pragma solidity ^0.4.11;
import "../math/Math.sol";
import "./StandardToken.sol";
import "./LimitedTransferToken.sol";
/**
* @title Vested token
* @dev Tokens that can be vested for a group of addresses.
*/
contract VestedToken is StandardToken, LimitedTransferToken {
uint256 MAX_GRANTS_PER_ADDRESS = 20;
struct TokenGrant {
address granter; // 20 bytes
uint256 value; // 32 bytes
uint64 cliff;
uint64 vesting;
uint64 start; // 3 * 8 = 24 bytes
bool revokable;
bool burnsOnRevoke; // 2 * 1 = 2 bits? or 2 bytes?
} // total 78 bytes = 3 sstore per operation (32 per sstore)
mapping (address => TokenGrant[]) public grants;
event NewTokenGrant(address indexed from, address indexed to, uint256 value, uint256 grantId);
/**
* @dev Grant tokens to a specified address
* @param _to address The address which the tokens will be granted to.
* @param _value uint256 The amount of tokens to be granted.
* @param _start uint64 Time of the beginning of the grant.
* @param _cliff uint64 Time of the cliff period.
* @param _vesting uint64 The vesting period.
*/
function grantVestedTokens(
address _to,
uint256 _value,
uint64 _start,
uint64 _cliff,
uint64 _vesting,
bool _revokable,
bool _burnsOnRevoke
) public {
// Check for date inconsistencies that may cause unexpected behavior
if (_cliff < _start || _vesting < _cliff) {
revert();
}
if (tokenGrantsCount(_to) > MAX_GRANTS_PER_ADDRESS) revert(); // To prevent a user being spammed and have his balance locked (out of gas attack when calculating vesting).
uint256 count = grants[_to].push(
TokenGrant(
_revokable ? msg.sender : 0, // avoid storing an extra 20 bytes when it is non-revokable
_value,
_cliff,
_vesting,
_start,
_revokable,
_burnsOnRevoke
)
);
transfer(_to, _value);
emit NewTokenGrant(msg.sender, _to, _value, count - 1);
}
/**
* @dev Revoke the grant of tokens of a specified address.
* @param _holder The address which will have its tokens revoked.
* @param _grantId The id of the token grant.
*/
function revokeTokenGrant(address _holder, uint256 _grantId) public {
TokenGrant storage grant = grants[_holder][_grantId];
if (!grant.revokable) { // Check if grant was revokable
revert();
}
if (grant.granter != msg.sender) { // Only granter can revoke it
revert();
}
address receiver = grant.burnsOnRevoke ? 0xdead : msg.sender;
uint256 nonVested = nonVestedTokens(grant, uint64(now));
// remove grant from array
delete grants[_holder][_grantId];
grants[_holder][_grantId] = grants[_holder][grants[_holder].length.sub(1)];
grants[_holder].length -= 1;
balances[receiver] = balances[receiver].add(nonVested);
balances[_holder] = balances[_holder].sub(nonVested);
emit Transfer(_holder, receiver, nonVested);
}
/**
* @dev Calculate the total amount of transferable tokens of a holder at a given time
* @param holder address The address of the holder
* @param time uint64 The specific time.
* @return An uint256 representing a holder's total amount of transferable tokens.
*/
function transferableTokens(address holder, uint64 time) view public returns (uint256) {
uint256 grantIndex = tokenGrantsCount(holder);
if (grantIndex == 0) return balanceOf(holder); // shortcut for holder without grants
// Iterate through all the grants the holder has, and add all non-vested tokens
uint256 nonVested = 0;
for (uint256 i = 0; i < grantIndex; i++) {
nonVested = SafeMath.add(nonVested, nonVestedTokens(grants[holder][i], time));
}
// Balance - totalNonVested is the amount of tokens a holder can transfer at any given time
uint256 vestedTransferable = SafeMath.sub(balanceOf(holder), nonVested);
// Return the minimum of how many vested can transfer and other value
// in case there are other limiting transferability factors (default is balanceOf)
return Math.min256(vestedTransferable, super.transferableTokens(holder, time));
}
/**
* @dev Check the amount of grants that an address has.
