JSONParser.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: set ts=8 sts=2 et sw=2 tw=80:
 * 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 "vm/JSONParser.h"

#include "mozilla/Range.h"
#include "mozilla/RangedPtr.h"
#include "mozilla/Sprintf.h"
#include "mozilla/TextUtils.h"

#include <ctype.h>

#include "jsnum.h"

#include "builtin/Array.h"
#include "util/StringBuffer.h"
#include "vm/Realm.h"

#include "vm/NativeObject-inl.h"

using namespace js;

using mozilla::IsAsciiDigit;
using mozilla::RangedPtr;

JSONParserBase::~JSONParserBase() {
  for (size_t i = 0; i < stack.length(); i++) {
    if (stack[i].state == FinishArrayElement) {
      js_delete(&stack[i].elements());
    } else {
      js_delete(&stack[i].properties());
    }
  }

  for (size_t i = 0; i < freeElements.length(); i++) {
    js_delete(freeElements[i]);
  }

  for (size_t i = 0; i < freeProperties.length(); i++) {
    js_delete(freeProperties[i]);
  }
}

void JSONParserBase::trace(JSTracer* trc) {
  for (auto& elem : stack) {
    if (elem.state == FinishArrayElement) {
      elem.elements().trace(trc);
    } else {
      elem.properties().trace(trc);
    }
  }
}

template <typename CharT>
void JSONParser<CharT>::getTextPosition(uint32_t* column, uint32_t* line) {
  CharPtr ptr = begin;
  uint32_t col = 1;
  uint32_t row = 1;
  for (; ptr < current; ptr++) {
    if (*ptr == '\n' || *ptr == '\r') {
      ++row;
      col = 1;
      // \r\n is treated as a single newline.
      if (ptr + 1 < current && *ptr == '\r' && *(ptr + 1) == '\n') {
        ++ptr;
      }
    } else {
      ++col;
    }
  }
  *column = col;
  *line = row;
}

template <typename CharT>
void JSONParser<CharT>::error(const char* msg) {
  if (errorHandling == RaiseError) {
    uint32_t column = 1, line = 1;
    getTextPosition(&column, &line);

    const size_t MaxWidth = sizeof("4294967295");
    char columnNumber[MaxWidth];
    SprintfLiteral(columnNumber, "%" PRIu32, column);
    char lineNumber[MaxWidth];
    SprintfLiteral(lineNumber, "%" PRIu32, line);

    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
                              JSMSG_JSON_BAD_PARSE, msg, lineNumber,
                              columnNumber);
  }
}

bool JSONParserBase::errorReturn() { return errorHandling == NoError; }

template <typename CharT>
template <JSONParserBase::StringType ST>
JSONParserBase::Token JSONParser<CharT>::readString() {
  MOZ_ASSERT(current < end);
  MOZ_ASSERT(*current == '"');

  /*
   * JSONString:
   *   /^"([^\u0000-\u001F"\\]|\\(["/\\bfnrt]|u[0-9a-fA-F]{4}))*"$/
   */

  if (++current == end) {
    error("unterminated string literal");
    return token(Error);
  }

  /*
   * Optimization: if the source contains no escaped characters, create the
   * string directly from the source text.
   */
  CharPtr start = current;
  for (; current < end; current++) {
    if (*current == '"') {
      size_t length = current - start;
      current++;
      JSFlatString* str = (ST == JSONParser::PropertyName)
                              ? AtomizeChars(cx, start.get(), length)
                              : NewStringCopyN<CanGC>(cx, start.get(), length);
      if (!str) {
        return token(OOM);
      }
      return stringToken(str);
    }

    if (*current == '\\') {
      break;
    }

    if (*current <= 0x001F) {
      error("bad control character in string literal");
      return token(Error);
    }
  }

