Move diff to core/diff

Signed-off-by: Derek McGowan <derek@mcg.dev>

core/diff/stream_unix.go

@@ -0,0 +1,165 @@
+//go:build !windows
+
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package diff
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"sync"
+
+	"github.com/containerd/containerd/v2/protobuf"
+	"github.com/containerd/containerd/v2/protobuf/proto"
+	"github.com/containerd/typeurl/v2"
+)
+
+// NewBinaryProcessor returns a binary processor for use with processing content streams
+func NewBinaryProcessor(ctx context.Context, imt, rmt string, stream StreamProcessor, name string, args, env []string, payload typeurl.Any) (StreamProcessor, error) {
+	cmd := exec.CommandContext(ctx, name, args...)
+	cmd.Env = os.Environ()
+	cmd.Env = append(cmd.Env, env...)
+
+	var payloadC io.Closer
+	if payload != nil {
+		pb := protobuf.FromAny(payload)
+		data, err := proto.Marshal(pb)
+		if err != nil {
+			return nil, err
+		}
+		r, w, err := os.Pipe()
+		if err != nil {
+			return nil, err
+		}
+		go func() {
+			io.Copy(w, bytes.NewReader(data))
+			w.Close()
+		}()
+
+		cmd.ExtraFiles = append(cmd.ExtraFiles, r)
+		payloadC = r
+	}
+	cmd.Env = append(cmd.Env, fmt.Sprintf("%s=%s", mediaTypeEnvVar, imt))
+	var (
+		stdin  io.Reader
+		closer func() error
+		err    error
+	)
+	if f, ok := stream.(RawProcessor); ok {
+		stdin = f.File()
+		closer = f.File().Close
+	} else {
+		stdin = stream
+	}
+	cmd.Stdin = stdin
+	r, w, err := os.Pipe()
+	if err != nil {
+		return nil, err
+	}
+	cmd.Stdout = w
+
+	stderr := bytes.NewBuffer(nil)
+	cmd.Stderr = stderr
+
+	if err := cmd.Start(); err != nil {
+		return nil, err
+	}
+	p := &binaryProcessor{
+		cmd:    cmd,
+		r:      r,
+		mt:     rmt,
+		stderr: stderr,
+		done:   make(chan struct{}),
+	}
+	go p.wait()
+
+	// close after start and dup
+	w.Close()
+	if closer != nil {
+		closer()
+	}
+	if payloadC != nil {
+		payloadC.Close()
+	}
+	return p, nil
+}
+
+type binaryProcessor struct {
+	cmd    *exec.Cmd
+	r      *os.File
+	mt     string
+	stderr *bytes.Buffer
+
+	mu  sync.Mutex
+	err error
+
+	// There is a race condition between waiting on c.cmd.Wait() and setting c.err within
+	// c.wait(), and reading that value from c.Err().
+	// Use done to wait for the returned error to be captured and set.
+	done chan struct{}
+}
+
+func (c *binaryProcessor) Err() error {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.err
+}
+
+func (c *binaryProcessor) wait() {
+	if err := c.cmd.Wait(); err != nil {
+		if _, ok := err.(*exec.ExitError); ok {
+			c.mu.Lock()
+			c.err = errors.New(c.stderr.String())
+			c.mu.Unlock()
+		}
+	}
+	close(c.done)
+}
+
+func (c *binaryProcessor) Wait(ctx context.Context) error {
+	select {
+	case <-c.done:
+		return c.Err()
+	case <-ctx.Done():
+		return ctx.Err()
+	}
+}
+
+func (c *binaryProcessor) File() *os.File {
+	return c.r
+}
+
+func (c *binaryProcessor) MediaType() string {
+	return c.mt
+}
+
+func (c *binaryProcessor) Read(p []byte) (int, error) {
+	return c.r.Read(p)
+}
+
+func (c *binaryProcessor) Close() error {
+	err := c.r.Close()
+	if kerr := c.cmd.Process.Kill(); err == nil {
+		err = kerr
+	}
+	return err
+}