string <-> hex conversion utilities (#470)

* string <-> hex conversion utilities

* Add tests

CHANGELOG.md

@@ -1,3 +1,7 @@
+# 1.4.0-beta.x
+
+- Added `stringToHex` and `hexToString` conversion utilities
+
 # 1.3.1
 
 - Remove the `ExtError` class, always prefer the standard JS `Error` object for errors. This would bre a breaking change for any appliactions using `ExtError`

packages/util/src/hex/index.ts

@@ -12,4 +12,5 @@ export { default as hexHasPrefix } from './hasPrefix';
 export { default as hexStripPrefix } from './stripPrefix';
 export { default as hexToBn } from './toBn';
 export { default as hexToNumber } from './toNumber';
+export { default as hexToString } from './toString';
 export { default as hexToU8a } from './toU8a';

packages/util/src/hex/toString.spec.ts

@@ -0,0 +1,19 @@
+// Copyright 2017-2019 @polkadot/util authors & contributors
+// This software may be modified and distributed under the terms
+// of the Apache-2.0 license. See the LICENSE file for details.
+
+import { hexToString } from '.';
+
+describe('hexToString', (): void => {
+  it('converts an empty to ""', (): void => {
+    expect(
+      hexToString()
+    ).toEqual('');
+  });
+
+  it('converts to a string from hex', (): void => {
+    expect(
+      hexToString('0x68656c6c6f')
+    ).toEqual('hello');
+  });
+});

packages/util/src/hex/toString.ts

@@ -0,0 +1,26 @@
+// Copyright 2017-2019 @polkadot/util authors & contributors
+// This software may be modified and distributed under the terms
+// of the Apache-2.0 license. See the LICENSE file for details.
+
+import u8aToString from '../u8a/toString';
+import hexToU8a from './toU8a';
+
+/**
+ * @name hexToU8a
+ * @summary Creates a Uint8Array object from a hex string.
+ * @description
+ * Hex input values return the actual bytes value converted to a string. Anything that is not a hex string (including the `0x` prefix) throws an error.
+ * @example
+ * <BR>
+ *
+ * ```javascript
+ * import { hexToString } from '@polkadot/util';
+ *
+ * hexToU8a('0x68656c6c6f'); // hello
+ * ```
+ */
+export default function hexToString (_value?: string | null): string {
+  return u8aToString(
+    hexToU8a(_value)
+  );
+}

packages/util/src/hex/toU8a.ts

@@ -8,7 +8,7 @@ import hexStripPrefix from './stripPrefix';
 
 /**
  * @name hexToU8a
- * @summary Creates a Buffer object from a hex string.
+ * @summary Creates a Uint8Array object from a hex string.
  * @description
  * `null` inputs returns an empty `Uint8Array` result. Hex input values return the actual bytes value converted to a Uint8Array. Anything that is not a hex string (including the `0x` prefix) throws an error.
  * @example

packages/util/src/string/index.ts

@@ -9,5 +9,6 @@
 export { default as stringCamelCase } from './camelCase';
 export { default as stringLowerFirst } from './lowerFirst';
 export { default as stringShorten } from './shorten';
+export { default as stringToHex } from './toHex';
 export { default as stringToU8a } from './toU8a';
 export { default as stringUpperFirst } from './upperFirst';

packages/util/src/string/toHex.spec.ts

@@ -0,0 +1,19 @@
+// Copyright 2017-2019 @polkadot/util authors & contributors
+// This software may be modified and distributed under the terms
+// of the Apache-2.0 license. See the LICENSE file for details.
+
+import { stringToHex } from '.';
+
+describe('hexToString', (): void => {
+  it('converts an empty to ""', (): void => {
+    expect(
+      stringToHex()
+    ).toEqual('0x');
+  });
+
+  it('converts to a hex from string', (): void => {
+    expect(
+      stringToHex('hello')
+    ).toEqual('0x68656c6c6f');
+  });
+});

packages/util/src/string/toHex.ts

@@ -0,0 +1,26 @@
+// Copyright 2017-2019 @polkadot/util authors & contributors
+// This software may be modified and distributed under the terms
+// of the Apache-2.0 license. See the LICENSE file for details.
+
+import u8aToHex from '../u8a/toHex';
+import stringToU8a from './toU8a';
+
+/**
+ * @name stringToHex
+ * @summary Creates a hex string from a utf-8 string
+ * @description
+ * String input values return the actual encoded hex value.
+ * @example
+ * <BR>
+ *
+ * ```javascript
+ * import { stringToHex } from '@polkadot/util';
+ *
+ * stringToU8a('hello'); // 0x68656c6c6f
+ * ```
+ */
+export default function stringToHex (value?: string): string {
+  return u8aToHex(
+    stringToU8a(value)
+  );
+}