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bytestream.go
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bytestream.go
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// Copyright 2022 Namespace Labs Inc; All rights reserved.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
package bytestream
import (
"bytes"
"context"
"crypto/sha256"
"io"
"namespacelabs.dev/foundation/schema"
)
type ByteStream interface {
ContentLength() uint64
Reader() (io.ReadCloser, error)
}
type ReaderAtCloser interface {
io.ReaderAt
io.Closer
}
type ByteStreamWithDigest interface {
ByteStream
ComputeDigest(context.Context) (schema.Digest, error)
}
func Digest(ctx context.Context, bs ByteStream) (schema.Digest, error) {
if cd, ok := bs.(interface {
ComputeDigest(context.Context) (schema.Digest, error)
}); ok {
return cd.ComputeDigest(ctx)
}
r, err := bs.Reader()
if err != nil {
return schema.Digest{}, err
}
defer r.Close()
h := sha256.New()
if _, err := io.Copy(h, r); err != nil {
return schema.Digest{}, err
}
return schema.FromHash("sha256", h), nil
}
func ReaderAt(bs ByteStream) (ReaderAtCloser, error) {
if v, ok := bs.(interface {
ReaderAt() (ReaderAtCloser, error)
}); ok {
return v.ReaderAt()
}
r, err := bs.Reader()
if err != nil {
return nil, err
}
defer r.Close()
// XXX expensive.
contents, err := io.ReadAll(r)
if err != nil {
return nil, err
}
return bytesReaderWithClose{Reader: bytes.NewReader(contents)}, nil
}
type bytesReaderWithClose struct {
*bytes.Reader
}
func (bytesReaderWithClose) Close() error { return nil }
type Static struct {
Contents []byte
}
func (s Static) ContentLength() uint64 { return uint64(len(s.Contents)) }
func (s Static) Reader() (io.ReadCloser, error) {
return io.NopCloser(bytes.NewReader(s.Contents)), nil
}
func WriteTo(w io.Writer, contents ByteStream) error {
r, err := contents.Reader()
if err != nil {
return err
}
defer r.Close()
if _, err := io.Copy(w, r); err != nil {
return err
}
return nil
}
func ReadAll(contents ByteStream) ([]byte, error) {
r, err := contents.Reader()
if err != nil {
return nil, err
}
defer r.Close()
return io.ReadAll(r)
}