mirror of
https://github.com/mozilla/gecko-dev.git
synced 2024-12-05 03:54:35 +00:00
222fa50b5a
--HG-- extra : rebase_source : 7bb59639b95ec7a05272ab0215bbc04a210c11d5
160 lines
4.5 KiB
C++
160 lines
4.5 KiB
C++
/* -*- Mode: C++; tab-width: 2; 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/. */
|
|
|
|
/*
|
|
* Operations for zeroing POD types, arrays, and so on.
|
|
*
|
|
* These operations are preferable to memset, memcmp, and the like because they
|
|
* don't require remembering to multiply by sizeof(T), array lengths, and so on
|
|
* everywhere.
|
|
*/
|
|
|
|
#ifndef mozilla_PodOperations_h
|
|
#define mozilla_PodOperations_h
|
|
|
|
#include "mozilla/Attributes.h"
|
|
#include "mozilla/Util.h"
|
|
|
|
#include <string.h>
|
|
|
|
namespace mozilla {
|
|
|
|
/** Set the contents of |t| to 0. */
|
|
template<typename T>
|
|
static void
|
|
PodZero(T* t)
|
|
{
|
|
memset(t, 0, sizeof(T));
|
|
}
|
|
|
|
/** Set the contents of |nelem| elements starting at |t| to 0. */
|
|
template<typename T>
|
|
static void
|
|
PodZero(T* t, size_t nelem)
|
|
{
|
|
/*
|
|
* This function is often called with 'nelem' small; we use an inline loop
|
|
* instead of calling 'memset' with a non-constant length. The compiler
|
|
* should inline the memset call with constant size, though.
|
|
*/
|
|
for (T* end = t + nelem; t < end; t++)
|
|
memset(t, 0, sizeof(T));
|
|
}
|
|
|
|
/*
|
|
* Arrays implicitly convert to pointers to their first element, which is
|
|
* dangerous when combined with the above PodZero definitions. Adding an
|
|
* overload for arrays is ambiguous, so we need another identifier. The
|
|
* ambiguous overload is left to catch mistaken uses of PodZero; if you get a
|
|
* compile error involving PodZero and array types, use PodArrayZero instead.
|
|
*/
|
|
template<typename T, size_t N>
|
|
static void PodZero(T (&t)[N]) MOZ_DELETE;
|
|
template<typename T, size_t N>
|
|
static void PodZero(T (&t)[N], size_t nelem) MOZ_DELETE;
|
|
|
|
/** Set the contents of the array |t| to zero. */
|
|
template <class T, size_t N>
|
|
static void
|
|
PodArrayZero(T (&t)[N])
|
|
{
|
|
memset(t, 0, N * sizeof(T));
|
|
}
|
|
|
|
/**
|
|
* Assign |*src| to |*dst|. The locations must not be the same and must not
|
|
* overlap.
|
|
*/
|
|
template<typename T>
|
|
static void
|
|
PodAssign(T* dst, const T* src)
|
|
{
|
|
MOZ_ASSERT(dst != src);
|
|
MOZ_ASSERT_IF(src < dst, PointerRangeSize(src, static_cast<const T*>(dst)) >= 1);
|
|
MOZ_ASSERT_IF(dst < src, PointerRangeSize(static_cast<const T*>(dst), src) >= 1);
|
|
memcpy(reinterpret_cast<char*>(dst), reinterpret_cast<const char*>(src), sizeof(T));
|
|
}
|
|
|
|
/**
|
|
* Copy |nelem| T elements from |src| to |dst|. The two memory ranges must not
|
|
* overlap!
|
|
*/
|
|
template<typename T>
|
|
MOZ_ALWAYS_INLINE static void
|
|
PodCopy(T* dst, const T* src, size_t nelem)
|
|
{
|
|
MOZ_ASSERT(dst != src);
|
|
MOZ_ASSERT_IF(src < dst, PointerRangeSize(src, static_cast<const T*>(dst)) >= nelem);
|
|
MOZ_ASSERT_IF(dst < src, PointerRangeSize(static_cast<const T*>(dst), src) >= nelem);
|
|
|
|
if (nelem < 128) {
|
|
/*
|
|
* Avoid using operator= in this loop, as it may have been
|
|
* intentionally deleted by the POD type.
|
|
*/
|
|
for (const T* srcend = src + nelem; src < srcend; src++, dst++)
|
|
PodAssign(dst, src);
|
|
} else {
|
|
memcpy(dst, src, nelem * sizeof(T));
|
|
}
|
|
}
|
|
|
|
template<typename T>
|
|
MOZ_ALWAYS_INLINE static void
|
|
PodCopy(volatile T* dst, const volatile T* src, size_t nelem)
|
|
{
|
|
MOZ_ASSERT(dst != src);
|
|
MOZ_ASSERT_IF(src < dst,
|
|
PointerRangeSize(src, static_cast<const volatile T*>(dst)) >= nelem);
|
|
MOZ_ASSERT_IF(dst < src,
|
|
PointerRangeSize(static_cast<const volatile T*>(dst), src) >= nelem);
|
|
|
|
/*
|
|
* Volatile |dst| requires extra work, because it's undefined behavior to
|
|
* modify volatile objects using the mem* functions. Just write out the
|
|
* loops manually, using operator= rather than memcpy for the same reason,
|
|
* and let the compiler optimize to the extent it can.
|
|
*/
|
|
for (const volatile T* srcend = src + nelem; src < srcend; src++, dst++)
|
|
*dst = *src;
|
|
}
|
|
|
|
/*
|
|
* Copy the contents of the array |src| into the array |dst|, both of size N.
|
|
* The arrays must not overlap!
|
|
*/
|
|
template <class T, size_t N>
|
|
static void
|
|
PodArrayCopy(T (&dst)[N], const T (&src)[N])
|
|
{
|
|
PodCopy(dst, src, N);
|
|
}
|
|
|
|
/**
|
|
* Determine whether the |len| elements at |one| are memory-identical to the
|
|
* |len| elements at |two|.
|
|
*/
|
|
template<typename T>
|
|
MOZ_ALWAYS_INLINE static bool
|
|
PodEqual(const T* one, const T* two, size_t len)
|
|
{
|
|
if (len < 128) {
|
|
const T* p1end = one + len;
|
|
const T* p1 = one;
|
|
const T* p2 = two;
|
|
for (; p1 < p1end; p1++, p2++) {
|
|
if (*p1 != *p2)
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
return !memcmp(one, two, len * sizeof(T));
|
|
}
|
|
|
|
} // namespace mozilla
|
|
|
|
#endif // mozilla_PodOperations_h_
|