1 files changed, 120 insertions, 0 deletions
diff --git a/bin/hnel.c b/bin/hnel.c
new file mode 100644
index 00000000..4fcc42a1
--- /dev/null
+++ b/bin/hnel.c
@@ -0,0 +1,120 @@
+/* Copyright (C) 2017  June 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 <stdbool.h>
+#include <stdlib.h>
+#include <string.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
+
+typedef unsigned char byte;
+
+static struct termios saveTerm;
+static void restoreTerm(void) {
+	tcsetattr(STDIN_FILENO, TCSADRAIN, &saveTerm);
+}
+
+int main(int argc, char *argv[]) {
+	int error;
+
+	if (argc < 4) return EX_USAGE;
+
+	byte table[256] = {0};
+	if (strlen(argv[1]) != strlen(argv[2])) return EX_USAGE;
+	for (const char *from = argv[1], *to = argv[2]; *from; ++from, ++to) {
+		table[(byte)*from] = *to;
+	}
+
+	error = tcgetattr(STDERR_FILENO, &saveTerm);
+	if (error) err(EX_IOERR, "tcgetattr");
+	atexit(restoreTerm);
+
+	struct termios raw = saveTerm;
+	cfmakeraw(&raw);
+	error = tcsetattr(STDERR_FILENO, TCSADRAIN, &raw);
+	if (error) err(EX_IOERR, "tcsetattr");
+
+	struct winsize window;
+	error = ioctl(STDERR_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[3], &argv[3]);
+		err(EX_NOINPUT, "%s", argv[3]);
+	}
+
+	bool enable = true;
+
+	byte buf[4096];
+	struct pollfd fds[2] = {
+		{ .fd = STDIN_FILENO, .events = POLLIN },
+		{ .fd = pty, .events = POLLIN },
+	};
+	while (0 < poll(fds, 2, -1)) {
+		if (fds[0].revents & POLLIN) {
+			ssize_t readSize = read(STDIN_FILENO, buf, sizeof(buf));
+			if (readSize < 0) err(EX_IOERR, "read(%d)", STDIN_FILENO);
+
+			if (readSize == 1) {
+				if (buf[0] == CTRL('S')) {
+					enable ^= true;
+					continue;
+				}
+
+				byte c = buf[0];
+				if (enable && table[c]) buf[0] = table[c];
+			}
+
+			ssize_t writeSize = write(pty, buf, readSize);
+			if (writeSize < 0) err(EX_IOERR, "write(%d)", pty);
+			if (writeSize < readSize) errx(EX_IOERR, "short write(%d)", pty);
+		}
+
+		if (fds[1].revents & POLLIN) {
+			ssize_t readSize = read(pty, buf, sizeof(buf));
+			if (readSize < 0) err(EX_IOERR, "read(%d)", pty);
+
+			ssize_t writeSize = write(STDOUT_FILENO, buf, readSize);
+			if (writeSize < 0) err(EX_IOERR, "write(%d)", STDOUT_FILENO);
+			if (writeSize < readSize) {
+				errx(EX_IOERR, "short write(%d)", STDOUT_FILENO);
+			}
+		}
+
+		int status;
+		pid_t dead = waitpid(pid, &status, WNOHANG);
+		if (dead < 0) err(EX_OSERR, "waitpid(%d)", pid);
+		if (dead) return WIFEXITED(status) ? WEXITSTATUS(status) : EX_SOFTWARE;
+	}
+	err(EX_IOERR, "poll");
+}