updated ringbuffer macros as per discussion on #109

libpd_wrapper/util/ringbuffer.c

@@ -16,16 +16,16 @@
 
 #ifdef __APPLE__ // apple atomics
 # include <libkern/OSAtomic.h>
-# define SYNC_FETCH(ptr, val) OSAtomicOr32Barrier(val, ptr)
-# define SYNC_COMPARE(ptr, oldval, newval) \
+# define SYNC_FETCH(ptr) OSAtomicOr32Barrier(0, (volatile uint32_t *)ptr)
+# define SYNC_COMPARE_AND_SWAP(ptr, oldval, newval) \
          OSAtomicCompareAndSwap32Barrier(oldval, newval, ptr) 
 #elif defined(_MSC_VER) // win api atomics
-# define SYNC_FETCH(ptr, val) InterlockedOr(ptr, val)
-# define SYNC_COMPARE(ptr, oldval, newval) \
+# define SYNC_FETCH(ptr) InterlockedOr(ptr, 0)
+# define SYNC_COMPARE_AND_SWAP(ptr, oldval, newval) \
          InterlockedCompareExchange(ptr, oldval, newval)
 #else // gcc atomics
-# define SYNC_FETCH(ptr, val) __sync_fetch_and_or(ptr, val)
-# define SYNC_COMPARE(ptr, oldval, newval) \
+# define SYNC_FETCH(ptr) __sync_fetch_and_or(ptr, 0)
+# define SYNC_COMPARE_AND_SWAP(ptr, oldval, newval) \
          __sync_val_compare_and_swap(ptr, oldval, newval)
 #endif
 
@@ -54,8 +54,8 @@ int rb_available_to_write(ring_buffer *buffer) {
     // Note: The largest possible result is buffer->size - 1 because
     // we adopt the convention that read_idx == write_idx means that the
     // buffer is empty.
-    int read_idx = SYNC_FETCH(&(buffer->read_idx), 0);
-    int write_idx = SYNC_FETCH(&(buffer->write_idx), 0);
+    int read_idx = SYNC_FETCH(&(buffer->read_idx));
+    int write_idx = SYNC_FETCH(&(buffer->write_idx));
     return (buffer->size + read_idx - write_idx - 1) % buffer->size;
   } else {
     return 0;
@@ -64,8 +64,8 @@ int rb_available_to_write(ring_buffer *buffer) {
 
 int rb_available_to_read(ring_buffer *buffer) {
   if (buffer) {
-    int read_idx = SYNC_FETCH(&(buffer->read_idx), 0);
-    int write_idx = SYNC_FETCH(&(buffer->write_idx), 0);
+    int read_idx = SYNC_FETCH(&(buffer->read_idx));
+    int write_idx = SYNC_FETCH(&(buffer->write_idx));
     return (buffer->size + write_idx - read_idx) % buffer->size;
   } else {
     return 0;
@@ -94,7 +94,7 @@ int rb_write_to_buffer(ring_buffer *buffer, int n, ...) {
     write_idx = (write_idx + len) % buffer->size;
   }
   va_end(args);
-  SYNC_COMPARE(&(buffer->write_idx), buffer->write_idx,
+  SYNC_COMPARE_AND_SWAP(&(buffer->write_idx), buffer->write_idx,
       write_idx);  // Includes memory barrier.
   return 0; 
 }
@@ -113,7 +113,7 @@ int rb_read_from_buffer(ring_buffer *buffer, char *dest, int len) {
     memcpy(dest, buffer->buf_ptr + read_idx, d);
     memcpy(dest + d, buffer->buf_ptr, len - d);
   }
-  SYNC_COMPARE(&(buffer->read_idx), buffer->read_idx,
+  SYNC_COMPARE_AND_SWAP(&(buffer->read_idx), buffer->read_idx,
        (read_idx + len) % buffer->size);  // Includes memory barrier.
   return 0; 
 }