third_party/WebKit/Source/core/html/track/vtt/VTTScanner.h

/*
 * Copyright (c) 2013, Opera Software ASA. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 * 3. Neither the name of Opera Software ASA 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 HOLDER 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.
 */

#ifndef VTTScanner_h
#define VTTScanner_h

#include "core/CoreExport.h"
#include "wtf/Allocator.h"
#include "wtf/text/ParsingUtilities.h"
#include "wtf/text/WTFString.h"

namespace blink {

// Helper class for "scanning" an input string and performing parsing of
// "micro-syntax"-like constructs.
//
// There's two primary operations: match and scan.
//
// The 'match' operation matches an explicitly or implicitly specified sequence
// against the characters ahead of the current input pointer, and returns true
// if the sequence can be matched.
//
// The 'scan' operation performs a 'match', and if the match is successful it
// advance the input pointer past the matched sequence.
class CORE_EXPORT VTTScanner {
  STACK_ALLOCATED();
  WTF_MAKE_NONCOPYABLE(VTTScanner);

 public:
  explicit VTTScanner(const String& line);

  typedef const LChar* Position;

  class Run {
    STACK_ALLOCATED();

   public:
    Run(Position start, Position end, bool is8Bit)
        : m_start(start), m_end(end), m_is8Bit(is8Bit) {}

    Position start() const { return m_start; }
    Position end() const { return m_end; }

    bool isEmpty() const { return m_start == m_end; }
    size_t length() const;

   private:
    Position m_start;
    Position m_end;
    bool m_is8Bit;
  };

  // Check if the input pointer points at the specified position.
  bool isAt(Position checkPosition) const {
    return getPosition() == checkPosition;
  }
  // Check if the input pointer points at the end of the input.
  bool isAtEnd() const { return getPosition() == end(); }
  // Match the character |c| against the character at the input pointer
  // (~lookahead).
  bool match(char c) const { return !isAtEnd() && currentChar() == c; }
  // Scan the character |c|.
  bool scan(char);
  // Scan the first |charactersCount| characters of the string |characters|.
  bool scan(const LChar* characters, size_t charactersCount);

  // Scan the literal |characters|.
  template <unsigned charactersCount>
  bool scan(const char (&characters)[charactersCount]);

  // Skip (advance the input pointer) as long as the specified
  // |characterPredicate| returns true, and the input pointer is not passed
  // the end of the input.
  template <bool characterPredicate(UChar)>
  void skipWhile();

  // Like skipWhile, but using a negated predicate.
  template <bool characterPredicate(UChar)>
  void skipUntil();

  // Return the run of characters for which the specified
  // |characterPredicate| returns true. The start of the run will be the
  // current input pointer.
  template <bool characterPredicate(UChar)>
  Run collectWhile();

  // Like collectWhile, but using a negated predicate.
  template <bool characterPredicate(UChar)>
  Run collectUntil();

  // Scan the string |toMatch|, using the specified |run| as the sequence to
  // match against.
  bool scanRun(const Run&, const String& toMatch);

  // Skip to the end of the specified |run|.
  void skipRun(const Run&);

  // Return the String made up of the characters in |run|, and advance the
  // input pointer to the end of the run.
  String extractString(const Run&);

  // Return a String constructed from the rest of the input (between input
  // pointer and end of input), and advance the input pointer accordingly.
  String restOfInputAsString();

  // Scan a set of ASCII digits from the input. Return the number of digits
  // scanned, and set |number| to the computed value. If the digits make up a
  // number that does not fit the 'int' type, |number| is set to INT_MAX.
  // Note: Does not handle sign.
  unsigned scanDigits(int& number);

  // Scan a floating point value on one of the forms: \d+\.? \d+\.\d+ \.\d+
  bool scanFloat(float& number);

  // Scan a floating point value (per scanFloat) followed by a '%'.
  bool scanPercentage(float& percentage);

 protected:
  Position getPosition() const { return m_data.characters8; }
  Position end() const { return m_end.characters8; }
  void seekTo(Position);
  UChar currentChar() const;
  void advance(unsigned amount = 1);
  // Adapt a UChar-predicate to an LChar-predicate.
  // (For use with skipWhile/Until from ParsingUtilities.h).
  template <bool characterPredicate(UChar)>
  static inline bool LCharPredicateAdapter(LChar c) {
    return characterPredicate(c);
  }
  union {
    const LChar* characters8;
    const UChar* characters16;
  } m_data;
  union {
    const LChar* characters8;
    const UChar* characters16;
  } m_end;
  bool m_is8Bit;
};

inline size_t VTTScanner::Run::length() const {
  if (m_is8Bit)
    return m_end - m_start;
  return reinterpret_cast<const UChar*>(m_end) -
         reinterpret_cast<const UChar*>(m_start);
}

template <unsigned charactersCount>
inline bool VTTScanner::scan(const char (&characters)[charactersCount]) {
  return scan(reinterpret_cast<const LChar*>(characters), charactersCount - 1);
}

template <bool characterPredicate(UChar)>
inline void VTTScanner::skipWhile() {
  if (m_is8Bit)
    ::skipWhile<LChar, LCharPredicateAdapter<characterPredicate>>(
        m_data.characters8, m_end.characters8);
  else
    ::skipWhile<UChar, characterPredicate>(m_data.characters16,
                                           m_end.characters16);
}

template <bool characterPredicate(UChar)>
inline void VTTScanner::skipUntil() {
  if (m_is8Bit)
    ::skipUntil<LChar, LCharPredicateAdapter<characterPredicate>>(
        m_data.characters8, m_end.characters8);
  else
    ::skipUntil<UChar, characterPredicate>(m_data.characters16,
                                           m_end.characters16);
}

template <bool characterPredicate(UChar)>
inline VTTScanner::Run VTTScanner::collectWhile() {
  if (m_is8Bit) {
    const LChar* current = m_data.characters8;
    ::skipWhile<LChar, LCharPredicateAdapter<characterPredicate>>(
        current, m_end.characters8);
    return Run(getPosition(), current, m_is8Bit);
  }
  const UChar* current = m_data.characters16;
  ::skipWhile<UChar, characterPredicate>(current, m_end.characters16);
  return Run(getPosition(), reinterpret_cast<Position>(current), m_is8Bit);
}

template <bool characterPredicate(UChar)>
inline VTTScanner::Run VTTScanner::collectUntil() {
  if (m_is8Bit) {
    const LChar* current = m_data.characters8;
    ::skipUntil<LChar, LCharPredicateAdapter<characterPredicate>>(
        current, m_end.characters8);
    return Run(getPosition(), current, m_is8Bit);
  }
  const UChar* current = m_data.characters16;
  ::skipUntil<UChar, characterPredicate>(current, m_end.characters16);
  return Run(getPosition(), reinterpret_cast<Position>(current), m_is8Bit);
}

inline void VTTScanner::seekTo(Position position) {
  DCHECK_LE(position, end());
  m_data.characters8 = position;
}

inline UChar VTTScanner::currentChar() const {
  DCHECK_LT(getPosition(), end());
  return m_is8Bit ? *m_data.characters8 : *m_data.characters16;
}

inline void VTTScanner::advance(unsigned amount) {
  DCHECK_LT(getPosition(), end());
  if (m_is8Bit)
    m_data.characters8 += amount;
  else
    m_data.characters16 += amount;
}

}  // namespace blink

#endif