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data.go
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data.go
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// Copyright (c) 2018 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Softwarw.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package docs
import (
"errors"
"fmt"
"io"
"github.com/m3db/m3/src/m3ninx/doc"
"github.com/m3db/m3/src/m3ninx/index/segment/fst/encoding"
)
const initialDataEncoderLen = 1024
// DataWriter writes the data file for documents.
type DataWriter struct {
writer io.Writer
enc *encoding.Encoder
}
// NewDataWriter returns a new DataWriter.
func NewDataWriter(w io.Writer) *DataWriter {
return &DataWriter{
writer: w,
enc: encoding.NewEncoder(initialDataEncoderLen),
}
}
func (w *DataWriter) Write(d doc.Metadata) (int, error) {
n := w.enc.PutBytes(d.ID)
n += w.enc.PutUvarint(uint64(len(d.Fields)))
for _, f := range d.Fields {
n += w.enc.PutBytes(f.Name)
n += w.enc.PutBytes(f.Value)
}
if err := w.write(); err != nil {
return 0, err
}
return n, nil
}
func (w *DataWriter) write() error {
b := w.enc.Bytes()
n, err := w.writer.Write(b)
if err != nil {
return err
}
if n < len(b) {
return io.ErrShortWrite
}
w.enc.Reset()
return nil
}
// Reset resets the DataWriter.
func (w *DataWriter) Reset(wr io.Writer) {
w.writer = wr
w.enc.Reset()
}
// DataReader is a reader for the data file for documents.
type DataReader struct {
data []byte
}
// NewDataReader returns a new DataReader.
func NewDataReader(data []byte) *DataReader {
return &DataReader{
data: data,
}
}
func (r *DataReader) Read(offset uint64) (doc.Metadata, error) {
if offset >= uint64(len(r.data)) {
return doc.Metadata{}, fmt.Errorf("invalid offset: %v is past the end of the data file", offset)
}
dec := encoding.NewDecoder(r.data[int(offset):])
id, err := dec.Bytes()
if err != nil {
return doc.Metadata{}, err
}
x, err := dec.Uvarint()
if err != nil {
return doc.Metadata{}, err
}
n := int(x)
d := doc.Metadata{
ID: id,
Fields: make([]doc.Field, n),
}
for i := 0; i < n; i++ {
name, err := dec.Bytes()
if err != nil {
return doc.Metadata{}, err
}
val, err := dec.Bytes()
if err != nil {
return doc.Metadata{}, err
}
d.Fields[i] = doc.Field{
Name: name,
Value: val,
}
}
return d, nil
}
// EncodedDataReader is a reader for the data file for encoded document metadata.
type EncodedDataReader struct {
data []byte
}
// NewEncodedDataReader returns a new EncodedDataReader.
func NewEncodedDataReader(data []byte) *EncodedDataReader {
return &EncodedDataReader{
data: data,
}
}
// Read reads a doc.Encoded from a data stream starting at the specified offset.
func (e *EncodedDataReader) Read(offset uint64) (doc.Encoded, error) {
if offset >= uint64(len(e.data)) {
return doc.Encoded{}, fmt.Errorf(
"invalid offset: %v is past the end of the data file", offset,
)
}
return doc.Encoded{
Bytes: e.data[int(offset):],
}, nil
}
// EncodedDocumentReader is a reader for reading documents from encoded metadata.
type EncodedDocumentReader struct {
currFields []doc.Field
}
// NewEncodedDocumentReader returns a new EncodedDocumentReader.
func NewEncodedDocumentReader() *EncodedDocumentReader {
return &EncodedDocumentReader{}
}
// Read reads a doc.Metadata from a doc.Encoded. Returned doc.Metadata should be
// processed before calling Read again as the underlying array pointed to by the Fields
// slice will be updated. This approach avoids allocating a new slice with a new backing
// array for every document processed, unlike (*DataReader).Read
func (r *EncodedDocumentReader) Read(encoded doc.Encoded) (doc.Metadata, error) {
for i := range r.currFields {
r.currFields[i] = doc.Field{}
}
r.currFields = r.currFields[:0]
id, buf, err := encoding.ReadBytes(encoded.Bytes)
if err != nil {
return doc.Metadata{}, err
}
x, buf, err := encoding.ReadUvarint(buf)
if err != nil {
return doc.Metadata{}, err
}
n := int(x)
var name, val []byte
for i := 0; i < n; i++ {
name, buf, err = encoding.ReadBytes(buf)
if err != nil {
return doc.Metadata{}, err
}
val, buf, err = encoding.ReadBytes(buf)
if err != nil {
return doc.Metadata{}, err
}
r.currFields = append(r.currFields, doc.Field{
Name: name,
Value: val,
})
}
return doc.Metadata{
ID: id,
Fields: r.currFields,
}, nil
}
// ReadEncodedDocumentID reads the document ID from the encoded document metadata.
func ReadEncodedDocumentID(encoded doc.Encoded) ([]byte, error) {
id, _, err := encoding.ReadBytes(encoded.Bytes)
return id, err
}
// MetadataFromDocument retrieves a doc.Metadata from a doc.Document.
func MetadataFromDocument(document doc.Document, reader *EncodedDocumentReader) (doc.Metadata, error) {
if d, ok := document.Metadata(); ok {
return d, nil
}
if e, ok := document.Encoded(); ok {
return reader.Read(e)
}
return doc.Metadata{}, errors.New("document does not contain metadata or encoded metadata")
}
// ReadIDFromDocument reads the document ID from the document.
func ReadIDFromDocument(document doc.Document) ([]byte, error) {
if d, ok := document.Metadata(); ok {
return d.ID, nil
}
if e, ok := document.Encoded(); ok {
return ReadEncodedDocumentID(e)
}
return nil, errors.New("document does not contain metadata or encoded metadata")
}