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tty: replace custom writer with File.Writer.initStreaming
Replace the custom VTable-based writer implementations in both PosixTty
and WindowsTty with std.fs.File.Writer.initStreaming(). This change
eliminates approximately 50 lines of custom drain logic while providing
better performance through built-in optimizations.
The File.Writer streaming mode is ideal for TTY operations since TTYs
are non-seekable streams. The standard library implementation provides
vectored I/O operations, efficient syscalls like sendfile when
appropriate, and cross-platform compatibility.
All existing APIs remain unchanged - write(), anyWriter(), and
bufferedWriter() methods continue to work as before. Buffer management
is now handled entirely by the standard library rather than custom
code.
Amp-Thread-ID: https://ampcode.com/threads/T-b6d69168-29b7-4ebf-b98f-a38a4e95a0db
Co-authored-by: Amp <amp@ampcode.com>
+21
-103
+21
-103
src/tty.zig
+21
-103
src/tty.zig
···
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/// The file descriptor of the tty
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fd: posix.fd_t,
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-
/// Write buffer
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-
buffer: []u8,
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-
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/// Embedded writer
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writer: std.io.Writer,
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+
/// File.Writer for efficient buffered writing
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writer: std.fs.File.Writer,
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pub const SignalHandler = struct {
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context: *anyopaque,
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callback: *const fn (context: *anyopaque) void,
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};
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-
/// VTable for embedded writer
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const vtable = std.io.Writer.VTable{
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.drain = drainVTable,
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};
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fn drainVTable(w: *std.io.Writer, data: []const []const u8, splat: usize) std.io.Writer.Error!usize {
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const self: *PosixTty = @fieldParentPtr("writer", w);
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-
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// First write any buffered data
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if (w.end > 0) {
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_ = posix.write(self.fd, w.buffer[0..w.end]) catch return error.WriteFailed;
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w.end = 0;
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}
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-
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// Write each slice in data
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var total: usize = 0;
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for (data[0..data.len-1]) |slice| {
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const n = posix.write(self.fd, slice) catch return error.WriteFailed;
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total += n;
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}
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-
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// Write the last slice `splat` times
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const pattern = data[data.len - 1];
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for (0..splat) |_| {
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const n = posix.write(self.fd, pattern) catch return error.WriteFailed;
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total += n;
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}
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-
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return total;
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}
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/// global signal handlers
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var handlers: [8]SignalHandler = undefined;
···
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posix.sigaction(posix.SIG.WINCH, &act, null);
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handler_installed = true;
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var self: PosixTty = .{
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const file = std.fs.File{ .handle = fd };
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+
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const self: PosixTty = .{
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.fd = fd,
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.termios = termios,
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-
.buffer = buffer,
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.writer = undefined, // Will be set after self is created
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};
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-
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// Initialize the writer to use our embedded buffer
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self.writer = .{
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.vtable = &vtable,
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.buffer = self.buffer,
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.end = 0,
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.writer = std.fs.File.Writer.initStreaming(file, buffer),
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};
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global_tty = self;
···
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/// Write bytes to the tty
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pub fn write(self: *PosixTty, bytes: []const u8) !usize {
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-
return self.writer.write(bytes);
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return self.writer.interface.write(bytes);
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}
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pub fn opaqueWrite(ptr: *const anyopaque, bytes: []const u8) !usize {
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const self: *PosixTty = @ptrCast(@alignCast(ptr));
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return self.writer.write(bytes);
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return self.writer.interface.write(bytes);
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}
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pub fn anyWriter(self: *PosixTty) std.io.AnyWriter {
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-
return .{
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.context = self,
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.writeFn = PosixTty.opaqueWrite,
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};
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return self.writer.interface.any();
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}
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pub fn read(self: *const PosixTty, buf: []u8) !usize {
···
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// a buffer to write key text into
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buf: [4]u8 = undefined,
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/// Write buffer
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buffer: []u8,
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-
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/// Embedded writer
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writer: std.io.Writer,
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/// File.Writer for efficient buffered writing
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writer: std.fs.File.Writer,
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/// The last mouse button that was pressed. We store the previous state of button presses on each
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/// mouse event so we can detect which button was released
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last_mouse_button_press: u16 = 0,
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/// VTable for embedded writer
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const vtable = std.io.Writer.VTable{
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.drain = drainVTable,
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};
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fn drainVTable(w: *std.io.Writer, data: []const []const u8, splat: usize) std.io.Writer.Error!usize {
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const self: *WindowsTty = @fieldParentPtr("writer", w);
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// First write any buffered data
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if (w.end > 0) {
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_ = windows.WriteFile(self.stdout, w.buffer[0..w.end], null) catch return error.WriteFailed;
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w.end = 0;
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}
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// Write each slice in data
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var total: usize = 0;
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for (data[0..data.len-1]) |slice| {
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const n = windows.WriteFile(self.stdout, slice, null) catch return error.WriteFailed;
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total += n;
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}
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// Write the last slice `splat` times
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const pattern = data[data.len - 1];
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for (0..splat) |_| {
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const n = windows.WriteFile(self.stdout, pattern, null) catch return error.WriteFailed;
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total += n;
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}
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return total;
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}
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const utf8_codepage: c_uint = 65001;
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···
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if (windows.kernel32.SetConsoleOutputCP(utf8_codepage) == 0)
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return windows.unexpectedError(windows.kernel32.GetLastError());
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var self: Tty = .{
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const file = std.fs.File{ .handle = stdout };
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+
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const self: Tty = .{
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.stdin = stdin,
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.stdout = stdout,
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.initial_codepage = initial_output_codepage,
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.initial_input_mode = initial_input_mode,
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.initial_output_mode = initial_output_mode,
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.buffer = buffer,
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.writer = undefined, // Will be set after self is created
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};
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// Initialize the writer to use our embedded buffer
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self.writer = .{
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.vtable = &vtable,
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.buffer = self.buffer,
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.end = 0,
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.writer = std.fs.File.Writer.initStreaming(file, buffer),
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};
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// save a copy of this tty as the global_tty for panic handling
···
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/// Write bytes to the tty
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pub fn write(self: *Tty, bytes: []const u8) !usize {
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-
return self.writer.write(bytes);
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+
return self.writer.interface.write(bytes);
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}
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pub fn opaqueWrite(ptr: *const anyopaque, bytes: []const u8) !usize {
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const self: *Tty = @ptrCast(@alignCast(ptr));
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return self.writer.write(bytes);
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+
return self.writer.interface.write(bytes);
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}
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pub fn anyWriter(self: *Tty) std.io.AnyWriter {
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-
return .{
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.context = self,
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.writeFn = Tty.opaqueWrite,
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-
};
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return self.writer.interface.any();
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}
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pub fn bufferedWriter(self: *Tty) *std.io.Writer {
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// The embedded writer is already buffered with a 4096-byte buffer
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return &self.writer;
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+
pub fn bufferedWriter(self: *Tty) std.io.AnyWriter {
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// File.Writer is already buffered
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return self.writer.interface.any();
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}
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pub fn nextEvent(self: *Tty, parser: *Parser, paste_allocator: ?std.mem.Allocator) !Event {