(start, end, tokenEnd, nullString))
             return Token::Null;
         break;
     case 't':
         if (parseConstToken(start, end, tokenEnd, trueString))
             return Token::BoolTrue;
         break;
     case 'f':
         if (parseConstToken(start, end, tokenEnd, falseString))
             return Token::BoolFalse;
         break;
     case '[':
         *tokenEnd = start + 1;
         return Token::ArrayBegin;
     case ']':
         *tokenEnd = start + 1;
         return Token::ArrayEnd;
     case ',':
         *tokenEnd = start + 1;
         return Token::ListSeparator;
     case '{':
         *tokenEnd = start + 1;
         return Token::ObjectBegin;
     case '}':
         *tokenEnd = start + 1;
         return Token::ObjectEnd;
     case ':':
         *tokenEnd = start + 1;
         return Token::ObjectPairSeparator;
     case '0':
     case '1':
     case '2':
     case '3':
     case '4':
     case '5':
     case '6':
     case '7':
     case '8':
     case '9':
     case '-':
         if (parseNumberToken(start, end, tokenEnd))
             return Token::Number;
         break;
     case '"':
         if (parseStringToken(start + 1, end, tokenEnd))
             return Token::String;
         break;
     }

     return Token::Invalid;
 }

 bool decodeString(const UChar* start, const UChar* end, StringBuilder& output)
 {
     while (start < end) {
         UChar c = *start++;
         if ('\\' != c) {
             output.append(c);
             continue;
         }
         if (UNLIKELY(start >= end))
             return false;
         c = *start++;
         switch (c) {
         case '"':
         case '/':
         case '\\':
             break;
         case 'b':
             c = '\b';
             break;
         case 'f':
             c = '\f';
             break;
         case 'n':
             c = '\n';
             break;
         case 'r':
             c = '\r';
             break;
         case 't':
             c = '\t';
             break;
         case 'v':
             c = '\v';
             break;
         case 'x':
             if (UNLIKELY(start + 1 >= end))
                 return false;
             c = toASCIIHexValue(start[0], start[1]);
             start += 2;
             break;
         case 'u':
             if (UNLIKELY(start + 3 >= end))
                 return false;
             c = toASCIIHexValue(start[0], start[1]) << 8 | toASCIIHexValue(start[2], start[3]);
             start += 4;
             break;
         default:
             return false;
         }
         output.append(c);
     }

     return true;
 }

 bool decodeString(const UChar* start, const UChar* end, String& output)
 {
     if (start == end) {
         output = emptyString();
         return true;
     }

     if (start > end)
         return false;

     StringBuilder buffer;
     buffer.reserveCapacity(end - start);
     if (!decodeString(start, end, buffer))
         return false;

     output = buffer.toString();
     return true;
 }

 RefPtr<JSON::Value> buildValue(const UChar* start, const UChar* end, const UChar** valueTokenEnd, int depth)
 {
     if (depth > stackLimit)
         return nullptr;

     RefPtr<JSON::Value> result;
     const UChar* tokenStart;
     const UChar* tokenEnd;
     Token token = parseToken(start, end, &tokenStart, &tokenEnd);
     switch (token) {
     case Token::Invalid:
         return nullptr;
     case Token::Null:
         result = JSON::Value::null();
         break;
     case Token::BoolTrue:
         result = JSON::Value::create(true);
         break;
     case Token::BoolFalse:
         result = JSON::Value::create(false);
         break;
     case Token::Number: {
         bool ok;
         double value = charactersToDouble(tokenStart, tokenEnd - tokenStart, &ok);
         if (!ok)
             return nullptr;
         result = JSON::Value::create(value);
         break;
     }
     case Token::String: {
         String value;
         bool ok = decodeString(tokenStart + 1, tokenEnd - 1, value);
         if (!ok)
             return nullptr;
         result = JSON::Value::create(value);
         break;
     }
     case Token::ArrayBegin: {
         Ref<JSON::Array> array = JSON::Array::create();
         start = tokenEnd;
         token = parseToken(start, end, &tokenStart, &tokenEnd);
         while (token != Token::ArrayEnd) {
             RefPtr<JSON::Value> arrayNode = buildValue(start, end, &tokenEnd, depth + 1);
             if (!arrayNode)
                 return nullptr;
             array->pushValue(WTFMove(arrayNode));

