Add isAscii (#629)

packages/util/src/is/ascii.spec.ts

@@ -0,0 +1,31 @@
+// Copyright 2017-2020 @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 { isAscii } from '.';
+
+describe('isAscii', (): void => {
+  it('returns true for an ASCII string', (): void => {
+    expect(isAscii('Hello\tWorld!\n\rTesting')).toEqual(true);
+  });
+
+  it('returns true for ASCII bytes', (): void => {
+    expect(isAscii(new Uint8Array([0x31, 0x32, 0x20, 10]))).toEqual(true);
+  });
+
+  it('returns true for empty string inputs', (): void => {
+    expect(isAscii('')).toEqual(true);
+  });
+
+  it('returns true for empty U8a inputs', (): void => {
+    expect(isAscii(new Uint8Array())).toEqual(true);
+  });
+
+  it('returns false for empty undefined inputs', (): void => {
+    expect(isAscii()).toEqual(false);
+  });
+
+  it('returns false for non-printable characters', (): void => {
+    expect(isAscii(new Uint8Array([5]))).toEqual(false);
+  });
+});

packages/util/src/is/ascii.ts

@@ -0,0 +1,24 @@
+// Copyright 2017-2020 @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 u8aToU8a from '../u8a/toU8a';
+import isString from './string';
+
+const FORMAT = [9, 10, 13];
+
+/**
+ * @name isAscii
+ * @summary Tests if the input is printable ASCII
+ * @description
+ * Checks to see if the input string or Uint8Array is printable ASCII, 32-127 + formatters
+ */
+export default function isAscii (value?: number[] | Buffer | Uint8Array | string | null): boolean {
+  if (!value) {
+    return isString(value);
+  }
+
+  const u8a = u8aToU8a(value);
+
+  return !u8a.some((byte) => (byte >= 127) || (byte < 32 && !FORMAT.includes(byte)));
+}

packages/util/src/is/index.ts

@@ -5,6 +5,7 @@
 /**
  * @summary Type checking utilities
  */
+export { default as isAscii } from './ascii';
 export { default as isBigInt } from './bigInt';
 export { default as isBn } from './bn';
 export { default as isBuffer } from './buffer';