feat: improved deploy progress reporting

See toolshed/abra#478

vendor/github.com/muesli/cancelreader/cancelreader_linux.go

@@ -0,0 +1,154 @@
+//go:build linux
+// +build linux
+
+package cancelreader
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+
+	"golang.org/x/sys/unix"
+)
+
+// NewReader returns a reader and a cancel function. If the input reader is a
+// File, the cancel function can be used to interrupt a blocking read call.
+// In this case, the cancel function returns true if the call was canceled
+// successfully. If the input reader is not a File, the cancel function
+// does nothing and always returns false. The Linux implementation is based on
+// the epoll mechanism.
+func NewReader(reader io.Reader) (CancelReader, error) {
+	file, ok := reader.(File)
+	if !ok {
+		return newFallbackCancelReader(reader)
+	}
+
+	epoll, err := unix.EpollCreate1(0)
+	if err != nil {
+		return nil, fmt.Errorf("create epoll: %w", err)
+	}
+
+	r := &epollCancelReader{
+		file:  file,
+		epoll: epoll,
+	}
+
+	r.cancelSignalReader, r.cancelSignalWriter, err = os.Pipe()
+	if err != nil {
+		_ = unix.Close(epoll)
+		return nil, err
+	}
+
+	err = unix.EpollCtl(epoll, unix.EPOLL_CTL_ADD, int(file.Fd()), &unix.EpollEvent{
+		Events: unix.EPOLLIN,
+		Fd:     int32(file.Fd()),
+	})
+	if err != nil {
+		_ = unix.Close(epoll)
+		return nil, fmt.Errorf("add reader to epoll interest list")
+	}
+
+	err = unix.EpollCtl(epoll, unix.EPOLL_CTL_ADD, int(r.cancelSignalReader.Fd()), &unix.EpollEvent{
+		Events: unix.EPOLLIN,
+		Fd:     int32(r.cancelSignalReader.Fd()),
+	})
+	if err != nil {
+		_ = unix.Close(epoll)
+		return nil, fmt.Errorf("add reader to epoll interest list")
+	}
+
+	return r, nil
+}
+
+type epollCancelReader struct {
+	file               File
+	cancelSignalReader File
+	cancelSignalWriter File
+	cancelMixin
+	epoll int
+}
+
+func (r *epollCancelReader) Read(data []byte) (int, error) {
+	if r.isCanceled() {
+		return 0, ErrCanceled
+	}
+
+	err := r.wait()
+	if err != nil {
+		if errors.Is(err, ErrCanceled) {
+			// remove signal from pipe
+			var b [1]byte
+			_, readErr := r.cancelSignalReader.Read(b[:])
+			if readErr != nil {
+				return 0, fmt.Errorf("reading cancel signal: %w", readErr)
+			}
+		}
+
+		return 0, err
+	}
+
+	return r.file.Read(data)
+}
+
+func (r *epollCancelReader) Cancel() bool {
+	r.setCanceled()
+
+	// send cancel signal
+	_, err := r.cancelSignalWriter.Write([]byte{'c'})
+	return err == nil
+}
+
+func (r *epollCancelReader) Close() error {
+	var errMsgs []string
+
+	// close kqueue
+	err := unix.Close(r.epoll)
+	if err != nil {
+		errMsgs = append(errMsgs, fmt.Sprintf("closing epoll: %v", err))
+	}
+
+	// close pipe
+	err = r.cancelSignalWriter.Close()
+	if err != nil {
+		errMsgs = append(errMsgs, fmt.Sprintf("closing cancel signal writer: %v", err))
+	}
+
+	err = r.cancelSignalReader.Close()
+	if err != nil {
+		errMsgs = append(errMsgs, fmt.Sprintf("closing cancel signal reader: %v", err))
+	}
+
+	if len(errMsgs) > 0 {
+		return fmt.Errorf(strings.Join(errMsgs, ", "))
+	}
+
+	return nil
+}
+
+func (r *epollCancelReader) wait() error {
+	events := make([]unix.EpollEvent, 1)
+
+	for {
+		_, err := unix.EpollWait(r.epoll, events, -1)
+		if errors.Is(err, unix.EINTR) {
+			continue // try again if the syscall was interrupted
+		}
+
+		if err != nil {
+			return fmt.Errorf("kevent: %w", err)
+		}
+
+		break
+	}
+
+	switch events[0].Fd {
+	case int32(r.file.Fd()):
+		return nil
+	case int32(r.cancelSignalReader.Fd()):
+		return ErrCanceled
+	}
+
+	return fmt.Errorf("unknown error")
+}