             // After a list value, we expect a comma or the end of the list.
             start = tokenEnd;
             token = parseToken(start, end, &tokenStart, &tokenEnd);
             if (token == Token::ListSeparator) {
                 start = tokenEnd;
                 token = parseToken(start, end, &tokenStart, &tokenEnd);
                 if (token == Token::ArrayEnd)
                     return nullptr;
             } else if (token != Token::ArrayEnd) {
                 // Unexpected value after list value. Bail out.
                 return nullptr;
             }
         }
         if (token != Token::ArrayEnd)
             return nullptr;
         result = WTFMove(array);
         break;
     }
     case Token::ObjectBegin: {
         Ref<JSON::Object> object = JSON::Object::create();
         start = tokenEnd;
         token = parseToken(start, end, &tokenStart, &tokenEnd);
         while (token != Token::ObjectEnd) {
             if (token != Token::String)
                 return nullptr;
             String key;
             if (!decodeString(tokenStart + 1, tokenEnd - 1, key))
                 return nullptr;
             start = tokenEnd;

             token = parseToken(start, end, &tokenStart, &tokenEnd);
             if (token != Token::ObjectPairSeparator)
                 return nullptr;
             start = tokenEnd;

             RefPtr<JSON::Value> value = buildValue(start, end, &tokenEnd, depth + 1);
             if (!value)
                 return nullptr;
             object->setValue(key, WTFMove(value));
             start = tokenEnd;

             // After a key/value pair, we expect a comma or the end of the
             // object.
             token = parseToken(start, end, &tokenStart, &tokenEnd);
             if (token == Token::ListSeparator) {
                 start = tokenEnd;
                 token = parseToken(start, end, &tokenStart, &tokenEnd);
                 if (token == Token::ObjectEnd)
                     return nullptr;
             } else if (token != Token::ObjectEnd) {
                 // Unexpected value after last object value. Bail out.
                 return nullptr;
             }
         }
         if (token != Token::ObjectEnd)
             return nullptr;
         result = WTFMove(object);
         break;
     }

     default:
         // We got a token that's not a value.
         return nullptr;
     }
     *valueTokenEnd = tokenEnd;
     return result;
 }

 inline void appendDoubleQuotedString(StringBuilder& builder, StringView string)
 {
     builder.append('"');
     for (UChar codeUnit : string.codeUnits()) {
         switch (codeUnit) {
         case '\b':
             builder.appendLiteral("\\b");
             continue;
         case '\f':
             builder.appendLiteral("\\f");
             continue;
         case '\n':
             builder.appendLiteral("\\n");
             continue;
         case '\r':
             builder.appendLiteral("\\r");
             continue;
         case '\t':
             builder.appendLiteral("\\t");
             continue;
         case '\\':
             builder.appendLiteral("\\\\");
             continue;
         case '"':
             builder.appendLiteral("\\\"");
             continue;
         }
         // We escape < and > to prevent script execution.
         if (codeUnit >= 32 && codeUnit < 127 && codeUnit != '<' && codeUnit != '>') {
             builder.append(codeUnit);
             continue;
         }
         // We could encode characters >= 127 as UTF-8 instead of \u escape sequences.
         // We could handle surrogates here if callers wanted that; for now we just
         // write them out as a \u sequence, so a surrogate pair appears as two of them.
         builder.appendLiteral("\\u");
         builder.append(upperNibbleToASCIIHexDigit(codeUnit >> 8));
         builder.append(lowerNibbleToASCIIHexDigit(codeUnit >> 8));
         builder.append(upperNibbleToASCIIHexDigit(codeUnit));
         builder.append(lowerNibbleToASCIIHexDigit(codeUnit));
     }
     builder.append('"');
 }

 } // anonymous namespace

 Ref<Value> Value::null()
 {
     return adoptRef(*new Value);
 }

 Ref<Value> Value::create(bool value)
 {
     return adoptRef(*new Value(value));
 }

 Ref<Value> Value::create(int value)
 {
     return adoptRef(*new Value(value));
 }

 Ref<Value> Value::create(double value)
 {
     return adoptRef(*new Value(value));
 }

 Ref<Value> Value::create(const String& value)
 {
     return adoptRef(*new Value(value));
 }

 Ref<Value> Value::create(const char* value)
 {
     return adoptRef(*new Value(value));
 }

 bool Value::asValue(RefPtr<Value>& value)
 {
     value = this;
     return true;
 }

 bool Value::asObject(RefPtr<Object>&)
 {
     return false;
 }

 bool Value::asArray(RefPtr<Array>&)
 {
     return false;
 }

 bool Value::parseJSON(const String& jsonInput, RefPtr<Value>& output)
 {
     // FIXME: This whole file should just use StringView instead of UChar/length and avoid upconverting.
     auto characters = StringView(jsonInput).upconvertedCharacters();
     const UChar* start = characters;
     const UChar* end = start + jsonInput.length();
     const UChar* tokenEnd;
     auto result = buildValue(start, end, &tokenEnd, 0);
     if (!result)
         return false;

