text: // Copyright 2018 PDFium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
  
  #include "core/fxcrt/fx_number.h"
  
  #include <limits>
  
  #include "core/fxcrt/fx_extension.h"
  #include "core/fxcrt/fx_safe_types.h"
  #include "core/fxcrt/fx_string.h"
  
  FX_Number::FX_Number()
      : m_bIsInteger(true), m_bIsSigned(false), m_UnsignedValue(0) {}
  
  FX_Number::FX_Number(int32_t value)
      : m_bIsInteger(true), m_bIsSigned(true), m_SignedValue(value) {}
  
  FX_Number::FX_Number(float value)
      : m_bIsInteger(false), m_bIsSigned(true), m_FloatValue(value) {}
  
  FX_Number::FX_Number(ByteStringView strc)
      : m_bIsInteger(true), m_bIsSigned(false), m_UnsignedValue(0) {
    if (strc.IsEmpty())
      return;
  
    if (strc.Contains('.')) {
      m_bIsInteger = false;
      m_bIsSigned = true;
      m_FloatValue = StringToFloat(strc);
      return;
    }
  
    // Note, numbers in PDF are typically of the form 123, -123, etc. But,
    // for things like the Permissions on the encryption hash the number is
    // actually an unsigned value. We use a uint32_t so we can deal with the
    // unsigned and then check for overflow if the user actually signed the value.
    // The Permissions flag is listed in Table 3.20 PDF 1.7 spec.
    FX_SAFE_UINT32 unsigned_val = 0;
    bool bNegative = false;
    size_t cc = 0;
    if (strc[0] == '+') {
      cc++;
      m_bIsSigned = true;
    } else if (strc[0] == '-') {
      bNegative = true;
      m_bIsSigned = true;
      cc++;
    }
  
    for (; cc < strc.GetLength() && std::isdigit(strc[cc]); ++cc) {
      // Deliberately not using FXSYS_DecimalCharToInt() in a tight loop to avoid
      // a duplicate std::isdigit() call. Note that the order of operation is
      // important to avoid unintentional overflows.
      unsigned_val = unsigned_val * 10 + (strc[cc] - '0');
    }
  
    uint32_t uValue = unsigned_val.ValueOrDefault(0);
    if (!m_bIsSigned) {
      m_UnsignedValue = uValue;
      return;
    }
  
    // We have a sign, so if the value was greater then the signed integer
    // limits, then we've overflowed and must reset to the default value.
    constexpr uint32_t uLimit =
        static_cast<uint32_t>(std::numeric_limits<int>::max());
  
    if (uValue > (bNegative ? uLimit + 1 : uLimit))
      uValue = 0;
  
    // Switch back to the int space so we can flip to a negative if we need.
    int32_t value = static_cast<int32_t>(uValue);
    if (bNegative) {
      // |value| is usually positive, except in the corner case of "-2147483648",
      // where |uValue| is 2147483648. When it gets casted to an int, |value|
      // becomes -2147483648. For this case, avoid undefined behavior, because
      // an int32_t cannot represent 2147483648.
      static constexpr int kMinInt = std::numeric_limits<int>::min();
      m_SignedValue = LIKELY(value != kMinInt) ? -value : kMinInt;
    } else {
      m_SignedValue = value;
    }
  }
  
  int32_t FX_Number::GetSigned() const {
    return m_bIsInteger ? m_SignedValue : static_cast<int32_t>(m_FloatValue);
  }
  
  float FX_Number::GetFloat() const {
    if (!m_bIsInteger)
      return m_FloatValue;
  
    return m_bIsSigned ? static_cast<float>(m_SignedValue)
                       : static_cast<float>(m_UnsignedValue);
  }
  