lib/yamlcpp/src/scanner.cpp

#include <cassert>
#include <memory>

#include "exp.h"
#include "scanner.h"
#include "token.h"
#include "yaml-cpp/exceptions.h"  // IWYU pragma: keep

namespace YAML {
Scanner::Scanner(std::istream& in)
    : INPUT(in),
      m_tokens{},
      m_startedStream(false),
      m_endedStream(false),
      m_simpleKeyAllowed(false),
      m_scalarValueAllowed(false),
      m_canBeJSONFlow(false),
      m_simpleKeys{},
      m_indents{},
      m_indentRefs{},
      m_flows{} {}

Scanner::~Scanner() = default;

bool Scanner::empty() {
  EnsureTokensInQueue();
  return m_tokens.empty();
}

void Scanner::pop() {
  EnsureTokensInQueue();
  if (!m_tokens.empty())
    m_tokens.pop();
}

Token& Scanner::peek() {
  EnsureTokensInQueue();
  assert(!m_tokens.empty());  // should we be asserting here? I mean, we really
                              // just be checking
                              // if it's empty before peeking.

#if 0
		static Token *pLast = 0;
		if(pLast != &m_tokens.front())
			std::cerr << "peek: " << m_tokens.front() << "\n";
		pLast = &m_tokens.front();
#endif

  return m_tokens.front();
}

Mark Scanner::mark() const { return INPUT.mark(); }

void Scanner::EnsureTokensInQueue() {
  while (true) {
    if (!m_tokens.empty()) {
      Token& token = m_tokens.front();

      // if this guy's valid, then we're done
      if (token.status == Token::VALID) {
        return;
      }

      // here's where we clean up the impossible tokens
      if (token.status == Token::INVALID) {
        m_tokens.pop();
        continue;
      }

      // note: what's left are the unverified tokens
    }

    // no token? maybe we've actually finished
    if (m_endedStream) {
      return;
    }

    // no? then scan...
    ScanNextToken();
  }
}

void Scanner::ScanNextToken() {
  if (m_endedStream) {
    return;
  }

  if (!m_startedStream) {
    return StartStream();
  }

  // get rid of whitespace, etc. (in between tokens it should be irrelevant)
  ScanToNextToken();

  // maybe need to end some blocks
  PopIndentToHere();

  // *****
  // And now branch based on the next few characters!
  // *****

  // end of stream
  if (!INPUT) {
    return EndStream();
  }

  if (INPUT.column() == 0 && INPUT.peek() == Keys::Directive) {
    return ScanDirective();
  }

  // document token
  if (INPUT.column() == 0 && Exp::DocStart().Matches(INPUT)) {
    return ScanDocStart();
  }

  if (INPUT.column() == 0 && Exp::DocEnd().Matches(INPUT)) {
    return ScanDocEnd();
  }

  // flow start/end/entry
  if (INPUT.peek() == Keys::FlowSeqStart ||
      INPUT.peek() == Keys::FlowMapStart) {
    return ScanFlowStart();
  }

  if (INPUT.peek() == Keys::FlowSeqEnd || INPUT.peek() == Keys::FlowMapEnd) {
    return ScanFlowEnd();
  }

  if (INPUT.peek() == Keys::FlowEntry) {
    // values starting with `,` are not allowed.
    // eg: reject `,foo`
    if (INPUT.column() == 0) {
      throw ParserException(INPUT.mark(), ErrorMsg::UNEXPECTED_FLOW);
    }
    // if we already parsed a quoted scalar value and we are not in a flow,
    // then `,` is not a valid character.
    // eg: reject `"foo",`
    if (!m_scalarValueAllowed) {
      throw ParserException(INPUT.mark(), ErrorMsg::UNEXPECTED_SCALAR);
    }
    return ScanFlowEntry();
  }

  // block/map stuff
  if (Exp::BlockEntry().Matches(INPUT)) {
    return ScanBlockEntry();
  }

  if ((InBlockContext() ? Exp::Key() : Exp::KeyInFlow()).Matches(INPUT)) {
    return ScanKey();
  }

  if (GetValueRegex().Matches(INPUT)) {
    return ScanValue();
  }

  // alias/anchor
  if (INPUT.peek() == Keys::Alias || INPUT.peek() == Keys::Anchor) {
    return ScanAnchorOrAlias();
  }

  // tag
  if (INPUT.peek() == Keys::Tag) {
    return ScanTag();
  }

  // special scalars
  if (InBlockContext() && (INPUT.peek() == Keys::LiteralScalar ||
                           INPUT.peek() == Keys::FoldedScalar)) {
    return ScanBlockScalar();
  }

  // if we already parsed a quoted scalar value in this line,
  // another scalar value is an error.
  // eg: reject `"foo" "bar"`
  if (!m_scalarValueAllowed) {
    throw ParserException(INPUT.mark(), ErrorMsg::UNEXPECTED_SCALAR);
  }

  if (INPUT.peek() == '\'' || INPUT.peek() == '\"') {
    return ScanQuotedScalar();
  }

  // plain scalars
  if ((InBlockContext() ? Exp::PlainScalar() : Exp::PlainScalarInFlow())
          .Matches(INPUT)) {
    return ScanPlainScalar();
  }

  // don't know what it is!
  throw ParserException(INPUT.mark(), ErrorMsg::UNKNOWN_TOKEN);
}

void Scanner::ScanToNextToken() {
  while (true) {
    // first eat whitespace
    while (INPUT && IsWhitespaceToBeEaten(INPUT.peek())) {
      if (InBlockContext() && Exp::Tab().Matches(INPUT)) {
        m_simpleKeyAllowed = false;
      }
      INPUT.eat(1);
    }

