A full decompilation and automatic security analysis of all contracts on the Ethereum and the Fantom blockchains. Updated hourly with new contracts uploaded to both networks. Analysis results by Dedaub.

Contract Library by Dedaub

CONFIG_TYPE_INBOUND_BLOCK_CONFIRMATIONS

CONFIG_TYPE_INBOUND_PROOF_LIBRARY_VERSION

CONFIG_TYPE_ORACLE

CONFIG_TYPE_OUTBOUND_BLOCK_CONFIRMATIONS

CONFIG_TYPE_OUTBOUND_PROOF_TYPE

CONFIG_TYPE_RELAYER

_address

accruedNativeFee

_chainId

_library

addInboundProofLibraryForChain

appConfig

inboundProofLibraryVersion

inboundBlockConfirmations

relayer

outboundProofType

outboundBlockConfirmations

oracle

chainAddressSizeMap

defaultAdapterParams

defaultAppConfig

_proofType

enableSupportedOutboundProof

endpoint

_dstChainId

_payload

_payInZRO

_adapterParams

estimateFees

nativeFee

zroFee

_remoteChainId

getAppConfig

_configType

getConfig

_path

getOutboundNonce

hashLookup

inboundProofLibrary

layerZeroToken

localChainId

maxInboundProofLibrary

nativeFees

nonceContract

owner

renounceOwnership

_refundAddress

_zroPaymentAddress

send

_size

setChainAddressSize

_config

setConfig

setDefaultAdapterParamsForChainId

_inboundProofLibraryVersion

_inboundBlockConfirmations

_relayer

_outboundProofType

_outboundBlockConfirmations

_oracle

setDefaultConfigForChainId

_layerZeroToken

setLayerZeroToken

_remoteUln

setRemoteUln

_treasury

setTreasury

supportedOutboundProof

newOwner

transferOwnership

treasuryContract

treasuryZROFees

ulnLookup

_srcChainId

_lookupHash

_confirmations

_blockData

updateHash

_dstAddress

_gasLimit

_transactionProof

validateTransactionProof

_amount

withdrawNative

withdrawZRO

// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: value }(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

Address.sol

// SPDX-License-Identifier: BUSL-1.1

// https://github.com/ensdomains/buffer

pragma solidity ^0.7.0;

/**
 * @dev A library for working with mutable byte buffers in Solidity.
 *
 * Byte buffers are mutable and expandable, and provide a variety of primitives
 * for writing to them. At any time you can fetch a bytes object containing the
 * current contents of the buffer. The bytes object should not be stored between
 * operations, as it may change due to resizing of the buffer.
 */
library Buffer {
    /**
     * @dev Represents a mutable buffer. Buffers have a current value (buf) and
     *      a capacity. The capacity may be longer than the current value, in
     *      which case it can be extended without the need to allocate more memory.
     */
    struct buffer {
        bytes buf;
        uint capacity;
    }

    /**
     * @dev Initializes a buffer with an initial capacity.a co
     * @param buf The buffer to initialize.
     * @param capacity The number of bytes of space to allocate the buffer.
     * @return The buffer, for chaining.
     */
    function init(buffer memory buf, uint capacity) internal pure returns (buffer memory) {
        if (capacity % 32 != 0) {
            capacity += 32 - (capacity % 32);
        }
        // Allocate space for the buffer data
        buf.capacity = capacity;
        assembly {
            let ptr := mload(0x40)
            mstore(buf, ptr)
            mstore(ptr, 0)
            mstore(0x40, add(32, add(ptr, capacity)))
        }
        return buf;
    }


    /**
     * @dev Writes a byte string to a buffer. Resizes if doing so would exceed
     *      the capacity of the buffer.
     * @param buf The buffer to append to.
     * @param off The start offset to write to.
     * @param rawData The data to append.
     * @param len The number of bytes to copy.
     * @return The original buffer, for chaining.
     */
    function writeRawBytes(
        buffer memory buf,
        uint off,
        bytes memory rawData,
        uint offData,
        uint len
    ) internal pure returns (buffer memory) {
        if (off + len > buf.capacity) {
            resize(buf, max(buf.capacity, len + off) * 2);
        }

        uint dest;
        uint src;
        assembly {
            // Memory address of the buffer data
            let bufptr := mload(buf)
            // Length of existing buffer data
            let buflen := mload(bufptr)
            // Start address = buffer address + offset + sizeof(buffer length)
            dest := add(add(bufptr, 32), off)
            // Update buffer length if we're extending it
            if gt(add(len, off), buflen) {
                mstore(bufptr, add(len, off))
            }
            src := add(rawData, offData)
        }

