libdpkg: Add new BUFFER_FILTER_NULL filter action

lib/dpkg/buffer.c

@@ -57,6 +57,8 @@ static off_t
 buffer_filter_init(struct buffer_data *data)
 {
 	switch (data->type) {
+	case BUFFER_FILTER_NULL:
+		break;
 	case BUFFER_FILTER_MD5:
 		buffer_md5_init(data);
 		break;
@@ -87,6 +89,8 @@ static off_t
 buffer_filter_done(struct buffer_data *data)
 {
 	switch (data->type) {
+	case BUFFER_FILTER_NULL:
+		break;
 	case BUFFER_FILTER_MD5:
 		buffer_md5_done(data);
 		break;
@@ -107,6 +111,7 @@ buffer_write(struct buffer_data *data, const void *buf, off_t length)
 		ret = fd_write(data->arg.i, buf, length);
 		break;
 	case BUFFER_WRITE_NULL:
+	case BUFFER_FILTER_NULL:
 		break;
 	case BUFFER_FILTER_MD5:
 		MD5Update(&(((struct buffer_md5_ctx *)data->arg.ptr)->ctx), buf, length);

lib/dpkg/buffer.h

@@ -35,6 +35,8 @@ DPKG_BEGIN_DECLS
 #define BUFFER_WRITE_VBUF		1
 #define BUFFER_WRITE_FD			2
 #define BUFFER_WRITE_NULL		3
+
+#define BUFFER_FILTER_NULL		4
 #define BUFFER_FILTER_MD5		5
 
 #define BUFFER_READ_FD			0