/
tuple_stream.go
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/
tuple_stream.go
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// Copyright 2021 Dolthub, Inc.
//
// 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 types
import (
"context"
"encoding/binary"
"errors"
"io"
"github.com/dolthub/dolt/go/libraries/utils/iohelp"
)
// TupleWriter is an interface for an object that supports Types.Tuples being written to it
type TupleWriter interface {
// WriteTuples writes the provided tuples
WriteTuples(...Tuple) error
// WriteNull write a null to the stream
WriteNull() error
// CopyFrom reads tuples from a reader and writes them
CopyFrom(TupleReader) error
}
// TupleReader is an interface for an object that supports reading types.Tuples
type TupleReader interface {
// Read reades the next tuple from the TupleReader
Read() (*Tuple, error)
}
// Closer is an interface for a class that can be closed
type Closer interface {
// Close should release any underlying resources
Close(context.Context) error
}
// TupleWriteCloser is an interface for a TupleWriter that has a Close method
type TupleWriteCloser interface {
TupleWriter
Closer
}
// TupleReadCloser is an interface for a TupleReader that has a Close method
type TupleReadCloser interface {
TupleReader
Closer
}
type tupleWriterImpl struct {
wr io.Writer
}
// NewTupleWriter returns a TupleWriteCloser that writes tuple data to the supplied io.Writer
func NewTupleWriter(wr io.Writer) TupleWriteCloser {
return &tupleWriterImpl{wr: wr}
}
var nullBytes [4]byte
func init() {
binary.BigEndian.PutUint32(nullBytes[:], 0)
}
func (twr *tupleWriterImpl) WriteNull() error {
return iohelp.WriteAll(twr.wr, nullBytes[:])
}
func (twr *tupleWriterImpl) write(t Tuple) error {
size := len(t.buff)
var sizeBytes [4]byte
binary.BigEndian.PutUint32(sizeBytes[:], uint32(size))
err := iohelp.WriteAll(twr.wr, sizeBytes[:])
if err != nil {
return err
}
return iohelp.WriteAll(twr.wr, t.buff)
}
// WriteTuples writes the provided tuples
func (twr *tupleWriterImpl) WriteTuples(tuples ...Tuple) error {
for _, t := range tuples {
err := twr.write(t)
if err != nil {
return err
}
}
return nil
}
// CopyFrom reads tuples from a reader and writes them
func (twr *tupleWriterImpl) CopyFrom(rd TupleReader) error {
for {
t, err := rd.Read()
if err == io.EOF {
break
} else if err != nil {
return err
}
if t != nil {
err = twr.write(*t)
} else {
err = twr.WriteNull()
}
if err != nil {
return err
}
}
return nil
}
// Close should release any underlying resources
func (twr *tupleWriterImpl) Close(context.Context) error {
closer, ok := twr.wr.(io.Closer)
if ok {
return closer.Close()
}
return nil
}
type tupleReaderImpl struct {
nbf *NomsBinFormat
vrw ValueReadWriter
rd io.Reader
}
// NewTupleReader returns a TupleReadCloser that reads tuple data from the supplied io.Reader
func NewTupleReader(nbf *NomsBinFormat, vrw ValueReadWriter, rd io.Reader) TupleReadCloser {
return &tupleReaderImpl{nbf: nbf, vrw: vrw, rd: rd}
}
// Read reades the next tuple from the TupleReader
func (trd *tupleReaderImpl) Read() (*Tuple, error) {
sizeBytes, err := iohelp.ReadNBytes(trd.rd, 4)
if err != nil {
return nil, err
}
// Nulls are encoded as 0 sized
size := binary.BigEndian.Uint32(sizeBytes)
if size == 0 {
return nil, nil
}
data, err := iohelp.ReadNBytes(trd.rd, int(size))
if err != nil {
if err == io.EOF {
return nil, errors.New("corrupt tuple stream")
}
return nil, err
}
return &Tuple{valueImpl{trd.vrw, trd.nbf, data, nil}}, nil
}
// Close should release any underlying resources
func (trd *tupleReaderImpl) Close(context.Context) error {
closer, ok := trd.rd.(io.Closer)
if ok {
return closer.Close()
}
return nil
}
type TupleReadingEditProvider struct {
rd TupleReader
reachedEOF bool
}
func TupleReaderAsEditProvider(rd TupleReader) EditProvider {
return &TupleReadingEditProvider{rd: rd}
}
func (t TupleReadingEditProvider) Next() (*KVP, error) {
k, err := t.rd.Read()
if err == io.EOF {
t.reachedEOF = true
return nil, io.EOF
} else if err != nil {
return nil, err
}
v, err := t.rd.Read()
if err == io.EOF {
return nil, errors.New("corrupt tuple stream")
} else if err != nil {
return nil, err
}
if v == nil {
return &KVP{Key: k}, nil
}
return &KVP{Key: k, Val: *v}, nil
}
// ReachedEOF returns true once all data is exhausted. If ReachedEOF returns false that does not mean that there
// is more data, only that io.EOF has not been returned previously. If ReachedEOF returns true then all edits have
// been read
func (t TupleReadingEditProvider) ReachedEOF() bool {
return t.reachedEOF
}
func (t TupleReadingEditProvider) Close(ctx context.Context) error {
if closer, ok := t.rd.(Closer); ok {
return closer.Close(ctx)
}
return nil
}