* Do not fuzz anything if 0 bytes were read.

* Added a debug message for fuzzing.

src/fuzz.c

@@ -42,8 +42,10 @@ void _zz_fuzz(int fd, uint8_t *buf, uint64_t len)
     unsigned long int pos = _zz_getpos(fd);
     unsigned int i, j, todo;
 
-    fuzz = _zz_getfuzz(fd);
+    debug("fuzz(%i, %lli@%li)", fd, (unsigned long long int)len,
+          (unsigned long int)pos);
 
+    fuzz = _zz_getfuzz(fd);
     aligned_buf = buf - pos;
 
     for(i = pos / CHUNKBYTES;

src/load-stream.c

@@ -167,8 +167,11 @@ size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream)
         /* XXX: the number of bytes read is not ret * size, because
          * a partial read may have advanced the stream pointer */
         long int newpos = ftell(stream);
-        _zz_fuzz(fd, ptr, newpos - pos);
-        _zz_setpos(fd, newpos);
+        if(newpos != pos)
+        {
+            _zz_fuzz(fd, ptr, newpos - pos);
+            _zz_setpos(fd, newpos);
+        }
     }
     return ret;
 }