Commit 651698d1 authored by Rémi Denis-Courmont's avatar Rémi Denis-Courmont
Browse files

Read/write locks

parent f3aaa6e2
......@@ -107,6 +107,7 @@ typedef pthread_t vlc_thread_t;
typedef pthread_mutex_t vlc_mutex_t;
#define VLC_STATIC_MUTEX PTHREAD_MUTEX_INITIALIZER
typedef pthread_cond_t vlc_cond_t;
typedef pthread_rwlock_t vlc_rwlock_t;
typedef pthread_key_t vlc_threadvar_t;
typedef struct vlc_timer_t vlc_timer_t;
......@@ -143,6 +144,17 @@ typedef struct
#define VLC_STATIC_MUTEX { 0, }
typedef HANDLE vlc_cond_t;
typedef struct
{
vlc_mutex_t mutex;
vlc_cond_t read_wait;
vlc_cond_t write_wait;
unsigned long readers;
unsigned long writers;
DWORD writer;
} vlc_rwlock_t;
typedef DWORD vlc_threadvar_t;
typedef struct vlc_timer_t vlc_timer_t;
struct vlc_timer_t
......@@ -176,6 +188,11 @@ VLC_EXPORT( void, vlc_cond_signal, (vlc_cond_t *) );
VLC_EXPORT( void, vlc_cond_broadcast, (vlc_cond_t *) );
VLC_EXPORT( void, vlc_cond_wait, (vlc_cond_t *, vlc_mutex_t *) );
VLC_EXPORT( int, vlc_cond_timedwait, (vlc_cond_t *, vlc_mutex_t *, mtime_t) );
VLC_EXPORT( void, vlc_rwlock_init, (vlc_rwlock_t *) );
VLC_EXPORT( void, vlc_rwlock_destroy, (vlc_rwlock_t *) );
VLC_EXPORT( void, vlc_rwlock_rdlock, (vlc_rwlock_t *) );
VLC_EXPORT( void, vlc_rwlock_wrlock, (vlc_rwlock_t *) );
VLC_EXPORT( void, vlc_rwlock_unlock, (vlc_rwlock_t *) );
VLC_EXPORT( int, vlc_threadvar_create, (vlc_threadvar_t * , void (*) (void *) ) );
VLC_EXPORT( void, vlc_threadvar_delete, (vlc_threadvar_t *) );
VLC_EXPORT( int, vlc_threadvar_set, (vlc_threadvar_t, void *) );
......
......@@ -519,6 +519,11 @@ vlc_poll
vlc_rand_bytes
vlc_release
vlc_restorecancel
vlc_rwlock_destroy
vlc_rwlock_init
vlc_rwlock_rdlock
vlc_rwlock_unlock
vlc_rwlock_wrlock
vlc_savecancel
vlc_sd_Create
vlc_sd_GetNames
......
......@@ -375,6 +375,51 @@ int vlc_cond_timedwait (vlc_cond_t *p_condvar, vlc_mutex_t *p_mutex,
return val;
}
/**
* Initializes a read/write lock.
*/
void vlc_rwlock_init (vlc_rwlock_t *lock)
{
if (pthread_rwlock_init (lock, NULL))
abort ();
}
/**
* Destroys an initialized unused read/write lock.
*/
void vlc_rwlock_destroy (vlc_rwlock_t *lock)
{
int val = pthread_rwlock_destroy (lock);
VLC_THREAD_ASSERT ("destroying R/W lock");
}
/**
* Acquires a read/write lock for reading. Recursion is allowed.
*/
void vlc_rwlock_rdlock (vlc_rwlock_t *lock)
{
int val = pthread_rwlock_rdlock (lock);
VLC_THREAD_ASSERT ("acquiring R/W lock for reading");
}
/**
* Acquires a read/write lock for writing. Recursion is not allowed.
*/
void vlc_rwlock_wrlock (vlc_rwlock_t *lock)
{
int val = pthread_rwlock_wrlock (lock);
VLC_THREAD_ASSERT ("acquiring R/W lock for writing");
}
/**
* Releases a read/write lock.
*/
void vlc_rwlock_unlock (vlc_rwlock_t *lock)
{
int val = pthread_rwlock_unlock (lock);
VLC_THREAD_ASSERT ("releasing R/W lock");
}
/**
* Allocates a thread-specific variable.
* @param key where to store the thread-specific variable handle
......
......@@ -34,6 +34,7 @@
#include "libvlc.h"
#include <stdarg.h>
#include <assert.h>
#include <limits.h>
static vlc_threadvar_t cancel_key;
......@@ -291,6 +292,82 @@ int vlc_cond_timedwait (vlc_cond_t *p_condvar, vlc_mutex_t *p_mutex,
return (result == WAIT_OBJECT_0) ? 0 : ETIMEDOUT;
}
/*** Read/write locks */
/* SRW (Slim Read Write) locks are available in Vista+ only */
void vlc_rwlock_init (vlc_rwlock_t *lock)
{
vlc_mutex_init (&lock->mutex);
vlc_cond_init (&lock->read_wait);
vlc_cond_init (&lock->write_wait);
lock->readers = 0; /* active readers */
lock->writers = 0; /* waiting or active writers */
lock->writer = 0; /* ID of active writer */
}
/**
* Destroys an initialized unused read/write lock.
*/
void vlc_rwlock_destroy (vlc_rwlock_t *lock)
{
vlc_cond_destroy (&lock->read_wait);
vlc_cond_destroy (&lock->write_wait);
vlc_mutex_destroy (&lock->mutex);
}
/**
* Acquires a read/write lock for reading. Recursion is allowed.
*/
void vlc_rwlock_rdlock (vlc_rwlock_t *lock)
{
vlc_mutex_lock (&lock->mutex);
while (lock->writers > 0) /* Favor writers to avoid starving */
vlc_cond_wait (&lock->read_wait, &lock->mutex);
if (lock->readers == ULONG_MAX)
abort ();
lock->readers++;
vlc_mutex_unlock (&lock->mutex);
}
/**
* Acquires a read/write lock for writing. Recursion is not allowed.
*/
void vlc_rwlock_wrlock (vlc_rwlock_t *lock)
{
vlc_mutex_lock (&lock->mutex);
if (lock->writers == ULONG_MAX)
abort ();
lock->writers++;
while ((lock->readers > 0) || (lock->writer != 0))
vlc_cond_wait (&lock->write_wait, &lock->mutex);
lock->writer = GetCurrentThreadId ();
vlc_mutex_unlock (&lock->mutex);
}
/**
* Releases a read/write lock.
*/
void vlc_rwlock_unlock (vlc_rwlock_t *lock)
{
vlc_mutex_lock (&lock->mutex);
if (lock->readers > 0)
lock->readers--; /* Read unlock */
else
{
lock->writer = 0; /* Write unlock */
assert (lock->writers > 0);
lock->writers--;
}
if (lock->writers > 0)
{
if (lock->readers == 0)
vlc_cond_signal (&lock->write_wait);
}
else
vlc_cond_broadcast (&lock->read_wait);
vlc_mutex_unlock (&lock->mutex);
}
/*** Thread-specific variables (TLS) ***/
int vlc_threadvar_create (vlc_threadvar_t *p_tls, void (*destr) (void *))
{
......
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