mirror of
https://github.com/mpv-player/mpv
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94 lines
2.9 KiB
C
94 lines
2.9 KiB
C
/*
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* This file is part of mpv.
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* Copyright (c) 2013 Stefano Pigozzi <stefano.pigozzi@gmail.com>
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*
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* mpv is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* mpv is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with mpv. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef MP_ATOMICS_H
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#define MP_ATOMICS_H
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#include <inttypes.h>
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#include "config.h"
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#define HAVE_ATOMICS 1
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#if HAVE_STDATOMIC
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#include <stdatomic.h>
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#else
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// Emulate the parts of C11 stdatomic.h needed by mpv.
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// Still relies on gcc/clang atomic builtins.
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typedef struct { volatile unsigned long v; } atomic_ulong;
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typedef struct { volatile int v; } atomic_int;
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typedef struct { volatile _Bool v; } atomic_bool;
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typedef struct { volatile long long v; } atomic_llong;
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typedef struct { volatile uint_least32_t v; } atomic_uint_least32_t;
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typedef struct { volatile unsigned long long v; } atomic_ullong;
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#define ATOMIC_VAR_INIT(x) \
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{.v = (x)}
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#define memory_order_relaxed 1
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#define memory_order_seq_cst 2
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#define atomic_load_explicit(p, e) atomic_load(p)
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#if HAVE_ATOMIC_BUILTINS
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#define atomic_load(p) \
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__atomic_load_n(&(p)->v, __ATOMIC_SEQ_CST)
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#define atomic_store(p, val) \
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__atomic_store_n(&(p)->v, val, __ATOMIC_SEQ_CST)
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#define atomic_fetch_add(a, b) \
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__atomic_fetch_add(&(a)->v, b, __ATOMIC_SEQ_CST)
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#define atomic_compare_exchange_strong(a, b, c) \
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__atomic_compare_exchange_n(&(a)->v, b, c, 0, __ATOMIC_SEQ_CST, \
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__ATOMIC_SEQ_CST)
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#elif HAVE_SYNC_BUILTINS
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#define atomic_load(p) \
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__sync_fetch_and_add(&(p)->v, 0)
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#define atomic_store(p, val) \
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(__sync_synchronize(), (p)->v = (val), __sync_synchronize())
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#define atomic_fetch_add(a, b) \
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__sync_fetch_and_add(&(a)->v, b)
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// Assumes __sync_val_compare_and_swap is "strong" (using the C11 meaning).
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#define atomic_compare_exchange_strong(p, old, new) \
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({ __typeof__((p)->v) val_ = __sync_val_compare_and_swap(&(p)->v, *(old), new); \
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bool ok_ = val_ == *(old); \
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if (!ok_) *(old) = val_; \
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ok_; })
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#else
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// This is extremely wrong. The build system actually disables code that has
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// a serious dependency on working atomics, so this is barely ok.
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#define atomic_load(p) ((p)->v)
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#define atomic_store(p, val) ((p)->v = (val))
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#define atomic_fetch_add(a, b) (((a)->v += (b)) - (b))
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#define atomic_compare_exchange_strong(p, old, new) \
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((p)->v == *(old) ? ((p)->v = (new), 1) : (*(old) = (p)->v, 0))
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#undef HAVE_ATOMICS
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#define HAVE_ATOMICS 0
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#endif /* no atomics */
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#endif /* else HAVE_STDATOMIC */
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#endif
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