lib9p: Rewrite the marshalers to support zero-copy for data

1 files changed, 29 insertions, 13 deletions

diff --git a/lib9p/9p.c b/lib9p/9p.c
index c54dae7..1caa01a 100644
--- a/lib9p/9p.c
+++ b/lib9p/9p.c
@@ -204,30 +204,42 @@ void lib9p_Rmsg_unmarshal(struct lib9p_ctx *ctx, uint8_t *net_bytes,
 static
 bool _lib9p_marshal(const struct _lib9p_send_tentry xxx_table[LIB9P_VER_NUM][0x80],
                     struct lib9p_ctx *ctx, enum lib9p_msg_type typ, void *body,
-                    uint8_t *ret_bytes) {
+                    size_t *ret_iov_cnt, struct iovec *ret_iov, uint8_t *ret_copied) {
 	struct _marshal_ctx subctx = {
 		/* input */
-		.ctx        = ctx,
+		.ctx             = ctx,
 
 		/* ouptut */
-		.net_bytes  = ret_bytes,
-		.net_offset = 0,
+		.net_iov_cnt     = 1,
+		.net_iov         = ret_iov,
+		.net_copied_size = 0,
+		.net_copied      = ret_copied,
 	};
 
 	struct _lib9p_send_tentry tentry = xxx_table[ctx->version][typ/2];
-	return tentry.marshal(&subctx, body);
+	bool ret_erred = tentry.marshal(&subctx, body);
+	if (ret_iov[subctx.net_iov_cnt-1].iov_len == 0)
+		subctx.net_iov_cnt--;
+	*ret_iov_cnt = subctx.net_iov_cnt;
+	return ret_erred;
 }
 
 bool lib9p_Tmsg_marshal(struct lib9p_ctx *ctx, enum lib9p_msg_type typ, void *body,
-                        uint8_t *ret_bytes) {
+                        struct lib9p_Tmsg_send_buf *ret) {
 	assert(typ % 2 == 0);
-	return _lib9p_marshal(_lib9p_table_Tmsg_send, ctx, typ, body, ret_bytes);
+	memset(ret, 0, sizeof(*ret));
+	return _lib9p_marshal(_lib9p_table_Tmsg_send,
+	                      ctx, typ, body,
+	                      &ret->iov_cnt, ret->iov, ret->copied);
 }
 
 bool lib9p_Rmsg_marshal(struct lib9p_ctx *ctx, enum lib9p_msg_type typ, void *body,
-                        uint8_t *ret_bytes) {
+                        struct lib9p_Rmsg_send_buf *ret) {
 	assert(typ % 2 == 1);
-	return _lib9p_marshal(_lib9p_table_Rmsg_send, ctx, typ, body, ret_bytes);
+	memset(ret, 0, sizeof(*ret));
+	return _lib9p_marshal(_lib9p_table_Rmsg_send,
+	                      ctx, typ, body,
+	                      &ret->iov_cnt, ret->iov, ret->copied);
 }
 
 /* `struct lib9p_stat` helpers ************************************************/
@@ -273,15 +285,19 @@ uint32_t lib9p_stat_marshal(struct lib9p_ctx *ctx, uint32_t max_net_size, struct
                             uint8_t *ret_bytes) {
 	struct lib9p_ctx _ctx = *ctx;
 	_ctx.max_msg_size = max_net_size;
+
+	struct iovec iov = {0};
 	struct _marshal_ctx subctx = {
 		/* input */
-		.ctx        = &_ctx,
+		.ctx             = &_ctx,
 
 		/* output */
-		.net_bytes  = ret_bytes,
-		.net_offset = 0,
+		.net_iov_cnt     = 1,
+		.net_iov         = &iov,
+		.net_copied_size = 0,
+		.net_copied      = ret_bytes,
 	};
 	if (_lib9p_stat_marshal(&subctx, obj))
 		return 0;
-	return subctx.net_offset;
+	return subctx.net_iov[0].iov_len;
 }