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fix: replace Windows input busy-poll with WaitForSingleObject #120

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fix: replace Windows input busy-poll with WaitForSingleObject #120

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16 changes: 12 additions & 4 deletions terminal_reader_windows.go
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Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,6 @@ import (
"context"
"fmt"
"strings"
"time"
"unicode/utf16"

"github.com/charmbracelet/x/ansi"
Expand All @@ -31,9 +30,10 @@ func (d *TerminalReader) streamData(ctx context.Context, readc chan []byte) erro
var buf bytes.Buffer
var records []xwindows.InputRecord
var err error
peekBuf := make([]xwindows.InputRecord, readBufSize) // pre-allocate, reused across iterations
for {
for {
records, err = peekNConsoleInputs(cc.conin, readBufSize)
records, err = peekNConsoleInputsInto(cc.conin, peekBuf)
if cc.isCanceled() {
return cancelreader.ErrCanceled
}
Expand All @@ -44,8 +44,10 @@ func (d *TerminalReader) streamData(ctx context.Context, readc chan []byte) erro
break
}

// Sleep for a bit to avoid busy waiting.
time.Sleep(10 * time.Millisecond)
// Block until input is available using a kernel wait instead of
// polling with PeekConsoleInput. This eliminates CPU usage when idle.
// A 1s timeout ensures cancellation is detected promptly.
windows.WaitForSingleObject(cc.conin, 1000)
}

records, err = readNConsoleInputs(cc.conin, uint32(len(records))) //nolint:gosec
Expand Down Expand Up @@ -291,6 +293,12 @@ func peekNConsoleInputs(console windows.Handle, maxEvents uint32) ([]xwindows.In
return records[:n], err
}

// peekNConsoleInputsInto reuses a pre-allocated buffer to avoid GC pressure.
func peekNConsoleInputsInto(console windows.Handle, buf []xwindows.InputRecord) ([]xwindows.InputRecord, error) {
n, err := peekConsoleInput(console, buf)
return buf[:n], err
}

//nolint:unused
func keyEventString(vkc, sc uint16, r rune, keyDown bool, cks uint32, repeatCount uint16) string {
var s strings.Builder
Expand Down