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110 lines
3.0 KiB
110 lines
3.0 KiB
package merkle
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import (
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"encoding/hex"
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"errors"
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"fmt"
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"net/url"
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"strings"
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)
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/*
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For generalized Merkle proofs, each layer of the proof may require an
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optional key. The key may be encoded either by URL-encoding or
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(upper-case) hex-encoding.
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TODO: In the future, more encodings may be supported, like base32 (e.g.
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/32:)
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For example, for a Cosmos-SDK application where the first two proof layers
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are ValueOps, and the third proof layer is an IAVLValueOp, the keys
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might look like:
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0: []byte("App")
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1: []byte("IBC")
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2: []byte{0x01, 0x02, 0x03}
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Assuming that we know that the first two layers are always ASCII texts, we
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probably want to use URLEncoding for those, whereas the third layer will
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require HEX encoding for efficient representation.
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kp := new(KeyPath)
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kp.AppendKey([]byte("App"), KeyEncodingURL)
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kp.AppendKey([]byte("IBC"), KeyEncodingURL)
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kp.AppendKey([]byte{0x01, 0x02, 0x03}, KeyEncodingURL)
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kp.String() // Should return "/App/IBC/x:010203"
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NOTE: Key paths must begin with a `/`.
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NOTE: All encodings *MUST* work compatibly, such that you can choose to use
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whatever encoding, and the decoded keys will always be the same. In other
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words, it's just as good to encode all three keys using URL encoding or HEX
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encoding... it just wouldn't be optimal in terms of readability or space
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efficiency.
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NOTE: Punycode will never be supported here, because not all values can be
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decoded. For example, no string decodes to the string "xn--blah" in
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Punycode.
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*/
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type keyEncoding int
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const (
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KeyEncodingURL keyEncoding = iota
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KeyEncodingHex
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KeyEncodingMax // Number of known encodings. Used for testing
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)
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type Key struct {
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name []byte
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enc keyEncoding
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}
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type KeyPath []Key
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func (pth KeyPath) AppendKey(key []byte, enc keyEncoding) KeyPath {
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return append(pth, Key{key, enc})
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}
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func (pth KeyPath) String() string {
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res := ""
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for _, key := range pth {
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switch key.enc {
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case KeyEncodingURL:
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res += "/" + url.PathEscape(string(key.name))
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case KeyEncodingHex:
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res += "/x:" + fmt.Sprintf("%X", key.name)
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default:
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panic("unexpected key encoding type")
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}
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}
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return res
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}
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// Decode a path to a list of keys. Path must begin with `/`.
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// Each key must use a known encoding.
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func KeyPathToKeys(path string) (keys [][]byte, err error) {
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if path == "" || path[0] != '/' {
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return nil, errors.New("key path string must start with a forward slash '/'")
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}
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parts := strings.Split(path[1:], "/")
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keys = make([][]byte, len(parts))
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for i, part := range parts {
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if strings.HasPrefix(part, "x:") {
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hexPart := part[2:]
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key, err := hex.DecodeString(hexPart)
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if err != nil {
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return nil, fmt.Errorf("decoding hex-encoded part #%d: /%s: %w", i, part, err)
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}
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keys[i] = key
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} else {
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key, err := url.PathUnescape(part)
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if err != nil {
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return nil, fmt.Errorf("decoding url-encoded part #%d: /%s: %w", i, part, err)
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}
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keys[i] = []byte(key) // TODO Test this with random bytes, I'm not sure that it works for arbitrary bytes...
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}
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}
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return keys, nil
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}
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