        // Copy word-length chunks while possible
        for (; len >= 32; len -= 32) {
            assembly {
                mstore(dest, mload(src))
            }
            dest += 32;
            src += 32;
        }

        // Copy remaining bytes
        uint mask = 256**(32 - len) - 1;
        assembly {
            let srcpart := and(mload(src), not(mask))
            let destpart := and(mload(dest), mask)
            mstore(dest, or(destpart, srcpart))
        }

        return buf;
    }

    /**
     * @dev Writes a byte string to a buffer. Resizes if doing so would exceed
     *      the capacity of the buffer.
     * @param buf The buffer to append to.
     * @param off The start offset to write to.
     * @param data The data to append.
     * @param len The number of bytes to copy.
     * @return The original buffer, for chaining.
     */
    function write(buffer memory buf, uint off, bytes memory data, uint len) internal pure returns (buffer memory) {
        require(len <= data.length);

        if (off + len > buf.capacity) {
            resize(buf, max(buf.capacity, len + off) * 2);
        }

        uint dest;
        uint src;
        assembly {
        // Memory address of the buffer data
            let bufptr := mload(buf)
        // Length of existing buffer data
            let buflen := mload(bufptr)
        // Start address = buffer address + offset + sizeof(buffer length)
            dest := add(add(bufptr, 32), off)
        // Update buffer length if we're extending it
            if gt(add(len, off), buflen) {
                mstore(bufptr, add(len, off))
            }
            src := add(data, 32)
        }

        // Copy word-length chunks while possible
        for (; len >= 32; len -= 32) {
            assembly {
                mstore(dest, mload(src))
            }
            dest += 32;
            src += 32;
        }

        // Copy remaining bytes
        uint mask = 256**(32 - len) - 1;
        assembly {
            let srcpart := and(mload(src), not(mask))
            let destpart := and(mload(dest), mask)
            mstore(dest, or(destpart, srcpart))
        }

        return buf;
    }

    function append(buffer memory buf, bytes memory data) internal pure returns (buffer memory) {
        return write(buf, buf.buf.length, data, data.length);
    }

    function resize(buffer memory buf, uint capacity) private pure {
        bytes memory oldbuf = buf.buf;
        init(buf, capacity);
        append(buf, oldbuf);
    }

    function max(uint a, uint b) private pure returns (uint) {
        if (a > b) {
            return a;
        }
        return b;
    }
}

Buffer.sol

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

Context.sol

// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

IERC20.sol

// SPDX-License-Identifier: BUSL-1.1

pragma solidity >=0.5.0;

import "ILayerZeroUserApplicationConfig.sol";

interface ILayerZeroEndpoint is ILayerZeroUserApplicationConfig {
    // @notice send a LayerZero message to the specified address at a LayerZero endpoint.
    // @param _dstChainId - the destination chain identifier
    // @param _destination - the address on destination chain (in bytes). address length/format may vary by chains
    // @param _payload - a custom bytes payload to send to the destination contract
    // @param _refundAddress - if the source transaction is cheaper than the amount of value passed, refund the additional amount to this address
    // @param _zroPaymentAddress - the address of the ZRO token holder who would pay for the transaction
    // @param _adapterParams - parameters for custom functionality. e.g. receive airdropped native gas from the relayer on destination
    function send(uint16 _dstChainId, bytes calldata _destination, bytes calldata _payload, address payable _refundAddress, address _zroPaymentAddress, bytes calldata _adapterParams) external payable;

    // @notice used by the messaging library to publish verified payload
    // @param _srcChainId - the source chain identifier
    // @param _srcAddress - the source contract (as bytes) at the source chain
    // @param _dstAddress - the address on destination chain
    // @param _nonce - the unbound message ordering nonce
    // @param _gasLimit - the gas limit for external contract execution
    // @param _payload - verified payload to send to the destination contract
    function receivePayload(uint16 _srcChainId, bytes calldata _srcAddress, address _dstAddress, uint64 _nonce, uint _gasLimit, bytes calldata _payload) external;

