add isc_buffer_copyregion

lib/isc/buffer.c

@@ -384,6 +384,24 @@ isc_buffer_putuint32(isc_buffer_t *b, isc_uint32_t val)
 	cp[3] = (val & 0x000000ff);
 }
 
+isc_result_t
+isc_buffer_copyregion(isc_buffer_t *b, isc_region_t *r) {
+	unsigned char *base;
+	unsigned int available;
+
+	REQUIRE(ISC_BUFFER_VALID(b));
+	REQUIRE(r != NULL);
+
+	base = (unsigned char *)b->base + b->used;
+	available = b->length - b->used;
+        if (r->length > available)
+		return (ISC_R_NOSPACE);
+	memcpy(base, r->base, r->length);
+	b->used += r->length;
+
+	return (ISC_R_SUCCESS);
+}
+
 isc_result_t
 isc_buffer_allocate(isc_mem_t *mctx, isc_buffer_t **dynbuffer,
 		    unsigned int length, unsigned int type)

lib/isc/include/isc/buffer.h

@@ -539,6 +539,23 @@ isc_buffer_putuint32(isc_buffer_t *b, isc_uint32_t val);
  *	The used pointer in 'b' is advanced by 4.
  */
 
+isc_result_t
+isc_buffer_copyregion(isc_buffer_t *b, isc_region_t *r);
+/*
+ * Copy the contents of 'r' into 'b'.
+ *
+ * Requires:
+ *	'b' is a valid buffer.
+ *
+ *	'r' is a valid region.
+ *
+ * Returns:
+ *
+ *	ISC_R_SUCCESS
+ *	ISC_R_NOSPACE			The available region of 'b' is not
+ *					big enough.
+ */
+
 ISC_LANG_ENDDECLS
 
 #endif /* ISC_BUFFER_H */