frostfs-sdk-go/object/erasurecode/constructor.go
Evgenii Stratonikov bd2d350b09 [#205] object: Initial EC implementation
Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>
2024-03-22 10:14:12 +00:00

87 lines
2.4 KiB
Go

package erasurecode
import (
"errors"
objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
"github.com/klauspost/reedsolomon"
)
var (
// ErrMalformedSlice is returned when a slice of EC chunks is inconsistent.
ErrMalformedSlice = errors.New("inconsistent EC headers")
// ErrInvShardNum is returned from NewConstructor when the number of shards is invalid.
ErrInvShardNum = reedsolomon.ErrInvShardNum
// ErrMaxShardNum is returned from NewConstructor when the number of shards is too big.
ErrMaxShardNum = reedsolomon.ErrMaxShardNum
)
// MaxShardCount is the maximum number of shards.
const MaxShardCount = 256
// Constructor is a wrapper around encoder allowing to reconstruct objects.
// It's methods are not thread-safe.
type Constructor struct {
enc reedsolomon.Encoder
headerLength uint32
payloadShards [][]byte
headerShards [][]byte
}
// NewConstructor returns new constructor instance.
func NewConstructor(dataCount int, parityCount int) (*Constructor, error) {
// The library supports up to 65536 shards with some restrictions.
// This can easily result in OOM or panic, thus SDK declares it's own restriction.
if dataCount+parityCount > MaxShardCount {
return nil, ErrMaxShardNum
}
enc, err := reedsolomon.New(dataCount, parityCount)
if err != nil {
return nil, err
}
return &Constructor{enc: enc}, nil
}
// clear clears internal state of the constructor, so it can be reused.
func (c *Constructor) clear() {
c.headerLength = 0
c.payloadShards = nil
c.headerShards = nil
}
func (c *Constructor) fillHeader(parts []*objectSDK.Object) error {
shards := make([][]byte, len(parts))
headerLength := 0
for i := range parts {
if parts[i] == nil {
continue
}
var err error
headerLength, err = validatePart(parts, i, headerLength)
if err != nil {
return err
}
shards[i] = parts[i].GetECHeader().Header()
}
c.headerLength = uint32(headerLength)
c.headerShards = shards
return nil
}
// fillPayload fills the payload shards.
// Currently there is no case when it can be called without reconstructing header,
// thus fillHeader() must be called before and this function performs no validation.
func (c *Constructor) fillPayload(parts []*objectSDK.Object) {
shards := make([][]byte, len(parts))
for i := range parts {
if parts[i] == nil {
continue
}
shards[i] = parts[i].Payload()
}
c.payloadShards = shards
}