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primitive.go
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primitive.go
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package vector
import (
"errors"
"io"
"github.com/brimdata/zed"
"github.com/brimdata/zed/zcode"
)
type PrimitiveWriter struct {
typ zed.Type
bytes zcode.Bytes
spiller *Spiller
segments []Segment
}
func NewPrimitiveWriter(typ zed.Type, spiller *Spiller) *PrimitiveWriter {
return &PrimitiveWriter{
typ: typ,
spiller: spiller,
}
}
func (p *PrimitiveWriter) Write(body zcode.Bytes) error {
p.bytes = zcode.Append(p.bytes, body)
var err error
if len(p.bytes) >= p.spiller.Thresh {
err = p.Flush(false)
}
return err
}
func (p *PrimitiveWriter) Flush(eof bool) error {
var err error
if len(p.bytes) > 0 {
p.segments, err = p.spiller.Write(p.segments, p.bytes)
p.bytes = p.bytes[:0]
}
return err
}
func (p *PrimitiveWriter) Segmap() []Segment {
return p.segments
}
func (p *PrimitiveWriter) Metadata() Metadata {
return &Primitive{
Typ: p.typ,
Segmap: p.segments,
}
}
type PrimitiveReader struct {
it zcode.Iter
segmap []Segment
reader io.ReaderAt
}
func NewPrimitiveReader(primitive *Primitive, reader io.ReaderAt) *PrimitiveReader {
return &PrimitiveReader{
reader: reader,
segmap: primitive.Segmap,
}
}
func (p *PrimitiveReader) Read(b *zcode.Builder) error {
zv, err := p.read()
if err == nil {
b.Append(zv)
}
return err
}
func (p *PrimitiveReader) read() (zcode.Bytes, error) {
if p.it == nil || p.it.Done() {
if len(p.segmap) == 0 {
return nil, io.EOF
}
if err := p.next(); err != nil {
return nil, err
}
}
return p.it.Next(), nil
}
func (p *PrimitiveReader) next() error {
segment := p.segmap[0]
p.segmap = p.segmap[1:]
if segment.Length > 2*MaxSegmentThresh {
return errors.New("segment too big")
}
b := make([]byte, segment.Length)
//XXX this where lots of seeks can happen until we put intelligent
// scheduling in a layer below this informed by the reassembly maps
// and the query that is going to run.
n, err := p.reader.ReadAt(b, segment.Offset)
if err != nil {
return err
}
if n < int(segment.Length) {
return errors.New("truncated read of ZST vector")
}
p.it = zcode.Iter(b)
return nil
}