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