From 742c6f32e038c90967e15f4740fcdacda1ad0f1f Mon Sep 17 00:00:00 2001
From: Matthias Benkard <code@mail.matthias.benkard.de>
Date: Thu, 7 Feb 2008 23:11:34 +0100
Subject: Objective-C layer: Implement locking using semaphores.

darcs-hash:3a1f9d1f6597b32c20efcd7ab2cf2721c1bdfe43
---
 Objective-C/libobjcl.h | 15 ++++++++++++++
 Objective-C/libobjcl.m | 53 ++++++++++++++++++++++++++++++++++++++++++++++++--
 configure.ac           |  2 ++
 3 files changed, 68 insertions(+), 2 deletions(-)

diff --git a/Objective-C/libobjcl.h b/Objective-C/libobjcl.h
index 270af45..afe9f56 100644
--- a/Objective-C/libobjcl.h
+++ b/Objective-C/libobjcl.h
@@ -43,6 +43,18 @@ typedef Ivar IVAR_T;
 typedef struct objc_ivar *IVAR_T;
 #endif
 
+#ifdef HAVE_SYS_SEM_H
+#include <sys/sem.h>
+/* According to the Single Unix Specification, Version 3, the semun
+   union type must be defined by the application writer as follows: */
+union semun
+{
+  int              val;    /* Value for SETVAL */
+  struct semid_ds *buf;    /* Buffer for IPC_STAT, IPC_SET */
+  unsigned short  *array;  /* Array for GETALL, SETALL */
+};
+#endif
+
 extern NSException *objcl_oom_exception;
 extern id objcl_current_exception;
 extern void *objcl_current_exception_lock;
@@ -159,3 +171,6 @@ objcl_acquire_lock (void *lock);
 
 void
 objcl_release_lock (void *lock);
+
+void
+objcl_initialise_lock (void **lock);
diff --git a/Objective-C/libobjcl.m b/Objective-C/libobjcl.m
index 3cbf3e5..3242fcf 100644
--- a/Objective-C/libobjcl.m
+++ b/Objective-C/libobjcl.m
@@ -65,6 +65,8 @@ objcl_initialise_runtime (void)
 #ifdef __NEXT_RUNTIME__
   PyObjC_SetupRuntimeCompat ();
 #endif
+
+  objcl_initialise_lock (&objcl_current_exception_lock);
 }
 
 
@@ -558,15 +560,62 @@ objcl_create_imp (IMP callback,
 }
 
 
+void
+objcl_initialise_lock (void **lock)
+{
+#ifdef HAVE_SYS_SEM_H
+  int sem;
+  union semun initop;
+
+  sem = semget (IPC_PRIVATE, 1, IPC_CREAT | 0600);
+  *lock = malloc (sizeof (int));
+  *((int *) *lock) = sem;
+
+  initop.val = 1;
+  semctl (sem, 0, SETVAL, initop);
+#else
+#warning "I do not know how to do locking on this platform."
+#endif
+}
+
+
 void
 objcl_acquire_lock (void *lock)
 {
-#warning "FIXME"
+#ifdef HAVE_SYS_SEM_H
+  struct sembuf op;
+  op.sem_num = 0; op.sem_op = +1; op.sem_flg = 0;
+
+  if ((semop (*((int *) lock), &op, 1)) < 0)
+    {
+      [[NSException exceptionWithName: @"MLKLockLossage"
+                    reason: @"Acquiring the exception lock failed (don't ask me why)."
+                    userInfo: nil] raise];
+    }
+
+  TRACE (@"Exception buffer locked.");
+#else
+#warning "I do not know how to do locking on this platform."
+#endif
 }
 
 
 void
 objcl_release_lock (void *lock)
 {
-#warning "FIXME"
+#ifdef HAVE_SYS_SEM_H
+  struct sembuf op;
+  op.sem_num = 0; op.sem_op = +1; op.sem_flg = 0;
+
+  if ((semop (*((int *) lock), &op, 1)) < 0)
+    {
+      [[NSException exceptionWithName: @"MLKLockLossage"
+                    reason: @"Acquiring the exception lock failed (don't ask me why)."
+                    userInfo: nil] raise];
+    }
+
+  TRACE (@"Exception buffer unlocked.");
+#else
+#warning "I do not know how to do locking on this platform."
+#endif
 }
diff --git a/configure.ac b/configure.ac
index 9ea32af..1a2b245 100644
--- a/configure.ac
+++ b/configure.ac
@@ -31,6 +31,8 @@ if test x$HAVE_LIBFFI = x1; then
   AC_CHECK_HEADERS([ffi.h ffi/ffi.h], [HAVE_ANY_FFI_H=1; break])
 fi
 
+AC_CHECK_HEADERS([sys/sem.h])
+
 AC_SUBST(HAVE_ANY_FFI_H)
 AC_SUBST(HAVE_LIBFFI)
 AC_CONFIG_HEADERS([config.h])
-- 
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