Merge John Bossom's code into the main trunk. See ChangeLog for details.snapshot-1999-01-04-1305

This will be tagged as snapshot-1999-01-04-1305

1 files changed, 254 insertions, 0 deletions

diff --git a/semaphore.c b/semaphore.c
new file mode 100644
index 0000000..c163336
--- /dev/null
+++ b/semaphore.c
@@ -0,0 +1,254 @@
+/*
+ * -------------------------------------------------------------
+ *
+ * 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 */