C: circular buffer

c/circular-buffer/src/circular_buffer.c

@@ -0,0 +1,75 @@
+#include <malloc.h>
+#include <errno.h>
+
+#include "circular_buffer.h"
+
+#define INC(v, size) {if (++v==size) v=0;}
+
+circular_buffer_t *new_circular_buffer(size_t size)
+{
+    circular_buffer_t *head = NULL;
+
+    if (size > 0) {
+        if ((head=malloc(sizeof(*head)))) {
+            clear_buffer(head);
+            head->size = size;
+            /* we could have only 1 alloc, I just prefer this double alloc
+             */
+            if (!(head->buf  = calloc(size, sizeof(buffer_value_t)))) {
+                free(head);
+                head = NULL;
+            }
+        }
+    }
+    return head;
+}
+
+int do_write(circular_buffer_t *b, buffer_value_t v, int f)
+{
+    if (!f  && b->used == b->size) {
+        errno = ENOBUFS;
+        return EXIT_FAILURE;
+    }
+    b->buf[b->head] = v;
+    INC(b->head, b->size);
+    if (f && b->used == b->size)                  /* overwrite and full */
+        INC(b->tail, b->size);
+    if (b->used < b->size)                        /* normal write */
+        b->used++;
+    return EXIT_SUCCESS;
+}
+
+int read(circular_buffer_t *b, buffer_value_t *p)
+{
+    if (!b->used) {
+        errno = ENODATA;
+        return EXIT_FAILURE;
+    }
+    b->used--;
+    *p = b->buf[b->tail];
+    INC(b->tail, b->size);
+    return EXIT_SUCCESS;
+}
+
+int clear_buffer(circular_buffer_t *b)
+{
+    b->head = 0;
+    b->tail = 0;
+    b->used = 0;
+    return EXIT_SUCCESS;
+}
+
+void delete_buffer(circular_buffer_t *b) {
+    free(b->buf);
+    free(b);
+}
+
+/* See GNUmakefile below for explanation
+ * https://github.com/braoult/exercism/blob/master/c/templates/GNUmakefile
+ */
+#ifdef UNIT_TEST
+int main(int ac, char **av)
+{
+    /* not done for circular buffer : simple exercise, with difficult testing */
+}
+#endif