  /*
   * Slow case: string contains escaped characters.  Copy a maximal sequence
   * of unescaped characters into a temporary buffer, then an escaped
   * character, and repeat until the entire string is consumed.
   */
  StringBuffer buffer(cx);
  do {
    if (start < current && !buffer.append(start.get(), current.get())) {
      return token(OOM);
    }

    if (current >= end) {
      break;
    }

    char16_t c = *current++;
    if (c == '"') {
      JSFlatString* str = (ST == JSONParser::PropertyName)
                              ? buffer.finishAtom()
                              : buffer.finishString();
      if (!str) {
        return token(OOM);
      }
      return stringToken(str);
    }

    if (c != '\\') {
      --current;
      error("bad character in string literal");
      return token(Error);
    }

    if (current >= end) {
      break;
    }

    switch (*current++) {
      case '"':
        c = '"';
        break;
      case '/':
        c = '/';
        break;
      case '\\':
        c = '\\';
        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 'u':
        if (end - current < 4 ||
            !(JS7_ISHEX(current[0]) && JS7_ISHEX(current[1]) &&
              JS7_ISHEX(current[2]) && JS7_ISHEX(current[3]))) {
          // Point to the first non-hexadecimal character (which may be
          // missing).
          if (current == end || !JS7_ISHEX(current[0])) {
            ;  // already at correct location
          } else if (current + 1 == end || !JS7_ISHEX(current[1])) {
            current += 1;
          } else if (current + 2 == end || !JS7_ISHEX(current[2])) {
            current += 2;
          } else if (current + 3 == end || !JS7_ISHEX(current[3])) {
            current += 3;
          } else {
            MOZ_CRASH("logic error determining first erroneous character");
          }

          error("bad Unicode escape");
          return token(Error);
        }
        c = (JS7_UNHEX(current[0]) << 12) | (JS7_UNHEX(current[1]) << 8) |
            (JS7_UNHEX(current[2]) << 4) | (JS7_UNHEX(current[3]));
        current += 4;
        break;

      default:
        current--;
        error("bad escaped character");
        return token(Error);
    }
    if (!buffer.append(c)) {
      return token(OOM);
    }

    start = current;
    for (; current < end; current++) {
      if (*current == '"' || *current == '\\' || *current <= 0x001F) {
        break;
      }
    }
  } while (current < end);

  error("unterminated string");
  return token(Error);
}

template <typename CharT>
JSONParserBase::Token JSONParser<CharT>::readNumber() {
  MOZ_ASSERT(current < end);
  MOZ_ASSERT(IsAsciiDigit(*current) || *current == '-');

  /*
   * JSONNumber:
   *   /^-?(0|[1-9][0-9]+)(\.[0-9]+)?([eE][\+\-]?[0-9]+)?$/
   */

  bool negative = *current == '-';

  /* -? */
  if (negative && ++current == end) {
    error("no number after minus sign");
    return token(Error);
  }

  const CharPtr digitStart = current;

  /* 0|[1-9][0-9]+ */
  if (!IsAsciiDigit(*current)) {
    error("unexpected non-digit");
    return token(Error);
  }
  if (*current++ != '0') {
    for (; current < end; current++) {
      if (!IsAsciiDigit(*current)) {
        break;
      }
    }
  }

  /* Fast path: no fractional or exponent part. */
  if (current == end ||
      (*current != '.' && *current != 'e' && *current != 'E')) {
    mozilla::Range<const CharT> chars(digitStart.get(), current - digitStart);
    if (chars.length() < strlen("9007199254740992")) {
      // If the decimal number is shorter than the length of 2**53, (the
      // largest number a double can represent with integral precision),
      // parse it using a decimal-only parser.  This comparison is
      // conservative but faster than a fully-precise check.
      double d = ParseDecimalNumber(chars);
      return numberToken(negative ? -d : d);
    }

    double d;
    if (!GetFullInteger(cx, digitStart.get(), current.get(), 10, &d)) {
      return token(OOM);
    }
    return numberToken(negative ? -d : d);
  }

