From 7e2e924362df5556ff55ee7e1b8738a05d067ec4 Mon Sep 17 00:00:00 2001
From: rpj <rpj>
Date: Tue, 4 Jun 2002 07:14:57 +0000
Subject: Another attempt to get sem_getvalue working.

---
 ChangeLog      |  9 +++++++++
 sem_getvalue.c | 28 ++++++++++------------------
 sem_post.c     |  4 ++--
 3 files changed, 21 insertions(+), 20 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 693e04d..8a36181 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2002-06-04  Rob Fanner  <rfanner@stonethree.com>
+
+	* sem_getvalue.c (sem_getvalue): The Johnson M. Hart
+	approach didn't work - we are forced to take an
+	intrusive approach. We try to decrement the sema
+	and then immediately release it again to get the
+	value. There is a small probability that this may
+	block other threads, but only momentarily.
+
 2002-06-03  Ross Johnson  <rpj@digit.ise.canberra.edu.au>
 
 	* sem_init.c (sem_init): Initialise Win32 semaphores
diff --git a/sem_getvalue.c b/sem_getvalue.c
index b3033d3..297bc6c 100644
--- a/sem_getvalue.c
+++ b/sem_getvalue.c
@@ -76,6 +76,7 @@ sem_getvalue(sem_t * sem, int * sval)
       */
 {
   int result = 0;
+	long value;
  
   if ( sem == NULL || *sem == NULL || sval == NULL )
     {
@@ -89,27 +90,17 @@ sem_getvalue(sem_t * sem, int * sval)
       result = ENOSYS;
  
 #else
-      long value = *sval;
- 
-			/* From "Win32 System Programming - Second Edition"
-			 * by Johnson M Hart, chapter 9, page 256 :
-			 *
-			 * "The release count must be greater than zero, but if it
-			 * would cause the semaphore count to exceed the maximum,
-			 * the call will fail, returning FALSE, and the count will
-			 * remain unchanged. Releasing a semaphore with a large count
-			 * is a method used to obtain the current count atomically
-			 * (of course, another thread might change the value immediately)."
-			 */
-
-      if ( ! ReleaseSemaphore( (*sem)->sem, _POSIX_SEM_VALUE_MAX + 1, &value) )
+			
+      if ( WaitForSingleObject( (*sem)->sem, 0 ) == WAIT_TIMEOUT )
         {
-          *sval = value;
+					/* Failed - must be zero. */
+          value = 0;
         }
       else
         {
-					/* This should NEVER occur. */
-          result = ENOSYS;
+					/* Decremented sema - release it and note the value. */
+					(void) ReleaseSemaphore( (*sem)->sem, 1L, &value );
+          value++;
         }
  
 #endif
@@ -121,7 +112,8 @@ sem_getvalue(sem_t * sem, int * sval)
       errno = result;
       return -1;
     }
- 
+
+	*sval = value;
   return 0;
  
 }   /* sem_getvalue */
diff --git a/sem_post.c b/sem_post.c
index afa7533..d055d93 100644
--- a/sem_post.c
+++ b/sem_post.c
@@ -76,7 +76,7 @@ sem_post (sem_t * sem)
 
   if (sem == NULL || *sem == NULL)
     {
-	result = EINVAL;
+			result = EINVAL;
     }
 
 #ifdef NEED_SEM
@@ -90,7 +90,7 @@ sem_post (sem_t * sem)
 #endif /* NEED_SEM */
 
     {
-	result = EINVAL;
+			result = EINVAL;
     }
 
   if (result != 0)
-- 
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