| 1. | pragma solidity 0.6.12; |
| 2. |
| 3. | interface IERC20 { |
| 4. | function totalSupply() external view returns (uint256); |
| 5. | function balanceOf(address account) external view returns (uint256); |
| 6. | function transfer(address recipient, uint256 amount) external returns (bool); |
| 7. | function allowance(address owner, address spender) external view returns (uint256); |
| 8. | function approve(address spender, uint256 amount) external returns (bool); |
| 9. | function transferFrom(address sender, address recipient, uint256 amount) external returns (bool); |
| 10. |
| 11. | event Transfer(address indexed from, address indexed to, uint256 value); |
| 12. | event Approval(address indexed owner, address indexed spender, uint256 value); |
| 13. | } |
| 14. |
| 15. | library SafeMath { |
| 16. | function add(uint256 a, uint256 b) internal pure returns (uint256) { |
| 17. | uint256 c = a + b; |
| 18. | require(c >= a, "SafeMath: addition overflow"); |
| 19. | return c; |
| 20. | } |
| 21. |
| 22. | function sub(uint256 a, uint256 b) internal pure returns (uint256) { |
| 23. | return sub(a, b, "SafeMath: subtraction overflow"); |
| 24. | } |
| 25. |
| 26. | function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) { |
| 27. | require(b <= a, errorMessage); |
| 28. | uint256 c = a - b; |
| 29. | return c; |
| 30. | } |
| 31. |
| 32. | function mul(uint256 a, uint256 b) internal pure returns (uint256) { |
| 33. | if (a == 0) { |
| 34. | return 0; |
| 35. | } |
| 36. | uint256 c = a * b; |
| 37. | require(c / a == b, "SafeMath: multiplication overflow"); |
| 38. | return c; |
| 39. | } |
| 40. |
| 41. | function div(uint256 a, uint256 b) internal pure returns (uint256) { |
| 42. | return div(a, b, "SafeMath: division by zero"); |
| 43. | } |
| 44. |
| 45. | function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) { |
| 46. | require(b > 0, errorMessage); |
| 47. | uint256 c = a / b; |
| 48. | return c; |
| 49. | } |
| 50. |
| 51. | function mod(uint256 a, uint256 b) internal pure returns (uint256) { |
| 52. | return mod(a, b, "SafeMath: modulo by zero"); |
| 53. | } |
| 54. |
| 55. | function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) { |
| 56. | require(b != 0, errorMessage); |
| 57. | return a % b; |
| 58. | } |
| 59. | } |
| 60. |
| 61. | abstract contract Context { |
| 62. | function _msgSender() internal view virtual returns (address payable) { |
| 63. | return msg.sender; |
| 64. | } |
| 65. |
| 66. | function _msgData() internal view virtual returns (bytes memory) { |
| 67. | this; |
| 68. | return msg.data; |
| 69. | } |
| 70. | } |
| 71. |