  /* (\.[0-9]+)? */
  if (current < end && *current == '.') {
    if (++current == end) {
      error("missing digits after decimal point");
      return token(Error);
    }
    if (!IsAsciiDigit(*current)) {
      error("unterminated fractional number");
      return token(Error);
    }
    while (++current < end) {
      if (!IsAsciiDigit(*current)) {
        break;
      }
    }
  }

  /* ([eE][\+\-]?[0-9]+)? */
  if (current < end && (*current == 'e' || *current == 'E')) {
    if (++current == end) {
      error("missing digits after exponent indicator");
      return token(Error);
    }
    if (*current == '+' || *current == '-') {
      if (++current == end) {
        error("missing digits after exponent sign");
        return token(Error);
      }
    }
    if (!IsAsciiDigit(*current)) {
      error("exponent part is missing a number");
      return token(Error);
    }
    while (++current < end) {
      if (!IsAsciiDigit(*current)) {
        break;
      }
    }
  }

  double d;
  if (!FullStringToDouble(cx, digitStart.get(), current.get(), &d)) {
    return token(OOM);
  }
  return numberToken(negative ? -d : d);
}

static inline bool IsJSONWhitespace(char16_t c) {
  return c == '\t' || c == '\r' || c == '\n' || c == ' ';
}

template <typename CharT>
JSONParserBase::Token JSONParser<CharT>::advance() {
  while (current < end && IsJSONWhitespace(*current)) {
    current++;
  }
  if (current >= end) {
    error("unexpected end of data");
    return token(Error);
  }

  switch (*current) {
    case '"':
      return readString<LiteralValue>();

    case '-':
    case '0':
    case '1':
    case '2':
    case '3':
    case '4':
    case '5':
    case '6':
    case '7':
    case '8':
    case '9':
      return readNumber();

    case 't':
      if (end - current < 4 || current[1] != 'r' || current[2] != 'u' ||
          current[3] != 'e') {
        error("unexpected keyword");
        return token(Error);
      }
      current += 4;
      return token(True);

    case 'f':
      if (end - current < 5 || current[1] != 'a' || current[2] != 'l' ||
          current[3] != 's' || current[4] != 'e') {
        error("unexpected keyword");
        return token(Error);
      }
      current += 5;
      return token(False);

    case 'n':
      if (end - current < 4 || current[1] != 'u' || current[2] != 'l' ||
          current[3] != 'l') {
        error("unexpected keyword");
        return token(Error);
      }
      current += 4;
      return token(Null);

    case '[':
      current++;
      return token(ArrayOpen);
    case ']':
      current++;
      return token(ArrayClose);

    case '{':
      current++;
      return token(ObjectOpen);
    case '}':
      current++;
      return token(ObjectClose);

    case ',':
      current++;
      return token(Comma);

    case ':':
      current++;
      return token(Colon);

    default:
      error("unexpected character");
      return token(Error);
  }
}

template <typename CharT>
JSONParserBase::Token JSONParser<CharT>::advanceAfterObjectOpen() {
  MOZ_ASSERT(current[-1] == '{');

  while (current < end && IsJSONWhitespace(*current)) {
    current++;
  }
  if (current >= end) {
    error("end of data while reading object contents");
    return token(Error);
  }

  if (*current == '"') {
    return readString<PropertyName>();
  }

  if (*current == '}') {
    current++;
    return token(ObjectClose);
  }

  error("expected property name or '}'");
  return token(Error);
}

template <typename CharT>
static inline void AssertPastValue(const RangedPtr<const CharT> current) {
  /*
   * We're past an arbitrary JSON value, so the previous character is
   * *somewhat* constrained, even if this assertion is pretty broad.  Don't
   * knock it till you tried it: this assertion *did* catch a bug once.
   */
  MOZ_ASSERT((current[-1] == 'l' && current[-2] == 'l' && current[-3] == 'u' &&
              current[-4] == 'n') ||
             (current[-1] == 'e' && current[-2] == 'u' && current[-3] == 'r' &&
              current[-4] == 't') ||
             (current[-1] == 'e' && current[-2] == 's' && current[-3] == 'l' &&
              current[-4] == 'a' && current[-5] == 'f') ||
             current[-1] == '}' || current[-1] == ']' || current[-1] == '"' ||
             IsAsciiDigit(current[-1]));
}