    // then eat a comment
    if (Exp::Comment().Matches(INPUT)) {
      // eat until line break
      while (INPUT && !Exp::Break().Matches(INPUT)) {
        INPUT.eat(1);
      }
    }

    // if it's NOT a line break, then we're done!
    if (!Exp::Break().Matches(INPUT)) {
      break;
    }

    // otherwise, let's eat the line break and keep going
    int n = Exp::Break().Match(INPUT);
    INPUT.eat(n);

    // oh yeah, and let's get rid of that simple key
    InvalidateSimpleKey();

    // new line - we accept a scalar value now
    m_scalarValueAllowed = true;

    // new line - we may be able to accept a simple key now
    if (InBlockContext()) {
      m_simpleKeyAllowed = true;
    }
  }
}

///////////////////////////////////////////////////////////////////////
// Misc. helpers

// IsWhitespaceToBeEaten
// . We can eat whitespace if it's a space or tab
// . Note: originally tabs in block context couldn't be eaten
//         "where a simple key could be allowed
//         (i.e., not at the beginning of a line, or following '-', '?', or
// ':')"
//   I think this is wrong, since tabs can be non-content whitespace; it's just
//   that they can't contribute to indentation, so once you've seen a tab in a
//   line, you can't start a simple key
bool Scanner::IsWhitespaceToBeEaten(char ch) {
  if (ch == ' ') {
    return true;
  }

  if (ch == '\t') {
    return true;
  }

  return false;
}

const RegEx& Scanner::GetValueRegex() const {
  if (InBlockContext()) {
    return Exp::Value();
  }

  return m_canBeJSONFlow ? Exp::ValueInJSONFlow() : Exp::ValueInFlow();
}

void Scanner::StartStream() {
  m_startedStream = true;
  m_simpleKeyAllowed = true;
  m_scalarValueAllowed = true;
  std::unique_ptr<IndentMarker> pIndent(
      new IndentMarker(-1, IndentMarker::NONE));
  m_indentRefs.push_back(std::move(pIndent));
  m_indents.push(&m_indentRefs.back());
}

void Scanner::EndStream() {
  // force newline
  if (INPUT.column() > 0) {
    INPUT.ResetColumn();
  }

  PopAllIndents();
  PopAllSimpleKeys();

  m_simpleKeyAllowed = false;
  m_scalarValueAllowed = false;
  m_endedStream = true;
}

Token* Scanner::PushToken(Token::TYPE type) {
  m_tokens.push(Token(type, INPUT.mark()));
  return &m_tokens.back();
}

Token::TYPE Scanner::GetStartTokenFor(IndentMarker::INDENT_TYPE type) const {
  switch (type) {
    case IndentMarker::SEQ:
      return Token::BLOCK_SEQ_START;
    case IndentMarker::MAP:
      return Token::BLOCK_MAP_START;
    case IndentMarker::NONE:
      assert(false);
      break;
  }
  assert(false);
  throw std::runtime_error("yaml-cpp: internal error, invalid indent type");
}

Scanner::IndentMarker* Scanner::PushIndentTo(int column,
                                             IndentMarker::INDENT_TYPE type) {
  // are we in flow?
  if (InFlowContext()) {
    return nullptr;
  }

  std::unique_ptr<IndentMarker> pIndent(new IndentMarker(column, type));
  IndentMarker& indent = *pIndent;
  const IndentMarker& lastIndent = *m_indents.top();

  // is this actually an indentation?
  if (indent.column < lastIndent.column) {
    return nullptr;
  }
  if (indent.column == lastIndent.column &&
      !(indent.type == IndentMarker::SEQ &&
        lastIndent.type == IndentMarker::MAP)) {
    return nullptr;
  }

  // push a start token
  indent.pStartToken = PushToken(GetStartTokenFor(type));

  // and then the indent
  m_indents.push(&indent);
  m_indentRefs.push_back(std::move(pIndent));
  return &m_indentRefs.back();
}

void Scanner::PopIndentToHere() {
  // are we in flow?
  if (InFlowContext()) {
    return;
  }

  // now pop away
  while (!m_indents.empty()) {
    const IndentMarker& indent = *m_indents.top();
    if (indent.column < INPUT.column()) {
      break;
    }
    if (indent.column == INPUT.column() &&
        !(indent.type == IndentMarker::SEQ &&
          !Exp::BlockEntry().Matches(INPUT))) {
      break;
    }

    PopIndent();
  }

  while (!m_indents.empty() &&
         m_indents.top()->status == IndentMarker::INVALID) {
    PopIndent();
  }
}

void Scanner::PopAllIndents() {
  // are we in flow?
  if (InFlowContext()) {
    return;
  }

  // now pop away
  while (!m_indents.empty()) {
    const IndentMarker& indent = *m_indents.top();
    if (indent.type == IndentMarker::NONE) {
      break;
    }

    PopIndent();
  }
}

void Scanner::PopIndent() {
  const IndentMarker& indent = *m_indents.top();
  m_indents.pop();

  if (indent.status != IndentMarker::VALID) {
    InvalidateSimpleKey();
    return;
  }

  if (indent.type == IndentMarker::SEQ) {
    m_tokens.push(Token(Token::BLOCK_SEQ_END, INPUT.mark()));
  } else if (indent.type == IndentMarker::MAP) {
    m_tokens.push(Token(Token::BLOCK_MAP_END, INPUT.mark()));
  }
}

int Scanner::GetTopIndent() const {
  if (m_indents.empty()) {
    return 0;
  }
  return m_indents.top()->column;
}

void Scanner::ThrowParserException(const std::string& msg) const {
  Mark mark = Mark::null_mark();
  if (!m_tokens.empty()) {
    const Token& token = m_tokens.front();
    mark = token.mark;
  }
  throw ParserException(mark, msg);
}
}  // namespace YAML