ringbuf initial version

firmware/slavechip/ringbuf_test.c

@@ -0,0 +1,11 @@
+#include "ringbuffer.h"
+
+
+ringbuf_t foo;
+char buf[22];
+
+
+int main(){
+    ringbuf_init(&foo,buf,sizeof(buf));
+}
+

firmware/slavechip/ringbuffer.c

@@ -0,0 +1,77 @@
+#include "ringbuffer.h"
+
+#include <util/atomic.h>
+
+
+/* Very generic implementation of an interrupt-safe ringbuffer
+ *
+ * Contention handling:
+ * - writing of pointers only with interrupt lock
+ * - reading of pointers allowed at any time
+ * - volatile not really necessary, unless you really need the functions to
+ *   react to freespace/newdata while they're running
+ * 
+ * PUT AND GET ARE NOT REENTRANT!
+ */
+
+void ringbuf_init(ringbuf_t *rb, char* buf, int size){
+    rb->startptr = buf;
+    rb->endptr = buf+size;
+    rb->readpos = buf;
+    rb->writepos = buf;
+}
+
+/* pushes a value onto the ringbuffer
+ * returns 0 on success, 1 on buffer full
+ */
+uint8_t ringbuf_put(ringbuf_t *rb, uint8_t value){
+    // calculate next ptr pos
+    char* next = rb->writepos + 1;
+    char* readpos;
+    if(next >= rb->endptr){
+        next = rb->startptr;
+    }
+    // check for space
+    ATOMIC_BLOCK(ATOMIC_RESTORESTATE){
+        readpos = rb->readpos;
+    }
+    if(next == readpos){
+        return(1); // give up
+    }
+    *(rb->writepos) = value;
+    ATOMIC_BLOCK(ATOMIC_RESTORESTATE){
+        rb->writepos = next;
+    }
+    return(0);
+}
+
+/* gets a value from the ringbuffer
+ * returns value on success, -1 on buffer empty
+ */
+int16_t ringbuf_get(ringbuf_t *rb){
+    uint8_t value;
+    char* next;
+    char* writepos;
+    // calculate next ptr pos
+    next = rb->readpos + 1;
+    if(next >= rb->endptr){
+        next = rb->startptr;
+    }
+    //check for empty
+    ATOMIC_BLOCK(ATOMIC_RESTORESTATE){
+        writepos = rb->writepos;
+    }
+    if(rb->readpos == writepos){
+        return(-1);
+    }
+    value = *(rb->readpos);
+    ATOMIC_BLOCK(ATOMIC_RESTORESTATE){
+        rb->readpos = next;
+    }
+    return(value);
+}
+
+
+
+
+

firmware/slavechip/ringbuffer.h

@@ -0,0 +1,12 @@
+#include <stdint.h>
+
+typedef struct {
+    char* startptr;
+    char* endptr; // points beyond last element
+    char* readpos;
+    char* writepos;
+} ringbuf_t;
+
+
+void ringbuf_init(ringbuf_t* rb, char* buf, int size);
+