Rewrite rewind in assembly

test/ref/test_rewind.c

@@ -0,0 +1,56 @@
+/*
+  !!DESCRIPTION!! fgets test
+  !!LICENCE!!     Public domain
+*/
+
+#include "common.h"
+
+#include <ctype.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+FILE *in;
+char bufA[32];
+char bufB[32];
+
+#define INFILE   "cf.in"
+
+int main(int argc,char **argv)
+{
+    static int r;
+
+    in = fopen(INFILE, "rb");
+    if (in == NULL) {
+        return EXIT_FAILURE;
+    }
+
+    r = fread(bufA, 1, sizeof(bufA), in);
+
+    if (r == 0) {
+      printf("Error: could not read.\n");
+      return EXIT_FAILURE;
+    }
+    fwrite(bufA, 1, r, stdout);
+
+    rewind(in);
+    printf("rewind.\n");
+    r = fread(bufB, 1, sizeof(bufB), in);
+
+    if (r == 0) {
+      printf("Error: could not re-read.\n");
+      return EXIT_FAILURE;
+    }
+    fwrite(bufB, 1, r, stdout);
+
+    fclose(in);
+
+    if (memcmp(bufA, bufB, sizeof(bufA))) {
+      printf("reads differ.\n");
+      return EXIT_FAILURE;
+    }
+
+    return 0;
+}