    // @notice get the inboundNonce of a receiver from a source chain which could be EVM or non-EVM chain
    // @param _srcChainId - the source chain identifier
    // @param _srcAddress - the source chain contract address
    function getInboundNonce(uint16 _srcChainId, bytes calldata _srcAddress) external view returns (uint64);

    // @notice get the outboundNonce from this source chain which, consequently, is always an EVM
    // @param _srcAddress - the source chain contract address
    function getOutboundNonce(uint16 _dstChainId, address _srcAddress) external view returns (uint64);

    // @notice gets a quote in source native gas, for the amount that send() requires to pay for message delivery
    // @param _dstChainId - the destination chain identifier
    // @param _userApplication - the user app address on this EVM chain
    // @param _payload - the custom message to send over LayerZero
    // @param _payInZRO - if false, user app pays the protocol fee in native token
    // @param _adapterParam - parameters for the adapter service, e.g. send some dust native token to dstChain
    function estimateFees(uint16 _dstChainId, address _userApplication, bytes calldata _payload, bool _payInZRO, bytes calldata _adapterParam) external view returns (uint nativeFee, uint zroFee);

    // @notice get this Endpoint's immutable source identifier
    function getChainId() external view returns (uint16);

    // @notice the interface to retry failed message on this Endpoint destination
    // @param _srcChainId - the source chain identifier
    // @param _srcAddress - the source chain contract address
    // @param _payload - the payload to be retried
    function retryPayload(uint16 _srcChainId, bytes calldata _srcAddress, bytes calldata _payload) external;

    // @notice query if any STORED payload (message blocking) at the endpoint.
    // @param _srcChainId - the source chain identifier
    // @param _srcAddress - the source chain contract address
    function hasStoredPayload(uint16 _srcChainId, bytes calldata _srcAddress) external view returns (bool);

    // @notice query if the _libraryAddress is valid for sending msgs.
    // @param _userApplication - the user app address on this EVM chain
    function getSendLibraryAddress(address _userApplication) external view returns (address);

    // @notice query if the _libraryAddress is valid for receiving msgs.
    // @param _userApplication - the user app address on this EVM chain
    function getReceiveLibraryAddress(address _userApplication) external view returns (address);

    // @notice query if the non-reentrancy guard for send() is on
    // @return true if the guard is on. false otherwise
    function isSendingPayload() external view returns (bool);

    // @notice query if the non-reentrancy guard for receive() is on
    // @return true if the guard is on. false otherwise
    function isReceivingPayload() external view returns (bool);

    // @notice get the configuration of the LayerZero messaging library of the specified version
    // @param _version - messaging library version
    // @param _chainId - the chainId for the pending config change
    // @param _userApplication - the contract address of the user application
    // @param _configType - type of configuration. every messaging library has its own convention.
    function getConfig(uint16 _version, uint16 _chainId, address _userApplication, uint _configType) external view returns (bytes memory);

    // @notice get the send() LayerZero messaging library version
    // @param _userApplication - the contract address of the user application
    function getSendVersion(address _userApplication) external view returns (uint16);

    // @notice get the lzReceive() LayerZero messaging library version
    // @param _userApplication - the contract address of the user application
    function getReceiveVersion(address _userApplication) external view returns (uint16);
}

ILayerZeroEndpoint.sol

// SPDX-License-Identifier: BUSL-1.1

pragma solidity >=0.7.0;

import "ILayerZeroUserApplicationConfig.sol";

interface ILayerZeroMessagingLibrary {
    // send(), messages will be inflight.
    function send(address _userApplication, uint64 _lastNonce, uint16 _chainId, bytes calldata _destination, bytes calldata _payload, address payable refundAddress, address _zroPaymentAddress, bytes calldata _adapterParams) external payable;

    // estimate native fee at the send side
    function estimateFees(uint16 _chainId, address _userApplication, bytes calldata _payload, bool _payInZRO, bytes calldata _adapterParam) external view returns (uint nativeFee, uint zroFee);

    //---------------------------------------------------------------------------
    // setConfig / getConfig are User Application (UA) functions to specify Oracle, Relayer, blockConfirmations, libraryVersion
    function setConfig(uint16 _chainId, address _userApplication, uint _configType, bytes calldata _config) external;

    function getConfig(uint16 _chainId, address _userApplication, uint _configType) external view returns (bytes memory);
}

