hare

commit a986adec473af9dd117676d15acf351d386017ee
parent 678e4f644cfd39043150f015ac7339d0d7555800
Author: Armin Preiml <apreiml@strohwolke.at>
Date:   Thu, 28 Sep 2023 07:58:09 +0200

bufio::scanner: support unread

Diffstat:
M
bufio/scanner.ha
 | 
9
+++++++++
M
bufio/scanner_test+test.ha
 | 
30
++++++++++++++++++++++++++++++
M
bufio/stream.ha
 | 
13
++++++++++---

3 files changed, 49 insertions(+), 3 deletions(-)
diff --git a/bufio/scanner.ha b/bufio/scanner.ha
@@ -271,6 +271,15 @@ export fn scan_buffer(scan: *scanner) []u8 = {
 	return scan.buffer[..scan.pending];
 };
 
+fn scan_unread(scan: *scanner, buf: []u8) void = {
+	if (len(buf) == 0) {
+		return;
+	};
+	assert(len(buf) <= scan.readout);
+	scan.buffer[scan.readout - len(buf)..scan.readout] = buf;
+	scan.readout -= len(buf);
+};
+
 // Reads a single byte from an [[io::handle]].
 export fn read_byte(file: io::handle) (u8 | io::EOF | io::error) = {
 	let buf: [1]u8 = [0...];
diff --git a/bufio/scanner_test+test.ha b/bufio/scanner_test+test.ha
@@ -119,7 +119,37 @@ use strings;
 	let in = memio::fixed(expected);
 
 	let scanner = newscanner(&in, 2);
+	defer finish(&scanner);
 	let result = io::drain(&scanner)!;
 	defer free(result);
 	assert(bytes::equal(expected, result));
 };
+
+@test fn scan_unread() void = {
+	const expected: str = " I will not repeat  \nDone!\n";
+	let in = memio::fixed(strings::toutf8(expected));
+
+	let scanner = newscanner(&in, 32);
+	defer finish(&scanner);
+	let l = scan_line(&scanner)! as const str;
+	assert(l == " I will not repeat  ");
+
+	unread(&scanner, strings::toutf8("\n"));
+	unread(&scanner, strings::toutf8(l));
+	let l = scan_line(&scanner)! as const str;
+	assert(l == " I will not repeat  ");
+
+	unread(&scanner, strings::toutf8("\n"));
+	unread(&scanner, strings::toutf8(strings::trim(l)));
+	let l = scan_line(&scanner)! as const str;
+	assert(l == "I will not repeat");
+
+	unread(&scanner, strings::toutf8("See?\n"));
+	let l = scan_line(&scanner)! as const str;
+	assert(l == "See?");
+
+	let l = scan_line(&scanner)! as const str;
+	assert(l == "Done!");
+
+	assert(scan_line(&scanner) is io::EOF);
+};
diff --git a/bufio/stream.ha b/bufio/stream.ha
@@ -128,15 +128,22 @@ export fn setflush(s: io::handle, b: []u8) void = {
 // buffered stream. Attempting to unread more data than can fit into the read
 // buffer will abort the program.
 export fn unread(s: io::handle, buf: []u8) void = {
-	let s = match (s) {
+	match (s) {
 	case let st: *io::stream =>
-		if (st.reader != &read) {
+		switch (st.reader) {
+		case &read =>
+			stream_unread(s: *stream, buf);
+		case &scan_read =>
+			scan_unread(s: *scanner, buf);
+		case =>
 			abort("Attempted unread on unbuffered stream");
 		};
-		yield st: *stream;
 	case =>
 		abort("Attempted unread on unbuffered stream");
 	};
+};
+
+fn stream_unread(s: *stream, buf: []u8) void = {
 	assert(s.rpos >= len(buf),
 		"Attempted to unread more data than buffer has available");
 	s.rbuffer[s.rpos - len(buf)..s.rpos] = buf;