Add support for Account Public Key data type (#35)

Per https://xrpl.org/base58-encodings.html

packages/ripple-address-codec/HISTORY.md

@@ -1,5 +1,14 @@
 # ripple-address-codec Release History
 
+## 4.1.0 (UNRELEASED)
+
+* Throwable 'unexpected_payload_length' error: The message has been expanded with ' Ensure that the bytes are a Buffer.'
+
+### New Features
+
+* `encodeAccountPublic` - Encode a public key, as for payment channels
+* `decodeAccountPublic` - Decode a public key, as for payment channels
+
 ## 4.0.0 (2019-10-08)
 
 ### Breaking Changes
@@ -14,4 +23,3 @@
 * `xAddressToClassicAddress` - Decode an X-address to account ID, tag, and network ID
 * `decodeXAddress` - Convert X-address to classic address, tag, and network ID
 * `isValidXAddress` - Check whether an X-address (X...) is valid
-

packages/ripple-address-codec/src/index.ts

@@ -6,6 +6,8 @@ import {
   decodeAccountID,
   encodeNodePublic,
   decodeNodePublic,
+  encodeAccountPublic,
+  decodeAccountPublic,
   isValidClassicAddress
 } from './xrp-codec'
 import * as assert from 'assert'
@@ -123,6 +125,8 @@ export {
   decodeAccountID, // Decode a classic address to its raw bytes
   encodeNodePublic, // Encode bytes to XRP Ledger node public key format
   decodeNodePublic, // Decode an XRP Ledger node public key into its raw bytes
+  encodeAccountPublic, // Encode a public key, as for payment channels
+  decodeAccountPublic, // Decode a public key, as for payment channels
   isValidClassicAddress, // Check whether a classic address (r...) is valid
   classicAddressToXAddress, // Derive X-address from classic address, tag, and network ID
   encodeXAddress, // Encode account ID, tag, and network ID to X-address

packages/ripple-address-codec/src/xrp-codec.test.ts

@@ -5,7 +5,7 @@ function toHex(bytes: Buffer) {
 }
 
 function toBytes(hex: string) {
-  return Buffer.from(hex, 'hex').toJSON().data
+  return Buffer.from(hex, 'hex')
 }
 
 /**
@@ -34,6 +34,10 @@ makeEncodeDecodeTest(api.encodeNodePublic, api.decodeNodePublic,
   'n9MXXueo837zYH36DvMc13BwHcqtfAWNJY5czWVbp7uYTj7x17TH',
   '0388E5BA87A000CB807240DF8C848EB0B5FFA5C8E5A521BC8E105C0F0A44217828')
 
+  makeEncodeDecodeTest(api.encodeAccountPublic, api.decodeAccountPublic,
+    'aB44YfzW24VDEJQ2UuLPV2PvqcPCSoLnL7y5M1EzhdW4LnK5xMS3',
+    '023693F15967AE357D0327974AD46FE3C127113B1110D6044FD41E723689F81CC6')
+
 test('can decode arbitrary seeds', function() {
   const decoded = api.decodeSeed('sEdTM1uX8pu2do5XvTnutH6HsouMaM2')
   expect(toHex(decoded.bytes)).toBe('4C3A1D213FBDFB14C7C28D609469B341')

packages/ripple-address-codec/src/xrp-codec.ts

@@ -37,7 +37,8 @@ class Codec {
 
   encodeVersioned(bytes: Buffer, versions: number[], expectedLength: number): string {
     if (expectedLength && bytes.length !== expectedLength) {
-      throw new Error('unexpected_payload_length: bytes.length does not match expectedLength')
+      throw new Error('unexpected_payload_length: bytes.length does not match expectedLength.' +
+        ' Ensure that the bytes are a Buffer.')
     }
     return this.encodeChecked(Buffer.from(concatArgs(versions, bytes)))
   }
@@ -122,9 +123,12 @@ class Codec {
 // Pure JavaScript hash functions in the browser, native hash functions in Node.js
 const createHash = require('create-hash')
 
-const NODE_PUBLIC = 28
-const ACCOUNT_ID = 0
-const FAMILY_SEED = 0x21 // 33
+// base58 encodings: https://xrpl.org/base58-encodings.html
+const ACCOUNT_ID = 0 // Account address (20 bytes)
+const ACCOUNT_PUBLIC_KEY = 0x23 // Account public key (33 bytes)
+const FAMILY_SEED = 0x21 // 33; Seed value (for secret keys) (16 bytes)
+const NODE_PUBLIC = 0x1C // 28; Validation public key (33 bytes)
+
 const ED25519_SEED = [0x01, 0xE1, 0x4B] // [1, 225, 75]
 
 const codecOptions = {
@@ -191,6 +195,16 @@ export function encodeNodePublic(bytes: Buffer): string {
   return codecWithXrpAlphabet.encode(bytes, opts)
 }
 
+export function encodeAccountPublic(bytes: Buffer): string {
+  const opts = {versions: [ACCOUNT_PUBLIC_KEY], expectedLength: 33}
+  return codecWithXrpAlphabet.encode(bytes, opts)
+}
+
+export function decodeAccountPublic(base58string: string): Buffer {
+  const opts = {versions: [ACCOUNT_PUBLIC_KEY], expectedLength: 33}
+  return codecWithXrpAlphabet.decode(base58string, opts).bytes
+}
+
 export function isValidClassicAddress(address: string): boolean {
   try {
     decodeAccountID(address)