constify padding functions

src/padding.h

@@ -25,11 +25,11 @@
  *
  */
 
-typedef void* pad_f(struct ws *ws, void *src, size_t len, size_t blocklen,
+typedef void* pad_f(struct ws *ws, const void *src, size_t len, size_t blocklen,
 		    size_t *newlen);
 
 static inline void *
-pad(struct ws *ws, void *src, size_t len, size_t blocklen, size_t *newlen,
+pad(struct ws *ws, const void *src, size_t len, size_t blocklen, size_t *newlen,
     size_t *padlen)
 {
 	void *dst;
@@ -45,7 +45,8 @@ pad(struct ws *ws, void *src, size_t len, size_t blocklen, size_t *newlen,
 }
 
 static void *
-pad_pkcs7(struct ws *ws, void *src, size_t len, size_t blocklen, size_t *newlen)
+pad_pkcs7(struct ws *ws, const void *src, size_t len, size_t blocklen,
+    size_t *newlen)
 {
 	size_t padlen;
 	unsigned char *dst;
@@ -59,7 +60,7 @@ pad_pkcs7(struct ws *ws, void *src, size_t len, size_t blocklen, size_t *newlen)
 }
 
 static void *
-pad_iso7816(struct ws *ws, void *src, size_t len, size_t blocklen,
+pad_iso7816(struct ws *ws, const void *src, size_t len, size_t blocklen,
 	    size_t *newlen)
 {
 	size_t padlen;
@@ -75,7 +76,8 @@ pad_iso7816(struct ws *ws, void *src, size_t len, size_t blocklen,
 }
 
 static void *
-pad_x923(struct ws *ws, void *src, size_t len, size_t blocklen, size_t *newlen)
+pad_x923(struct ws *ws, const void *src, size_t len, size_t blocklen,
+    size_t *newlen)
 {
 	size_t padlen;
 	unsigned char *dst;