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98 lines
3.7 KiB
C
98 lines
3.7 KiB
C
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/*
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* Implements various macros meant to ease the use of variadic macros.
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*/
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#ifndef mozilla_MacroArgs_h
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#define mozilla_MacroArgs_h
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// Concatenates pre-processor tokens in a way that can be used with __LINE__.
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#define MOZ_CONCAT2(x, y) x##y
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#define MOZ_CONCAT(x, y) MOZ_CONCAT2(x, y)
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/*
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* MOZ_ARG_COUNT(...) counts the number of variadic arguments.
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* You must pass in between 0 and 50 (inclusive) variadic arguments.
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* For example:
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*
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* MOZ_ARG_COUNT() expands to 0
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* MOZ_ARG_COUNT(a) expands to 1
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* MOZ_ARG_COUNT(a, b) expands to 2
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*
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* Implementation notes:
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* The `##__VA_ARGS__` form is a GCC extension that removes the comma if
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* __VA_ARGS__ is empty. It is supported by Clang too. MSVC ignores ##,
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* and its default behavior is already to strip the comma when __VA_ARGS__
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* is empty.
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*
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* So MOZ_MACROARGS_ARG_COUNT_HELPER() expands to
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* (_, 50, 49, ...)
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* MOZ_MACROARGS_ARG_COUNT_HELPER(a) expands to
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* (_, a, 50, 49, ...)
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* etc.
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*/
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#define MOZ_ARG_COUNT(...) \
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MOZ_MACROARGS_ARG_COUNT_HELPER2(MOZ_MACROARGS_ARG_COUNT_HELPER(__VA_ARGS__))
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#define MOZ_MACROARGS_ARG_COUNT_HELPER(...) \
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(_, ##__VA_ARGS__, 50, 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, \
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36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, \
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17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
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#define MOZ_MACROARGS_ARG_COUNT_HELPER2(aArgs) \
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MOZ_MACROARGS_ARG_COUNT_HELPER3 aArgs
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#define MOZ_MACROARGS_ARG_COUNT_HELPER3( \
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a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15, a16, \
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a17, a18, a19, a20, a21, a22, a23, a24, a25, a26, a27, a28, a29, a30, a31, \
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a32, a33, a34, a35, a36, a37, a38, a39, a40, a41, a42, a43, a44, a45, a46, \
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a47, a48, a49, a50, a51, ...) \
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a51
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/*
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* MOZ_PASTE_PREFIX_AND_ARG_COUNT(aPrefix, ...) counts the number of variadic
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* arguments and prefixes it with |aPrefix|. For example:
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*
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* MOZ_PASTE_PREFIX_AND_ARG_COUNT(, foo, 42) expands to 2
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* MOZ_PASTE_PREFIX_AND_ARG_COUNT(A, foo, 42, bar) expands to A3
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* MOZ_PASTE_PREFIX_AND_ARG_COUNT(A) expands to A0
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* MOZ_PASTE_PREFIX_AND_ARG_COUNT() expands to 0, but MSVC warns there
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* aren't enough arguments given.
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*
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* You must pass in between 0 and 50 (inclusive) variadic arguments, past
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* |aPrefix|.
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*/
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#define MOZ_PASTE_PREFIX_AND_ARG_COUNT_GLUE(a, b) a b
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#define MOZ_PASTE_PREFIX_AND_ARG_COUNT(aPrefix, ...) \
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MOZ_PASTE_PREFIX_AND_ARG_COUNT_GLUE(MOZ_CONCAT, \
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(aPrefix, MOZ_ARG_COUNT(__VA_ARGS__)))
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/*
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* MOZ_ARGS_AFTER_N expands to its arguments excluding the first |N|
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* arguments. For example:
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*
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* MOZ_ARGS_AFTER_2(a, b, c, d) expands to: c, d
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*/
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#define MOZ_ARGS_AFTER_1(a1, ...) __VA_ARGS__
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#define MOZ_ARGS_AFTER_2(a1, a2, ...) __VA_ARGS__
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/*
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* MOZ_ARG_N expands to its |N|th argument.
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*/
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#define MOZ_ARG_1(a1, ...) a1
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#define MOZ_ARG_2(a1, a2, ...) a2
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#define MOZ_ARG_3(a1, a2, a3, ...) a3
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#define MOZ_ARG_4(a1, a2, a3, a4, ...) a4
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#define MOZ_ARG_5(a1, a2, a3, a4, a5, ...) a5
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#define MOZ_ARG_6(a1, a2, a3, a4, a5, a6, ...) a6
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#define MOZ_ARG_7(a1, a2, a3, a4, a5, a6, a7, ...) a7
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#define MOZ_ARG_8(a1, a2, a3, a4, a5, a6, a7, a8, ...) a8
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#define MOZ_ARG_9(a1, a2, a3, a4, a5, a6, a7, a8, a9, ...) a9
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#endif /* mozilla_MacroArgs_h */
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