basic pty opening

src/Pty.zig

@@ -0,0 +1,76 @@
+//! Linux PTY creation and management. This is just a thin layer on top
+//! of Linux syscalls. The caller is responsible for detail-oriented handling
+//! of the returned file handles.
+const Pty = @This();
+
+const std = @import("std");
+const testing = std.testing;
+const linux = std.os.linux;
+const fd_t = std.os.fd_t;
+const winsize = linux.winsize;
+const c = @cImport({
+    @cInclude("pty.h");
+});
+
+/// The file descriptors for the master and slave side of the pty.
+master: fd_t,
+slave: fd_t,
+
+/// Open a new PTY with the given initial size.
+pub fn open(size: winsize) !Pty {
+    var master_fd: fd_t = undefined;
+    var slave_fd: fd_t = undefined;
+    if (c.openpty(
+        &master_fd,
+        &slave_fd,
+        null,
+        null,
+        @ptrCast([*c]const c.struct_winsize, &size),
+    ) < 0)
+        return error.OpenptyFailed;
+
+    return Pty{
+        .master = master_fd,
+        .slave = slave_fd,
+    };
+}
+
+pub fn deinit(self: *Pty) void {
+    std.os.close(self.master);
+    self.* = undefined;
+}
+
+/// Return the size of the pty.
+pub fn getSize(self: Pty) !winsize {
+    var ws: winsize = undefined;
+    if (linux.ioctl(self.master, linux.T.IOCGWINSZ, @ptrToInt(&ws)) < 0)
+        return error.IoctlFailed;
+
+    return ws;
+}
+
+/// Set the size of the pty.
+pub fn setSize(self: Pty, size: winsize) !void {
+    if (linux.ioctl(self.master, linux.T.IOCSWINSZ, @ptrToInt(&size)) < 0)
+        return error.IoctlFailed;
+}
+
+test {
+    var ws: winsize = .{
+        .ws_row = 50,
+        .ws_col = 80,
+        .ws_xpixel = 1,
+        .ws_ypixel = 1,
+    };
+
+    var pty = try open(ws);
+    defer pty.deinit();
+
+    // Initialize size should match what we gave it
+    try testing.expectEqual(ws, try pty.getSize());
+
+    // Can set and read new sizes
+    ws.ws_row *= 2;
+    try pty.setSize(ws);
+    try testing.expectEqual(ws, try pty.getSize());
+}