Atomic operations (currently same ones as in garbage collector)

include/vlc_atomic.h

+/*****************************************************************************
+ * vlc_atomic.h:
+ *****************************************************************************
+ * Copyright (C) 2010 Rémi Denis-Courmont
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
+ *****************************************************************************/
+
+#ifndef VLC_ATOMIC_H
+# define VLC_ATOMIC_H
+
+/**
+ * \file
+ * Atomic operations do not require locking, but they are not very powerful.
+ */
+
+/**
+ * Memory storage space for an atom. Never access it directly.
+ */
+typedef union
+{
+    uintptr_t u;
+    intptr_t  s;
+} vlc_atomic_t;
+
+/* All functions return the atom value _after_ the operation. */
+
+VLC_EXPORT(uintptr_t, vlc_atomic_get, (const vlc_atomic_t *));
+VLC_EXPORT(uintptr_t, vlc_atomic_set, (vlc_atomic_t *, uintptr_t));
+VLC_EXPORT(uintptr_t, vlc_atomic_add, (vlc_atomic_t *, uintptr_t));
+
+static inline uintptr_t vlc_atomic_sub (vlc_atomic_t *atom, uintptr_t v)
+{
+    return vlc_atomic_add (atom, -v);
+}
+
+static inline uintptr_t vlc_atomic_inc (vlc_atomic_t *atom)
+{
+    return vlc_atomic_add (atom, 1);
+}
+
+static inline uintptr_t vlc_atomic_dec (vlc_atomic_t *atom)
+{
+    return vlc_atomic_sub (atom, 1);
+}
+
+#endif

src/Makefile.am

@@ -46,6 +46,7 @@ pluginsinclude_HEADERS = \
 	../include/vlc_aout_mixer.h \
 	../include/vlc_arrays.h \
 	../include/vlc_art_finder.h \
+	../include/vlc_atomic.h \
 	../include/vlc_avcodec.h \
 	../include/vlc_bits.h \
 	../include/vlc_block.h \
@@ -271,17 +272,20 @@ endif
 endif
 
 SOURCES_libvlc_beos = \
+	misc/atomic.c \
 	misc/pthread.c \
 	$(NULL)
 
 SOURCES_libvlc_darwin = \
 	config/dirs_macos.c \
+	misc/atomic.c \
 	misc/pthread.c \
 	misc/darwin_specific.c \
 	$(NULL)
 
 SOURCES_libvlc_linux = \
 	config/dirs_xdg.c \
+	misc/atomic.c \
 	misc/pthread.c \
 	misc/linux_specific.c \
 	$(NULL)
@@ -289,12 +293,14 @@ SOURCES_libvlc_linux = \
 SOURCES_libvlc_win32 = \
 	win32/dirs.c \
 	win32/specific.c \
+	win32/atomic.c \
 	win32/thread.c \
 	win32/winsock.c \
 	$(NULL)
 
 SOURCES_libvlc_other = \
 	config/dirs_xdg.c \
+	misc/atomic.c \
 	misc/pthread.c \
 	misc/not_specific.c
 

src/libvlccore.sym

@@ -497,6 +497,9 @@ vlc_clone
 VLC_CompileBy
 VLC_CompileHost
 VLC_Compiler
+vlc_atomic_get
+vlc_atomic_set
+vlc_atomic_add
 vlc_cond_broadcast
 vlc_cond_destroy
 vlc_cond_init

src/misc/atomic.c

+/*****************************************************************************
+ * atomic.c:
+ *****************************************************************************
+ * Copyright (C) 2010 Rémi Denis-Courmont
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
+ *****************************************************************************/
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <vlc_common.h>
+#include <vlc_atomic.h>
+
+#if defined (__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4)
+/* GCC intrinsics */
+
+uintptr_t vlc_atomic_get (const vlc_atomic_t *atom)
+{
+    __sync_synchronize ();
+    return atom->u;
+}
+
+uintptr_t vlc_atomic_set (vlc_atomic_t *atom, uintptr_t v)
+{
+    atom->u = v;
+    __sync_synchronize ();
+    return v;
+}
+
+uintptr_t vlc_atomic_add (vlc_atomic_t *atom, uintptr_t v)
+{
+    return __sync_add_and_fetch (&atom->u, v);
+}
+
+#else
+/* Worst-case fallback implementation with a mutex */
+
+static vlc_mutex_t lock = VLC_STATIC_MUTEX;
+
+uintptr_t vlc_atomic_get (const vlc_atomic_t *atom)
+{
+    uintptr_t v;
+
+    vlc_mutex_lock (&lock);
+    v = atom->u;
+    vlc_mutex_unlock (&lock);
+    return v;
+}
+
+uintptr_t vlc_atomic_set (vlc_atomic_t *atom, uintptr_t v)
+{
+    vlc_mutex_lock (&lock);
+    atom->u = v;
+    vlc_mutex_unlock (&lock);
+    return v;
+}
+
+uintptr_t vlc_atomic_add (vlc_atomic_t *atom, uintptr_t v)
+{
+    vlc_mutex_lock (&lock);
+    atom->u += v;
+    v = atom->u;
+    vlc_mutex_unlock (&lock);
+    return v;
+}
+
+#endif

src/win32/atomic.c

+/*****************************************************************************
+ * atomic.c:
+ *****************************************************************************
+ * Copyright (C) 2010 Rémi Denis-Courmont
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
+ *****************************************************************************/
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <vlc_common.h>
+#include <vlc_atomic.h>
+
+uintptr_t vlc_atomic_get (const vlc_atomic_t *atom)
+{
+    return atom->u;
+}
+
+uintptr_t vlc_atomic_set (vlc_atomic_t *atom, uintptr_t v)
+{
+    atom->u = v;
+    return v;
+}
+
+uintptr_t vlc_atomic_add (vlc_atomic_t *atom, uintptr_t v)
+{
+#if defined (WIN64)
+    return InterlockedAdd64 (&atom->s, v);
+#else
+    return InterlockedAdd (&atom->s, v);
+#endif
+}