forked from keybase/client
/
browser_file.go
108 lines (88 loc) · 2.35 KB
/
browser_file.go
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// Copyright 2018 Keybase Inc. All rights reserved.
// Use of this source code is governed by a BSD
// license that can be found in the LICENSE file.
package libgit
import (
"io"
"github.com/pkg/errors"
billy "gopkg.in/src-d/go-billy.v4"
"gopkg.in/src-d/go-git.v4/plumbing/object"
)
const (
browserFileDefaultMaxBufSize = 4 * 1024 * 1024 // 4 MB
)
type browserFile struct {
f *object.File
r io.ReadCloser
maxBufSize int64
}
var _ billy.File = (*browserFile)(nil)
func newBrowserFile(f *object.File) (*browserFile, error) {
r, err := f.Reader()
if err != nil {
return nil, err
}
return &browserFile{
f: f,
r: r,
maxBufSize: browserFileDefaultMaxBufSize,
}, nil
}
func (bf *browserFile) Name() string {
return bf.f.Name
}
func (bf *browserFile) Write(_ []byte) (n int, err error) {
return 0, errors.New("browser files can't be written")
}
func (bf *browserFile) Read(p []byte) (n int, err error) {
return bf.r.Read(p)
}
func (bf *browserFile) ReadAt(p []byte, off int64) (n int, err error) {
// Sadly go-git doesn't expose a `ReadAt` or `Seek` interface for
// this, but we can probably implement it if needed. Instead, use
// a new Reader object and just scan starting from the beginning.
r, err := bf.f.Reader()
if err != nil {
return 0, err
}
defer func() {
_ = r.Close()
}()
dataToSkip := off
bufSize := dataToSkip
if bufSize > bf.maxBufSize {
bufSize = bf.maxBufSize
}
buf := make([]byte, bufSize)
// Skip past the data we don't care about, one chunk at a time.
for dataToSkip > 0 {
toRead := int64(len(buf))
if dataToSkip < toRead {
toRead = dataToSkip
}
// Throwaway data.
n, err := r.Read(buf[:toRead])
if err != nil {
return 0, err
}
dataToSkip -= int64(n)
}
return r.Read(p)
}
func (bf *browserFile) Seek(offset int64, whence int) (int64, error) {
// TODO if needed: we'd have to track the offset of `bf.r`
// manually, the same way we do in `libfs.File`.
return 0, errors.New("browser files can't seek")
}
func (bf *browserFile) Close() error {
return bf.r.Close()
}
func (bf *browserFile) Lock() error {
return errors.New("browser files can't be locked")
}
func (bf *browserFile) Unlock() error {
return errors.New("browser files can't be unlocked")
}
func (bf *browserFile) Truncate(size int64) error {
return errors.New("browser files can't be truncated")
}