     for (const UChar* valueEnd = tokenEnd; valueEnd < end; ++valueEnd) {
         if (!isSpaceOrNewline(*valueEnd))
             return false;
     }

     output = WTFMove(result);
     return true;
 }

 String Value::toJSONString() const
 {
     StringBuilder result;
     result.reserveCapacity(512);
     writeJSON(result);
     return result.toString();
 }

 bool Value::asBoolean(bool& output) const
 {
     if (type() != Type::Boolean)
         return false;

     output = m_value.boolean;
     return true;
 }

 bool Value::asDouble(double& output) const
 {
     if (type() != Type::Double)
         return false;

     output = m_value.number;
     return true;
 }

 bool Value::asDouble(float& output) const
 {
     if (type() != Type::Double)
         return false;

     output = static_cast<float>(m_value.number);
     return true;
 }

 bool Value::asInteger(int& output) const
 {
     if (type() != Type::Integer && type() != Type::Double)
         return false;

     output = static_cast<int>(m_value.number);
     return true;
 }

 bool Value::asInteger(unsigned& output) const
 {
     if (type() != Type::Integer && type() != Type::Double)
         return false;

     output = static_cast<unsigned>(m_value.number);
     return true;
 }

 bool Value::asInteger(long& output) const
 {
     if (type() != Type::Integer && type() != Type::Double)
         return false;

     output = static_cast<long>(m_value.number);
     return true;
 }

 bool Value::asInteger(long long& output) const
 {
     if (type() != Type::Integer && type() != Type::Double)
         return false;

     output = static_cast<long long>(m_value.number);
     return true;
 }

 bool Value::asInteger(unsigned long& output) const
 {
     if (type() != Type::Integer && type() != Type::Double)
         return false;

     output = static_cast<unsigned long>(m_value.number);
     return true;
 }

 bool Value::asInteger(unsigned long long& output) const
 {
     if (type() != Type::Integer && type() != Type::Double)
         return false;

     output = static_cast<unsigned long long>(m_value.number);
     return true;
 }

 bool Value::asString(String& output) const
 {
     if (type() != Type::String)
         return false;

     output = m_value.string;
     return true;
 }

 void Value::writeJSON(StringBuilder& output) const
 {
     switch (m_type) {
     case Type::Null:
         output.appendLiteral("null");
         break;
     case Type::Boolean:
         if (m_value.boolean)
             output.appendLiteral("true");
         else
             output.appendLiteral("false");
         break;
     case Type::String:
         appendDoubleQuotedString(output, m_value.string);
         break;
     case Type::Double:
     case Type::Integer: {
         if (!std::isfinite(m_value.number))
             output.appendLiteral("null");
         else
             output.appendECMAScriptNumber(m_value.number);
         break;
     }
     default:
         ASSERT_NOT_REACHED();
     }
 }

 size_t Value::memoryCost() const
 {
     size_t memoryCost = sizeof(this);
     if (m_type == Type::String && m_value.string)
         memoryCost += m_value.string->sizeInBytes();
     return memoryCost;
 }

 ObjectBase::~ObjectBase()
 {
 }

 bool ObjectBase::asObject(RefPtr<Object>& output)
 {
     COMPILE_ASSERT(sizeof(Object) == sizeof(ObjectBase), cannot_cast);

     output = static_cast<Object*>(this);
     return true;
 }

 Object* ObjectBase::openAccessors()
 {
     COMPILE_ASSERT(sizeof(Object) == sizeof(ObjectBase), cannot_cast);

     return static_cast<Object*>(this);
 }

 size_t ObjectBase::memoryCost() const
 {
     size_t memoryCost = Value::memoryCost();
     for (const auto& entry : m_map) {
         memoryCost += entry.key.sizeInBytes();
         if (entry.value)
             memoryCost += entry.value->memoryCost();
     }
     return memoryCost;
 }

 bool ObjectBase::getBoolean(const String& name, bool& output) const
 {
     RefPtr<Value> value;
     if (!getValue(name, value))
         return false;

     return value->asBoolean(output);
 }

 bool ObjectBase::getString(const String& name, String& output) const
 {
     RefPtr<Value> value;
     if (!getValue(name, value))
         return false;

     return value->asString(output);
 }

 bool ObjectBase::getObject(const String& name, RefPtr<Object>& output) const
 {
     RefPtr<Value> value;
     if (!getValue(name, value))
         return false;

     return value->asObject(output);
 }

 bool ObjectBase::getArray(const String& name, RefPtr<Array>& output) const
 {
     RefPtr<Value> value;
     if (!getValue(name, value))
         return false;