ILayerZeroMessagingLibrary.sol

// SPDX-License-Identifier: BUSL-1.1

pragma solidity >=0.7.0;

import "ILayerZeroUserApplicationConfig.sol";
import "ILayerZeroMessagingLibrary.sol";

interface ILayerZeroMessagingLibraryV2 is ILayerZeroMessagingLibrary {
    function getOutboundNonce(uint16 _chainId, bytes calldata _path) external view returns (uint64);
}

ILayerZeroMessagingLibraryV2.sol

// SPDX-License-Identifier: BUSL-1.1

pragma solidity >=0.7.0;

interface ILayerZeroOracleV2 {
    // @notice query price and assign jobs at the same time
    // @param _dstChainId - the destination endpoint identifier
    // @param _outboundProofType - the proof type identifier to specify proof to be relayed
    // @param _outboundBlockConfirmation - block confirmation delay before relaying blocks
    // @param _userApplication - the source sending contract address
    function assignJob(uint16 _dstChainId, uint16 _outboundProofType, uint64 _outboundBlockConfirmation, address _userApplication) external returns (uint price);

    // @notice query the oracle price for relaying block information to the destination chain
    // @param _dstChainId the destination endpoint identifier
    // @param _outboundProofType the proof type identifier to specify the data to be relayed
    // @param _outboundBlockConfirmation - block confirmation delay before relaying blocks
    // @param _userApplication - the source sending contract address
    function getFee(uint16 _dstChainId, uint16 _outboundProofType, uint64 _outboundBlockConfirmation, address _userApplication) external view returns (uint price);

    // @notice withdraw the accrued fee in ultra light node
    // @param _to - the fee receiver
    // @param _amount - the withdrawal amount
    function withdrawFee(address payable _to, uint _amount) external;
}

ILayerZeroOracleV2.sol

// SPDX-License-Identifier: BUSL-1.1

pragma solidity >=0.5.0;

interface ILayerZeroReceiver {
    // @notice LayerZero endpoint will invoke this function to deliver the message on the destination
    // @param _srcChainId - the source endpoint identifier
    // @param _srcAddress - the source sending contract address from the source chain
    // @param _nonce - the ordered message nonce
    // @param _payload - the signed payload is the UA bytes has encoded to be sent
    function lzReceive(uint16 _srcChainId, bytes calldata _srcAddress, uint64 _nonce, bytes calldata _payload) external;
}

ILayerZeroReceiver.sol

// SPDX-License-Identifier: BUSL-1.1

pragma solidity >=0.7.0;

interface ILayerZeroRelayerV2 {
    // @notice query price and assign jobs at the same time
    // @param _dstChainId - the destination endpoint identifier
    // @param _outboundProofType - the proof type identifier to specify proof to be relayed
    // @param _userApplication - the source sending contract address. relayers may apply price discrimination to user apps
    // @param _payloadSize - the length of the payload. it is an indicator of gas usage for relaying cross-chain messages
    // @param _adapterParams - optional parameters for extra service plugins, e.g. sending dust tokens at the destination chain
    function assignJob(uint16 _dstChainId, uint16 _outboundProofType, address _userApplication, uint _payloadSize, bytes calldata _adapterParams) external returns (uint price);

    // @notice query the relayer price for relaying the payload and its proof to the destination chain
    // @param _dstChainId - the destination endpoint identifier
    // @param _outboundProofType - the proof type identifier to specify proof to be relayed
    // @param _userApplication - the source sending contract address. relayers may apply price discrimination to user apps
    // @param _payloadSize - the length of the payload. it is an indicator of gas usage for relaying cross-chain messages
    // @param _adapterParams - optional parameters for extra service plugins, e.g. sending dust tokens at the destination chain
    function getFee(uint16 _dstChainId, uint16 _outboundProofType, address _userApplication, uint _payloadSize, bytes calldata _adapterParams) external view returns (uint price);

    // @notice withdraw the accrued fee in ultra light node
    // @param _to - the fee receiver
    // @param _amount - the withdrawal amount
    function withdrawFee(address payable _to, uint _amount) external;
}

ILayerZeroRelayerV2.sol

// SPDX-License-Identifier: BUSL-1.1

pragma solidity >=0.5.0;

interface ILayerZeroTreasury {
    function getFees(bool payInZro, uint relayerFee, uint oracleFee) external view returns (uint);
}

