hare

commit 7a36e9e335d2ea7ecfe3d5b76fe97c1038a8577d
parent a20ec460699dc41e5b20b73210f91b8b9e204249
Author: Drew DeVault <sir@cmpwn.com>
Date:   Tue,  8 Feb 2022 11:13:00 +0100

io::limit: better define limit exceeded cases

Signed-off-by: Drew DeVault <sir@cmpwn.com>

Diffstat:
M
io/+test/limit.ha
 | 
2
++
M
io/limit.ha
 | 
12
++++++++++--

2 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/io/+test/limit.ha b/io/+test/limit.ha
@@ -22,6 +22,7 @@ use errors;
 	case error =>
 		abort();
 	};
+	assert(read(&rlimit, buf) is io::EOF);
 
 	let wlimit = limitwriter(&source, 20);
 	match (read(&wlimit, buf)) {
@@ -41,4 +42,5 @@ use errors;
 	case error =>
 		abort();
 	};
+	assert(write(&wlimit, buf) as size == 0z);
 };
diff --git a/io/limit.ha b/io/limit.ha
@@ -14,7 +14,8 @@ fn limitstream_create(source: handle, limit: size) limitstream = {
 
 // Create an overlay stream that only allows a limited amount of bytes to be
 // read from the underlying stream. This stream does not need to be closed, and
-// closing it does not close the underlying stream.
+// closing it does not close the underlying stream. Reading any data beyond the
+// given limit causes the reader to return [[io::EOF]].
 export fn limitreader(source: handle, limit: size) limitstream = {
 	let stream = limitstream_create(source, limit);
 	stream.reader = &limit_read;
@@ -23,7 +24,8 @@ export fn limitreader(source: handle, limit: size) limitstream = {
 
 // Create an overlay stream that only allows a limited amount of bytes to be
 // written to the underlying stream. This stream does not need to be closed, and
-// closing it does not close the underlying stream.
+// closing it does not close the underlying stream. Writing beyond the given
+// limit causes the writer to return short writes (as few as zero bytes).
 export fn limitwriter(source: handle, limit: size) limitstream = {
 	let stream = limitstream_create(source, limit);
 	stream.writer = &limit_write;
@@ -32,6 +34,9 @@ export fn limitwriter(source: handle, limit: size) limitstream = {
 
 fn limit_read(s: *stream, buf: []u8) (size | EOF | error) = {
 	let stream = s: *limitstream;
+	if (stream.limit == 0) {
+		return io::EOF;
+	};
 	if (len(buf) > stream.limit) {
 		buf = buf[..stream.limit];
 	};
@@ -41,6 +46,9 @@ fn limit_read(s: *stream, buf: []u8) (size | EOF | error) = {
 
 fn limit_write(s: *stream, buf: const []u8) (size | error) = {
 	let stream = s: *limitstream;
+	if (stream.limit == 0) {
+		return 0;
+	};
 	let slice = if (len(buf) > stream.limit) {
 		yield buf[..stream.limit];
 	} else {