     return value->asArray(output);
 }

 bool ObjectBase::getValue(const String& name, RefPtr<Value>& output) const
 {
     Dictionary::const_iterator findResult = m_map.find(name);
     if (findResult == m_map.end())
         return false;

     output = findResult->value;
     return true;
 }

 void ObjectBase::remove(const String& name)
 {
     m_map.remove(name);
     m_order.removeFirst(name);
 }

 void ObjectBase::writeJSON(StringBuilder& output) const
 {
     output.append('{');
     for (size_t i = 0; i < m_order.size(); ++i) {
         auto findResult = m_map.find(m_order[i]);
         ASSERT(findResult != m_map.end());
         if (i)
             output.append(',');
         appendDoubleQuotedString(output, findResult->key);
         output.append(':');
         findResult->value->writeJSON(output);
     }
     output.append('}');
 }

 ObjectBase::ObjectBase()
     : Value(Type::Object)
     , m_map()
     , m_order()
 {
 }

 ArrayBase::~ArrayBase()
 {
 }

 bool ArrayBase::asArray(RefPtr<Array>& output)
 {
     COMPILE_ASSERT(sizeof(ArrayBase) == sizeof(Array), cannot_cast);
     output = static_cast<Array*>(this);
     return true;
 }

 void ArrayBase::writeJSON(StringBuilder& output) const
 {
     output.append('[');
     for (Vector<RefPtr<Value>>::const_iterator it = m_map.begin(); it != m_map.end(); ++it) {
         if (it != m_map.begin())
             output.append(',');
         (*it)->writeJSON(output);
     }
     output.append(']');
 }

 ArrayBase::ArrayBase()
     : Value(Type::Array)
     , m_map()
 {
 }

 RefPtr<Value> ArrayBase::get(size_t index) const
 {
     RELEASE_ASSERT_WITH_SECURITY_IMPLICATION(index < m_map.size());
     return m_map[index];
 }

 Ref<Object> Object::create()
 {
     return adoptRef(*new Object);
 }

 Ref<Array> Array::create()
 {
     return adoptRef(*new Array);
 }

 size_t ArrayBase::memoryCost() const
 {
     size_t memoryCost = Value::memoryCost();
     for (const auto& item : m_map) {
         if (item)
             memoryCost += item->memoryCost();
     }
     return memoryCost;
 }

 } // namespace JSONImpl
 } // namespace WTF
	/*
	* Copyright (C) 2010 Google Inc. All rights reserved.
	* Copyright (C) 2014 University of Washington. All rights reserved.
	* Copyright (C) 2017-2019 Apple Inc. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions are
	* met:
	*
	* * Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* * Redistributions in binary form must reproduce the above
	* copyright notice, this list of conditions and the following disclaimer
	* in the documentation and/or other materials provided with the
	* distribution.
	* * Neither the name of Google Inc. nor the names of its
	* contributors may be used to endorse or promote products derived from
	* this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "config.h"
	#include <wtf/JSONValues.h>

	#include <wtf/text/StringBuilder.h>

	namespace WTF {
	namespace JSONImpl {

	namespace {

	static const int stackLimit = 1000;

	enum class Token {
	ObjectBegin,
	ObjectEnd,
	ArrayBegin,
	ArrayEnd,
	String,
	Number,
	BoolTrue,
	BoolFalse,
	Null,
	ListSeparator,
	ObjectPairSeparator,
	Invalid,
	};

	const char* const nullString = "null";
	const char* const trueString = "true";
	const char* const falseString = "false";

	bool parseConstToken(const UChar* start, const UChar* end, const UChar** tokenEnd, const char* token)
	{
	while (start < end && token != '\0' && start++ == *token++) { }

	if (*token != '\0')
	return false;

	*tokenEnd = start;
	return true;
	}

	bool readInt(const UChar* start, const UChar* end, const UChar** tokenEnd, bool canHaveLeadingZeros)
	{
	if (start == end)
	return false;

	bool haveLeadingZero = '0' == *start;
	int length = 0;
	while (start < end && '0' <= start && start <= '9') {
	++start;
	++length;
	}

	if (!length)
	return false;

	if (!canHaveLeadingZeros && length > 1 && haveLeadingZero)
	return false;

	*tokenEnd = start;
	return true;
	}

	bool parseNumberToken(const UChar* start, const UChar* end, const UChar** tokenEnd)
	{
	// We just grab the number here. We validate the size in DecodeNumber.
	// According to RFC 4627, a valid number is: [minus] int [frac] [exp]
	if (start == end)
	return false;

