vendor: initial vendor

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

vendor/github.com/containerd/containerd/content/helpers.go

@@ -0,0 +1,208 @@
+/*
+   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 content
+
+import (
+	"context"
+	"io"
+	"io/ioutil"
+	"math/rand"
+	"sync"
+	"time"
+
+	"github.com/containerd/containerd/errdefs"
+	"github.com/opencontainers/go-digest"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+	"github.com/pkg/errors"
+)
+
+var bufPool = sync.Pool{
+	New: func() interface{} {
+		buffer := make([]byte, 1<<20)
+		return &buffer
+	},
+}
+
+// NewReader returns a io.Reader from a ReaderAt
+func NewReader(ra ReaderAt) io.Reader {
+	rd := io.NewSectionReader(ra, 0, ra.Size())
+	return rd
+}
+
+// ReadBlob retrieves the entire contents of the blob from the provider.
+//
+// Avoid using this for large blobs, such as layers.
+func ReadBlob(ctx context.Context, provider Provider, desc ocispec.Descriptor) ([]byte, error) {
+	ra, err := provider.ReaderAt(ctx, desc)
+	if err != nil {
+		return nil, err
+	}
+	defer ra.Close()
+
+	p := make([]byte, ra.Size())
+
+	_, err = ra.ReadAt(p, 0)
+	return p, err
+}
+
+// WriteBlob writes data with the expected digest into the content store. If
+// expected already exists, the method returns immediately and the reader will
+// not be consumed.
+//
+// This is useful when the digest and size are known beforehand.
+//
+// Copy is buffered, so no need to wrap reader in buffered io.
+func WriteBlob(ctx context.Context, cs Ingester, ref string, r io.Reader, desc ocispec.Descriptor, opts ...Opt) error {
+	cw, err := OpenWriter(ctx, cs, WithRef(ref), WithDescriptor(desc))
+	if err != nil {
+		if !errdefs.IsAlreadyExists(err) {
+			return errors.Wrap(err, "failed to open writer")
+		}
+
+		return nil // all ready present
+	}
+	defer cw.Close()
+
+	return Copy(ctx, cw, r, desc.Size, desc.Digest, opts...)
+}
+
+// OpenWriter opens a new writer for the given reference, retrying if the writer
+// is locked until the reference is available or returns an error.
+func OpenWriter(ctx context.Context, cs Ingester, opts ...WriterOpt) (Writer, error) {
+	var (
+		cw    Writer
+		err   error
+		retry = 16
+	)
+	for {
+		cw, err = cs.Writer(ctx, opts...)
+		if err != nil {
+			if !errdefs.IsUnavailable(err) {
+				return nil, err
+			}
+
+			// TODO: Check status to determine if the writer is active,
+			// continue waiting while active, otherwise return lock
+			// error or abort. Requires asserting for an ingest manager
+
+			select {
+			case <-time.After(time.Millisecond * time.Duration(rand.Intn(retry))):
+				if retry < 2048 {
+					retry = retry << 1
+				}
+				continue
+			case <-ctx.Done():
+				// Propagate lock error
+				return nil, err
+			}
+
+		}
+		break
+	}
+
+	return cw, err
+}
+
+// Copy copies data with the expected digest from the reader into the
+// provided content store writer. This copy commits the writer.
+//
+// This is useful when the digest and size are known beforehand. When
+// the size or digest is unknown, these values may be empty.
+//
+// Copy is buffered, so no need to wrap reader in buffered io.
+func Copy(ctx context.Context, cw Writer, r io.Reader, size int64, expected digest.Digest, opts ...Opt) error {
+	ws, err := cw.Status()
+	if err != nil {
+		return errors.Wrap(err, "failed to get status")
+	}
+
+	if ws.Offset > 0 {
+		r, err = seekReader(r, ws.Offset, size)
+		if err != nil {
+			return errors.Wrapf(err, "unable to resume write to %v", ws.Ref)
+		}
+	}
+
+	if _, err := copyWithBuffer(cw, r); err != nil {
+		return errors.Wrap(err, "failed to copy")
+	}
+
+	if err := cw.Commit(ctx, size, expected, opts...); err != nil {
+		if !errdefs.IsAlreadyExists(err) {
+			return errors.Wrapf(err, "failed commit on ref %q", ws.Ref)
+		}
+	}
+
+	return nil
+}
+
+// CopyReaderAt copies to a writer from a given reader at for the given
+// number of bytes. This copy does not commit the writer.
+func CopyReaderAt(cw Writer, ra ReaderAt, n int64) error {
+	ws, err := cw.Status()
+	if err != nil {
+		return err
+	}
+
+	_, err = copyWithBuffer(cw, io.NewSectionReader(ra, ws.Offset, n))
+	return err
+}
+
+// seekReader attempts to seek the reader to the given offset, either by
+// resolving `io.Seeker`, by detecting `io.ReaderAt`, or discarding
+// up to the given offset.
+func seekReader(r io.Reader, offset, size int64) (io.Reader, error) {
+	// attempt to resolve r as a seeker and setup the offset.
+	seeker, ok := r.(io.Seeker)
+	if ok {
+		nn, err := seeker.Seek(offset, io.SeekStart)
+		if nn != offset {
+			return nil, errors.Wrapf(err, "failed to seek to offset %v", offset)
+		}
+
+		if err != nil {
+			return nil, err
+		}
+
+		return r, nil
+	}
+
+	// ok, let's try io.ReaderAt!
+	readerAt, ok := r.(io.ReaderAt)
+	if ok && size > offset {
+		sr := io.NewSectionReader(readerAt, offset, size)
+		return sr, nil
+	}
+
+	// well then, let's just discard up to the offset
+	n, err := copyWithBuffer(ioutil.Discard, io.LimitReader(r, offset))
+	if err != nil {
+		return nil, errors.Wrap(err, "failed to discard to offset")
+	}
+	if n != offset {
+		return nil, errors.Errorf("unable to discard to offset")
+	}
+
+	return r, nil
+}
+
+func copyWithBuffer(dst io.Writer, src io.Reader) (written int64, err error) {
+	buf := bufPool.Get().(*[]byte)
+	written, err = io.CopyBuffer(dst, src, *buf)
+	bufPool.Put(buf)
+	return
+}