mfbt/Casting.h
author Ehsan Akhgari <ehsan@mozilla.com>
Thu, 18 Jul 2013 13:59:53 -0400
changeset 140909 552bca1bc885acca25c1c431e39a872b6f703b24
parent 140115 f55906cadf07a9ef44cc4ce2574fe35f3dc85672
permissions -rw-r--r--
Bug 895322 - Part 1: Replace the usages of MOZ_STATIC_ASSERT with C++11 static_assert; r=Waldo This patch was mostly generated by running the following scripts on the codebase, with some manual changes made afterwards: # static_assert.sh #!/bin/bash # Command to convert an NSPR integer type to the equivalent standard integer type function convert() { echo "Converting $1 to $2..." find . ! -wholename "*nsprpub*" \ ! -wholename "*security/nss*" \ ! -wholename "*/.hg*" \ ! -wholename "obj-ff-dbg*" \ ! -name nsXPCOMCID.h \ ! -name prtypes.h \ -type f \ \( -iname "*.cpp" \ -o -iname "*.h" \ -o -iname "*.cc" \ -o -iname "*.mm" \) | \ xargs -n 1 `dirname $0`/assert_replacer.py #sed -i -e "s/\b$1\b/$2/g" } convert MOZ_STATIC_ASSERT static_assert hg rev --no-backup mfbt/Assertions.h \ media/webrtc/signaling/src/sipcc/core/includes/ccapi.h \ modules/libmar/src/mar_private.h \ modules/libmar/src/mar.h # assert_replacer.py #!/usr/bin/python import sys import re pattern = re.compile(r"\bMOZ_STATIC_ASSERT\b") def replaceInPlace(fname): print fname f = open(fname, "rw+") lines = f.readlines() for i in range(0, len(lines)): while True: index = re.search(pattern, lines[i]) if index != None: index = index.start() lines[i] = lines[i][0:index] + "static_assert" + lines[i][index+len("MOZ_STATIC_ASSERT"):] for j in range(i + 1, len(lines)): if lines[j].find(" ", index) == index: lines[j] = lines[j][0:index] + lines[j][index+4:] else: break else: break f.seek(0, 0) f.truncate() f.write("".join(lines)) f.close() argc = len(sys.argv) for i in range(1, argc): replaceInPlace(sys.argv[i])

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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/. */

/* Cast operations to supplement the built-in casting operations. */

#ifndef mozilla_Casting_h
#define mozilla_Casting_h

#include "mozilla/Assertions.h"
#include "mozilla/TypeTraits.h"

#include <limits.h>

namespace mozilla {

/**
 * Return a value of type |To|, containing the underlying bit pattern of |from|.
 *
 * |To| and |From| must be types of the same size; be careful of cross-platform
 * size differences, or this might fail to compile on some but not all
 * platforms.
 */
template<typename To, typename From>
inline To
BitwiseCast(const From from)
{
  static_assert(sizeof(From) == sizeof(To),
                "To and From must have the same size");
  union {
    From from;
    To to;
  } u;
  u.from = from;
  return u.to;
}

namespace detail {

enum ToSignedness { ToIsSigned, ToIsUnsigned };
enum FromSignedness { FromIsSigned, FromIsUnsigned };

template<typename From,
         typename To,
         FromSignedness = IsSigned<From>::value ? FromIsSigned : FromIsUnsigned,
         ToSignedness = IsSigned<To>::value ? ToIsSigned : ToIsUnsigned>
struct BoundsCheckImpl;

// Implicit conversions on operands to binary operations make this all a bit
// hard to verify.  Attempt to ease the pain below by *only* comparing values
// that are obviously the same type (and will undergo no further conversions),
// even when it's not strictly necessary, for explicitness.

enum UUComparison { FromIsBigger, FromIsNotBigger };

// Unsigned-to-unsigned range check

template<typename From, typename To,
         UUComparison = (sizeof(From) > sizeof(To)) ? FromIsBigger : FromIsNotBigger>
struct UnsignedUnsignedCheck;

template<typename From, typename To>
struct UnsignedUnsignedCheck<From, To, FromIsBigger>
{
  public:
    static bool checkBounds(const From from) {
      return from <= From(To(-1));
    }
};

template<typename From, typename To>
struct UnsignedUnsignedCheck<From, To, FromIsNotBigger>
{
  public:
    static bool checkBounds(const From from) {
      return true;
    }
};

template<typename From, typename To>
struct BoundsCheckImpl<From, To, FromIsUnsigned, ToIsUnsigned>
{
  public:
    static bool checkBounds(const From from) {
      return UnsignedUnsignedCheck<From, To>::checkBounds(from);
    }
};

// Signed-to-unsigned range check

template<typename From, typename To>
struct BoundsCheckImpl<From, To, FromIsSigned, ToIsUnsigned>
{
  public:
    static bool checkBounds(const From from) {
      if (from < 0)
        return false;
      if (sizeof(To) >= sizeof(From))
        return true;
      return from <= From(To(-1));
    }
};

// Unsigned-to-signed range check

enum USComparison { FromIsSmaller, FromIsNotSmaller };

template<typename From, typename To,
         USComparison = (sizeof(From) < sizeof(To)) ? FromIsSmaller : FromIsNotSmaller>
struct UnsignedSignedCheck;

template<typename From, typename To>
struct UnsignedSignedCheck<From, To, FromIsSmaller>
{
  public:
    static bool checkBounds(const From from) {
      return true;
    }
};

template<typename From, typename To>
struct UnsignedSignedCheck<From, To, FromIsNotSmaller>
{
  public:
    static bool checkBounds(const From from) {
      const To MaxValue = To((1ULL << (CHAR_BIT * sizeof(To) - 1)) - 1);
      return from <= From(MaxValue);
    }
};

template<typename From, typename To>
struct BoundsCheckImpl<From, To, FromIsUnsigned, ToIsSigned>
{
  public:
    static bool checkBounds(const From from) {
      return UnsignedSignedCheck<From, To>::checkBounds(from);
    }
};

// Signed-to-signed range check

template<typename From, typename To>
struct BoundsCheckImpl<From, To, FromIsSigned, ToIsSigned>
{
  public:
    static bool checkBounds(const From from) {
      if (sizeof(From) <= sizeof(To))
        return true;
      const To MaxValue = To((1ULL << (CHAR_BIT * sizeof(To) - 1)) - 1);
      const To MinValue = -MaxValue - To(1);
      return From(MinValue) <= from &&
             From(from) <= From(MaxValue);
    }
};

template<typename From, typename To,
         bool TypesAreIntegral = IsIntegral<From>::value && IsIntegral<To>::value>
class BoundsChecker;

template<typename From>
class BoundsChecker<From, From, true>
{
  public:
    static bool checkBounds(const From from) { return true; }
};

template<typename From, typename To>
class BoundsChecker<From, To, true>
{
  public:
    static bool checkBounds(const From from) {
      return BoundsCheckImpl<From, To>::checkBounds(from);
    }
};

template<typename From, typename To>
inline bool
IsInBounds(const From from)
{
  return BoundsChecker<From, To>::checkBounds(from);
}

} // namespace detail

/**
 * Cast a value of integral type |From| to a value of integral type |To|,
 * asserting that the cast will be a safe cast per C++ (that is, that |to| is in
 * the range of values permitted for the type |From|).
 */
template<typename To, typename From>
inline To
SafeCast(const From from)
{
  MOZ_ASSERT((detail::IsInBounds<From, To>(from)));
  return static_cast<To>(from);
}

} // namespace mozilla

#endif /* mozilla_Casting_h */