provableAPI_0.4.25.sol

// <provableAPI>
// Release targetted at solc 0.4.25 to silence compiler warning/error messages, compatible down to 0.4.22

/*
Copyright (c) 2015-2016 Oraclize SRL
Copyright (c) 2016-2019 Oraclize LTD
Copyright (c) 2019 Provable Things Limited



Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:



The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.



THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/

pragma solidity >= 0.4.22 < 0.5;// Incompatible compiler version... please select one stated within pragma solidity or use different provableAPI version

contract ProvableI {
    address public cbAddress;
    function query(uint _timestamp, string _datasource, string _arg) external payable returns (bytes32 _id);
    function query_withGasLimit(uint _timestamp, string _datasource, string _arg, uint _gaslimit) external payable returns (bytes32 _id);
    function query2(uint _timestamp, string _datasource, string _arg1, string _arg2) public payable returns (bytes32 _id);
    function query2_withGasLimit(uint _timestamp, string _datasource, string _arg1, string _arg2, uint _gaslimit) external payable returns (bytes32 _id);
    function queryN(uint _timestamp, string _datasource, bytes _argN) public payable returns (bytes32 _id);
    function queryN_withGasLimit(uint _timestamp, string _datasource, bytes _argN, uint _gaslimit) external payable returns (bytes32 _id);
    function getPrice(string _datasource) public returns (uint _dsprice);
    function getPrice(string _datasource, uint gaslimit) public returns (uint _dsprice);
    function setProofType(byte _proofType) external;
    function setCustomGasPrice(uint _gasPrice) external;
    function randomDS_getSessionPubKeyHash() external constant returns(bytes32);
}

contract OracleAddrResolverI {
    function getAddress() public returns (address _addr);
}

/*
Begin solidity-cborutils

https://github.com/smartcontractkit/solidity-cborutils

MIT License

Copyright (c) 2018 SmartContract ChainLink, Ltd.

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
 */

library Buffer {
    struct buffer {
        bytes buf;
        uint capacity;
    }

    function init(buffer memory buf, uint _capacity) internal pure {
        uint capacity = _capacity;
        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(ptr, capacity))
        }
    }

    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;
    }

    /**
     * @dev Appends a byte array to the end of the buffer. Resizes if doing so
     *      would exceed the capacity of the buffer.
     * @param buf The buffer to append to.
     * @param data The data to append.
     * @return The original buffer.
     */
    function append(buffer memory buf, bytes data) internal pure returns(buffer memory) {
        if(data.length + buf.buf.length > buf.capacity) {
            resize(buf, max(buf.capacity, data.length) * 2);
        }

        uint dest;
        uint src;
        uint len = data.length;
        assembly {
            // Memory address of the buffer data
            let bufptr := mload(buf)
            // Length of existing buffer data
            let buflen := mload(bufptr)
            // Start address = buffer address + buffer length + sizeof(buffer length)
            dest := add(add(bufptr, buflen), 32)
            // Update buffer length
            mstore(bufptr, add(buflen, mload(data)))
            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;
    }

    /**
     * @dev Appends a byte to the end of the buffer. Resizes if doing so would
     * exceed the capacity of the buffer.
     * @param buf The buffer to append to.
     * @param data The data to append.
     * @return The original buffer.
     */
    function append(buffer memory buf, uint8 data) internal pure {
        if(buf.buf.length + 1 > buf.capacity) {
            resize(buf, buf.capacity * 2);
        }

        assembly {
            // Memory address of the buffer data
            let bufptr := mload(buf)
            // Length of existing buffer data
            let buflen := mload(bufptr)
            // Address = buffer address + buffer length + sizeof(buffer length)
            let dest := add(add(bufptr, buflen), 32)
            mstore8(dest, data)
            // Update buffer length
            mstore(bufptr, add(buflen, 1))
        }
    }

    /**
     * @dev Appends a byte to the end of the buffer. Resizes if doing so would
     * exceed the capacity of the buffer.
     * @param buf The buffer to append to.
     * @param data The data to append.
     * @return The original buffer.
     */
    function appendInt(buffer memory buf, uint data, uint len) internal pure returns(buffer memory) {
        if(len + buf.buf.length > buf.capacity) {
            resize(buf, max(buf.capacity, len) * 2);
        }

        uint mask = 256 ** len - 1;
        assembly {
            // Memory address of the buffer data
            let bufptr := mload(buf)
            // Length of existing buffer data
            let buflen := mload(bufptr)
            // Address = buffer address + buffer length + sizeof(buffer length) + len
            let dest := add(add(bufptr, buflen), len)
            mstore(dest, or(and(mload(dest), not(mask)), data))
            // Update buffer length
            mstore(bufptr, add(buflen, len))
        }
        return buf;
    }
}

library CBOR {
    using Buffer for Buffer.buffer;

    uint8 private constant MAJOR_TYPE_INT = 0;
    uint8 private constant MAJOR_TYPE_NEGATIVE_INT = 1;
    uint8 private constant MAJOR_TYPE_BYTES = 2;
    uint8 private constant MAJOR_TYPE_STRING = 3;
    uint8 private constant MAJOR_TYPE_ARRAY = 4;
    uint8 private constant MAJOR_TYPE_MAP = 5;
    uint8 private constant MAJOR_TYPE_CONTENT_FREE = 7;

    function encodeType(Buffer.buffer memory buf, uint8 major, uint value) private pure {
        if(value <= 23) {
            buf.append(uint8((major << 5) | value));
        } else if(value <= 0xFF) {
            buf.append(uint8((major << 5) | 24));
            buf.appendInt(value, 1);
        } else if(value <= 0xFFFF) {
            buf.append(uint8((major << 5) | 25));
            buf.appendInt(value, 2);
        } else if(value <= 0xFFFFFFFF) {
            buf.append(uint8((major << 5) | 26));
            buf.appendInt(value, 4);
        } else if(value <= 0xFFFFFFFFFFFFFFFF) {
            buf.append(uint8((major << 5) | 27));
            buf.appendInt(value, 8);
        }
    }

