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+/*
+ * -------------------------------------------------------------
+ *
+ * $Header: /cvs/pthreads-win32/pthreads/semaphore.c,v 1.1.2.1 1998/12/28 23:01:14 rpj Exp $
+ *
+ * Module: semaphore.c
+ *
+ * Purpose:
+ * Semaphores aren't actually part of the PThreads standard.
+ * They are defined by the POSIX Standard:
+ *
+ * POSIX 1003.1b-1993 (POSIX.1b)
+ *
+ * They are supposed to follow the older UNIX convention for
+ * reporting errors. That is, on failure they are supposed
+ * to return a value of -1 and store the appropriate error
+ * number into 'errno'.
+ * HOWEVER,errno cannot be modified in a multithreaded
+ * program on WIN32; therefore, the value is returned as
+ * the function value.
+ * It is recommended that you compare for zero (0) for success
+ * instead of -1 for failure when checking the status of
+ * these functions.
+ *
+ * Contents:
+ * Public Methods Author
+ * -------------- ------
+ * sem_init John E. Bossom Mar 1998
+ * sem_destroy John E. Bossom Mar 1998
+ * sem_trywait John E. Bossom Mar 1998
+ * sem_wait John E. Bossom Mar 1998
+ * sem_post John E. Bossom Mar 1998
+ *
+ * Private Methods
+ * ---------------
+ *
+ * -------------------------------------------------------------
+ */
+#include <pthread.h>
+#include <windows.h>
+#include <process.h>
+#include <errno.h>
+#include <string.h>
+
+#include "semaphore.h"
+
+
+
+int
+sem_init (sem_t * sem, int pshared, unsigned int value)
+ /*
+ * ------------------------------------------------------
+ * DOCPUBLIC
+ * This function initializes an unnamed semaphore. the
+ * initial value of the semaphore is 'value'
+ *
+ * PARAMETERS
+ * sem
+ * pointer to an instance of sem_t
+ *
+ * pshared
+ * if zero, this semaphore may only be shared between
+ * threads in the same process.
+ * if nonzero, the semaphore can be shared between
+ * processes
+ *
+ * value
+ * initial value of the semaphore counter
+ *
+ * DESCRIPTION
+ * This function initializes an unnamed semaphore. The
+ * initial value of the semaphore is set to 'value'.
+ *
+ * RESULTS
+ * 0 successfully created semaphore,
+ * EINVAL 'sem' is not a valid semaphore,
+ * ENOSPC a required resource has been exhausted,
+ * ENOSYS semaphores are not supported,
+ * EPERM the process lacks appropriate privilege
+ *
+ * ------------------------------------------------------
+ */
+{
+ int result = 0;
+
+ if (pshared != 0)
+ {
+ /*
+ * Creating a semaphore that can be shared between
+ * processes
+ */
+ result = EPERM;
+
+ }
+ else
+ {
+ /*
+ * NOTE: Taking advantage of the fact that
+ * sem_t is a simple structure with one entry;
+ * We don't have to allocate it...
+ */
+ *sem = CreateSemaphore (
+ 0,
+ value,
+ 0x7FFFFFF,
+ NULL);
+
+ if (*sem == 0)
+ {
+ result = ENOSPC;
+ }
+ }
+
+ return (result);
+
+} /* sem_init */
+
+
+int
+sem_destroy (sem_t * sem)
+ /*
+ * ------------------------------------------------------
+ * DOCPUBLIC
+ * This function destroys an unnamed semaphore.
+ *
+ * PARAMETERS
+ * sem
+ * pointer to an instance of sem_t
+ *
+ * DESCRIPTION
+ * This function destroys an unnamed semaphore.
+ *
+ * RESULTS
+ * 0 successfully destroyed semaphore,
+ * EINVAL 'sem' is not a valid semaphore,
+ * ENOSYS semaphores are not supported,
+ * EBUSY threads (or processes) are currently
+ * blocked on 'sem'
+ *
+ * ------------------------------------------------------
+ */
+{
+ return ((sem == NULL)
+ ? EINVAL
+ : (CloseHandle (*sem)
+ ? 0
+ : EINVAL));
+
+} /* sem_destroy */
+
+
+int
+sem_trywait (sem_t * sem)
+ /*
+ * ------------------------------------------------------
+ * DOCPUBLIC
+ * This function tries to wait on a semaphore.
+ *
+ * PARAMETERS
+ * sem
+ * pointer to an instance of sem_t
+ *
+ * DESCRIPTION
+ * This function tries to wait on a semaphore. If the
+ * semaphore value is greater than zero, it decreases
+ * its value by one. If the semaphore value is zero, then
+ * this function returns immediately with the error EAGAIN
+ *
+ * RESULTS
+ * 0 successfully destroyed semaphore,
+ * EAGAIN the semaphore was already locked,
+ * EINVAL 'sem' is not a valid semaphore,
+ * ENOSYS semaphores are not supported,
+ * EINTR the function was interrupted by a signal,
+ * EDEADLK a deadlock condition was detected.
+ *
+ * ------------------------------------------------------
+ */
+{
+ return ((sem == NULL)
+ ? EINVAL
+ : ((WaitForSingleObject (*sem, 0) == WAIT_TIMEOUT)
+ ? EAGAIN
+ : 0));
+
+} /* sem_trywait */
+
+
+int
+sem_wait (sem_t * sem)
+ /*
+ * ------------------------------------------------------
+ * DOCPUBLIC
+ * This function waits on a semaphore.
+ *
+ * PARAMETERS
+ * sem
+ * pointer to an instance of sem_t
+ *
+ * DESCRIPTION
+ * This function waits on a semaphore. If the
+ * semaphore value is greater than zero, it decreases
+ * its value by one. If the semaphore value is zero, then
+ * the calling thread (or process) is blocked until it can
+ * successfully decrease the value or until interrupted by
+ * a signal.
+ *
+ * RESULTS
+ * 0 successfully destroyed semaphore,
+ * EINVAL 'sem' is not a valid semaphore,
+ * ENOSYS semaphores are not supported,
+ * EINTR the function was interrupted by a signal,
+ * EDEADLK a deadlock condition was detected.
+ *
+ * ------------------------------------------------------
+ */
+{
+
+ return ((sem == NULL)
+ ? EINVAL
+ : pthreadCancelableWait (*sem)
+ );
+
+} /* sem_wait */
+
+
+int
+sem_post (sem_t * sem)
+ /*
+ * ------------------------------------------------------
+ * DOCPUBLIC
+ * This function posts a wakeup to a semaphore.
+ *
+ * PARAMETERS
+ * sem
+ * pointer to an instance of sem_t
+ *
+ * DESCRIPTION
+ * This function posts a wakeup to a semaphore. If there
+ * are waiting threads (or processes), on is awakened;
+ * otherwise, the semaphore value is incremented by one.
+ *
+ * RESULTS
+ * 0 successfully destroyed semaphore,
+ * EINVAL 'sem' is not a valid semaphore,
+ * ENOSYS semaphores are not supported,
+ *
+ * ------------------------------------------------------
+ */
+{
+ return ((sem == NULL)
+ ? EINVAL
+ : (ReleaseSemaphore (*sem, 1, 0)
+ ? 0
+ : EINVAL));
+
+} /* sem_post */