	UChar c = *start;
	if ('-' == c)
	++start;

	if (!readInt(start, end, &start, false))
	return false;

	if (start == end) {
	*tokenEnd = start;
	return true;
	}

	// Optional fraction part.
	c = *start;
	if ('.' == c) {
	++start;
	if (!readInt(start, end, &start, true))
	return false;
	if (start == end) {
	*tokenEnd = start;
	return true;
	}
	c = *start;
	}

	// Optional exponent part.
	if ('e' == c \|\| 'E' == c) {
	++start;
	if (start == end)
	return false;
	c = *start;
	if ('-' == c \|\| '+' == c) {
	++start;
	if (start == end)
	return false;
	}
	if (!readInt(start, end, &start, true))
	return false;
	}

	*tokenEnd = start;
	return true;
	}

	bool readHexDigits(const UChar* start, const UChar* end, const UChar** tokenEnd, int digits)
	{
	if (end - start < digits)
	return false;

	for (int i = 0; i < digits; ++i) {
	if (!isASCIIHexDigit(*start++))
	return false;
	}

	*tokenEnd = start;
	return true;
	}

	bool parseStringToken(const UChar* start, const UChar* end, const UChar** tokenEnd)
	{
	while (start < end) {
	UChar c = *start++;
	if ('\\' == c && start < end) {
	c = *start++;
	// Make sure the escaped char is valid.
	switch (c) {
	case 'x':
	if (!readHexDigits(start, end, &start, 2))
	return false;
	break;
	case 'u':
	if (!readHexDigits(start, end, &start, 4))
	return false;
	break;
	case '\\':
	case '/':
	case 'b':
	case 'f':
	case 'n':
	case 'r':
	case 't':
	case 'v':
	case '"':
	break;
	default:
	return false;
	}
	} else if ('"' == c) {
	*tokenEnd = start;
	return true;
	}
	}

	return false;
	}

	Token parseToken(const UChar* start, const UChar* end, const UChar tokenStart, const UChar tokenEnd)
	{
	while (start < end && isSpaceOrNewline(*start))
	++start;

	if (start == end)
	return Token::Invalid;

	*tokenStart = start;

	switch (*start) {
	case 'n':
	if (parseConstToken(start, end, tokenEnd, nullString))
	return Token::Null;
	break;
	case 't':
	if (parseConstToken(start, end, tokenEnd, trueString))
	return Token::BoolTrue;
	break;
	case 'f':
	if (parseConstToken(start, end, tokenEnd, falseString))
	return Token::BoolFalse;
	break;
	case '[':
	*tokenEnd = start + 1;
	return Token::ArrayBegin;
	case ']':
	*tokenEnd = start + 1;
	return Token::ArrayEnd;
	case ',':
	*tokenEnd = start + 1;
	return Token::ListSeparator;
	case '{':
	*tokenEnd = start + 1;
	return Token::ObjectBegin;
	case '}':
	*tokenEnd = start + 1;
	return Token::ObjectEnd;
	case ':':
	*tokenEnd = start + 1;
	return Token::ObjectPairSeparator;
	case '0':
	case '1':
	case '2':
	case '3':
	case '4':
	case '5':
	case '6':
	case '7':
	case '8':
	case '9':
	case '-':
	if (parseNumberToken(start, end, tokenEnd))
	return Token::Number;
	break;
	case '"':
	if (parseStringToken(start + 1, end, tokenEnd))
	return Token::String;
	break;
	}

	return Token::Invalid;
	}

	bool decodeString(const UChar* start, const UChar* end, StringBuilder& output)
	{
	while (start < end) {
	UChar c = *start++;
	if ('\\' != c) {
	output.append(c);
	continue;
	}
	if (UNLIKELY(start >= end))
	return false;
	c = *start++;
	switch (c) {
	case '"':
	case '/':
	case '\\':
	break;
	case 'b':
	c = '\b';
	break;
	case 'f':
	c = '\f';
	break;
	case 'n':
	c = '\n';
	break;
	case 'r':
	c = '\r';
	break;
	case 't':
	c = '\t';
	break;
	case 'v':
	c = '\v';
	break;
	case 'x':
	if (UNLIKELY(start + 1 >= end))
	return false;
	c = toASCIIHexValue(start[0], start[1]);
	start += 2;
	break;
	case 'u':
	if (UNLIKELY(start + 3 >= end))
	return false;
	c = toASCIIHexValue(start[0], start[1]) << 8 \| toASCIIHexValue(start[2], start[3]);
	start += 4;
	break;
	default:
	return false;
	}
	output.append(c);
	}

	return true;
	}

	bool decodeString(const UChar* start, const UChar* end, String& output)
	{
	if (start == end) {
	output = emptyString();
	return true;
	}

	if (start > end)
	return false;

