Add example usage of ring

example/ex.c

@@ -0,0 +1,68 @@
+#include <ring.h>
+#include <stdio.h>
+#include <string.h>
+
+int main(int argc, char **argv) {
+  struct ring_t buf;
+  struct ring_t *res = ring_new(&buf, 20);
+
+  if(res == NULL) {
+    fprintf(stderr, "uh oh\n");
+    return 1;
+  }
+
+  char *write_str = strdup("abcdefghijklmnopqrstuvwxyz");
+  size_t len = ring_write(&buf, write_str, 26);
+
+  if(len != 6) {
+    fprintf(stderr, "what happened? (%zu)\n", len);
+    return 1;
+  }
+
+  len = 5;
+  char *read_str = ring_read(&buf, &len);
+
+  if(len) {
+    fprintf(stderr, "that's not good (%zu)\n", len);
+    return 1;
+  }
+
+  printf("first read: %s\n", read_str);
+  len = ring_write(&buf, write_str + 20, 6);
+
+  if(len != 1) {
+    fprintf(stderr, "you should probably fix this\n");
+    return 1;
+  }
+
+  len = 10;
+  read_str = ring_read(&buf, &len);
+
+  if(len) {
+    fprintf(stderr, "hmmmm\n");
+    return 1;
+  }
+
+  printf("second read: %s\n", read_str);
+
+  len = ring_write(&buf, write_str + 25, 1);
+  len = ring_write(&buf, write_str, 26);
+
+  printf("didn't write %zu characters\n", len);
+
+  len = 20;
+  read_str = ring_read(&buf, &len);
+
+  printf("final read (20): %s\n", read_str);
+  ring_del(&buf);
+
+  return 0;
+}
+
+/*
+struct ring_t *ring_new(struct ring_t *buf, size_t len);
+size_t ring_write(struct ring_t *buf, char *str, size_t orig_len);
+char *ring_read(struct ring_t *buf, size_t *len);
+char *ring_readln(struct ring_t *buf, size_t *len);
+void ring_del(struct ring_t *buf);
+*/