template <typename CharT>
JSONParserBase::Token JSONParser<CharT>::advanceAfterArrayElement() {
  AssertPastValue(current);

  while (current < end && IsJSONWhitespace(*current)) {
    current++;
  }
  if (current >= end) {
    error("end of data when ',' or ']' was expected");
    return token(Error);
  }

  if (*current == ',') {
    current++;
    return token(Comma);
  }

  if (*current == ']') {
    current++;
    return token(ArrayClose);
  }

  error("expected ',' or ']' after array element");
  return token(Error);
}

template <typename CharT>
JSONParserBase::Token JSONParser<CharT>::advancePropertyName() {
  MOZ_ASSERT(current[-1] == ',');

  while (current < end && IsJSONWhitespace(*current)) {
    current++;
  }
  if (current >= end) {
    error("end of data when property name was expected");
    return token(Error);
  }

  if (*current == '"') {
    return readString<PropertyName>();
  }

  error("expected double-quoted property name");
  return token(Error);
}

template <typename CharT>
JSONParserBase::Token JSONParser<CharT>::advancePropertyColon() {
  MOZ_ASSERT(current[-1] == '"');

  while (current < end && IsJSONWhitespace(*current)) {
    current++;
  }
  if (current >= end) {
    error("end of data after property name when ':' was expected");
    return token(Error);
  }

  if (*current == ':') {
    current++;
    return token(Colon);
  }

  error("expected ':' after property name in object");
  return token(Error);
}

template <typename CharT>
JSONParserBase::Token JSONParser<CharT>::advanceAfterProperty() {
  AssertPastValue(current);

  while (current < end && IsJSONWhitespace(*current)) {
    current++;
  }
  if (current >= end) {
    error("end of data after property value in object");
    return token(Error);
  }

  if (*current == ',') {
    current++;
    return token(Comma);
  }

  if (*current == '}') {
    current++;
    return token(ObjectClose);
  }

  error("expected ',' or '}' after property value in object");
  return token(Error);
}

inline bool JSONParserBase::finishObject(MutableHandleValue vp,
                                         PropertyVector& properties) {
  MOZ_ASSERT(&properties == &stack.back().properties());

  JSObject* obj = ObjectGroup::newPlainObject(
      cx, properties.begin(), properties.length(), GenericObject);
  if (!obj) {
    return false;
  }

  vp.setObject(*obj);
  if (!freeProperties.append(&properties)) {
    return false;
  }
  stack.popBack();

  if (!stack.empty() && stack.back().state == FinishArrayElement) {
    const ElementVector& elements = stack.back().elements();
    if (!CombinePlainObjectPropertyTypes(cx, obj, elements.begin(),
                                         elements.length())) {
      return false;
    }
  }

  return true;
}

inline bool JSONParserBase::finishArray(MutableHandleValue vp,
                                        ElementVector& elements) {
  MOZ_ASSERT(&elements == &stack.back().elements());

  ArrayObject* obj = ObjectGroup::newArrayObject(
      cx, elements.begin(), elements.length(), GenericObject);
  if (!obj) {
    return false;
  }

  vp.setObject(*obj);
  if (!freeElements.append(&elements)) {
    return false;
  }
  stack.popBack();

  if (!stack.empty() && stack.back().state == FinishArrayElement) {
    const ElementVector& elements = stack.back().elements();
    if (!CombineArrayElementTypes(cx, obj, elements.begin(),
                                  elements.length())) {
      return false;
    }
  }

  return true;
}

template <typename CharT>
bool JSONParser<CharT>::parse(MutableHandleValue vp) {
  RootedValue value(cx);
  MOZ_ASSERT(stack.empty());

  vp.setUndefined();

