src/lib_json/json_reader.cpp

// Copyright 2007-2011 Baptiste Lepilleur
// Distributed under MIT license, or public domain if desired and
// recognized in your jurisdiction.
// See file LICENSE for detail or copy at http://jsoncpp.sourceforge.net/LICENSE

#if !defined(JSON_IS_AMALGAMATION)
#include <json/assertions.h>
#include <json/reader.h>
#include <json/value.h>
#include "json_tool.h"
#endif // if !defined(JSON_IS_AMALGAMATION)
#include <utility>
#include <cstdio>
#include <cassert>
#include <cstring>
#include <istream>

#if defined(_MSC_VER) && _MSC_VER < 1500 // VC++ 8.0 and below
#define snprintf _snprintf
#endif

#if defined(_MSC_VER) && _MSC_VER >= 1400 // VC++ 8.0
// Disable warning about strdup being deprecated.
#pragma warning(disable : 4996)
#endif

namespace Json {

// Implementation of class Features
// ////////////////////////////////

Features::Features()
    : allowComments_(true), strictRoot_(false),
      allowDroppedNullPlaceholders_(false), allowNumericKeys_(false) {}

Features Features::all() { return Features(); }

Features Features::strictMode() {
  Features features;
  features.allowComments_ = false;
  features.strictRoot_ = true;
  features.allowDroppedNullPlaceholders_ = false;
  features.allowNumericKeys_ = false;
  return features;
}

// Implementation of class Reader
// ////////////////////////////////

static inline bool in(Reader::Char c,
                      Reader::Char c1,
                      Reader::Char c2,
                      Reader::Char c3,
                      Reader::Char c4) {
  return c == c1 || c == c2 || c == c3 || c == c4;
}

static inline bool in(Reader::Char c,
                      Reader::Char c1,
                      Reader::Char c2,
                      Reader::Char c3,
                      Reader::Char c4,
                      Reader::Char c5) {
  return c == c1 || c == c2 || c == c3 || c == c4 || c == c5;
}

static bool containsNewLine(Reader::Location begin, Reader::Location end) {
  for (; begin < end; ++begin)
    if (*begin == '\n' || *begin == '\r')
      return true;
  return false;
}

// Class Reader
// //////////////////////////////////////////////////////////////////

Reader::Reader()
    : errors_(), document_(), begin_(), end_(), current_(), lastValueEnd_(),
      lastValue_(), commentsBefore_(), features_(Features::all()),
      collectComments_() {}

Reader::Reader(const Features& features)
    : errors_(), document_(), begin_(), end_(), current_(), lastValueEnd_(),
      lastValue_(), commentsBefore_(), features_(features), collectComments_() {
}

bool
Reader::parse(const std::string& document, Value& root, bool collectComments) {
  document_ = document;
  const char* begin = document_.c_str();
  const char* end = begin + document_.length();
  return parse(begin, end, root, collectComments);
}

bool Reader::parse(std::istream& sin, Value& root, bool collectComments) {
  // std::istream_iterator<char> begin(sin);
  // std::istream_iterator<char> end;
  // Those would allow streamed input from a file, if parse() were a
  // template function.

  // Since std::string is reference-counted, this at least does not
  // create an extra copy.
  std::string doc;
  std::getline(sin, doc, (char)EOF);
  return parse(doc, root, collectComments);
}

bool Reader::parse(const char* beginDoc,
                   const char* endDoc,
                   Value& root,
                   bool collectComments) {
  if (!features_.allowComments_) {
    collectComments = false;
  }

  begin_ = beginDoc;
  end_ = endDoc;
  collectComments_ = collectComments;
  current_ = begin_;
  lastValueEnd_ = 0;
  lastValue_ = 0;
  commentsBefore_ = "";
  errors_.clear();
  while (!nodes_.empty())
    nodes_.pop();
  nodes_.push(&root);

  bool successful = readValue();
  Token token;
  skipCommentTokens(token);
  if (collectComments_ && !commentsBefore_.empty())
    root.setComment(commentsBefore_, commentAfter);
  if (features_.strictRoot_) {
    if (!root.isArray() && !root.isObject()) {
      // Set error location to start of doc, ideally should be first token found
      // in doc
      token.type_ = tokenError;
      token.start_ = beginDoc;
      token.end_ = endDoc;
      addError(
          "A valid JSON document must be either an array or an object value.",
          token);
      return false;
    }
  }
  return successful;
}

