hare

commit 3c90d8bc46e9a957bc28559a3de3698fdfecbcb6
parent 25d3f6ac79a2ee07214f02af4f31540089274d12
Author: Drew DeVault <sir@cmpwn.com>
Date:   Fri, 26 Feb 2021 15:42:11 -0500

io: add io::tee

Diffstat:
A
io/tee.ha
 | 
34
++++++++++++++++++++++++++++++++++

1 file changed, 34 insertions(+), 0 deletions(-)
diff --git a/io/tee.ha b/io/tee.ha
@@ -0,0 +1,34 @@
+type tee_stream = struct {
+	stream: stream,
+	source: *stream,
+	sink: *stream,
+};
+
+// Creates a reader which copies reads into a sink before forwarding them to the
+// caller. Does not close the secondary streams when the tee stream is closed.
+export fn tee(source: *stream, sink: *stream) *stream = {
+	return alloc(tee_stream {
+		stream = stream {
+			reader = &tee_read,
+			closer = &tee_close,
+			...
+		},
+		source = source,
+		sink = sink,
+	}): *io::stream;
+};
+
+fn tee_read(s: *stream, buf: []u8) (size | EOF | error) = {
+	let s = s: *tee_stream;
+	let z = match (read(s.source, buf)) {
+		err: error => return err,
+		EOF => return EOF,
+		z: size => z,
+	};
+	for (let n = 0z; n < z) {
+		n += write(s.sink, buf[n..z])?;
+	};
+	return z;
+};
+
+fn tee_close(s: *stream) void = free(s);