--- tar.c	2014-03-25 04:10:42.000000000 -0400
+++ tar.c	2021-02-15 21:31:22.208797000 -0500
@@ -41,5 +41,5 @@
 #define SAFE_ATOL8(_buff) (safe_atol8((_buff),sizeof(_buff)))
 
-LISP decode_tartype(char c)
+static LISP decode_tartype(char c)
 {switch(c)
    {case 0:
@@ -61,13 +61,13 @@
       return(NIL);}}
 
-static struct tar_header *get_tar_header(LISP bytes)
-{long n;
- struct tar_header *h;
- h = (struct tar_header *) get_c_string_dim(bytes,&n);
+static const struct tar_header *get_tar_header(LISP bytes)
+{unsigned long n;
+ const struct tar_header *h;
+ h = (const struct tar_header *) get_c_string_dim(bytes,&n);
  if (n < sizeof(struct tar_header)) err("too small for tar header",bytes);
  return(h);}
 
-LISP decode_tar_header(LISP bytes)
-{struct tar_header *h = get_tar_header(bytes);
+static LISP decode_tar_header(LISP bytes)
+{const struct tar_header *h = get_tar_header(bytes);
  return(listn(16,
 	      cons(cintern("name"),
@@ -104,14 +104,14 @@
 		   strcons(SAFE_STRLEN(h->prefix),h->prefix))));}
 
-static unsigned long checksum(void *start,
-			    void *end)
-{unsigned char *ptr;
+static unsigned long checksum(const void *start,
+			    const void *end)
+{const unsigned char *ptr;
  unsigned long sum = 0;
- for(ptr=(unsigned char *)start;ptr<(unsigned char *)end;++ptr)
+ for(ptr=(const unsigned char *)start; ptr < (const unsigned char *)end; ++ptr)
    sum += *ptr;
  return(sum);}
 
-LISP checksum_tar_header(LISP bytes,LISP whole)
-{struct tar_header *h = get_tar_header(bytes);
+static LISP checksum_tar_header(LISP bytes,LISP whole)
+{const struct tar_header *h = get_tar_header(bytes);
  if NNULLP(whole)
    return(flocons(checksum(&h->name[0],
@@ -123,4 +123,6 @@
 			   &h->end_pad[sizeof(h->end_pad)])));}
 
+void init_tar(void);	/* Our sole exported function */
+
 void init_tar(void)
 {init_subr_1("decode-tar-header",decode_tar_header);
@@ -130,3 +132,2 @@
 	NIL);
  init_tar_version();}
-