50 lines
1.3 KiB
C
50 lines
1.3 KiB
C
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#pragma once
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/*
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Simple Reader/Writer lock. Lets unlimited readers through but a writer will lock exclusively
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not meant for high-throughput uses
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this is useful when writes are very infrequent
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*/
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#include <bfc/platform/types.h>
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#include <windows.h>
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typedef size_t simple_rwlock_t;
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static const size_t simple_rwlock_writer_active = 1; // writer active flag
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static const size_t simple_rwlock_reader_increment= 2; // to adjust reader count
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static inline void simple_rwlock_write_lock(simple_rwlock_t *lock)
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{
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while (InterlockedCompareExchangePointer((PVOID volatile*)lock, (PVOID)simple_rwlock_writer_active, 0))
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{
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// nop
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}
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}
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static inline void simple_rwlock_write_unlock(simple_rwlock_t *lock)
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{
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#ifdef _WIN64
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InterlockedExchangeAdd64((LONGLONG volatile*)lock, -simple_rwlock_writer_active);
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#else
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InterlockedExchangeAdd((LONG volatile*)lock, -simple_rwlock_writer_active);
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#endif
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}
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static inline void simple_rwlock_read_lock(simple_rwlock_t *lock)
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{
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InterlockedExchangeAdd((LONG volatile*)lock, simple_rwlock_reader_increment);
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while ((*lock & simple_rwlock_writer_active))
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{
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// nope
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}
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}
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static inline void simple_rwlock_read_unlock(simple_rwlock_t *lock)
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{
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#ifdef _WIN64
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InterlockedExchangeAdd64((LONGLONG volatile*)lock, -simple_rwlock_reader_increment);
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#else
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InterlockedExchangeAdd((LONG volatile*)lock, -simple_rwlock_reader_increment);
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#endif
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}
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