storj/pkg/ranger/readerat.go
2018-06-19 18:59:09 +03:00

62 lines
1.2 KiB
Go

// Copyright (C) 2018 Storj Labs, Inc.
// See LICENSE for copying information.
package ranger
import (
"context"
"io"
)
type readerAtRanger struct {
r io.ReaderAt
size int64
}
// ReaderAtRanger converts a ReaderAt with a given size to a Ranger
func ReaderAtRanger(r io.ReaderAt, size int64) Ranger {
return &readerAtRanger{
r: r,
size: size,
}
}
func (r *readerAtRanger) Size() int64 {
return r.size
}
type readerAtReader struct {
r io.ReaderAt
offset, length int64
}
func (r *readerAtRanger) Range(ctx context.Context, offset, length int64) (io.ReadCloser, error) {
if offset < 0 {
return nil, Error.New("negative offset")
}
if length < 0 {
return nil, Error.New("negative length")
}
if offset+length > r.size {
return nil, Error.New("buffer runoff")
}
return &readerAtReader{r: r.r, offset: offset, length: length}, nil
}
func (r *readerAtReader) Read(p []byte) (n int, err error) {
if r.length == 0 {
return 0, io.EOF
}
if int64(len(p)) > r.length {
p = p[:r.length]
}
n, err = r.r.ReadAt(p, r.offset)
r.offset += int64(n)
r.length -= int64(n)
return n, err
}
func (r *readerAtReader) Close() error {
return nil
}