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