ILayerZeroTreasury.sol

// SPDX-License-Identifier: BUSL-1.1

pragma solidity >=0.7.0;
pragma abicoder v2;

interface ILayerZeroUltraLightNodeV2 {
    // Relayer functions
    function validateTransactionProof(uint16 _srcChainId, address _dstAddress, uint _gasLimit, bytes32 _lookupHash, bytes32 _blockData, bytes calldata _transactionProof) external;

    // an Oracle delivers the block data using updateHash()
    function updateHash(uint16 _srcChainId, bytes32 _lookupHash, uint _confirmations, bytes32 _blockData) external;

    // can only withdraw the receivable of the msg.sender
    function withdrawNative(address payable _to, uint _amount) external;

    function withdrawZRO(address _to, uint _amount) external;

    // view functions
    function getAppConfig(uint16 _remoteChainId, address _userApplicationAddress) external view returns (ApplicationConfiguration memory);

    function accruedNativeFee(address _address) external view returns (uint);

    struct ApplicationConfiguration {
        uint16 inboundProofLibraryVersion;
        uint64 inboundBlockConfirmations;
        address relayer;
        uint16 outboundProofType;
        uint64 outboundBlockConfirmations;
        address oracle;
    }

    event HashReceived(uint16 indexed srcChainId, address indexed oracle, bytes32 lookupHash, bytes32 blockData, uint confirmations);
    event RelayerParams(bytes adapterParams, uint16 outboundProofType);
    event Packet(bytes payload);
    event InvalidDst(uint16 indexed srcChainId, bytes srcAddress, address indexed dstAddress, uint64 nonce, bytes32 payloadHash);
    event PacketReceived(uint16 indexed srcChainId, bytes srcAddress, address indexed dstAddress, uint64 nonce, bytes32 payloadHash);
    event AppConfigUpdated(address indexed userApplication, uint indexed configType, bytes newConfig);
    event AddInboundProofLibraryForChain(uint16 indexed chainId, address lib);
    event EnableSupportedOutboundProof(uint16 indexed chainId, uint16 proofType);
    event SetChainAddressSize(uint16 indexed chainId, uint size);
    event SetDefaultConfigForChainId(uint16 indexed chainId, uint16 inboundProofLib, uint64 inboundBlockConfirm, address relayer, uint16 outboundProofType, uint64 outboundBlockConfirm, address oracle);
    event SetDefaultAdapterParamsForChainId(uint16 indexed chainId, uint16 indexed proofType, bytes adapterParams);
    event SetLayerZeroToken(address indexed tokenAddress);
    event SetRemoteUln(uint16 indexed chainId, bytes32 uln);
    event SetTreasury(address indexed treasuryAddress);
    event WithdrawZRO(address indexed msgSender, address indexed to, uint amount);
    event WithdrawNative(address indexed msgSender, address indexed to, uint amount);
}

ILayerZeroUltraLightNodeV2.sol

// SPDX-License-Identifier: BUSL-1.1

pragma solidity >=0.5.0;

interface ILayerZeroUserApplicationConfig {
    // @notice set the configuration of the LayerZero messaging library of the specified version
    // @param _version - messaging library version
    // @param _chainId - the chainId for the pending config change
    // @param _configType - type of configuration. every messaging library has its own convention.
    // @param _config - configuration in the bytes. can encode arbitrary content.
    function setConfig(uint16 _version, uint16 _chainId, uint _configType, bytes calldata _config) external;

    // @notice set the send() LayerZero messaging library version to _version
    // @param _version - new messaging library version
    function setSendVersion(uint16 _version) external;

    // @notice set the lzReceive() LayerZero messaging library version to _version
    // @param _version - new messaging library version
    function setReceiveVersion(uint16 _version) external;

    // @notice Only when the UA needs to resume the message flow in blocking mode and clear the stored payload
    // @param _srcChainId - the chainId of the source chain
    // @param _srcAddress - the contract address of the source contract at the source chain
    function forceResumeReceive(uint16 _srcChainId, bytes calldata _srcAddress) external;
}

