Add StreamProcessor for apply

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

diff/stream.go

@@ -0,0 +1,234 @@
+/*
+   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 (
+	"context"
+	"io"
+	"os"
+	"os/exec"
+
+	"github.com/containerd/containerd/archive/compression"
+	"github.com/containerd/containerd/images"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+	"github.com/pkg/errors"
+)
+
+var (
+	handlers []Handler
+
+	// ErrNoProcessor is returned when no stream processor is avaliable for a media-type
+	ErrNoProcessor = errors.New("no processor for media-type")
+)
+
+func init() {
+	// register the default compression handler
+	RegisterProcessor(compressedHandler)
+}
+
+// RegisterProcessor registers a stream processor for media-types
+func RegisterProcessor(handler Handler) {
+	handlers = append(handlers, handler)
+}
+
+// GetProcessor returns the processor for a media-type
+func GetProcessor(ctx context.Context, mediaType string, stream StreamProcessor, payloads map[string]interface{}) (StreamProcessor, error) {
+	// reverse this list so that user configured handlers come up first
+	for i := len(handlers); i >= 0; i-- {
+		processor, ok := handlers[i](ctx, mediaType)
+		if ok {
+			return processor(ctx, stream, payloads)
+		}
+	}
+	return nil, ErrNoProcessor
+}
+
+// Handler checks a media-type and initializes the processor
+type Handler func(ctx context.Context, mediaType string) (StreamProcessorInit, bool)
+
+// StaticHandler returns the processor init func for a static media-type
+func StaticHandler(expectedMediaType string, fn StreamProcessorInit) Handler {
+	return func(ctx context.Context, mediaType string) (StreamProcessorInit, bool) {
+		if mediaType == expectedMediaType {
+			return fn, true
+		}
+		return nil, false
+	}
+}
+
+// StreamProcessorInit returns the initialized stream processor
+type StreamProcessorInit func(ctx context.Context, stream StreamProcessor, payloads map[string]interface{}) (StreamProcessor, error)
+
+// RawProcessor provides access to direct fd for processing
+type RawProcessor interface {
+	// File returns the fd for the read stream of the underlying processor
+	File() *os.File
+}
+
+// StreamProcessor handles processing a content stream and transforming it into a different media-type
+type StreamProcessor interface {
+	io.ReadCloser
+
+	// MediaType is the resulting media-type that the processor processes the stream into
+	MediaType() string
+}
+
+func compressedHandler(ctx context.Context, mediaType string) (StreamProcessorInit, bool) {
+	compressed, err := images.IsCompressedDiff(ctx, mediaType)
+	if err != nil {
+		return nil, false
+	}
+	if compressed {
+		return func(ctx context.Context, stream StreamProcessor, payloads map[string]interface{}) (StreamProcessor, error) {
+			ds, err := compression.DecompressStream(stream)
+			if err != nil {
+				return nil, err
+			}
+
+			return &compressedProcessor{
+				rc: ds,
+			}, nil
+		}, true
+	}
+	return func(ctx context.Context, stream StreamProcessor, payloads map[string]interface{}) (StreamProcessor, error) {
+		return &stdProcessor{
+			rc: stream,
+		}, nil
+	}, true
+}
+
+// NewProcessorChain initialized the root StreamProcessor
+func NewProcessorChain(mt string, r io.Reader) StreamProcessor {
+	return &processorChain{
+		mt: mt,
+		rc: r,
+	}
+}
+
+type processorChain struct {
+	mt string
+	rc io.Reader
+}
+
+func (c *processorChain) MediaType() string {
+	return c.mt
+}
+
+func (c *processorChain) Read(p []byte) (int, error) {
+	return c.rc.Read(p)
+}
+
+func (c *processorChain) Close() error {
+	return nil
+}
+
+type stdProcessor struct {
+	rc StreamProcessor
+}
+
+func (c *stdProcessor) MediaType() string {
+	return ocispec.MediaTypeImageLayer
+}
+
+func (c *stdProcessor) Read(p []byte) (int, error) {
+	return c.rc.Read(p)
+}
+
+func (c *stdProcessor) Close() error {
+	return nil
+}
+
+type compressedProcessor struct {
+	rc io.ReadCloser
+}
+
+func (c *compressedProcessor) MediaType() string {
+	return ocispec.MediaTypeImageLayer
+}
+
+func (c *compressedProcessor) Read(p []byte) (int, error) {
+	return c.rc.Read(p)
+}
+
+func (c *compressedProcessor) Close() error {
+	return c.rc.Close()
+}
+
+// NewBinaryProcessor returns a binary processor for use with processing content streams
+func NewBinaryProcessor(ctx context.Context, mt string, stream StreamProcessor, name string, args ...string) (StreamProcessor, error) {
+	cmd := exec.CommandContext(ctx, name, args...)
+	var (
+		stdin *os.File
+		err   error
+	)
+	if f, ok := stream.(RawProcessor); ok {
+		stdin = f.File()
+	} else {
+		r, w, err := os.Pipe()
+		if err != nil {
+			return nil, err
+		}
+		stdin = r
+		go func() {
+			io.Copy(w, stream)
+		}()
+	}
+	cmd.Stdin = stdin
+	r, w, err := os.Pipe()
+	if err != nil {
+		return nil, err
+	}
+	cmd.Stdout = w
+	if err := cmd.Start(); err != nil {
+		return nil, err
+	}
+	// close after start and dup
+	stdin.Close()
+	w.Close()
+
+	return &binaryProcessor{
+		cmd: cmd,
+		r:   r,
+		mt:  mt,
+	}, nil
+}
+
+type binaryProcessor struct {
+	cmd *exec.Cmd
+	r   *os.File
+	mt  string
+}
+
+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
+}