4 files changed, 107 insertions, 1 deletions
diff --git a/bin/.gitignore b/bin/.gitignore
index c84d690b..4e9c104e 100644
--- a/bin/.gitignore
+++ b/bin/.gitignore
@@ -6,6 +6,7 @@ dtch
 gfxx
 glitch
 hnel
+modem
 pbcopy
 pbd
 pbpaste
diff --git a/bin/Makefile b/bin/Makefile
index 685ea6f0..92c02f26 100644
--- a/bin/Makefile
+++ b/bin/Makefile
@@ -1,4 +1,4 @@
-ANY_BINS = atch brot dtch gfxx glitch hnel pbcopy pbd pbpaste pngo scheme wake xx
+ANY_BINS = atch brot dtch gfxx glitch hnel modem pbcopy pbd pbpaste pngo scheme wake xx
 BSD_BINS = klon watch
 LIN_BINS = bri fbatt fbclock
 ALL_BINS = $(ANY_BINS) $(BSD_BINS) $(LIN_BINS)
diff --git a/bin/README b/bin/README
index c15f6f5a..0ea3970a 100644
--- a/bin/README
+++ b/bin/README
@@ -96,6 +96,10 @@ Klondike solitaire for curses. BSD-only for arc4random_uniform.
     1-7 tableau
     ^M  auto-foundation
 
+                                 modem
+
+PTY wrapper with a fixed baud rate of 19.2 kbps.
+
                            pbd/pbcopy/pbpaste
 
 TCP server which pipes into macOS pbcopy(1) and from pbpaste(1), and
diff --git a/bin/modem.c b/bin/modem.c
new file mode 100644
index 00000000..47a4ddaf
--- /dev/null
+++ b/bin/modem.c
@@ -0,0 +1,101 @@
+/* Copyright (C) 2018  Curtis McEnroe <june@causal.agency>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <err.h>
+#include <poll.h>
+#include <stdlib.h>
+#include <sys/ioctl.h>
+#include <sys/wait.h>
+#include <sysexits.h>
+#include <termios.h>
+#include <unistd.h>
+
+#if defined __FreeBSD__
+#include <libutil.h>
+#elif defined __linux__
+#include <pty.h>
+#else
+#include <util.h>
+#endif
+
+static const int BAUD_RATE = 19200;
+
+static struct termios saveTerm;
+static void restoreTerm(void) {
+	tcsetattr(STDIN_FILENO, TCSADRAIN, &saveTerm);
+}
+
+int main(int argc, char *argv[]) {
+	int error;
+
+	if (argc < 2) return EX_USAGE;
+
+	error = tcgetattr(STDIN_FILENO, &saveTerm);
+	if (error) err(EX_IOERR, "tcgetattr");
+	atexit(restoreTerm);
+
+	struct termios raw;
+	cfmakeraw(&raw);
+	error = tcsetattr(STDIN_FILENO, TCSADRAIN, &raw);
+	if (error) err(EX_IOERR, "tcsetattr");
+
+	struct winsize window;
+	error = ioctl(STDIN_FILENO, TIOCGWINSZ, &window);
+	if (error) err(EX_IOERR, "TIOCGWINSZ");
+
+	int pty;
+	pid_t pid = forkpty(&pty, NULL, NULL, &window);
+	if (pid < 0) err(EX_OSERR, "forkpty");
+
+	if (!pid) {
+		execvp(argv[1], &argv[1]);
+		err(EX_NOINPUT, "%s", argv[1]);
+	}
+
+	for (;;) {
+		usleep(8 * 1000000 / BAUD_RATE);
+
+		struct pollfd fds[2] = {
+			{ .events = POLLIN, .fd = STDIN_FILENO },
+			{ .events = POLLIN, .fd = pty },
+		};
+		int n = poll(fds, 2, -1);
+		if (n < 0) err(EX_IOERR, "poll");
+
+		if (fds[0].revents) {
+			char c;
+			ssize_t size = read(STDIN_FILENO, &c, 1);
+			if (size < 0) err(EX_IOERR, "read(%d)", STDIN_FILENO);
+
+			size = write(pty, &c, 1);
+			if (size < 0) err(EX_IOERR, "write(%d)", pty);
+		}
+
+		if (fds[1].revents) {
+			char c;
+			ssize_t size = read(pty, &c, 1);
+			if (size < 0) err(EX_IOERR, "read(%d)", pty);
+
+			size = write(STDOUT_FILENO, &c, 1);
+			if (size < 0) err(EX_IOERR, "write(%d)", STDOUT_FILENO);
+		}
+
+		int status;
+		pid_t dead = waitpid(pid, &status, WNOHANG);
+		if (dead < 0) err(EX_OSERR, "waitpid");
+		if (dead) return WIFEXITED(status) ? WEXITSTATUS(status) : EX_SOFTWARE;
+	}
+}