ILayerZeroUserApplicationConfig.sol

// SPDX-License-Identifier: BUSL-1.1

pragma solidity >=0.7.0;
pragma abicoder v2;

import "LayerZeroPacket.sol";

interface ILayerZeroValidationLibrary {
    function validateProof(bytes32 blockData, bytes calldata _data, uint _remoteAddressSize) external returns (LayerZeroPacket.Packet memory packet);
}

ILayerZeroValidationLibrary.sol

// SPDX-License-Identifier: BUSL-1.1

pragma solidity 0.7.6;

import "Buffer.sol";
import "SafeMath.sol";

library LayerZeroPacket {
    using Buffer for Buffer.buffer;
    using SafeMath for uint;

    struct Packet {
        uint16 srcChainId;
        uint16 dstChainId;
        uint64 nonce;
        address dstAddress;
        bytes srcAddress;
        bytes32 ulnAddress;
        bytes payload;
    }

    function getPacket(
        bytes memory data,
        uint16 srcChain,
        uint sizeOfSrcAddress,
        bytes32 ulnAddress
    ) internal pure returns (LayerZeroPacket.Packet memory) {
        uint16 dstChainId;
        address dstAddress;
        uint size;
        uint64 nonce;

        // The log consists of the destination chain id and then a bytes payload
        //      0--------------------------------------------31
        // 0   |  total bytes size
        // 32  |  destination chain id
        // 64  |  bytes offset
        // 96  |  bytes array size
        // 128 |  payload
        assembly {
            dstChainId := mload(add(data, 32))
            size := mload(add(data, 96)) /// size of the byte array
            nonce := mload(add(data, 104)) // offset to convert to uint64  128  is index -24
            dstAddress := mload(add(data, sub(add(128, sizeOfSrcAddress), 4))) // offset to convert to address 12 -8
        }

        Buffer.buffer memory srcAddressBuffer;
        srcAddressBuffer.init(sizeOfSrcAddress);
        srcAddressBuffer.writeRawBytes(0, data, 136, sizeOfSrcAddress); // 128 + 8

        uint payloadSize = size.sub(28).sub(sizeOfSrcAddress);
        Buffer.buffer memory payloadBuffer;
        payloadBuffer.init(payloadSize);
        payloadBuffer.writeRawBytes(0, data, sizeOfSrcAddress.add(156), payloadSize); // 148 + 8
        return LayerZeroPacket.Packet(srcChain, dstChainId, nonce, dstAddress, srcAddressBuffer.buf, ulnAddress, payloadBuffer.buf);
    }

    function getPacketV2(
        bytes memory data,
        uint sizeOfSrcAddress,
        bytes32 ulnAddress
    ) internal pure returns (LayerZeroPacket.Packet memory) {
        // packet def: abi.encodePacked(nonce, srcChain, srcAddress, dstChain, dstAddress, payload);
        // data def: abi.encode(packet) = offset(32) + length(32) + packet
        //              if from EVM
        // 0 - 31       0 - 31          |  total bytes size
        // 32 - 63      32 - 63         |  location
        // 64 - 95      64 - 95         |  size of the packet
        // 96 - 103     96 - 103        |  nonce
        // 104 - 105    104 - 105       |  srcChainId
        // 106 - P      106 - 125       |  srcAddress, where P = 106 + sizeOfSrcAddress - 1,
        // P+1 - P+2    126 - 127       |  dstChainId
        // P+3 - P+22   128 - 147       |  dstAddress
        // P+23 - END   148 - END       |  payload

        // decode the packet
        uint256 realSize;
        uint64 nonce;
        uint16 srcChain;
        uint16 dstChain;
        address dstAddress;
        assembly {
            realSize := mload(add(data, 64))
            nonce := mload(add(data, 72)) // 104 - 32
            srcChain := mload(add(data, 74)) // 106 - 32
            dstChain := mload(add(data, add(76, sizeOfSrcAddress))) // P + 3 - 32 = 105 + size + 3 - 32 = 76 + size
            dstAddress := mload(add(data, add(96, sizeOfSrcAddress))) // P + 23 - 32 = 105 + size + 23 - 32 = 96 + size
        }

        require(srcChain != 0, "LayerZeroPacket: invalid packet");

