mirror of
https://github.com/classilla/tenfourfox.git
synced 2024-08-15 02:29:04 +00:00
222 lines
5.3 KiB
C++
222 lines
5.3 KiB
C++
/* -*- 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
|
|
* |aFrom|.
|
|
*
|
|
* |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 aFrom)
|
|
{
|
|
static_assert(sizeof(From) == sizeof(To),
|
|
"To and From must have the same size");
|
|
union
|
|
{
|
|
From mFrom;
|
|
To mTo;
|
|
} u;
|
|
u.mFrom = aFrom;
|
|
return u.mTo;
|
|
}
|
|
|
|
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 aFrom)
|
|
{
|
|
return aFrom <= From(To(-1));
|
|
}
|
|
};
|
|
|
|
template<typename From, typename To>
|
|
struct UnsignedUnsignedCheck<From, To, FromIsNotBigger>
|
|
{
|
|
public:
|
|
static bool checkBounds(const From aFrom)
|
|
{
|
|
return true;
|
|
}
|
|
};
|
|
|
|
template<typename From, typename To>
|
|
struct BoundsCheckImpl<From, To, FromIsUnsigned, ToIsUnsigned>
|
|
{
|
|
public:
|
|
static bool checkBounds(const From aFrom)
|
|
{
|
|
return UnsignedUnsignedCheck<From, To>::checkBounds(aFrom);
|
|
}
|
|
};
|
|
|
|
// Signed-to-unsigned range check
|
|
|
|
template<typename From, typename To>
|
|
struct BoundsCheckImpl<From, To, FromIsSigned, ToIsUnsigned>
|
|
{
|
|
public:
|
|
static bool checkBounds(const From aFrom)
|
|
{
|
|
if (aFrom < 0) {
|
|
return false;
|
|
}
|
|
if (sizeof(To) >= sizeof(From)) {
|
|
return true;
|
|
}
|
|
return aFrom <= 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 aFrom)
|
|
{
|
|
return true;
|
|
}
|
|
};
|
|
|
|
template<typename From, typename To>
|
|
struct UnsignedSignedCheck<From, To, FromIsNotSmaller>
|
|
{
|
|
public:
|
|
static bool checkBounds(const From aFrom)
|
|
{
|
|
const To MaxValue = To((1ULL << (CHAR_BIT * sizeof(To) - 1)) - 1);
|
|
return aFrom <= From(MaxValue);
|
|
}
|
|
};
|
|
|
|
template<typename From, typename To>
|
|
struct BoundsCheckImpl<From, To, FromIsUnsigned, ToIsSigned>
|
|
{
|
|
public:
|
|
static bool checkBounds(const From aFrom)
|
|
{
|
|
return UnsignedSignedCheck<From, To>::checkBounds(aFrom);
|
|
}
|
|
};
|
|
|
|
// Signed-to-signed range check
|
|
|
|
template<typename From, typename To>
|
|
struct BoundsCheckImpl<From, To, FromIsSigned, ToIsSigned>
|
|
{
|
|
public:
|
|
static bool checkBounds(const From aFrom)
|
|
{
|
|
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) <= aFrom &&
|
|
From(aFrom) <= 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 aFrom) { return true; }
|
|
};
|
|
|
|
template<typename From, typename To>
|
|
class BoundsChecker<From, To, true>
|
|
{
|
|
public:
|
|
static bool checkBounds(const From aFrom)
|
|
{
|
|
return BoundsCheckImpl<From, To>::checkBounds(aFrom);
|
|
}
|
|
};
|
|
|
|
template<typename From, typename To>
|
|
inline bool
|
|
IsInBounds(const From aFrom)
|
|
{
|
|
return BoundsChecker<From, To>::checkBounds(aFrom);
|
|
}
|
|
|
|
} // 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
|
|
AssertedCast(const From aFrom)
|
|
{
|
|
MOZ_ASSERT((detail::IsInBounds<From, To>(aFrom)));
|
|
return static_cast<To>(aFrom);
|
|
}
|
|
|
|
} // namespace mozilla
|
|
|
|
#endif /* mozilla_Casting_h */
|