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35 lines
1.4 KiB
C++
35 lines
1.4 KiB
C++
// Copyright 2014 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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// From Chromium src/base/macros.h
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#include <cstddef> // For size_t.
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// The arraysize(arr) macro returns the # of elements in an array arr.
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// The expression is a compile-time constant, and therefore can be
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// used in defining new arrays, for example. If you use arraysize on
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// a pointer by mistake, you will get a compile-time error.
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//
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// One caveat is that arraysize() doesn't accept any array of an
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// anonymous type or a type defined inside a function. In these rare
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// cases, you have to use the unsafe ARRAYSIZE_UNSAFE() macro below. This is
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// due to a limitation in C++'s template system. The limitation might
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// eventually be removed, but it hasn't happened yet.
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// This template function declaration is used in defining arraysize.
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// Note that the function doesn't need an implementation, as we only
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// use its type.
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template <typename T, size_t N>
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char (&ArraySizeHelper(T (&array)[N]))[N];
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// That gcc wants both of these prototypes seems mysterious. VC, for
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// its part, can't decide which to use (another mystery). Matching of
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// template overloads: the final frontier.
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#ifndef _MSC_VER
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template <typename T, size_t N>
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char (&ArraySizeHelper(const T (&array)[N]))[N];
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#endif
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#define arraysize(array) (sizeof(ArraySizeHelper(array)))
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