Add pair to/fromJson (#123)

packages/util/src/is/hex.js

@@ -9,7 +9,7 @@ const HEX_REGEX = /^0x[a-fA-F0-9]+$/;
 
 /**
   @name isHex
-  @signature isHex (value: string, bitLength: number = -1): boolean
+  @signature isHex (value: mixed, bitLength: number = -1): boolean
   @summary Tests for a hex string.
   @description
     Checks to see if the input value is a `0x` prefixed hex string. Optionally (`bitLength` !== -1) checks to see if the bitLength is correct.
@@ -19,10 +19,12 @@ const HEX_REGEX = /^0x[a-fA-F0-9]+$/;
     isHex('0x1234'); // => true
     isHex('0x1234', 8); // => false
 */
-module.exports = function isHex (value: string, bitLength: number = -1): boolean {
+module.exports = function isHex (value: mixed, bitLength: number = -1): boolean {
+  // $FlowFixMe for the regex we have a string
   const isValidHex = value === '0x' || (isString(value) && HEX_REGEX.test(value));
 
   if (isValidHex && bitLength !== -1) {
+    // $FlowFixMe type is a string as checked above
     return value.length === (2 + bitLength / 4);
   }
 

packages/util/src/u8a/fixLength.js

@@ -16,7 +16,7 @@
     u8aFixLength('0x12', 16) // => 0x0012
     u8aFixLength('0x1234', 8) // => 0x12
 */
-module.exports = function u8aFixLength (value: Uint8Array, bitLength: number = -1): Uint8Array {
+module.exports = function u8aFixLength (value: Uint8Array, bitLength: number = -1, atStart?: boolean = false): Uint8Array {
   const byteLength = Math.ceil(bitLength / 8);
 
   if (bitLength === -1 || value.length === byteLength) {
@@ -29,7 +29,11 @@ module.exports = function u8aFixLength (value: Uint8Array, bitLength: number = -
 
   const result = new Uint8Array(byteLength);
 
-  result.set(value, byteLength - value.length);
+  if (atStart) {
+    result.set(value, 0);
+  } else {
+    result.set(value, byteLength - value.length);
+  }
 
   return result;
 };