Make the VDP ptr argument const

bin/varnishd/cache/cache.h

@@ -283,7 +283,8 @@ enum vdp_action {
 	VDP_FLUSH,
 	VDP_FINISH,
 };
-typedef int vdp_bytes(struct req *, enum vdp_action, void *ptr, ssize_t len);
+typedef int vdp_bytes(struct req *, enum vdp_action, const void *ptr,
+    ssize_t len);
 
 /*--------------------------------------------------------------------*/
 
@@ -842,7 +843,7 @@ int HTTP1_IterateReqBody(struct req *req, req_body_iter_f *func, void *priv);
 void V1D_Deliver(struct req *);
 
 static inline int
-VDP_bytes(struct req *req, enum vdp_action act, void *ptr, ssize_t len)
+VDP_bytes(struct req *req, enum vdp_action act, const void *ptr, ssize_t len)
 {
 	int i, retval;
 

bin/varnishd/cache/cache_gzip.c

@@ -315,7 +315,7 @@ VGZ_WrwInit(struct vgz *vg)
  */
 
 int __match_proto__(vdp_bytes)
-VDP_gunzip(struct req *req, enum vdp_action act, void *ptr, ssize_t len)
+VDP_gunzip(struct req *req, enum vdp_action act, const void *ptr, ssize_t len)
 {
 	enum vgzret_e vr;
 	size_t dl;

bin/varnishd/cache/cache_http1_deliver.c

@@ -36,7 +36,7 @@
 /*--------------------------------------------------------------------*/
 
 static int __match_proto__(vdp_bytes)
-v1d_bytes(struct req *req, enum vdp_action act, void *ptr, ssize_t len)
+v1d_bytes(struct req *req, enum vdp_action act, const void *ptr, ssize_t len)
 {
 	ssize_t wl = 0;
 
@@ -58,11 +58,12 @@ v1d_bytes(struct req *req, enum vdp_action act, void *ptr, ssize_t len)
 /*--------------------------------------------------------------------*/
 
 static int __match_proto__(vdp_bytes)
-v1d_range_bytes(struct req *req, enum vdp_action act, void *ptr, ssize_t len)
+v1d_range_bytes(struct req *req, enum vdp_action act, const void *ptr,
+    ssize_t len)
 {
 	int retval = 0;
 	ssize_t l;
-	char *p = ptr;
+	const char *p = ptr;
 
 	CHECK_OBJ_NOTNULL(req, REQ_MAGIC);
 	l = req->range_low - req->range_off;