        Buffer.buffer memory srcAddressBuffer;
        srcAddressBuffer.init(sizeOfSrcAddress);
        srcAddressBuffer.writeRawBytes(0, data, 106, sizeOfSrcAddress);

        uint nonPayloadSize = sizeOfSrcAddress.add(32);// 2 + 2 + 8 + 20, 32 + 20 = 52 if sizeOfSrcAddress == 20
        uint payloadSize = realSize.sub(nonPayloadSize);
        Buffer.buffer memory payloadBuffer;
        payloadBuffer.init(payloadSize);
        payloadBuffer.writeRawBytes(0, data, nonPayloadSize.add(96), payloadSize);

        return LayerZeroPacket.Packet(srcChain, dstChain, nonce, dstAddress, srcAddressBuffer.buf, ulnAddress, payloadBuffer.buf);
    }

    function getPacketV3(
        bytes memory data,
        uint sizeOfSrcAddress,
        bytes32 ulnAddress
    ) internal pure returns (LayerZeroPacket.Packet memory) {
        // data def: abi.encodePacked(nonce, srcChain, srcAddress, dstChain, dstAddress, payload);
        //              if from EVM
        // 0 - 31       0 - 31          |  total bytes size
        // 32 - 39      32 - 39         |  nonce
        // 40 - 41      40 - 41         |  srcChainId
        // 42 - P       42 - 61         |  srcAddress, where P = 41 + sizeOfSrcAddress,
        // P+1 - P+2    62 - 63         |  dstChainId
        // P+3 - P+22   64 - 83         |  dstAddress
        // P+23 - END   84 - END        |  payload

        // decode the packet
        uint256 realSize = data.length;
        uint nonPayloadSize = sizeOfSrcAddress.add(32);// 2 + 2 + 8 + 20, 32 + 20 = 52 if sizeOfSrcAddress == 20
        require(realSize >= nonPayloadSize, "LayerZeroPacket: invalid packet");
        uint payloadSize = realSize - nonPayloadSize;

        uint64 nonce;
        uint16 srcChain;
        uint16 dstChain;
        address dstAddress;
        assembly {
            nonce := mload(add(data, 8)) // 40 - 32
            srcChain := mload(add(data, 10)) // 42 - 32
            dstChain := mload(add(data, add(12, sizeOfSrcAddress))) // P + 3 - 32 = 41 + size + 3 - 32 = 12 + size
            dstAddress := mload(add(data, add(32, sizeOfSrcAddress))) // P + 23 - 32 = 41 + size + 23 - 32 = 32 + size
        }

        require(srcChain != 0, "LayerZeroPacket: invalid packet");

        Buffer.buffer memory srcAddressBuffer;
        srcAddressBuffer.init(sizeOfSrcAddress);
        srcAddressBuffer.writeRawBytes(0, data, 42, sizeOfSrcAddress);

        Buffer.buffer memory payloadBuffer;
        if (payloadSize > 0) {
            payloadBuffer.init(payloadSize);
            payloadBuffer.writeRawBytes(0, data, nonPayloadSize.add(32), payloadSize);
        }

        return LayerZeroPacket.Packet(srcChain, dstChain, nonce, dstAddress, srcAddressBuffer.buf, ulnAddress, payloadBuffer.buf);
    }
}

LayerZeroPacket.sol

// SPDX-License-Identifier: BUSL-1.1

pragma solidity 0.7.6;

import "ILayerZeroEndpoint.sol";

contract NonceContract {
    ILayerZeroEndpoint public immutable endpoint;
    // outboundNonce = [dstChainId][remoteAddress + localAddress]
    mapping(uint16 => mapping(bytes => uint64)) public outboundNonce;

    constructor(address _endpoint) {
        endpoint = ILayerZeroEndpoint(_endpoint);
    }

    function increment(uint16 _chainId, address _ua, bytes calldata _path) external returns (uint64) {
        require(endpoint.getSendLibraryAddress(_ua) == msg.sender, "NonceContract: msg.sender is not valid sendlibrary");
        return ++outboundNonce[_chainId][_path];
    }
}

NonceContract.sol

// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

import "Context.sol";
/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor () {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

Ownable.sol

// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor () {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and make it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;

        _;

        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}

ReentrancyGuard.sol

// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

import "IERC20.sol";
import "SafeMath.sol";
import "Address.sol";

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;

    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(value);
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

SafeERC20.sol

// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) return (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) return 0;
        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a % b;
    }
}

SafeMath.sol

UltraLightNodeV2.sol

__ANONYMOUS__

0x4d73adb72bc3dd368966edd0f0b2148401a178e2