101 lines
1.9 KiB
Go
101 lines
1.9 KiB
Go
package cid
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import (
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"bytes"
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"encoding/binary"
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"encoding/hex"
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"errors"
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"github.com/multiformats/go-multibase"
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)
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var MAGIC_BYTES = []byte{0x26, 0x1f}
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var (
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ErrMissingEmptySize = errors.New("Missing or empty size")
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ErrInvalidCIDMagic = errors.New("CID magic bytes missing or invalid")
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)
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type CID struct {
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Hash [32]byte
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Size uint64
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}
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func (c CID) StringHash() string {
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return hex.EncodeToString(c.Hash[:])
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}
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func Encode(hash []byte, size uint64) (string, error) {
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var hashBytes [32]byte
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copy(hashBytes[:], hash)
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return EncodeFixed(hashBytes, size)
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}
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func EncodeFixed(hash [32]byte, size uint64) (string, error) {
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sizeBytes := make([]byte, 8)
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binary.LittleEndian.PutUint64(sizeBytes, size)
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prefixedHash := append(MAGIC_BYTES, hash[:]...)
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prefixedHash = append(prefixedHash, sizeBytes...)
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return multibase.Encode(multibase.Base58BTC, prefixedHash)
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}
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func EncodeString(hash string, size uint64) (string, error) {
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hashBytes, err := hex.DecodeString(hash)
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if err != nil {
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return "", err
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}
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return Encode(hashBytes, size)
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}
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func Valid(cid string) (bool, error) {
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_, err := maybeDecode(cid)
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if err != nil {
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return false, err
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}
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return true, nil
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}
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func Decode(cid string) (*CID, error) {
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data, err := maybeDecode(cid)
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if err != nil {
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return &CID{}, err
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}
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data = data[len(MAGIC_BYTES):]
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var hash [32]byte
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copy(hash[:], data[:])
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size := binary.LittleEndian.Uint64(data[32:])
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return &CID{Hash: hash, Size: size}, nil
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}
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func maybeDecode(cid string) ([]byte, error) {
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_, data, err := multibase.Decode(cid)
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if err != nil {
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return nil, err
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}
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if bytes.Compare(data[0:len(MAGIC_BYTES)], MAGIC_BYTES) != 0 {
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return nil, ErrInvalidCIDMagic
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}
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sizeBytes := data[len(MAGIC_BYTES)+32:]
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if len(sizeBytes) == 0 {
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return nil, ErrMissingEmptySize
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}
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size := binary.LittleEndian.Uint64(sizeBytes)
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if size == 0 {
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return nil, ErrMissingEmptySize
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}
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return data, nil
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}
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