frostfs-s3-gw/api/layer/multi_object_reader.go
Denis Kirillov 1a09041cd1 [#63] Simplify multiObjectReader and add tests
Signed-off-by: Denis Kirillov <d.kirillov@yadro.com>
2023-07-20 14:00:15 +03:00

149 lines
3 KiB
Go

package layer
import (
"context"
"errors"
"fmt"
"io"
"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/data"
oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
)
type partObj struct {
OID oid.ID
Size uint64
}
type readerInitiator interface {
initFrostFSObjectPayloadReader(ctx context.Context, p getFrostFSParams) (io.Reader, error)
}
// implements io.Reader of payloads of the object list stored in the FrostFS network.
type multiObjectReader struct {
ctx context.Context
layer readerInitiator
startPartOffset uint64
endPartLength uint64
prm getFrostFSParams
curIndex int
curReader io.Reader
parts []partObj
}
type multiObjectReaderConfig struct {
layer readerInitiator
// the offset of complete object and total size to read
off, ln uint64
bktInfo *data.BucketInfo
parts []partObj
}
var (
errOffsetIsOutOfRange = errors.New("offset is out of payload range")
errLengthIsOutOfRange = errors.New("length is out of payload range")
errEmptyPartsList = errors.New("empty parts list")
errorZeroRangeLength = errors.New("zero range length")
)
func newMultiObjectReader(ctx context.Context, cfg multiObjectReaderConfig) (*multiObjectReader, error) {
if len(cfg.parts) == 0 {
return nil, errEmptyPartsList
}
r := &multiObjectReader{
ctx: ctx,
layer: cfg.layer,
prm: getFrostFSParams{
bktInfo: cfg.bktInfo,
},
parts: cfg.parts,
}
if cfg.off+cfg.ln == 0 {
return r, nil
}
if cfg.off > 0 && cfg.ln == 0 {
return nil, errorZeroRangeLength
}
startPartIndex, startPartOffset := findStartPart(cfg)
if startPartIndex == -1 {
return nil, errOffsetIsOutOfRange
}
r.startPartOffset = startPartOffset
endPartIndex, endPartLength := findEndPart(cfg)
if endPartIndex == -1 {
return nil, errLengthIsOutOfRange
}
r.endPartLength = endPartLength
r.parts = cfg.parts[startPartIndex : endPartIndex+1]
return r, nil
}
func findStartPart(cfg multiObjectReaderConfig) (index int, offset uint64) {
return findPartByPosition(cfg.off, cfg.parts)
}
func findEndPart(cfg multiObjectReaderConfig) (index int, length uint64) {
return findPartByPosition(cfg.off+cfg.ln, cfg.parts)
}
func findPartByPosition(position uint64, parts []partObj) (index int, positionInPart uint64) {
for i, part := range parts {
if position <= part.Size {
return i, position
}
position -= part.Size
}
return -1, 0
}
func (x *multiObjectReader) Read(p []byte) (n int, err error) {
if x.curReader != nil {
n, err = x.curReader.Read(p)
if !errors.Is(err, io.EOF) {
return n, err
}
x.curIndex++
}
if x.curIndex == len(x.parts) {
return n, io.EOF
}
x.prm.oid = x.parts[x.curIndex].OID
if x.curIndex == 0 {
x.prm.off = x.startPartOffset
x.prm.ln = x.parts[x.curIndex].Size - x.startPartOffset
}
if x.curIndex == len(x.parts)-1 {
x.prm.ln = x.endPartLength - x.prm.off
}
x.curReader, err = x.layer.initFrostFSObjectPayloadReader(x.ctx, x.prm)
if err != nil {
return n, fmt.Errorf("init payload reader for the next part: %w", err)
}
x.prm.off = 0
x.prm.ln = 0
next, err := x.Read(p[n:])
return n + next, err
}