lib9p_srv: Adopt a pread_to-like interface

1 files changed, 41 insertions, 12 deletions

diff --git a/lib9p/srv.c b/lib9p/srv.c
index ecdf169..03d7b93 100644
--- a/lib9p/srv.c
+++ b/lib9p/srv.c
@@ -1185,6 +1185,11 @@ static void handle_Tread(struct srv_req *ctx,
 
 	/* TODO: serialize simultaneous reads to the same FID */
 
+	/* req->count <= CONFIG_9P_SRV_MAX_MSG_SIZE <= CONFIG_9P_SRV_MAX_HOSTMSG_SIZE <= SIZE_MAX */
+	assert(req->count <= SIZE_MAX);
+	/* req->offset is u64, uoff is u64 */
+	static_assert(req->offset <= UOFF_MAX);
+
 	if (req->count > ctx->basectx.max_msg_size - lib9p_version_min_Rread_size(ctx->basectx.version))
 		req->count = ctx->basectx.max_msg_size - lib9p_version_min_Rread_size(ctx->basectx.version);
 
@@ -1219,20 +1224,44 @@ static void handle_Tread(struct srv_req *ctx,
 	ctx->user = srv_userid_decref(ctx->user);
 }
 
-static void handle_read_file(struct srv_req *ctx, struct srv_fidinfo *fidinfo, uint64_t offset, uint32_t count) {
-	iovec_or_error r = LO_CALL(fidinfo->file.io, pread, ctx, count, offset);
-	if (r.is_err) {
-		srv_respond(ctx, read, NULL, r.err);
-		return;
-	}
+struct rread_writer {
+	struct srv_req  *ctx;
+	size_t           count;
+	bool             written;
+
+};
+LO_IMPLEMENTATION_STATIC(io_writer, struct rread_writer, rread);
+
+static size_t_and_error rread_writev(struct rread_writer *self, const struct iovec *iov, int iovcnt) {
+	assert(self);
+	assert(!self->written);
+	assert(iovcnt == 1);
+	assert(iov);
+	assert(iov->iov_len <= self->count);
+
 	struct lib9p_msg_Rread resp = {
-		.tag = ctx->tag,
-		.count = r.iovec.iov_len,
-		.data = r.iovec.iov_base,
+		.tag = self->ctx->tag,
+		.count = iov->iov_len,
+		.data = iov->iov_base,
 	};
-	if (resp.count > count)
-		resp.count = count;
-	srv_respond(ctx, read, &resp, ERROR_NULL);
+
+	srv_respond(self->ctx, read, &resp, ERROR_NULL);
+
+	self->written = true;
+	return ERROR_AND(size_t, iov->iov_len, ERROR_NULL);
+}
+
+static void handle_read_file(struct srv_req *ctx, struct srv_fidinfo *fidinfo, uint64_t offset, uint32_t count) {
+	struct rread_writer _writer = {
+		.ctx     = ctx,
+		.count   = (size_t) count,
+		.written = false,
+	};
+	lo_interface io_writer writer = LO_BOX(io_writer, &_writer);
+	error err = LO_CALL(fidinfo->file.io, pread, ctx, writer, offset, count);
+	assert(ERROR_IS_NULL(err) == _writer.written);
+	if (!ERROR_IS_NULL(err))
+		srv_respond(ctx, read, NULL, err);
 }
 
 #if _LIB9P_ENABLE_stat