* @param _holder The holder of the grants.
* @return A uint256 representing the total amount of grants.
*/
function tokenGrantsCount(address _holder) public view returns (uint256 index) {
return grants[_holder].length;
}
/**
* @dev Calculate amount of vested tokens at a specific time.
* @param tokens uint256 The amount of tokens granted.
* @param time uint64 The time to be checked
* @param start uint64 A time representing the beginning of the grant
* @param cliff uint64 The cliff period.
* @param vesting uint64 The vesting period.
* @return An uint256 representing the amount of vested tokens of a specific grant.
* transferableTokens
* | _/-------- vestedTokens rect
* | _/
* | _/
* | _/
* | _/
* | /
* | .|
* | . |
* | . |
* | . |
* | . |
* | . |
* +===+===========+---------+----------> time
* Start Clift Vesting
*/
function calculateVestedTokens(
uint256 tokens,
uint256 time,
uint256 start,
uint256 cliff,
uint256 vesting) public view returns (uint256)
{
// Shortcuts for before cliff and after vesting cases.
if (time < cliff) return 0;
if (time >= vesting) return tokens;
// Interpolate all vested tokens.
// As before cliff the shortcut returns 0, we can use just calculate a value
// in the vesting rect (as shown in above's figure)
// vestedTokens = tokens * (time - start) / (vesting - start)
uint256 vestedTokens = SafeMath.div(
SafeMath.mul(
tokens,
SafeMath.sub(time, start)
),
SafeMath.sub(vesting, start)
);
return vestedTokens;
}
/**
* @dev Get all information about a specific grant.
* @param _holder The address which will have its tokens revoked.
* @param _grantId The id of the token grant.
* @return Returns all the values that represent a TokenGrant(address, value, start, cliff,
* revokability, burnsOnRevoke, and vesting) plus the vested value at the current time.
*/
function tokenGrant(address _holder, uint256 _grantId) public view returns (address granter, uint256 value, uint256 vested, uint64 start, uint64 cliff, uint64 vesting, bool revokable, bool burnsOnRevoke) {
TokenGrant storage grant = grants[_holder][_grantId];
granter = grant.granter;
value = grant.value;
start = grant.start;
cliff = grant.cliff;
vesting = grant.vesting;
revokable = grant.revokable;
burnsOnRevoke = grant.burnsOnRevoke;
vested = vestedTokens(grant, uint64(now));
}
/**
* @dev Get the amount of vested tokens at a specific time.
* @param grant TokenGrant The grant to be checked.
* @param time The time to be checked
* @return An uint256 representing the amount of vested tokens of a specific grant at a specific time.
*/
function vestedTokens(TokenGrant memory grant, uint64 time) private view returns (uint256) {
return calculateVestedTokens(
grant.value,
uint256(time),
uint256(grant.start),
uint256(grant.cliff),
uint256(grant.vesting)
);
}
/**
* @dev Calculate the amount of non vested tokens at a specific time.
* @param grant TokenGrant The grant to be checked.
* @param time uint64 The time to be checked
* @return An uint256 representing the amount of non vested tokens of a specific grant on the
* passed time frame.
*/
function nonVestedTokens(TokenGrant memory grant, uint64 time) private view returns (uint256) {
return grant.value.sub(vestedTokens(grant, time));
}
/**
* @dev Calculate the date when the holder can trasfer all its tokens
* @param holder address The address of the holder
* @return An uint256 representing the date of the last transferable tokens.
*/
function lastTokenIsTransferableDate(address holder) view public returns (uint64 date) {
date = uint64(now);
uint256 grantIndex = grants[holder].length;
for (uint256 i = 0; i < grantIndex; i++) {
date = Math.max64(grants[holder][i].vesting, date);
}
}
}