bool Reader::readValue() {
  Token token;
  skipCommentTokens(token);
  bool successful = true;

  if (collectComments_ && !commentsBefore_.empty()) {
    // Remove newline characters at the end of the comments
    size_t lastNonNewline = commentsBefore_.find_last_not_of("\r\n");
    if (lastNonNewline != std::string::npos) {
      commentsBefore_.erase(lastNonNewline + 1);
    } else {
      commentsBefore_.clear();
    }

    currentValue().setComment(commentsBefore_, commentBefore);
    commentsBefore_ = "";
  }

  switch (token.type_) {
  case tokenObjectBegin:
    successful = readObject(token);
    currentValue().setOffsetLimit(current_ - begin_);
    break;
  case tokenArrayBegin:
    successful = readArray(token);
    currentValue().setOffsetLimit(current_ - begin_);
    break;
  case tokenNumber:
    successful = decodeNumber(token);
    break;
  case tokenString:
    successful = decodeString(token);
    break;
  case tokenTrue:
    currentValue() = true;
    currentValue().setOffsetStart(token.start_ - begin_);
    currentValue().setOffsetLimit(token.end_ - begin_);
    break;
  case tokenFalse:
    currentValue() = false;
    currentValue().setOffsetStart(token.start_ - begin_);
    currentValue().setOffsetLimit(token.end_ - begin_);
    break;
  case tokenNull:
    currentValue() = Value();
    currentValue().setOffsetStart(token.start_ - begin_);
    currentValue().setOffsetLimit(token.end_ - begin_);
    break;
  case tokenArraySeparator:
    if (features_.allowDroppedNullPlaceholders_) {
      // "Un-read" the current token and mark the current value as a null
      // token.
      current_--;
      currentValue() = Value();
      currentValue().setOffsetStart(current_ - begin_ - 1);
      currentValue().setOffsetLimit(current_ - begin_);
      break;
    }
  // Else, fall through...
  default:
    currentValue().setOffsetStart(token.start_ - begin_);
    currentValue().setOffsetLimit(token.end_ - begin_);
    return addError("Syntax error: value, object or array expected.", token);
  }

  if (collectComments_) {
    lastValueEnd_ = current_;
    lastValue_ = &currentValue();
  }

  return successful;
}

void Reader::skipCommentTokens(Token& token) {
  if (features_.allowComments_) {
    do {
      readToken(token);
    } while (token.type_ == tokenComment);
  } else {
    readToken(token);
  }
}

bool Reader::expectToken(TokenType type, Token& token, const char* message) {
  readToken(token);
  if (token.type_ != type)
    return addError(message, token);
  return true;
}

bool Reader::readToken(Token& token) {
  skipSpaces();
  token.start_ = current_;
  Char c = getNextChar();
  bool ok = true;
  switch (c) {
  case '{':
    token.type_ = tokenObjectBegin;
    break;
  case '}':
    token.type_ = tokenObjectEnd;
    break;
  case '[':
    token.type_ = tokenArrayBegin;
    break;
  case ']':
    token.type_ = tokenArrayEnd;
    break;
  case '"':
    token.type_ = tokenString;
    ok = readString();
    break;
  case '/':
    token.type_ = tokenComment;
    ok = readComment();
    break;
  case '0':
  case '1':
  case '2':
  case '3':
  case '4':
  case '5':
  case '6':
  case '7':
  case '8':
  case '9':
  case '-':
    token.type_ = tokenNumber;
    readNumber();
    break;
  case 't':
    token.type_ = tokenTrue;
    ok = match("rue", 3);
    break;
  case 'f':
    token.type_ = tokenFalse;
    ok = match("alse", 4);
    break;
  case 'n':
    token.type_ = tokenNull;
    ok = match("ull", 3);
    break;
  case ',':
    token.type_ = tokenArraySeparator;
    break;
  case ':':
    token.type_ = tokenMemberSeparator;
    break;
  case 0:
    token.type_ = tokenEndOfStream;
    break;
  default:
    ok = false;
    break;
  }
  if (!ok)
    token.type_ = tokenError;
  token.end_ = current_;
  return true;
}