	StringBuilder buffer;
	buffer.reserveCapacity(end - start);
	if (!decodeString(start, end, buffer))
	return false;

	output = buffer.toString();
	return true;
	}

	RefPtr<JSON::Value> buildValue(const UChar* start, const UChar* end, const UChar** valueTokenEnd, int depth)
	{
	if (depth > stackLimit)
	return nullptr;

	RefPtr<JSON::Value> result;
	const UChar* tokenStart;
	const UChar* tokenEnd;
	Token token = parseToken(start, end, &tokenStart, &tokenEnd);
	switch (token) {
	case Token::Invalid:
	return nullptr;
	case Token::Null:
	result = JSON::Value::null();
	break;
	case Token::BoolTrue:
	result = JSON::Value::create(true);
	break;
	case Token::BoolFalse:
	result = JSON::Value::create(false);
	break;
	case Token::Number: {
	bool ok;
	double value = charactersToDouble(tokenStart, tokenEnd - tokenStart, &ok);
	if (!ok)
	return nullptr;
	result = JSON::Value::create(value);
	break;
	}
	case Token::String: {
	String value;
	bool ok = decodeString(tokenStart + 1, tokenEnd - 1, value);
	if (!ok)
	return nullptr;
	result = JSON::Value::create(value);
	break;
	}
	case Token::ArrayBegin: {
	Ref<JSON::Array> array = JSON::Array::create();
	start = tokenEnd;
	token = parseToken(start, end, &tokenStart, &tokenEnd);
	while (token != Token::ArrayEnd) {
	RefPtr<JSON::Value> arrayNode = buildValue(start, end, &tokenEnd, depth + 1);
	if (!arrayNode)
	return nullptr;
	array->pushValue(WTFMove(arrayNode));

	// After a list value, we expect a comma or the end of the list.
	start = tokenEnd;
	token = parseToken(start, end, &tokenStart, &tokenEnd);
	if (token == Token::ListSeparator) {
	start = tokenEnd;
	token = parseToken(start, end, &tokenStart, &tokenEnd);
	if (token == Token::ArrayEnd)
	return nullptr;
	} else if (token != Token::ArrayEnd) {
	// Unexpected value after list value. Bail out.
	return nullptr;
	}
	}
	if (token != Token::ArrayEnd)
	return nullptr;
	result = WTFMove(array);
	break;
	}
	case Token::ObjectBegin: {
	Ref<JSON::Object> object = JSON::Object::create();
	start = tokenEnd;
	token = parseToken(start, end, &tokenStart, &tokenEnd);
	while (token != Token::ObjectEnd) {
	if (token != Token::String)
	return nullptr;
	String key;
	if (!decodeString(tokenStart + 1, tokenEnd - 1, key))
	return nullptr;
	start = tokenEnd;

	token = parseToken(start, end, &tokenStart, &tokenEnd);
	if (token != Token::ObjectPairSeparator)
	return nullptr;
	start = tokenEnd;

	RefPtr<JSON::Value> value = buildValue(start, end, &tokenEnd, depth + 1);
	if (!value)
	return nullptr;
	object->setValue(key, WTFMove(value));
	start = tokenEnd;

	// After a key/value pair, we expect a comma or the end of the
	// object.
	token = parseToken(start, end, &tokenStart, &tokenEnd);
	if (token == Token::ListSeparator) {
	start = tokenEnd;
	token = parseToken(start, end, &tokenStart, &tokenEnd);
	if (token == Token::ObjectEnd)
	return nullptr;
	} else if (token != Token::ObjectEnd) {
	// Unexpected value after last object value. Bail out.
	return nullptr;
	}
	}
	if (token != Token::ObjectEnd)
	return nullptr;
	result = WTFMove(object);
	break;
	}

	default:
	// We got a token that's not a value.
	return nullptr;
	}
	*valueTokenEnd = tokenEnd;
	return result;
	}

