io.go

// +build !windows

package proc

import (
	"context"
	"fmt"
	"io"
	"sync"
	"syscall"

	"github.com/containerd/fifo"
	runc "github.com/containerd/go-runc"
)

var bufPool = sync.Pool{
	New: func() interface{} {
		buffer := make([]byte, 32<<10)
		return &buffer
	},
}

func copyPipes(ctx context.Context, rio runc.IO, stdin, stdout, stderr string, wg, cwg *sync.WaitGroup) error {
	for name, dest := range map[string]func(wc io.WriteCloser, rc io.Closer){
		stdout: func(wc io.WriteCloser, rc io.Closer) {
			wg.Add(1)
			cwg.Add(1)
			go func() {
				cwg.Done()
				p := bufPool.Get().(*[]byte)
				defer bufPool.Put(p)
				io.CopyBuffer(wc, rio.Stdout(), *p)
				wg.Done()
				wc.Close()
				rc.Close()
			}()
		},
		stderr: func(wc io.WriteCloser, rc io.Closer) {
			wg.Add(1)
			cwg.Add(1)
			go func() {
				cwg.Done()
				p := bufPool.Get().(*[]byte)
				defer bufPool.Put(p)

				io.CopyBuffer(wc, rio.Stderr(), *p)
				wg.Done()
				wc.Close()
				rc.Close()
			}()
		},
	} {
		fw, err := fifo.OpenFifo(ctx, name, syscall.O_WRONLY, 0)
		if err != nil {
			return fmt.Errorf("containerd-shim: opening %s failed: %s", name, err)
		}
		fr, err := fifo.OpenFifo(ctx, name, syscall.O_RDONLY, 0)
		if err != nil {
			return fmt.Errorf("containerd-shim: opening %s failed: %s", name, err)
		}
		dest(fw, fr)
	}
	if stdin == "" {
		rio.Stdin().Close()
		return nil
	}
	f, err := fifo.OpenFifo(ctx, stdin, syscall.O_RDONLY, 0)
	if err != nil {
		return fmt.Errorf("containerd-shim: opening %s failed: %s", stdin, err)
	}
	cwg.Add(1)
	go func() {
		cwg.Done()
		p := bufPool.Get().(*[]byte)
		defer bufPool.Put(p)

		io.CopyBuffer(rio.Stdin(), f, *p)
		rio.Stdin().Close()
		f.Close()
	}()
	return nil
}