fx_number.cpp

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// Copyright 2018 The PDFium Authors
// 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 <ctype.h>
 
#include <limits>
 
#include "core/fxcrt/fx_extension.h"
#include "core/fxcrt/fx_safe_types.h"
#include "core/fxcrt/fx_string.h"
#include "core/fxcrt/numerics/safe_conversions.h"
 
FX_Number::FX_Number() = default;
 
FX_Number::FX_Number(int32_t value) : value_(value) {}
 
FX_Number::FX_Number(float value) : value_(value) {}
 
FX_Number::FX_Number(ByteStringView strc) {
  if (strc.IsEmpty())
    return;
 
  if (strc.Contains('.')) {
    value_ = 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 bIsSigned = false;
  bool bNegative = false;
  size_t cc = 0;
  if (strc[0] == '+') {
    bIsSigned = true;
    cc++;
  } else if (strc[0] == '-') {
    bIsSigned = true;
    bNegative = true;
    cc++;
  }
 
  for (; cc < strc.GetLength() && isdigit(strc[cc]); ++cc) {
    // Deliberately not using FXSYS_DecimalCharToInt() in a tight loop to avoid
    // a duplicate 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 (!bIsSigned) {
    value_ = 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();
    value_ = LIKELY(value != kMinInt) ? -value : kMinInt;
  } else {
    value_ = value;
  }
}
 
bool FX_Number::IsInteger() const {
  return absl::holds_alternative<uint32_t>(value_) ||
         absl::holds_alternative<int32_t>(value_);
}
 
bool FX_Number::IsSigned() const {
  return absl::holds_alternative<int32_t>(value_) ||
         absl::holds_alternative<float>(value_);
}
 
int32_t FX_Number::GetSigned() const {
  if (absl::holds_alternative<uint32_t>(value_)) {
    return static_cast<int32_t>(absl::get<uint32_t>(value_));
  }
  if (absl::holds_alternative<int32_t>(value_)) {
    return absl::get<int32_t>(value_);
  }
  return pdfium::saturated_cast<int32_t>(absl::get<float>(value_));
}
 
float FX_Number::GetFloat() const {
  if (absl::holds_alternative<uint32_t>(value_)) {
    return static_cast<float>(absl::get<uint32_t>(value_));
  }
  if (absl::holds_alternative<int32_t>(value_)) {
    return static_cast<float>(absl::get<int32_t>(value_));
  }
  return absl::get<float>(value_);
}