  Token token;
  ParserState state = JSONValue;
  while (true) {
    switch (state) {
      case FinishObjectMember: {
        PropertyVector& properties = stack.back().properties();
        properties.back().value = value;

        token = advanceAfterProperty();
        if (token == ObjectClose) {
          if (!finishObject(&value, properties)) {
            return false;
          }
          break;
        }
        if (token != Comma) {
          if (token == OOM) {
            return false;
          }
          if (token != Error) {
            error(
                "expected ',' or '}' after property-value pair in object "
                "literal");
          }
          return errorReturn();
        }
        token = advancePropertyName();
        /* FALL THROUGH */
      }

      JSONMember:
        if (token == String) {
          jsid id = AtomToId(atomValue());
          PropertyVector& properties = stack.back().properties();
          if (!properties.append(IdValuePair(id))) {
            return false;
          }
          token = advancePropertyColon();
          if (token != Colon) {
            MOZ_ASSERT(token == Error);
            return errorReturn();
          }
          goto JSONValue;
        }
        if (token == OOM) {
          return false;
        }
        if (token != Error) {
          error("property names must be double-quoted strings");
        }
        return errorReturn();

      case FinishArrayElement: {
        ElementVector& elements = stack.back().elements();
        if (!elements.append(value.get())) {
          return false;
        }
        token = advanceAfterArrayElement();
        if (token == Comma) {
          goto JSONValue;
        }
        if (token == ArrayClose) {
          if (!finishArray(&value, elements)) {
            return false;
          }
          break;
        }
        MOZ_ASSERT(token == Error);
        return errorReturn();
      }

      JSONValue:
      case JSONValue:
        token = advance();
      JSONValueSwitch:
        switch (token) {
          case String:
            value = stringValue();
            break;
          case Number:
            value = numberValue();
            break;
          case True:
            value = BooleanValue(true);
            break;
          case False:
            value = BooleanValue(false);
            break;
          case Null:
            value = NullValue();
            break;

          case ArrayOpen: {
            ElementVector* elements;
            if (!freeElements.empty()) {
              elements = freeElements.popCopy();
              elements->clear();
            } else {
              elements = cx->new_<ElementVector>(cx);
              if (!elements) {
                return false;
              }
            }
            if (!stack.append(elements)) {
              js_delete(elements);
              return false;
            }

            token = advance();
            if (token == ArrayClose) {
              if (!finishArray(&value, *elements)) {
                return false;
              }
              break;
            }
            goto JSONValueSwitch;
          }

          case ObjectOpen: {
            PropertyVector* properties;
            if (!freeProperties.empty()) {
              properties = freeProperties.popCopy();
              properties->clear();
            } else {
              properties = cx->new_<PropertyVector>(cx);
              if (!properties) {
                return false;
              }
            }
            if (!stack.append(properties)) {
              js_delete(properties);
              return false;
            }

            token = advanceAfterObjectOpen();
            if (token == ObjectClose) {
              if (!finishObject(&value, *properties)) {
                return false;
              }
              break;
            }
            goto JSONMember;
          }

          case ArrayClose:
          case ObjectClose:
          case Colon:
          case Comma:
            // Move the current pointer backwards so that the position
            // reported in the error message is correct.
            --current;
            error("unexpected character");
            return errorReturn();

          case OOM:
            return false;

          case Error:
            return errorReturn();
        }
        break;
    }

    if (stack.empty()) {
      break;
    }
    state = stack.back().state;
  }

  for (; current < end; current++) {
    if (!IsJSONWhitespace(*current)) {
      error("unexpected non-whitespace character after JSON data");
      return errorReturn();
    }
  }

  MOZ_ASSERT(end == current);
  MOZ_ASSERT(stack.empty());

  vp.set(value);
  return true;
}

template class js::JSONParser<Latin1Char>;
template class js::JSONParser<char16_t>;