	inline void appendDoubleQuotedString(StringBuilder& builder, StringView string)
	{
	builder.append('"');
	for (UChar codeUnit : string.codeUnits()) {
	switch (codeUnit) {
	case '\b':
	builder.appendLiteral("\\b");
	continue;
	case '\f':
	builder.appendLiteral("\\f");
	continue;
	case '\n':
	builder.appendLiteral("\\n");
	continue;
	case '\r':
	builder.appendLiteral("\\r");
	continue;
	case '\t':
	builder.appendLiteral("\\t");
	continue;
	case '\\':
	builder.appendLiteral("\\\\");
	continue;
	case '"':
	builder.appendLiteral("\\\"");
	continue;
	}
	// We escape < and > to prevent script execution.
	if (codeUnit >= 32 && codeUnit < 127 && codeUnit != '<' && codeUnit != '>') {
	builder.append(codeUnit);
	continue;
	}
	// We could encode characters >= 127 as UTF-8 instead of \u escape sequences.
	// We could handle surrogates here if callers wanted that; for now we just
	// write them out as a \u sequence, so a surrogate pair appears as two of them.
	builder.appendLiteral("\\u");
	builder.append(upperNibbleToASCIIHexDigit(codeUnit >> 8));
	builder.append(lowerNibbleToASCIIHexDigit(codeUnit >> 8));
	builder.append(upperNibbleToASCIIHexDigit(codeUnit));
	builder.append(lowerNibbleToASCIIHexDigit(codeUnit));
	}
	builder.append('"');
	}

	} // anonymous namespace

	Ref<Value> Value::null()
	{
	return adoptRef(*new Value);
	}

	Ref<Value> Value::create(bool value)
	{
	return adoptRef(*new Value(value));
	}

	Ref<Value> Value::create(int value)
	{
	return adoptRef(*new Value(value));
	}

	Ref<Value> Value::create(double value)
	{
	return adoptRef(*new Value(value));
	}

	Ref<Value> Value::create(const String& value)
	{
	return adoptRef(*new Value(value));
	}

	Ref<Value> Value::create(const char* value)
	{
	return adoptRef(*new Value(value));
	}

	bool Value::asValue(RefPtr<Value>& value)
	{
	value = this;
	return true;
	}

	bool Value::asObject(RefPtr<Object>&)
	{
	return false;
	}

	bool Value::asArray(RefPtr<Array>&)
	{
	return false;
	}

	bool Value::parseJSON(const String& jsonInput, RefPtr<Value>& output)
	{
	// FIXME: This whole file should just use StringView instead of UChar/length and avoid upconverting.
	auto characters = StringView(jsonInput).upconvertedCharacters();
	const UChar* start = characters;
	const UChar* end = start + jsonInput.length();
	const UChar* tokenEnd;
	auto result = buildValue(start, end, &tokenEnd, 0);
	if (!result)
	return false;

	for (const UChar* valueEnd = tokenEnd; valueEnd < end; ++valueEnd) {
	if (!isSpaceOrNewline(*valueEnd))
	return false;
	}

	output = WTFMove(result);
	return true;
	}

	String Value::toJSONString() const
	{
	StringBuilder result;
	result.reserveCapacity(512);
	writeJSON(result);
	return result.toString();
	}

	bool Value::asBoolean(bool& output) const
	{
	if (type() != Type::Boolean)
	return false;

	output = m_value.boolean;
	return true;
	}

	bool Value::asDouble(double& output) const
	{
	if (type() != Type::Double)
	return false;

	output = m_value.number;
	return true;
	}

	bool Value::asDouble(float& output) const
	{
	if (type() != Type::Double)
	return false;

	output = static_cast<float>(m_value.number);
	return true;
	}

	bool Value::asInteger(int& output) const
	{
	if (type() != Type::Integer && type() != Type::Double)
	return false;

	output = static_cast<int>(m_value.number);
	return true;
	}

	bool Value::asInteger(unsigned& output) const
	{
	if (type() != Type::Integer && type() != Type::Double)
	return false;

	output = static_cast<unsigned>(m_value.number);
	return true;
	}

	bool Value::asInteger(long& output) const
	{
	if (type() != Type::Integer && type() != Type::Double)
	return false;

	output = static_cast<long>(m_value.number);
	return true;
	}

	bool Value::asInteger(long long& output) const
	{
	if (type() != Type::Integer && type() != Type::Double)
	return false;

	output = static_cast<long long>(m_value.number);
	return true;
	}

	bool Value::asInteger(unsigned long& output) const
	{
	if (type() != Type::Integer && type() != Type::Double)
	return false;

	output = static_cast<unsigned long>(m_value.number);
	return true;
	}

	bool Value::asInteger(unsigned long long& output) const
	{
	if (type() != Type::Integer && type() != Type::Double)
	return false;

	output = static_cast<unsigned long long>(m_value.number);
	return true;
	}

	bool Value::asString(String& output) const
	{
	if (type() != Type::String)
	return false;

	output = m_value.string;
	return true;
	}

	void Value::writeJSON(StringBuilder& output) const
	{
	switch (m_type) {
	case Type::Null:
	output.appendLiteral("null");
	break;
	case Type::Boolean:
	if (m_value.boolean)
	output.appendLiteral("true");
	else
	output.appendLiteral("false");
	break;
	case Type::String:
	appendDoubleQuotedString(output, m_value.string);
	break;
	case Type::Double:
	case Type::Integer: {
	if (!std::isfinite(m_value.number))
	output.appendLiteral("null");
	else
	output.appendECMAScriptNumber(m_value.number);
	break;
	}
	default:
	ASSERT_NOT_REACHED();
	}
	}

	size_t Value::memoryCost() const
	{
	size_t memoryCost = sizeof(this);
	if (m_type == Type::String && m_value.string)
	memoryCost += m_value.string->sizeInBytes();
	return memoryCost;
	}

