@0x/contracts-test-utils: Add toHex(), hexInvert(), hexLeftPad(), and hexRightPad() hex utils.

contracts/test-utils/CHANGELOG.json

@@ -65,6 +65,10 @@
             {
                 "note": "`web3Wrapper` is created with `shouldAllowUnlimitedContractSize` if `UNLIMITED_CONTRACT_SIZE` environment variable is set.",
                 "pr": 2075
+            },
+            {
+                "note": "Add `toHex()`, `hexLeftPad()`, `hexRightPad()`, and 'hexInvert()' hex utils",
+                "pr": "TODO"
             }
         ]
     },

contracts/test-utils/src/hex_utils.ts

@@ -1,15 +1,63 @@
+import { BigNumber } from '@0x/utils';
 import * as crypto from 'crypto';
 import * as ethUtil from 'ethereumjs-util';
 
+import { constants } from './constants';
+
+const { WORD_LENGTH } = constants;
+
 /**
  * Concatenate all arguments as a hex string.
  */
 export function hexConcat(...args: Array<string | number | Buffer>): string {
     return ethUtil.bufferToHex(Buffer.concat(args.map(h => ethUtil.toBuffer(h))));
 }
+
 /**
  * Generate a random hex string.
  */
-export function hexRandom(size: number = 32): string {
+export function hexRandom(size: number = WORD_LENGTH): string {
     return ethUtil.bufferToHex(crypto.randomBytes(size));
 }
+
+/**
+ * Left-pad a hex number to a number of bytes.
+ */
+export function hexLeftPad(n: string | BigNumber | number, size: number = WORD_LENGTH): string {
+    return ethUtil.bufferToHex(ethUtil.setLengthLeft(toHex(n), size));
+}
+
+/**
+ * Right-pad a hex number to a number of bytes.
+ */
+export function hexRightPad(n: string | BigNumber | number, size: number = WORD_LENGTH): string {
+    return ethUtil.bufferToHex(ethUtil.setLengthRight(toHex(n), size));
+}
+
+/**
+ * Inverts a hex word.
+ */
+export function hexInvert(n: string | BigNumber | number, size: number = WORD_LENGTH): string {
+    const buf = ethUtil.setLengthLeft(toHex(n), size);
+    // tslint:disable-next-line: no-bitwise
+    return ethUtil.bufferToHex(Buffer.from(buf.map(b => ~b)));
+}
+
+/**
+ * Convert a string, a number, or a BigNumber into a hex string.
+ */
+export function toHex(n: string | BigNumber | number): string {
+    let hex = '0x00';
+    if (typeof(n) === 'number') {
+        hex = `0x${n.toString(16)}`;
+    } else if (BigNumber.isBigNumber(n)) {
+        hex = `0x${n.toString(16)}`;
+    } else {
+        if (/^0x/.test(n)) {
+            hex = n;
+        } else {
+            hex = `0x${parseInt(n, 10).toString(16)}`;
+        }
+    }
+    return hex;
+}

contracts/test-utils/src/index.ts

@@ -28,7 +28,7 @@ export { bytes32Values, testCombinatoriallyWithReferenceFunc, uint256Values } fr
 export { TransactionFactory } from './transaction_factory';
 export { MutatorContractFunction, TransactionHelper } from './transaction_helper';
 export { testWithReferenceFuncAsync } from './test_with_reference';
-export { hexConcat, hexRandom } from './hex_utils';
+export { hexConcat, hexLeftPad, hexInvert, hexRandom, hexRightPad, toHex } from './hex_utils';
 export {
     BatchMatchOrder,
     ContractName,