portal/cid/cid.go

76 lines
1.4 KiB
Go

package cid
import (
"bytes"
"encoding/binary"
"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 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
}