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