src: initial commit of jio WIP source

This is a very quick and dirty experimental hack written in some
sort of bastard continuation-passing style in C w/io_uring using
journal-file introspection and manipulation duty as an excuse for
its existence.

Consider this unfinished prototype quality code.

1 files changed, 96 insertions, 0 deletions

diff --git a/src/readfile.c b/src/readfile.c
new file mode 100644
index 0000000..8af7438
--- /dev/null
+++ b/src/readfile.c
@@ -0,0 +1,96 @@
+/*
+ *  Copyright (C) 2020 - Vito Caputo - <vcaputo@pengaru.com>
+ *
+ *  This program is free software: you can redistribute it and/or modify it
+ *  under the terms of the GNU General Public License version 3 as published
+ *  by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <fcntl.h>
+#include <liburing.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <iou.h>
+#include <thunk.h>
+
+#include "readfile.h"
+#include "op.h"
+
+/* Implements iou-based file read into a supplied buffer.
+ */
+
+
+/* call user-supplied closure now that buf is populated */
+THUNK_DEFINE_STATIC(read_done, iou_t *, iou, iou_op_t *, op, int, fd, char *, buf, size_t *, size, thunk_t *, closure)
+{
+	assert(iou);
+	assert(op);
+	assert(closure);
+
+	if (op->result < 0)
+		return op->result;
+
+	(void) close(fd);
+
+	*size = op->result;
+
+	return thunk_dispatch(closure);
+}
+
+
+/* ask iou to read from the opened fd into buf */
+THUNK_DEFINE_STATIC(open_done, iou_t *, iou, iou_op_t *, op, char *, buf, size_t *, size, thunk_t *, closure)
+{
+	thunk_t		*read_closure;
+	iou_op_t	*read_op;
+
+	assert(iou);
+	assert(op);
+
+	if (op->result < 0)
+		return op->result;
+
+	read_op = iou_op_new(iou);
+	if (!read_op)
+		return -ENOMEM;
+
+	read_closure = THUNK(read_done(iou, read_op, op->result, buf, size, closure));
+	if (!read_closure)
+		return -ENOMEM;
+
+	io_uring_prep_read(read_op->sqe, op->result, buf, *size, 0);
+	op_queue(iou, read_op, read_closure);
+
+	return 0;
+}
+
+
+/* read a file into a buffer via iou, dispatching closure when complete */
+/* size specifies the buf size, and will also get the length of what's read
+ * written to it upon completion.
+ */
+/* returns < 0 on error, 0 on successful queueing of operation */
+THUNK_DEFINE(readfile, iou_t *, iou, const char *, path, char *, buf, size_t *, size, thunk_t *, closure)
+{
+	iou_op_t	*op;
+
+	op = iou_op_new(iou);
+	if (!op)
+		return -ENOMEM;
+
+	/* req iou to open path, passing the req to read its contents */
+	io_uring_prep_openat(op->sqe, 0, path, 0, O_RDONLY);
+	op_queue(iou, op, THUNK(open_done(iou, op, buf, size, closure)));
+
+	return 0;
+}