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embed std.io.Writer in WindowsTty with 4096-byte buffer
Apply the same Writer API integration to WindowsTty that was done for
PosixTty. This provides consistent buffered writing capabilities across
both Windows and POSIX platforms using Zig 0.15.1's new Writer API.
The embedded writer uses @fieldParentPtr to access the parent WindowsTty
instance from the drain function, enabling efficient writes to the
Windows console handle when the buffer is full or flushed.
Add write() method and update opaqueWrite() to use the embedded writer
instead of direct windows.WriteFile() calls, providing automatic
buffering for better performance by reducing system call overhead.
Amp-Thread-ID: https://ampcode.com/threads/T-e1192d32-b3c3-43a6-b434-33fe5664bf0a
Co-authored-by: Amp <amp@ampcode.com>
+58
-6
+58
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src/tty.zig
+58
-6
src/tty.zig
···
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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: [4096]u8,
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+
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/// Embedded writer
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writer: std.io.Writer,
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+
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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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/// The input mode set by init
···
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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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const self: Tty = .{
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var 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 = undefined,
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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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};
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// save a copy of this tty as the global_tty for panic handling
···
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};
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}
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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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}
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pub fn opaqueWrite(ptr: *const anyopaque, bytes: []const u8) !usize {
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const self: *const Tty = @ptrCast(@alignCast(ptr));
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return windows.WriteFile(self.stdout, bytes, null);
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const self: *Tty = @ptrCast(@alignCast(ptr));
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return self.writer.write(bytes);
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}
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pub fn anyWriter(self: *const Tty) std.io.AnyWriter {
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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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}
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pub fn bufferedWriter(self: *const Tty) std.io.BufferedWriter(4096, std.io.AnyWriter) {
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return std.io.bufferedWriter(self.anyWriter());
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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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}
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pub fn nextEvent(self: *Tty, parser: *Parser, paste_allocator: ?std.mem.Allocator) !Event {