restic/fuse/file.go

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package fuse
import (
"sync"
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"github.com/restic/restic"
"github.com/restic/restic/backend"
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"github.com/restic/restic/pack"
"bazil.org/fuse"
"bazil.org/fuse/fs"
"golang.org/x/net/context"
)
// Statically ensure that *file implements the given interface
var _ = fs.HandleReader(&file{})
var _ = fs.HandleReleaser(&file{})
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// BlobLoader is an abstracted repository with a reduced set of methods used
// for fuse operations.
type BlobLoader interface {
LookupBlobSize(backend.ID) (uint, error)
LoadBlob(pack.BlobType, backend.ID, []byte) ([]byte, error)
}
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type file struct {
repo BlobLoader
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node *restic.Node
sizes []uint
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blobs [][]byte
}
const defaultBlobSize = 128 * 1024
var blobPool = sync.Pool{
New: func() interface{} {
return make([]byte, defaultBlobSize)
},
}
func newFile(repo BlobLoader, node *restic.Node) (*file, error) {
sizes := make([]uint, len(node.Content))
for i, id := range node.Content {
size, err := repo.LookupBlobSize(id)
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if err != nil {
return nil, err
}
sizes[i] = size
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}
return &file{
repo: repo,
node: node,
sizes: sizes,
blobs: make([][]byte, len(node.Content)),
}, nil
}
func (f *file) Attr(ctx context.Context, a *fuse.Attr) error {
a.Inode = f.node.Inode
a.Mode = f.node.Mode
a.Size = f.node.Size
return nil
}
func (f *file) getBlobAt(i int) (blob []byte, err error) {
if f.blobs[i] != nil {
return f.blobs[i], nil
}
buf := blobPool.Get().([]byte)
buf = buf[:cap(buf)]
if uint(len(buf)) < f.sizes[i] {
if len(buf) > defaultBlobSize {
blobPool.Put(buf)
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}
buf = make([]byte, f.sizes[i])
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}
blob, err = f.repo.LoadBlob(pack.Data, f.node.Content[i], buf)
if err != nil {
return nil, err
}
f.blobs[i] = blob
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return blob, nil
}
func (f *file) Read(ctx context.Context, req *fuse.ReadRequest, resp *fuse.ReadResponse) error {
offset := req.Offset
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// Skip blobs before the offset
startContent := 0
for offset > int64(f.sizes[startContent]) {
offset -= int64(f.sizes[startContent])
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startContent++
}
dst := resp.Data[0:req.Size]
readBytes := 0
remainingBytes := req.Size
for i := startContent; remainingBytes > 0 && i < len(f.sizes); i++ {
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blob, err := f.getBlobAt(i)
if err != nil {
return err
}
if offset > 0 {
blob = blob[offset:len(blob)]
offset = 0
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}
copied := copy(dst, blob)
remainingBytes -= copied
readBytes += copied
dst = dst[copied:]
}
resp.Data = resp.Data[:readBytes]
return nil
}
func (f *file) Release(ctx context.Context, req *fuse.ReleaseRequest) error {
for i := range f.blobs {
if f.blobs[i] != nil {
blobPool.Put(f.blobs[i])
f.blobs[i] = nil
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}
}
return nil
}