1 files changed, 32 insertions, 41 deletions
diff --git a/packages/contracts/src/utils/asset_proxy_utils.ts b/packages/contracts/src/utils/asset_proxy_utils.ts
index 7fcf3dd26..835f444f6 100644
--- a/packages/contracts/src/utils/asset_proxy_utils.ts
+++ b/packages/contracts/src/utils/asset_proxy_utils.ts
@@ -1,66 +1,57 @@
 import { BigNumber } from '@0xproject/utils';
+import BN = require('bn.js');
+import ethUtil = require('ethereumjs-util');
 import * as Web3 from 'web3';
 
 import { AssetProxyId } from './types';
 
-export function zeroPad(value: string, width: number): string {
-    return '0'.repeat(width - value.length) + value;
+export function encodeAssetProxyId(assetProxyId: AssetProxyId): Buffer {
+    const formattedAssetProxyId = new BN(assetProxyId);
+    const encodedAssetProxyId = ethUtil.toUnsigned(formattedAssetProxyId);
+    return encodedAssetProxyId;
 }
 
-export function encodeAssetProxyId(assetProxyId: AssetProxyId, encodedMetadata: { value: string }) {
-    encodedMetadata.value += zeroPad(new BigNumber(assetProxyId).toString(16), 2);
-}
-
-export function encodeAddress(address: string, encodedMetadata: { value: string }) {
-    encodedMetadata.value += zeroPad(address.replace('0x', ''), 40);
+export function encodeAddress(address: string): Buffer {
+    if (!ethUtil.isValidAddress(address)) {
+        throw new Error(`Invalid Address: ${address}`);
+    }
+    const encodedAddress = ethUtil.toBuffer(address);
+    return encodedAddress;
 }
 
-export function encodeUint256(value: BigNumber, encodedMetadata: { value: string }) {
-    encodedMetadata.value += zeroPad(value.toString(16), 64);
+export function encodeUint256(value: BigNumber): Buffer {
+    const formattedValue = new BN(value.toString(10));
+    const encodedValue = ethUtil.toUnsigned(formattedValue);
+    return encodedValue;
 }
 
 export function encodeERC20ProxyMetadata_V1(tokenAddress: string) {
     // Encode metadata
-    const encodedMetadata = { value: '0x' };
-    encodeAssetProxyId(AssetProxyId.ERC20_V1, encodedMetadata);
-    encodeAddress(tokenAddress, encodedMetadata);
-
-    // Verify encoding length - '0x' plus 21 bytes of encoded data
-    if (encodedMetadata.value.length != 44) {
-        throw Error('Bad encoding length. Expected 44, got ' + encodedMetadata.value.length);
-    }
+    const encodedAssetProxyId = encodeAssetProxyId(AssetProxyId.ERC20_V1);
+    const encodedAddress = encodeAddress(tokenAddress);
+    const encodedMetadata = Buffer.concat([encodedAssetProxyId, encodedAddress]);
+    const encodedMetadataHex = ethUtil.bufferToHex(encodedMetadata);
 
-    // Return encoded metadata
-    return encodedMetadata.value;
+    return encodedMetadataHex;
 }
 
 export function encodeERC20ProxyMetadata(tokenAddress: string) {
     // Encode metadata
-    const encodedMetadata = { value: '0x' };
-    encodeAssetProxyId(AssetProxyId.ERC20, encodedMetadata);
-    encodeAddress(tokenAddress, encodedMetadata);
+    const encodedAssetProxyId = encodeAssetProxyId(AssetProxyId.ERC20);
+    const encodedAddress = encodeAddress(tokenAddress);
+    const encodedMetadata = Buffer.concat([encodedAssetProxyId, encodedAddress]);
+    const encodedMetadataHex = ethUtil.bufferToHex(encodedMetadata);
 
-    // Verify encoding length - '0x' plus 21 bytes of encoded data
-    if (encodedMetadata.value.length != 44) {
-        throw Error('Bad encoding length. Expected 44, got ' + encodedMetadata.value.length);
-    }
-
-    // Return encoded metadata
-    return encodedMetadata.value;
+    return encodedMetadataHex;
 }
 
 export function encodeERC721ProxyMetadata(tokenAddress: string, tokenId: BigNumber) {
     // Encode metadata
-    const encodedMetadata = { value: '0x' };
-    encodeAssetProxyId(AssetProxyId.ERC721, encodedMetadata);
-    encodeAddress(tokenAddress, encodedMetadata);
-    encodeUint256(tokenId, encodedMetadata);
-
-    // Verify encoding length - '0x' plus 53 bytes of encoded data
-    if (encodedMetadata.value.length != 108) {
-        throw Error('Bad encoding length. Expected 108, got ' + encodedMetadata.value.length);
-    }
+    const encodedAssetProxyId = encodeAssetProxyId(AssetProxyId.ERC721);
+    const encodedAddress = encodeAddress(tokenAddress);
+    const encodedTokenId = encodeUint256(tokenId);
+    const encodedMetadata = Buffer.concat([encodedAssetProxyId, encodedAddress, encodedTokenId]);
+    const encodedMetadataHex = ethUtil.bufferToHex(encodedMetadata);
 
-    // Return encoded metadata
-    return encodedMetadata.value;
+    return encodedMetadataHex;
 }