void Reader::skipSpaces() {
  while (current_ != end_) {
    Char c = *current_;
    if (c == ' ' || c == '\t' || c == '\r' || c == '\n')
      ++current_;
    else
      break;
  }
}

bool Reader::match(Location pattern, int patternLength) {
  if (end_ - current_ < patternLength)
    return false;
  int index = patternLength;
  while (index--)
    if (current_[index] != pattern[index])
      return false;
  current_ += patternLength;
  return true;
}

bool Reader::readComment() {
  Location commentBegin = current_ - 1;
  Char c = getNextChar();
  bool successful = false;
  if (c == '*')
    successful = readCStyleComment();
  else if (c == '/')
    successful = readCppStyleComment();
  if (!successful)
    return false;

  if (collectComments_) {
    CommentPlacement placement = commentBefore;
    if (lastValueEnd_ && !containsNewLine(lastValueEnd_, commentBegin)) {
      if (c != '*' || !containsNewLine(commentBegin, current_))
        placement = commentAfterOnSameLine;
    }

    addComment(commentBegin, current_, placement);
  }
  return true;
}

void
Reader::addComment(Location begin, Location end, CommentPlacement placement) {
  assert(collectComments_);
  if (placement == commentAfterOnSameLine) {
    assert(lastValue_ != 0);
    lastValue_->setComment(std::string(begin, end), placement);
  } else {
    commentsBefore_ += std::string(begin, end);
  }
}

bool Reader::readCStyleComment() {
  while (current_ != end_) {
    Char c = getNextChar();
    if (c == '*' && *current_ == '/')
      break;
  }
  return getNextChar() == '/';
}

bool Reader::readCppStyleComment() {
  while (current_ != end_) {
    Char c = getNextChar();
    if (c == '\r' || c == '\n')
      break;
  }
  return true;
}

void Reader::readNumber() {
  while (current_ != end_) {
    if (!(*current_ >= '0' && *current_ <= '9') &&
        !in(*current_, '.', 'e', 'E', '+', '-'))
      break;
    ++current_;
  }
}

bool Reader::readString() {
  Char c = 0;
  while (current_ != end_) {
    c = getNextChar();
    if (c == '\\')
      getNextChar();
    else if (c == '"')
      break;
  }
  return c == '"';
}

bool Reader::readObject(Token& tokenStart) {
  Token tokenName;
  std::string name;
  currentValue() = Value(objectValue);
  currentValue().setOffsetStart(tokenStart.start_ - begin_);
  while (readToken(tokenName)) {
    bool initialTokenOk = true;
    while (tokenName.type_ == tokenComment && initialTokenOk)
      initialTokenOk = readToken(tokenName);
    if (!initialTokenOk)
      break;
    if (tokenName.type_ == tokenObjectEnd && name.empty()) // empty object
      return true;
    name = "";
    if (tokenName.type_ == tokenString) {
      if (!decodeString(tokenName, name))
        return recoverFromError(tokenObjectEnd);
    } else if (tokenName.type_ == tokenNumber && features_.allowNumericKeys_) {
      Value numberName;
      if (!decodeNumber(tokenName, numberName))
        return recoverFromError(tokenObjectEnd);
      name = numberName.asString();
    } else {
      break;
    }

    Token colon;
    if (!readToken(colon) || colon.type_ != tokenMemberSeparator) {
      return addErrorAndRecover(
          "Missing ':' after object member name", colon, tokenObjectEnd);
    }
    Value& value = currentValue()[name];
    nodes_.push(&value);
    bool ok = readValue();
    nodes_.pop();
    if (!ok) // error already set
      return recoverFromError(tokenObjectEnd);

    Token comma;
    if (!readToken(comma) ||
        (comma.type_ != tokenObjectEnd && comma.type_ != tokenArraySeparator &&
         comma.type_ != tokenComment)) {
      return addErrorAndRecover(
          "Missing ',' or '}' in object declaration", comma, tokenObjectEnd);
    }
    bool finalizeTokenOk = true;
    while (comma.type_ == tokenComment && finalizeTokenOk)
      finalizeTokenOk = readToken(comma);
    if (comma.type_ == tokenObjectEnd)
      return true;
  }
  return addErrorAndRecover(
      "Missing '}' or object member name", tokenName, tokenObjectEnd);
}

bool Reader::readArray(Token& tokenStart) {
  currentValue() = Value(arrayValue);
  currentValue().setOffsetStart(tokenStart.start_ - begin_);
  skipSpaces();
  if (*current_ == ']') // empty array
  {
    Token endArray;
    readToken(endArray);
    return true;
  }
  int index = 0;
  for (;;) {
    Value& value = currentValue()[index++];
    nodes_.push(&value);
    bool ok = readValue();
    nodes_.pop();
    if (!ok) // error already set
      return recoverFromError(tokenArrayEnd);

