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144/**
145 * @notice Triggers an approval from owner to spends
146 * @param owner The address to approve from
147 * @param spender The address to be approved
148 * @param rawAmount The number of tokens that are approved (2^256-1 means infinite)
149 * @param deadline The time at which to expire the signature
150 * @param v The recovery byte of the signature
151 * @param r Half of the ECDSA signature pair
152 * @param s Half of the ECDSA signature pair
153 */
154function permit(
155    address owner,
156    address spender,
157    uint256 rawAmount,
158    uint256 deadline,
159    uint8 v,
160    bytes32 r,
161    bytes32 s
162) external {
163    uint96 amount;
164    if (rawAmount == type(uint256).max) {
165        amount = type(uint96).max;
166    } else {
167        amount = safe96(rawAmount, 'Ptp::permit: amount exceeds 96 bits');
168    }
169
170    bytes32 domainSeparator = keccak256(
171        abi.encode(DOMAIN_TYPEHASH, keccak256(bytes(name)), getChainId(), address(this))
172    );
173    bytes32 structHash = keccak256(
174        abi.encode(PERMIT_TYPEHASH, owner, spender, rawAmount, nonces[owner]++, deadline)
175    );
176    bytes32 digest = keccak256(abi.encodePacked('\x19\x01', domainSeparator, structHash));
177    address signatory = ecrecover(digest, v, r, s);
178    require(signatory != address(0), 'Ptp::permit: invalid signature');
179    require(signatory == owner, 'Ptp::permit: unauthorized');
180    require(block.timestamp <= deadline, 'Ptp::permit: signature expired');
181
182    allowances[owner][spender] = amount;
183
184    emit Approval(owner, spender, amount);
185}