third_party/WebKit/Source/core/svg/SVGParserUtilities.cpp

/*
 * Copyright (C) 2002, 2003 The Karbon Developers
 * Copyright (C) 2006 Alexander Kellett <lypanov@kde.org>
 * Copyright (C) 2006, 2007 Rob Buis <buis@kde.org>
 * Copyright (C) 2007, 2009, 2013 Apple Inc. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public License
 * along with this library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 */

#include "core/svg/SVGParserUtilities.h"

#include "wtf/MathExtras.h"
#include <limits>

namespace blink {

template <typename FloatType>
static inline bool isValidRange(const FloatType& x) {
  static const FloatType max = std::numeric_limits<FloatType>::max();
  return x >= -max && x <= max;
}

// We use this generic parseNumber function to allow the Path parsing code to
// work at a higher precision internally, without any unnecessary runtime cost
// or code complexity.
template <typename CharType, typename FloatType>
static bool genericParseNumber(const CharType*& cursor,
                               const CharType* end,
                               FloatType& number,
                               WhitespaceMode mode) {
  FloatType integer, decimal, frac, exponent;
  int sign, expsign;

  exponent = 0;
  integer = 0;
  frac = 1;
  decimal = 0;
  sign = 1;
  expsign = 1;

  if (mode & AllowLeadingWhitespace)
    skipOptionalSVGSpaces(cursor, end);

  const CharType* ptr = cursor;
  // read the sign
  if (ptr < end && *ptr == '+')
    ptr++;
  else if (ptr < end && *ptr == '-') {
    ptr++;
    sign = -1;
  }

  if (ptr == end || ((*ptr < '0' || *ptr > '9') && *ptr != '.'))
    // The first character of a number must be one of [0-9+-.]
    return false;

  // read the integer part, build right-to-left
  const CharType* digitsStart = ptr;
  while (ptr < end && *ptr >= '0' && *ptr <= '9')
    ++ptr;  // Advance to first non-digit.

  if (ptr != digitsStart) {
    const CharType* ptrScanIntPart = ptr - 1;
    FloatType multiplier = 1;
    while (ptrScanIntPart >= digitsStart) {
      integer += multiplier * static_cast<FloatType>(*(ptrScanIntPart--) - '0');
      multiplier *= 10;
    }
    // Bail out early if this overflows.
    if (!isValidRange(integer))
      return false;
  }

  if (ptr < end && *ptr == '.') {  // read the decimals
    ptr++;

    // There must be a least one digit following the .
    if (ptr >= end || *ptr < '0' || *ptr > '9')
      return false;

    while (ptr < end && *ptr >= '0' && *ptr <= '9')
      decimal += (*(ptr++) - '0') * (frac *= static_cast<FloatType>(0.1));
  }

  // When we get here we should have consumed either a digit for the integer
  // part or a fractional part (with at least one digit after the '.'.)
  ASSERT(digitsStart != ptr);

  // read the exponent part
  if (ptr + 1 < end && (*ptr == 'e' || *ptr == 'E') &&
      (ptr[1] != 'x' && ptr[1] != 'm')) {
    ptr++;

    // read the sign of the exponent
    if (*ptr == '+')
      ptr++;
    else if (*ptr == '-') {
      ptr++;
      expsign = -1;
    }

    // There must be an exponent
    if (ptr >= end || *ptr < '0' || *ptr > '9')
      return false;

    while (ptr < end && *ptr >= '0' && *ptr <= '9') {
      exponent *= static_cast<FloatType>(10);
      exponent += *ptr - '0';
      ptr++;
    }
    // Make sure exponent is valid.
    if (!isValidRange(exponent) ||
        exponent > std::numeric_limits<FloatType>::max_exponent)
      return false;
  }

  number = integer + decimal;
  number *= sign;

  if (exponent)
    number *=
        static_cast<FloatType>(pow(10.0, expsign * static_cast<int>(exponent)));

  // Don't return Infinity() or NaN().
  if (!isValidRange(number))
    return false;

  // A valid number has been parsed. Commit cursor.
  cursor = ptr;

  if (mode & AllowTrailingWhitespace)
    skipOptionalSVGSpacesOrDelimiter(cursor, end);

  return true;
}

bool parseNumber(const LChar*& ptr,
                 const LChar* end,
                 float& number,
                 WhitespaceMode mode) {
  return genericParseNumber(ptr, end, number, mode);
}

bool parseNumber(const UChar*& ptr,
                 const UChar* end,
                 float& number,
                 WhitespaceMode mode) {
  return genericParseNumber(ptr, end, number, mode);
}

// only used to parse largeArcFlag and sweepFlag which must be a "0" or "1"
// and might not have any whitespace/comma after it
template <typename CharType>
bool genericParseArcFlag(const CharType*& ptr,
                         const CharType* end,
                         bool& flag) {
  if (ptr >= end)
    return false;
  const CharType flagChar = *ptr;
  if (flagChar == '0')
    flag = false;
  else if (flagChar == '1')
    flag = true;
  else
    return false;

  ptr++;
  skipOptionalSVGSpacesOrDelimiter(ptr, end);

  return true;
}

bool parseArcFlag(const LChar*& ptr, const LChar* end, bool& flag) {
  return genericParseArcFlag(ptr, end, flag);
}

bool parseArcFlag(const UChar*& ptr, const UChar* end, bool& flag) {
  return genericParseArcFlag(ptr, end, flag);
}

template <typename CharType>
static bool genericParseNumberOptionalNumber(const CharType*& ptr,
                                             const CharType* end,
                                             float& x,
                                             float& y) {
  if (!parseNumber(ptr, end, x))
    return false;

  if (ptr == end)
    y = x;
  else if (!parseNumber(ptr, end, y, AllowLeadingAndTrailingWhitespace))
    return false;

  return ptr == end;
}

bool parseNumberOptionalNumber(const String& string, float& x, float& y) {
  if (string.isEmpty())
    return false;

  if (string.is8Bit()) {
    const LChar* ptr = string.characters8();
    const LChar* end = ptr + string.length();
    return genericParseNumberOptionalNumber(ptr, end, x, y);
  }
  const UChar* ptr = string.characters16();
  const UChar* end = ptr + string.length();
  return genericParseNumberOptionalNumber(ptr, end, x, y);
}

}  // namespace blink