    Token token;
    // Accept Comment after last item in the array.
    ok = readToken(token);
    while (token.type_ == tokenComment && ok) {
      ok = readToken(token);
    }
    bool badTokenType =
        (token.type_ != tokenArraySeparator && token.type_ != tokenArrayEnd);
    if (!ok || badTokenType) {
      return addErrorAndRecover(
          "Missing ',' or ']' in array declaration", token, tokenArrayEnd);
    }
    if (token.type_ == tokenArrayEnd)
      break;
  }
  return true;
}

bool Reader::decodeNumber(Token& token) {
  Value decoded;
  if (!decodeNumber(token, decoded))
    return false;
  currentValue() = decoded;
  currentValue().setOffsetStart(token.start_ - begin_);
  currentValue().setOffsetLimit(token.end_ - begin_);
  return true;
}

bool Reader::decodeNumber(Token& token, Value& decoded) {
  bool isDouble = false;
  for (Location inspect = token.start_; inspect != token.end_; ++inspect) {
    isDouble = isDouble || in(*inspect, '.', 'e', 'E', '+') ||
               (*inspect == '-' && inspect != token.start_);
  }
  if (isDouble)
    return decodeDouble(token, decoded);
  // Attempts to parse the number as an integer. If the number is
  // larger than the maximum supported value of an integer then
  // we decode the number as a double.
  Location current = token.start_;
  bool isNegative = *current == '-';
  if (isNegative)
    ++current;
  Value::LargestUInt maxIntegerValue =
      isNegative ? Value::LargestUInt(-Value::minLargestInt)
                 : Value::maxLargestUInt;
  Value::LargestUInt threshold = maxIntegerValue / 10;
  Value::LargestUInt value = 0;
  while (current < token.end_) {
    Char c = *current++;
    if (c < '0' || c > '9')
      return addError("'" + std::string(token.start_, token.end_) +
                          "' is not a number.",
                      token);
    Value::UInt digit(c - '0');
    if (value >= threshold) {
      // We've hit or exceeded the max value divided by 10 (rounded down). If
      // a) we've only just touched the limit, b) this is the last digit, and
      // c) it's small enough to fit in that rounding delta, we're okay.
      // Otherwise treat this number as a double to avoid overflow.
      if (value > threshold || current != token.end_ ||
          digit > maxIntegerValue % 10) {
        return decodeDouble(token, decoded);
      }
    }
    value = value * 10 + digit;
  }
  if (isNegative)
    decoded = -Value::LargestInt(value);
  else if (value <= Value::LargestUInt(Value::maxInt))
    decoded = Value::LargestInt(value);
  else
    decoded = value;
  return true;
}

bool Reader::decodeDouble(Token& token) {
  Value decoded;
  if (!decodeDouble(token, decoded))
    return false;
  currentValue() = decoded;
  currentValue().setOffsetStart(token.start_ - begin_);
  currentValue().setOffsetLimit(token.end_ - begin_);
  return true;
}

bool Reader::decodeDouble(Token& token, Value& decoded) {
  double value = 0;
  const int bufferSize = 32;
  int count;
  int length = int(token.end_ - token.start_);

  // Sanity check to avoid buffer overflow exploits.
  if (length < 0) {
    return addError("Unable to parse token length", token);
  }

