From e6cd09a02a10d0bb557ba861a23d2a9e56b0261f Mon Sep 17 00:00:00 2001
From: Jaco Greeff <jacogr@gmail.com>
Date: Wed, 6 Dec 2017 22:05:10 +0100
Subject: [PATCH] hexFixLength (#42)

* hexFixLength

* Update @polkadot/api-jsonrpc
---
 package.json              |  4 ++--
 src/hex/fixLength.js      | 23 +++++++++++++++++++++++
 src/hex/fixLength.spec.js | 35 +++++++++++++++++++++++++++++++++++
 src/hex/index.js          |  2 ++
 yarn.lock                 |  6 +++---
 5 files changed, 65 insertions(+), 5 deletions(-)
 create mode 100644 src/hex/fixLength.js
 create mode 100644 src/hex/fixLength.spec.js

diff --git a/package.json b/package.json
index 1792e8a7f..730970044 100644
--- a/package.json
+++ b/package.json
@@ -29,8 +29,8 @@
     "test": "jest --coverage"
   },
   "devDependencies": {
-    "@polkadot/api-jsonrpc": "^0.5.11",
-    "@polkadot/dev": "^0.12.6"
+    "@polkadot/api-jsonrpc": "^0.6.1",
+    "@polkadot/dev": "^0.13.1"
   },
   "dependencies": {
     "babel-runtime": "^6.26.0",
diff --git a/src/hex/fixLength.js b/src/hex/fixLength.js
new file mode 100644
index 000000000..683cfa278
--- /dev/null
+++ b/src/hex/fixLength.js
@@ -0,0 +1,23 @@
+// ISC, Copyright 2017 Jaco Greeff
+// @flow
+
+const assert = require('../assert');
+const isHex = require('../is/hex');
+const hexAddPrefix = require('./addPrefix');
+const hexStripPrefix = require('./stripPrefix');
+
+const ZEROS = '0000000000000000000000000000000000000000000000000000000000000000';
+
+module.exports = function hexFixLength (value: string, bitLength: number = -1): string {
+  assert(isHex(value), `Expected hex input value, found '${value}' instead`);
+
+  if (bitLength === -1) {
+    return value;
+  }
+
+  const byteLength = -1 * (bitLength / 8) * 2;
+
+  return hexAddPrefix(
+    `${ZEROS}${hexStripPrefix(value)}`.slice(byteLength)
+  );
+};
diff --git a/src/hex/fixLength.spec.js b/src/hex/fixLength.spec.js
new file mode 100644
index 000000000..1b21bee72
--- /dev/null
+++ b/src/hex/fixLength.spec.js
@@ -0,0 +1,35 @@
+// ISC, Copyright 2017 Jaco Greeff
+
+const { hexFixLength } = require('./index');
+
+describe('hexFixLength', () => {
+  it('throws an exception on non-hex inputs', () => {
+    expect(
+      () => hexFixLength('notAHex')
+    ).toThrow(/Expected hex input value/);
+  });
+
+  it('returns bitLength === -1 as-is', () => {
+    expect(
+      hexFixLength('0x12345678')
+    ).toEqual('0x12345678');
+  });
+
+  it('trims values when bitLength > length', () => {
+    expect(
+      hexFixLength('0x12345678', 16)
+    ).toEqual('0x5678');
+  });
+
+  it('adds zeros when bitLength < length', () => {
+    expect(
+      hexFixLength('0x1234', 32)
+    ).toEqual('0x00001234');
+  });
+
+  it('does not change when bitlength === length', () => {
+    expect(
+      hexFixLength('0x12345678', 32)
+    ).toEqual('0x12345678');
+  });
+});
diff --git a/src/hex/index.js b/src/hex/index.js
index 806f66861..42ef0ad37 100644
--- a/src/hex/index.js
+++ b/src/hex/index.js
@@ -2,6 +2,7 @@
 // @flow
 
 const hexAddPrefix = require('./addPrefix');
+const hexFixLength = require('./fixLength');
 const hexFromBn = require('./fromBn');
 const hexFromBuffer = require('./fromBuffer');
 const hexFromNumber = require('./fromNumber');
@@ -16,6 +17,7 @@ const hexToNumber = require('./toNumber');
 */
 module.exports = {
   hexAddPrefix,
+  hexFixLength,
   hexFromBn,
   hexFromBuffer,
   hexFromNumber,
diff --git a/yarn.lock b/yarn.lock
index 8861b84bb..9e79e470a 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -60,9 +60,9 @@
   dependencies:
     babel-runtime "^6.26.0"
 
-"@polkadot/dev@^0.12.6":
-  version "0.12.6"
-  resolved "https://registry.yarnpkg.com/@polkadot/dev/-/dev-0.12.6.tgz#1b2ffec13b3ebfc0a0e58253ee5eb8495482d91d"
+"@polkadot/dev@^0.13.1":
+  version "0.13.1"
+  resolved "https://registry.yarnpkg.com/@polkadot/dev/-/dev-0.13.1.tgz#7fd7bb6f5d343b0bbfa277abe24c46de909e854c"
   dependencies:
     babel-cli "^6.26.0"
     babel-core "^6.26.0"