1 files changed, 130 insertions, 0 deletions
diff --git a/tests/sys/kern/tty/readsz.c b/tests/sys/kern/tty/readsz.c
new file mode 100644
index 000000000000..95dafa02472f
--- /dev/null
+++ b/tests/sys/kern/tty/readsz.c
@@ -0,0 +1,130 @@
+/*-
+ * Copyright (c) 2024 Kyle Evans <kevans@FreeBSD.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <sys/param.h>
+
+#include <err.h>
+#include <errno.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+static void
+usage(void)
+{
+
+	fprintf(stderr, "usage: %s [-b bytes | -c lines | -e] [-s buffer-size]\n",
+	    getprogname());
+	exit(1);
+}
+
+int
+main(int argc, char *argv[])
+{
+	char *buf;
+	const char *errstr;
+	size_t bufsz = 0, reps;
+	ssize_t ret;
+	enum { MODE_BYTES, MODE_COUNT, MODE_EOF } mode;
+	int ch;
+
+	/*
+	 * -b specifies number of bytes.
+	 * -c specifies number of read() calls.
+	 * -e specifies eof (default)
+	 * -s to pass a buffer size
+	 *
+	 * Reading N lines is the same as -c with a high buffer size.
+	 */
+	mode = MODE_EOF;
+	while ((ch = getopt(argc, argv, "b:c:es:")) != -1) {
+		switch (ch) {
+		case 'b':
+			mode = MODE_BYTES;
+			reps = strtonum(optarg, 0, SSIZE_MAX, &errstr);
+			if (errstr != NULL)
+				errx(1, "strtonum: %s", errstr);
+			break;
+		case 'c':
+			mode = MODE_COUNT;
+			reps = strtonum(optarg, 1, SSIZE_MAX, &errstr);
+			if (errstr != NULL)
+				errx(1, "strtonum: %s", errstr);
+			break;
+		case 'e':
+			mode = MODE_EOF;
+			break;
+		case 's':
+			bufsz = strtonum(optarg, 1, SSIZE_MAX, &errstr);
+			if (errstr != NULL)
+				errx(1, "strtonum: %s", errstr);
+			break;
+		default:
+			usage();
+		}
+	}
+
+	if (bufsz == 0) {
+		if (mode == MODE_BYTES)
+			bufsz = reps;
+		else
+			bufsz = LINE_MAX;
+	}
+
+	buf = malloc(bufsz);
+	if (buf == NULL)
+		err(1, "malloc");
+
+	for (;;) {
+		size_t readsz;
+
+		/*
+		 * Be careful not to over-read if we're in byte-mode.  In every other
+		 * mode, we'll read as much as we can.
+		 */
+		if (mode == MODE_BYTES)
+			readsz = MIN(bufsz, reps);
+		else
+			readsz = bufsz;
+
+		ret = read(STDIN_FILENO, buf, readsz);
+		if (ret == -1 && errno == EINTR)
+			continue;
+		if (ret == -1)
+			err(1, "read");
+		if (ret == 0) {
+			if (mode == MODE_EOF)
+				return (0);
+			errx(1, "premature EOF");
+		}
+
+		/* Write out what we've got */
+		write(STDOUT_FILENO, buf, ret);
+
+		/*
+		 * Bail out if we've hit our metric (byte mode / count mode).
+		 */
+		switch (mode) {
+		case MODE_BYTES:
+			reps -= ret;
+			if (reps == 0)
+				return (0);
+			break;
+		case MODE_COUNT:
+			reps--;
+			if (reps == 0)
+				return (0);
+			break;
+		default:
+			break;
+		}
+	}
+
+	return (0);
+}