1 files changed, 113 insertions, 0 deletions
diff --git a/cas.c b/cas.c
new file mode 100644
index 0000000..284c6dc
--- /dev/null
+++ b/cas.c
@@ -0,0 +1,113 @@
+/*
+ * File     : atomic.c
+ * Author   : Jérémy Zurcher  <jeremy@asynk.ch>
+ * Date     : 01/11/09 
+ * License  :
+ *
+ *  Permission is hereby granted, free of charge, to any person obtaining
+ *  a copy of this software and associated documentation files (the
+ *  "Software"), to deal in the Software without restriction, including
+ *  without limitation the rights to use, copy, modify, merge, publish,
+ *  distribute, sublicense, and/or sell copies of the Software, and to
+ *  permit persons to whom the Software is furnished to do so, subject to
+ *  the following conditions:
+ *  
+ *  The above copyright notice and this permission notice shall be
+ *  included in all copies or substantial portions of the Software.
+ *  
+ *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ *  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ *  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ *  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ *  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ *  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ *  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ */
+
+#include <stdio.h>
+
+typedef struct split {
+    volatile void *ptr;
+    volatile unsigned int count;
+} split_t;
+
+typedef union pointer {
+    split_t split;
+    volatile unsigned long long concat;
+} pointer_t;
+
+
+/* CMPXCHG8B m64   Compare EDX:EAX with m64. If equal, set ZF and load ECX:EBX into m64. Else, clear ZF and load m64 into EDX:EAX. */
+static inline unsigned int compare_and_swap(volatile unsigned long long *mem,
+                                            volatile unsigned long long old,
+                                            volatile unsigned long long new) {
+    char result;
+    __asm__ __volatile__("lock; cmpxchg8b %0; setz %1;"
+            : "=m"(*mem), "=q"(result)
+            : "m"(*mem), "d" ((unsigned long)(old>>32)), "a" ((unsigned long)old),
+            "c" ((unsigned long)(new>>32)), "b" ((unsigned long)new)
+            : "memory");
+    return (int)result;
+}
+
+/* CMPXCHG8B m64   Compare EDX:EAX with m64. If equal, set ZF and load ECX:EBX into m64. Else, clear ZF and load m64 into EDX:EAX. */
+static inline unsigned int cas( volatile split_t *mem,
+                                volatile split_t old,
+                                volatile split_t new ) {
+    char result;
+    __asm__ __volatile__("lock; cmpxchg8b %0; setz %1;"
+            : "=m"(*mem), "=q"(result)
+            : "m"(*mem), "d" (old.count), "a" (old.ptr),
+            "c" (new.count), "b" (new.ptr)
+            : "memory");
+    return (int)result;
+}
+
+
+int test_compare_and_swap () {
+    pointer_t mem, old, new;
+    return compare_and_swap(&mem.concat, old.concat, new.concat);
+}
+
+int test_cas () {
+    pointer_t mem, old, new;
+    return cas(&mem.split, old.split, new.split);
+}
+
+int main( int argc, char*argv[], char*env[] ) {
+    int ret;
+
+    pointer_t mem, old, new;
+    
+    mem.split.count = 0;
+    old.split.count = 6;
+    new.split.count = 666;
+    mem.split.ptr = (void*)&argc;
+    old.split.ptr = (void*)&argc;
+    new.split.ptr = (void*)&argv;
+
+    ret = compare_and_swap(&mem.concat, old.concat, new.concat);
+    printf("ret %d -> (%d,%X)\n", ret, mem.split.count, (unsigned int)mem.split.ptr);
+
+    mem.split.count=6;
+    ret = compare_and_swap(&mem.concat, old.concat, new.concat);
+    printf("ret %d -> (%d,%X)\n", ret, mem.split.count, (unsigned int)mem.split.ptr);
+
+    mem.split.count = 0;
+    old.split.count = 6;
+    new.split.count = 666;
+    mem.split.ptr = (void*)&argc;
+    old.split.ptr = (void*)&argc;
+    new.split.ptr = (void*)&argv;
+
+    ret = cas(&mem.split, old.split, new.split);
+    printf("ret %d -> (%d,%X)\n", ret, mem.split.count, (unsigned int)mem.split.ptr);
+
+    mem.split.count=6;
+    ret = cas(&mem.split, old.split, new.split);
+    printf("ret %d -> (%d,%X)\n", ret, mem.split.count, (unsigned int)mem.split.ptr);
+
+    return 0;
+}
+