  // Avoid using a string constant for the format control string given to
  // sscanf, as this can cause hard to debug crashes on OS X. See here for more
  // info:
  //
  //     http://developer.apple.com/library/mac/#DOCUMENTATION/DeveloperTools/gcc-4.0.1/gcc/Incompatibilities.html
  char format[] = "%lf";

  if (length <= bufferSize) {
    Char buffer[bufferSize + 1];
    memcpy(buffer, token.start_, length);
    buffer[length] = 0;
    count = sscanf(buffer, format, &value);
  } else {
    std::string buffer(token.start_, token.end_);
    count = sscanf(buffer.c_str(), format, &value);
  }

  if (count != 1)
    return addError("'" + std::string(token.start_, token.end_) +
                        "' is not a number.",
                    token);
  decoded = value;
  return true;
}

bool Reader::decodeString(Token& token) {
  std::string decoded;
  if (!decodeString(token, decoded))
    return false;
  currentValue() = decoded;
  currentValue().setOffsetStart(token.start_ - begin_);
  currentValue().setOffsetLimit(token.end_ - begin_);
  return true;
}

bool Reader::decodeString(Token& token, std::string& decoded) {
  decoded.reserve(token.end_ - token.start_ - 2);
  Location current = token.start_ + 1; // skip '"'
  Location end = token.end_ - 1;       // do not include '"'
  while (current != end) {
    Char c = *current++;
    if (c == '"')
      break;
    else if (c == '\\') {
      if (current == end)
        return addError("Empty escape sequence in string", token, current);
      Char escape = *current++;
      switch (escape) {
      case '"':
        decoded += '"';
        break;
      case '/':
        decoded += '/';
        break;
      case '\\':
        decoded += '\\';
        break;
      case 'b':
        decoded += '\b';
        break;
      case 'f':
        decoded += '\f';
        break;
      case 'n':
        decoded += '\n';
        break;
      case 'r':
        decoded += '\r';
        break;
      case 't':
        decoded += '\t';
        break;
      case 'u': {
        unsigned int unicode;
        if (!decodeUnicodeCodePoint(token, current, end, unicode))
          return false;
        decoded += codePointToUTF8(unicode);
      } break;
      default:
        return addError("Bad escape sequence in string", token, current);
      }
    } else {
      decoded += c;
    }
  }
  return true;
}

bool Reader::decodeUnicodeCodePoint(Token& token,
                                    Location& current,
                                    Location end,
                                    unsigned int& unicode) {

  if (!decodeUnicodeEscapeSequence(token, current, end, unicode))
    return false;
  if (unicode >= 0xD800 && unicode <= 0xDBFF) {
    // surrogate pairs
    if (end - current < 6)
      return addError(
          "additional six characters expected to parse unicode surrogate pair.",
          token,
          current);
    unsigned int surrogatePair;
    if (*(current++) == '\\' && *(current++) == 'u') {
      if (decodeUnicodeEscapeSequence(token, current, end, surrogatePair)) {
        unicode = 0x10000 + ((unicode & 0x3FF) << 10) + (surrogatePair & 0x3FF);
      } else
        return false;
    } else
      return addError("expecting another \\u token to begin the second half of "
                      "a unicode surrogate pair",
                      token,
                      current);
  }
  return true;
}

bool Reader::decodeUnicodeEscapeSequence(Token& token,
                                         Location& current,
                                         Location end,
                                         unsigned int& unicode) {
  if (end - current < 4)
    return addError(
        "Bad unicode escape sequence in string: four digits expected.",
        token,
        current);
  unicode = 0;
  for (int index = 0; index < 4; ++index) {
    Char c = *current++;
    unicode *= 16;
    if (c >= '0' && c <= '9')
      unicode += c - '0';
    else if (c >= 'a' && c <= 'f')
      unicode += c - 'a' + 10;
    else if (c >= 'A' && c <= 'F')
      unicode += c - 'A' + 10;
    else
      return addError(
          "Bad unicode escape sequence in string: hexadecimal digit expected.",
          token,
          current);
  }
  return true;
}

bool
Reader::addError(const std::string& message, Token& token, Location extra) {
  ErrorInfo info;
  info.token_ = token;
  info.message_ = message;
  info.extra_ = extra;
  errors_.push_back(info);
  return false;
}

bool Reader::recoverFromError(TokenType skipUntilToken) {
  int errorCount = int(errors_.size());
  Token skip;
  for (;;) {
    if (!readToken(skip))
      errors_.resize(errorCount); // discard errors caused by recovery
    if (skip.type_ == skipUntilToken || skip.type_ == tokenEndOfStream)
      break;
  }
  errors_.resize(errorCount);
  return false;
}

bool Reader::addErrorAndRecover(const std::string& message,
                                Token& token,
                                TokenType skipUntilToken) {
  addError(message, token);
  return recoverFromError(skipUntilToken);
}

