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reader.go
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/
reader.go
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/*
* MinIO Cloud Storage, (C) 2019 MinIO, 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 simdj
import (
"fmt"
"io"
"sync"
"github.com/minio/simdjson-go"
"storj.io/minio/pkg/s3select/json"
"storj.io/minio/pkg/s3select/sql"
)
// Reader - JSON record reader for S3Select.
type Reader struct {
args *json.ReaderArgs
input chan simdjson.Stream
decoded chan simdjson.Object
// err will only be returned after decoded has been closed.
err *error
readCloser io.ReadCloser
exitReader chan struct{}
readerWg sync.WaitGroup
}
// Read - reads single record.
func (r *Reader) Read(dst sql.Record) (sql.Record, error) {
v, ok := <-r.decoded
if !ok {
if r.err != nil && *r.err != nil {
return nil, errJSONParsingError(*r.err)
}
return nil, io.EOF
}
dstRec, ok := dst.(*Record)
if !ok {
dstRec = &Record{}
}
dstRec.object = v
return dstRec, nil
}
// Close - closes underlying reader.
func (r *Reader) Close() error {
// Close the input.
// Potentially racy if the stream decoder is still reading.
if r.readCloser != nil {
r.readCloser.Close()
}
if r.exitReader != nil {
close(r.exitReader)
r.readerWg.Wait()
r.exitReader = nil
r.input = nil
}
return nil
}
// startReader will start a reader that accepts input from r.input.
// Input should be root -> object input. Each root indicates a record.
// If r.input is closed, it is assumed that no more input will come.
// When this function returns r.readerWg will be decremented and r.decoded will be closed.
// On errors, r.err will be set. This should only be accessed after r.decoded has been closed.
func (r *Reader) startReader() {
defer r.readerWg.Done()
defer close(r.decoded)
var tmpObj simdjson.Object
for {
var in simdjson.Stream
select {
case in = <-r.input:
case <-r.exitReader:
return
}
if in.Error != nil && in.Error != io.EOF {
r.err = &in.Error
return
}
if in.Value == nil {
if in.Error == io.EOF {
return
}
continue
}
i := in.Value.Iter()
readloop:
for {
var next simdjson.Iter
typ, err := i.AdvanceIter(&next)
if err != nil {
r.err = &err
return
}
switch typ {
case simdjson.TypeNone:
break readloop
case simdjson.TypeRoot:
typ, obj, err := next.Root(nil)
if err != nil {
r.err = &err
return
}
if typ != simdjson.TypeObject {
if typ == simdjson.TypeNone {
continue
}
err = fmt.Errorf("unexpected json type below root :%v", typ)
r.err = &err
return
}
o, err := obj.Object(&tmpObj)
if err != nil {
r.err = &err
return
}
select {
case <-r.exitReader:
return
case r.decoded <- *o:
}
default:
err = fmt.Errorf("unexpected root json type:%v", typ)
r.err = &err
return
}
}
if in.Error == io.EOF {
return
}
}
}
// NewReader - creates new JSON reader using readCloser.
func NewReader(readCloser io.ReadCloser, args *json.ReaderArgs) *Reader {
r := Reader{
args: args,
readCloser: readCloser,
decoded: make(chan simdjson.Object, 1000),
input: make(chan simdjson.Stream, 2),
exitReader: make(chan struct{}),
}
simdjson.ParseNDStream(readCloser, r.input, nil)
r.readerWg.Add(1)
go r.startReader()
return &r
}
// NewElementReader - creates new JSON reader using readCloser.
func NewElementReader(ch chan simdjson.Object, err *error, args *json.ReaderArgs) *Reader {
return &Reader{
args: args,
decoded: ch,
err: err,
readCloser: nil,
}
}
// NewTapeReaderChan will start a reader that will read input from the provided channel.
func NewTapeReaderChan(pj chan simdjson.Stream, args *json.ReaderArgs) *Reader {
r := Reader{
args: args,
decoded: make(chan simdjson.Object, 1000),
input: pj,
exitReader: make(chan struct{}),
}
r.readerWg.Add(1)
go r.startReader()
return &r
}