gecko-dev/dom/xslt/base/txDouble.cpp

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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 "mozilla/FloatingPoint.h"

#include "nsString.h"
#include "txCore.h"
#include "txXMLUtils.h"
#include <math.h>
#include <stdlib.h>
#include <algorithm>
#ifdef WIN32
#  include <float.h>
#endif
#include "prdtoa.h"

/*
 * Utility class for doubles
 */

/*
 * Converts the given String to a double, if the String value does not
 * represent a double, NaN will be returned
 */
class txStringToDouble {
 public:
  txStringToDouble() : mState(eWhitestart), mSign(ePositive) {}

  void Parse(const nsAString& aSource) {
    if (mState == eIllegal) {
      return;
    }
    uint32_t i = 0;
    char16_t c;
    auto len = aSource.Length();
    for (; i < len; ++i) {
      c = aSource[i];
      switch (mState) {
        case eWhitestart:
          if (c == '-') {
            mState = eDecimal;
            mSign = eNegative;
          } else if (c >= '0' && c <= '9') {
            mState = eDecimal;
            mBuffer.Append((char)c);
          } else if (c == '.') {
            mState = eMantissa;
            mBuffer.Append((char)c);
          } else if (!XMLUtils::isWhitespace(c)) {
            mState = eIllegal;
            return;
          }
          break;
        case eDecimal:
          if (c >= '0' && c <= '9') {
            mBuffer.Append((char)c);
          } else if (c == '.') {
            mState = eMantissa;
            mBuffer.Append((char)c);
          } else if (XMLUtils::isWhitespace(c)) {
            mState = eWhiteend;
          } else {
            mState = eIllegal;
            return;
          }
          break;
        case eMantissa:
          if (c >= '0' && c <= '9') {
            mBuffer.Append((char)c);
          } else if (XMLUtils::isWhitespace(c)) {
            mState = eWhiteend;
          } else {
            mState = eIllegal;
            return;
          }
          break;
        case eWhiteend:
          if (!XMLUtils::isWhitespace(c)) {
            mState = eIllegal;
            return;
          }
          break;
        default:
          break;
      }
    }
  }

  double getDouble() {
    if (mState == eIllegal || mBuffer.IsEmpty() ||
        (mBuffer.Length() == 1 && mBuffer[0] == '.')) {
      return mozilla::UnspecifiedNaN<double>();
    }
    return mSign * PR_strtod(mBuffer.get(), 0);
  }

 private:
  nsAutoCString mBuffer;
  enum { eWhitestart, eDecimal, eMantissa, eWhiteend, eIllegal } mState;
  enum { eNegative = -1, ePositive = 1 } mSign;
};

double txDouble::toDouble(const nsAString& aSrc) {
  txStringToDouble sink;
  sink.Parse(aSrc);
  return sink.getDouble();
}

/*
 * Converts the value of the given double to a String, and places
 * The result into the destination String.
 * @return the given dest string
 */
void txDouble::toString(double aValue, nsAString& aDest) {
  // check for special cases

  if (mozilla::IsNaN(aValue)) {
    aDest.AppendLiteral("NaN");
    return;
  }
  if (mozilla::IsInfinite(aValue)) {
    if (aValue < 0) aDest.Append(char16_t('-'));
    aDest.AppendLiteral("Infinity");
    return;
  }

  // Mantissa length is 17, so this is plenty
  const int buflen = 20;
  char buf[buflen];

  int intDigits, sign;
  char* endp;
  PR_dtoa(aValue, 0, 0, &intDigits, &sign, &endp, buf, buflen - 1);

  // compute length
  int32_t length = endp - buf;
  if (length > intDigits) {
    // decimal point needed
    ++length;
    if (intDigits < 1) {
      // leading zeros, -intDigits + 1
      length += 1 - intDigits;
    }
  } else {
    // trailing zeros, total length given by intDigits
    length = intDigits;
  }
  if (aValue < 0) ++length;
  // grow the string
  uint32_t oldlength = aDest.Length();
  if (!aDest.SetLength(oldlength + length, mozilla::fallible))
    return;  // out of memory
  auto dest = aDest.BeginWriting();
  std::advance(dest, oldlength);
  if (aValue < 0) {
    *dest = '-';
    ++dest;
  }
  int i;
  // leading zeros
  if (intDigits < 1) {
    *dest = '0';
    ++dest;
    *dest = '.';
    ++dest;
    for (i = 0; i > intDigits; --i) {
      *dest = '0';
      ++dest;
    }
  }
  // mantissa
  int firstlen = std::min<size_t>(intDigits, endp - buf);
  for (i = 0; i < firstlen; i++) {
    *dest = buf[i];
    ++dest;
  }
  if (i < endp - buf) {
    if (i > 0) {
      *dest = '.';
      ++dest;
    }
    for (; i < endp - buf; i++) {
      *dest = buf[i];
      ++dest;
    }
  }
  // trailing zeros
  for (; i < intDigits; i++) {
    *dest = '0';
    ++dest;
  }
}