	ObjectBase::~ObjectBase()
	{
	}

	bool ObjectBase::asObject(RefPtr<Object>& output)
	{
	COMPILE_ASSERT(sizeof(Object) == sizeof(ObjectBase), cannot_cast);

	output = static_cast<Object*>(this);
	return true;
	}

	Object* ObjectBase::openAccessors()
	{
	COMPILE_ASSERT(sizeof(Object) == sizeof(ObjectBase), cannot_cast);

	return static_cast<Object*>(this);
	}

	size_t ObjectBase::memoryCost() const
	{
	size_t memoryCost = Value::memoryCost();
	for (const auto& entry : m_map) {
	memoryCost += entry.key.sizeInBytes();
	if (entry.value)
	memoryCost += entry.value->memoryCost();
	}
	return memoryCost;
	}

	bool ObjectBase::getBoolean(const String& name, bool& output) const
	{
	RefPtr<Value> value;
	if (!getValue(name, value))
	return false;

	return value->asBoolean(output);
	}

	bool ObjectBase::getString(const String& name, String& output) const
	{
	RefPtr<Value> value;
	if (!getValue(name, value))
	return false;

	return value->asString(output);
	}

	bool ObjectBase::getObject(const String& name, RefPtr<Object>& output) const
	{
	RefPtr<Value> value;
	if (!getValue(name, value))
	return false;

	return value->asObject(output);
	}

	bool ObjectBase::getArray(const String& name, RefPtr<Array>& output) const
	{
	RefPtr<Value> value;
	if (!getValue(name, value))
	return false;

	return value->asArray(output);
	}

	bool ObjectBase::getValue(const String& name, RefPtr<Value>& output) const
	{
	Dictionary::const_iterator findResult = m_map.find(name);
	if (findResult == m_map.end())
	return false;

	output = findResult->value;
	return true;
	}

	void ObjectBase::remove(const String& name)
	{
	m_map.remove(name);
	m_order.removeFirst(name);
	}

	void ObjectBase::writeJSON(StringBuilder& output) const
	{
	output.append('{');
	for (size_t i = 0; i < m_order.size(); ++i) {
	auto findResult = m_map.find(m_order[i]);
	ASSERT(findResult != m_map.end());
	if (i)
	output.append(',');
	appendDoubleQuotedString(output, findResult->key);
	output.append(':');
	findResult->value->writeJSON(output);
	}
	output.append('}');
	}

	ObjectBase::ObjectBase()
	: Value(Type::Object)
	, m_map()
	, m_order()
	{
	}

	ArrayBase::~ArrayBase()
	{
	}

	bool ArrayBase::asArray(RefPtr<Array>& output)
	{
	COMPILE_ASSERT(sizeof(ArrayBase) == sizeof(Array), cannot_cast);
	output = static_cast<Array*>(this);
	return true;
	}

	void ArrayBase::writeJSON(StringBuilder& output) const
	{
	output.append('[');
	for (Vector<RefPtr<Value>>::const_iterator it = m_map.begin(); it != m_map.end(); ++it) {
	if (it != m_map.begin())
	output.append(',');
	(*it)->writeJSON(output);
	}
	output.append(']');
	}

	ArrayBase::ArrayBase()
	: Value(Type::Array)
	, m_map()
	{
	}

	RefPtr<Value> ArrayBase::get(size_t index) const
	{
	RELEASE_ASSERT_WITH_SECURITY_IMPLICATION(index < m_map.size());
	return m_map[index];
	}

	Ref<Object> Object::create()
	{
	return adoptRef(*new Object);
	}

	Ref<Array> Array::create()
	{
	return adoptRef(*new Array);
	}

	size_t ArrayBase::memoryCost() const
	{
	size_t memoryCost = Value::memoryCost();
	for (const auto& item : m_map) {
	if (item)
	memoryCost += item->memoryCost();
	}
	return memoryCost;
	}

	} // namespace JSONImpl
	} // namespace WTF