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/* SoX Resampler Library Copyright (c) 2007-13 robs@users.sourceforge.net
* Licence for this file: LGPL v2.1 See LICENCE for details. */
/* Concurrent Control with "Readers" and "Writers", P.J. Courtois et al, 1971 */
#if !defined ccrw2_included
#define ccrw2_included
#if defined SOXR_LIB
#include "internal.h"
#endif
#if defined _OPENMP
#include <omp.h>
typedef struct {
int readcount, writecount; /* initial value = 0 */
omp_lock_t mutex_1, mutex_2, mutex_3, w, r; /* initial value = 1 */
} ccrw2_t; /* Problem #2: `writers-preference' */
#define ccrw2_become_reader(p) do {\
omp_set_lock(&p.mutex_3);\
omp_set_lock(&p.r);\
omp_set_lock(&p.mutex_1);\
if (++p.readcount == 1) omp_set_lock(&p.w);\
omp_unset_lock(&p.mutex_1);\
omp_unset_lock(&p.r);\
omp_unset_lock(&p.mutex_3);\
} while (0)
#define ccrw2_cease_reading(p) do {\
omp_set_lock(&p.mutex_1);\
if (!--p.readcount) omp_unset_lock(&p.w);\
omp_unset_lock(&p.mutex_1);\
} while (0)
#define ccrw2_become_writer(p) do {\
omp_set_lock(&p.mutex_2);\
if (++p.writecount == 1) omp_set_lock(&p.r);\
omp_unset_lock(&p.mutex_2);\
omp_set_lock(&p.w);\
} while (0)
#define ccrw2_cease_writing(p) do {\
omp_unset_lock(&p.w);\
omp_set_lock(&p.mutex_2);\
if (!--p.writecount) omp_unset_lock(&p.r);\
omp_unset_lock(&p.mutex_2);\
} while (0)
#define ccrw2_init(p) do {\
omp_init_lock(&p.mutex_1);\
omp_init_lock(&p.mutex_2);\
omp_init_lock(&p.mutex_3);\
omp_init_lock(&p.w);\
omp_init_lock(&p.r);\
} while (0)
#define ccrw2_clear(p) do {\
omp_destroy_lock(&p.r);\
omp_destroy_lock(&p.w);\
omp_destroy_lock(&p.mutex_3);\
omp_destroy_lock(&p.mutex_2);\
omp_destroy_lock(&p.mutex_1);\
} while (0)
#else
typedef int ccrw2_t;
#define ccrw2_become_reader(x) (void)(x)
#define ccrw2_cease_reading(x) (void)(x)
#define ccrw2_become_writer(x) (void)(x)
#define ccrw2_cease_writing(x) (void)(x)
#define ccrw2_init(x) (void)(x)
#define ccrw2_clear(x) (void)(x)
#endif /* _OPENMP */
#endif
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