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gob.go
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gob.go
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/*
* Copyright 2016 ClusterHQ
*
* 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 gob
import (
"encoding/gob"
"fmt"
"io"
"github.com/ClusterHQ/fli/dl/encdec"
"github.com/ClusterHQ/fli/dl/record"
)
type (
// recordsHeader is the header for an array of records
recordsHeader struct {
NumRecs int // How many records are in already-encoded record list
}
encoder struct {
enc *gob.Encoder
}
decoder struct {
dec *gob.Decoder
}
// Factory is a helper for creating a new record encode/decode factory
Factory struct {
}
)
var (
_ encdec.Factory = Factory{}
_ encdec.Encoder = &encoder{}
_ encdec.Decoder = &decoder{}
)
// register registers all record types in order to be able to decoded/encoded by gob
func init() {
gob.Register(&record.Mkdir{})
gob.Register(&record.Pwrite{})
gob.Register(&record.Hardlink{})
gob.Register(&record.Symlink{})
gob.Register(&record.Truncate{})
gob.Register(&record.Chown{})
gob.Register(&record.Create{})
gob.Register(&record.Remove{})
gob.Register(&record.Setxattr{})
gob.Register(&record.Rmxattr{})
gob.Register(&record.Rename{})
gob.Register(&record.Mknod{})
gob.Register(&record.Chmod{})
gob.Register(&record.Setmtime{})
gob.Register(&record.EOT{})
}
// NewEncoder returns a new encoder
func (f Factory) NewEncoder(target io.Writer) encdec.Encoder {
return newEnc(target)
}
// NewDecoder returns a new decoder
func (f Factory) NewDecoder(src io.Reader) encdec.Decoder {
return newDec(src)
}
// Type returns the encoder/decoder's type
func (f Factory) Type() encdec.Type {
return encdec.Gob
}
// newEnc returns a new gob encoder to user. It will act on a passed-in object that implements io.Writer interface
func newEnc(w io.Writer) *encoder {
return &encoder{enc: gob.NewEncoder(w)}
}
// newDec returns a new gob decoder to caller. It will act on a passed-in object that implements io.Reader interface
func newDec(r io.Reader) *decoder {
return &decoder{dec: gob.NewDecoder(r)}
}
// encRecs encodes records
func (g *encoder) encRecs(recs []record.Record) error {
return g.enc.Encode(&recs)
}
// encRecHdr encodes a RecHeader object
func (g *encoder) encRecHdr(h recordsHeader) error {
return g.enc.Encode(h)
}
// decRecs decodes []records.Record
func (g *decoder) decRecs() ([]record.Record, error) {
var recs []record.Record
err := g.dec.Decode(&recs)
if err != nil {
return nil, err
}
return recs, nil
}
// decRecHdr decodes an encoded ChunkHeader object.
func (g *decoder) decRecHdr() (recordsHeader, error) {
var hdr recordsHeader
err := g.dec.Decode(&hdr)
return hdr, err
}
// Encode implements encoder
func (g *encoder) Encode(recs []record.Record) error {
hdr := recordsHeader{NumRecs: len(recs)}
err := g.encRecHdr(hdr)
if err != nil {
return err
}
err = g.encRecs(recs)
return err
}
// Decode implements decoder
func (g *decoder) Decode() ([]record.Record, error) {
var (
recs []record.Record
hdr recordsHeader
)
hdr, err := g.decRecHdr()
if err != nil && err != io.EOF {
return nil, err
}
recs, err = g.decRecs()
if err != nil {
return nil, err
}
if len(recs) != hdr.NumRecs {
err = fmt.Errorf("Erorr: unpacked unexpected number of records. Expected %d, got %d",
hdr.NumRecs, len(recs))
return nil, err
}
return recs, nil
}