Value& Reader::currentValue() { return *(nodes_.top()); }

Reader::Char Reader::getNextChar() {
  if (current_ == end_)
    return 0;
  return *current_++;
}

void Reader::getLocationLineAndColumn(Location location,
                                      int& line,
                                      int& column) const {
  Location current = begin_;
  Location lastLineStart = current;
  line = 0;
  while (current < location && current != end_) {
    Char c = *current++;
    if (c == '\r') {
      if (*current == '\n')
        ++current;
      lastLineStart = current;
      ++line;
    } else if (c == '\n') {
      lastLineStart = current;
      ++line;
    }
  }
  // column & line start at 1
  column = int(location - lastLineStart) + 1;
  ++line;
}

std::string Reader::getLocationLineAndColumn(Location location) const {
  int line, column;
  getLocationLineAndColumn(location, line, column);
  char buffer[18 + 16 + 16 + 1];
#if defined(_MSC_VER) && defined(__STDC_SECURE_LIB__)
#if defined(WINCE)
  _snprintf(buffer, sizeof(buffer), "Line %d, Column %d", line, column);
#else
  sprintf_s(buffer, sizeof(buffer), "Line %d, Column %d", line, column);
#endif
#else
  snprintf(buffer, sizeof(buffer), "Line %d, Column %d", line, column);
#endif
  return buffer;
}

// Deprecated. Preserved for backward compatibility
std::string Reader::getFormatedErrorMessages() const {
  return getFormattedErrorMessages();
}

std::string Reader::getFormattedErrorMessages() const {
  std::string formattedMessage;
  for (Errors::const_iterator itError = errors_.begin();
       itError != errors_.end();
       ++itError) {
    const ErrorInfo& error = *itError;
    formattedMessage +=
        "* " + getLocationLineAndColumn(error.token_.start_) + "\n";
    formattedMessage += "  " + error.message_ + "\n";
    if (error.extra_)
      formattedMessage +=
          "See " + getLocationLineAndColumn(error.extra_) + " for detail.\n";
  }
  return formattedMessage;
}

std::vector<Reader::StructuredError> Reader::getStructuredErrors() const {
  std::vector<Reader::StructuredError> allErrors;
  for (Errors::const_iterator itError = errors_.begin();
       itError != errors_.end();
       ++itError) {
    const ErrorInfo& error = *itError;
    Reader::StructuredError structured;
    structured.offset_start = error.token_.start_ - begin_;
    structured.offset_limit = error.token_.end_ - begin_;
    structured.message = error.message_;
    allErrors.push_back(structured);
  }
  return allErrors;
}

bool Reader::pushError(const Value& value, const std::string& message) {
  size_t length = end_ - begin_;
  if(value.getOffsetStart() > length
    || value.getOffsetLimit() > length)
    return false;
  Token token;
  token.type_ = tokenError;
  token.start_ = begin_ + value.getOffsetStart();
  token.end_ = end_ + value.getOffsetLimit();
  ErrorInfo info;
  info.token_ = token;
  info.message_ = message;
  info.extra_ = 0;
  errors_.push_back(info);
  return true;
}

bool Reader::pushError(const Value& value, const std::string& message, const Value& extra) {
  size_t length = end_ - begin_;
  if(value.getOffsetStart() > length
    || value.getOffsetLimit() > length
    || extra.getOffsetLimit() > length)
    return false;
  Token token;
  token.type_ = tokenError;
  token.start_ = begin_ + value.getOffsetStart();
  token.end_ = begin_ + value.getOffsetLimit();
  ErrorInfo info;
  info.token_ = token;
  info.message_ = message;
  info.extra_ = begin_ + extra.getOffsetStart();
  errors_.push_back(info);
  return true;
}

bool Reader::good() const {
  return !errors_.size();
}

std::istream& operator>>(std::istream& sin, Value& root) {
  Json::Reader reader;
  bool ok = reader.parse(sin, root, true);
  if (!ok) {
    fprintf(stderr,
            "Error from reader: %s",
            reader.getFormattedErrorMessages().c_str());

    JSON_FAIL_MESSAGE("reader error");
  }
  return sin;
}

} // namespace Json