Merge branch 'master' into addSchemas

# Conflicts:
#	package.json

3 files changed, 30 insertions, 0 deletions

diff --git a/package.json b/package.json
index f6740b268..950ad0d38 100644
--- a/package.json
+++ b/package.json
@@ -37,6 +37,7 @@
     "@types/mocha": "^2.2.41",
     "@types/node": "^7.0.22",
     "awesome-typescript-loader": "^3.1.3",
+    "bignumber.js": "^4.0.2",
     "chai": "^3.5.0",
     "mocha": "^3.4.1",
     "npm-run-all": "^4.0.2",
@@ -55,6 +56,7 @@
     "bignumber.js": "^4.0.2",
     "ethereumjs-util": "^5.1.1",
     "jsonschema": "^1.1.1",
+    "lodash": "^4.17.4",
     "web3": "^0.19.0"
   }
 }
diff --git a/src/ts/0x.js.ts b/src/ts/0x.js.ts
index 8de87e96e..1cc2d8b44 100644
--- a/src/ts/0x.js.ts
+++ b/src/ts/0x.js.ts
@@ -12,6 +12,8 @@ export interface ECSignature {
     s: string;
 }
 
+const MAX_DIGITS_IN_UNSIGNED_256_INT = 78;
+
 export class ZeroEx {
     /**
      * Verifies that the elliptic curve signature `signature` was generated
@@ -35,4 +37,17 @@ export class ZeroEx {
             return false;
         }
     }
+    /**
+     * Generates pseudo-random 256 bit salt.
+     * The salt is used to ensure that the 0x order generated has a unique orderHash that does
+     * not collide with any other outstanding orders.
+     */
+    public static generatePseudoRandomSalt(): BigNumber.BigNumber {
+        // BigNumber.random returns a pseudo-random number between 0 & 1 with a passed in number of decimal places.
+        // Source: https://mikemcl.github.io/bignumber.js/#random
+        const randomNumber = BigNumber.random(MAX_DIGITS_IN_UNSIGNED_256_INT);
+        const factor = new BigNumber(10).pow(MAX_DIGITS_IN_UNSIGNED_256_INT - 1);
+        const salt = randomNumber.times(factor).round();
+        return salt;
+    }
 }
diff --git a/test/0x.js.ts b/test/0x.js.ts
index 4d0b03a2a..2c4471e0f 100644
--- a/test/0x.js.ts
+++ b/test/0x.js.ts
@@ -1,6 +1,7 @@
 import {ZeroEx} from '../src/ts/0x.js';
 import {expect} from 'chai';
 import 'mocha';
+import * as BigNumber from 'bignumber.js';
 
 describe('ZeroEx library', () => {
     describe('#isValidSignature', () => {
@@ -89,4 +90,16 @@ describe('ZeroEx library', () => {
             expect(isValid).to.be.true;
         });
     });
+    describe('#generateSalt', () => {
+        it('generates different salts', () => {
+            const equal = ZeroEx.generatePseudoRandomSalt().eq(ZeroEx.generatePseudoRandomSalt());
+            expect(equal).to.be.false;
+        });
+        it('generates salt in range [0..2^256)', () => {
+            const salt = ZeroEx.generatePseudoRandomSalt();
+            expect(salt.greaterThanOrEqualTo(0)).to.be.true;
+            const twoPow256 = new BigNumber(2).pow(256);
+            expect(salt.lessThan(twoPow256)).to.be.true;
+        });
+    });
 });