Add a function to test if the input gzip buffer is empty.

bin/varnishd/cache.h

@@ -627,8 +627,9 @@ void Fetch_Init(void);
 struct vgz;
 
 struct vgz *VGZ_NewUngzip(const struct sess *sp, struct ws *tmp);
-void VGZ_Ibuf(struct vgz *, const void *, size_t len);
-void VGZ_Obuf(struct vgz *, const void *, size_t len);
+void VGZ_Ibuf(struct vgz *, const void *, ssize_t len);
+int VGZ_IbufEmpty(struct vgz *vg);
+void VGZ_Obuf(struct vgz *, const void *, ssize_t len);
 int VGZ_Gzip(struct vgz *, const void **, size_t *len, int flag);
 int VGZ_Gunzip(struct vgz *, const void **, size_t *len);
 void VGZ_Destroy(struct vgz **);

bin/varnishd/cache_gzip.c

@@ -190,7 +190,7 @@ VGZ_NewGzip(const struct sess *sp, struct ws *tmp)
 /*--------------------------------------------------------------------*/
 
 void
-VGZ_Ibuf(struct vgz *vg, const void *ptr, size_t len)
+VGZ_Ibuf(struct vgz *vg, const void *ptr, ssize_t len)
 {
 
 	CHECK_OBJ_NOTNULL(vg, VGZ_MAGIC);
@@ -200,10 +200,18 @@ VGZ_Ibuf(struct vgz *vg, const void *ptr, size_t len)
 	vg->vz.avail_in = len;
 }
 
+int
+VGZ_IbufEmpty(struct vgz *vg)
+{
+
+	CHECK_OBJ_NOTNULL(vg, VGZ_MAGIC);
+	return (vg->vz.avail_in == 0);
+}
+
 /*--------------------------------------------------------------------*/
 
 void
-VGZ_Obuf(struct vgz *vg, const void *ptr, size_t len)
+VGZ_Obuf(struct vgz *vg, const void *ptr, ssize_t len)
 {
 
 	CHECK_OBJ_NOTNULL(vg, VGZ_MAGIC);