Uint and Time helpers (#375)

* Add uint64 conversion library

* Add timestamp getter to Initializable and 64 bit version for block

contracts/common/Initializable.sol

@@ -5,9 +5,10 @@
 pragma solidity ^0.4.18;
 
 import "../apps/AppStorage.sol";
+import "../common/TimeHelpers.sol";
 
 
-contract Initializable is AppStorage {
+contract Initializable is AppStorage, TimeHelpers {
     modifier onlyInit {
         require(initializationBlock == 0);
         _;
@@ -31,13 +32,4 @@ contract Initializable is AppStorage {
     function initialized() internal onlyInit {
         initializationBlock = getBlockNumber();
     }
-
-    /**
-    * @dev Returns the current block number.
-    *      Using a function rather than `block.number` allows us to easily mock the block number in
-    *      tests.
-    */
-    function getBlockNumber() internal view returns (uint256) {
-        return block.number;
-    }
 }

contracts/common/TimeHelpers.sol

@@ -0,0 +1,48 @@
+/*
+ * SPDX-License-Identitifer:    MIT
+ */
+
+pragma solidity ^0.4.18;
+
+import "./Uint256Helpers.sol";
+
+
+contract TimeHelpers {
+    using Uint256Helpers for uint256;
+
+    /**
+    * @dev Returns the current block number.
+    *      Using a function rather than `block.number` allows us to easily mock the block number in
+    *      tests.
+    */
+    function getBlockNumber() internal view returns (uint256) {
+        return block.number;
+    }
+
+    /**
+    * @dev Returns the current block number, converted to uint64.
+    *      Using a function rather than `block.number` allows us to easily mock the block number in
+    *      tests.
+    */
+    function getBlockNumber64() internal view returns (uint64) {
+        return getBlockNumber().toUint64();
+    }
+
+    /**
+    * @dev Returns the current timestamp.
+    *      Using a function rather than `now` allows us to easily mock it in
+    *      tests.
+    */
+    function getTimestamp() internal view returns (uint256) {
+        return now;
+    }
+
+    /**
+    * @dev Returns the current timestamp, covnerted to uint64.
+    *      Using a function rather than `now` allows us to easily mock it in
+    *      tests.
+    */
+    function getTimestamp64() internal view returns (uint64) {
+        return getTimestamp().toUint64();
+    }
+}

contracts/common/Uint256Helpers.sol

@@ -0,0 +1,11 @@
+pragma solidity ^0.4.18;
+
+
+library Uint256Helpers {
+    uint256 public constant MAX_UINT64 = uint64(-1);
+
+    function toUint64(uint256 a) internal pure returns (uint64) {
+        require(a <= MAX_UINT64);
+        return uint64(a);
+    }
+}

test/lib_uint256_helpers.js

@@ -0,0 +1,21 @@
+const { assertRevert } = require('./helpers/assertThrow')
+
+contract('Uint256 Helpers test', accounts => {
+  let uint256Mock
+
+  before(async () => {
+    uint256Mock = await artifacts.require('Uint256Mock').new()
+  })
+
+  it('converts from uint256 to uint64', async () => {
+    const a = 1234
+    assert.equal((await uint256Mock.convert.call(a)).toString(), a, "Values should match")
+  })
+
+  it('fails converting from uint256 to uint64 if too big', async () => {
+    const a = new web3.BigNumber(2).pow(64)
+    return assertRevert(async () => {
+      await uint256Mock.convert(a)
+    })
+  })
+})

test/mocks/TimeHelpersMock.sol

@@ -0,0 +1,30 @@
+pragma solidity 0.4.18;
+
+import "../../contracts/common/TimeHelpers.sol";
+
+
+contract TimeHelpersMock is TimeHelpers {
+    function getBlockNumberDirect() public view returns (uint256) {
+        return block.number;
+    }
+
+    function getBlockNumberExt() public view returns (uint256) {
+        return getBlockNumber();
+    }
+
+    function getBlockNumber64Ext() public view returns (uint64) {
+        return getBlockNumber64();
+    }
+
+    function getTimestampDirect() public view returns (uint256) {
+        return now;
+    }
+
+    function getTimestampExt() public view returns (uint256) {
+        return getTimestamp();
+    }
+
+    function getTimestamp64Ext() public view returns (uint64) {
+        return getTimestamp64();
+    }
+}

test/mocks/Uint256Mock.sol

@@ -0,0 +1,12 @@
+pragma solidity 0.4.18;
+
+import "../../contracts/common/Uint256Helpers.sol";
+
+
+contract Uint256Mock {
+    using Uint256Helpers for uint256;
+
+    function convert(uint256 a) public pure returns (uint64) {
+        return a.toUint64();
+    }
+}

test/time_helpers.js

@@ -0,0 +1,17 @@
+contract('TimeHelpers test', accounts => {
+  let timeHelpersMock
+
+  before(async () => {
+    timeHelpersMock = await artifacts.require('TimeHelpersMock').new()
+  })
+
+  it('checks block number', async () => {
+    assert.equal((await timeHelpersMock.getBlockNumberExt.call()).toString(), (await timeHelpersMock.getBlockNumber64Ext.call()).toString(), "block numbers should match")
+    assert.equal((await timeHelpersMock.getBlockNumberExt.call()).toString(), (await timeHelpersMock.getBlockNumberDirect.call()).toString(), web3.eth.blockNumber, "block number should match with real one", "block number should match with real one")
+  })
+
+  it('checks time stamp', async () => {
+    assert.equal((await timeHelpersMock.getTimestampExt.call()).toString(), (await timeHelpersMock.getTimestamp64Ext.call()).toString(), "time stamps should match")
+    assert.equal((await timeHelpersMock.getTimestampExt.call()).toString(), (await timeHelpersMock.getTimestampDirect.call()).toString(), "time stamp should match with real one")
+  })
+})