    function encodeIndefiniteLengthType(Buffer.buffer memory buf, uint8 major) private pure {
        buf.append(uint8((major << 5) | 31));
    }

    function encodeUInt(Buffer.buffer memory buf, uint value) internal pure {
        encodeType(buf, MAJOR_TYPE_INT, value);
    }

    function encodeInt(Buffer.buffer memory buf, int value) internal pure {
        if(value >= 0) {
            encodeType(buf, MAJOR_TYPE_INT, uint(value));
        } else {
            encodeType(buf, MAJOR_TYPE_NEGATIVE_INT, uint(-1 - value));
        }
    }

    function encodeBytes(Buffer.buffer memory buf, bytes value) internal pure {
        encodeType(buf, MAJOR_TYPE_BYTES, value.length);
        buf.append(value);
    }

    function encodeString(Buffer.buffer memory buf, string value) internal pure {
        encodeType(buf, MAJOR_TYPE_STRING, bytes(value).length);
        buf.append(bytes(value));
    }

    function startArray(Buffer.buffer memory buf) internal pure {
        encodeIndefiniteLengthType(buf, MAJOR_TYPE_ARRAY);
    }

    function startMap(Buffer.buffer memory buf) internal pure {
        encodeIndefiniteLengthType(buf, MAJOR_TYPE_MAP);
    }

    function endSequence(Buffer.buffer memory buf) internal pure {
        encodeIndefiniteLengthType(buf, MAJOR_TYPE_CONTENT_FREE);
    }
}

/*
End solidity-cborutils
 */

contract usingProvable {
    uint constant day = 60*60*24;
    uint constant week = 60*60*24*7;
    uint constant month = 60*60*24*30;
    byte constant proofType_NONE = 0x00;
    byte constant proofType_TLSNotary = 0x10;
    byte constant proofType_Ledger = 0x30;
    byte constant proofType_Android = 0x40;
    byte constant proofType_Native = 0xF0;
    byte constant proofStorage_IPFS = 0x01;
    uint8 constant networkID_auto = 0;
    uint8 constant networkID_mainnet = 1;
    uint8 constant networkID_testnet = 2;
    uint8 constant networkID_morden = 2;
    uint8 constant networkID_consensys = 161;

    OracleAddrResolverI OAR;

    ProvableI provable;
    modifier provableAPI {
        if((address(OAR)==0)||(getCodeSize(address(OAR))==0))
            provable_setNetwork(networkID_auto);

        if(address(provable) != OAR.getAddress())
            provable = ProvableI(OAR.getAddress());

        _;
    }
    modifier coupon(string code){
        provable = ProvableI(OAR.getAddress());
        _;
    }

    function provable_setNetwork(uint8 networkID) internal returns(bool){
      return provable_setNetwork();
      networkID; // silence the warning and remain backwards compatible
    }
    function provable_setNetwork() internal returns(bool){
        if (getCodeSize(0x1d3B2638a7cC9f2CB3D298A3DA7a90B67E5506ed)>0){ //mainnet
            OAR = OracleAddrResolverI(0x1d3B2638a7cC9f2CB3D298A3DA7a90B67E5506ed);
            provable_setNetworkName("eth_mainnet");
            return true;
        }
        if (getCodeSize(0xc03A2615D5efaf5F49F60B7BB6583eaec212fdf1)>0){ //ropsten testnet
            OAR = OracleAddrResolverI(0xc03A2615D5efaf5F49F60B7BB6583eaec212fdf1);
            provable_setNetworkName("eth_ropsten3");
            return true;
        }
        if (getCodeSize(0xB7A07BcF2Ba2f2703b24C0691b5278999C59AC7e)>0){ //kovan testnet
            OAR = OracleAddrResolverI(0xB7A07BcF2Ba2f2703b24C0691b5278999C59AC7e);
            provable_setNetworkName("eth_kovan");
            return true;
        }
        if (getCodeSize(0x146500cfd35B22E4A392Fe0aDc06De1a1368Ed48)>0){ //rinkeby testnet
            OAR = OracleAddrResolverI(0x146500cfd35B22E4A392Fe0aDc06De1a1368Ed48);
            provable_setNetworkName("eth_rinkeby");
            return true;
        }
        if (getCodeSize(0xa2998EFD205FB9D4B4963aFb70778D6354ad3A41)>0){ //goerli testnet
            OAR = OracleAddrResolverI(0xa2998EFD205FB9D4B4963aFb70778D6354ad3A41);
            provable_setNetworkName("eth_goerli");
            return true;
        }
        if (getCodeSize(0x6f485C8BF6fc43eA212E93BBF8ce046C7f1cb475)>0){ //ethereum-bridge
            OAR = OracleAddrResolverI(0x6f485C8BF6fc43eA212E93BBF8ce046C7f1cb475);
            return true;
        }
        if (getCodeSize(0x20e12A1F859B3FeaE5Fb2A0A32C18F5a65555bBF)>0){ //ether.camp ide
            OAR = OracleAddrResolverI(0x20e12A1F859B3FeaE5Fb2A0A32C18F5a65555bBF);
            return true;
        }
        if (getCodeSize(0x51efaF4c8B3C9AfBD5aB9F4bbC82784Ab6ef8fAA)>0){ //browser-solidity
            OAR = OracleAddrResolverI(0x51efaF4c8B3C9AfBD5aB9F4bbC82784Ab6ef8fAA);
            return true;
        }
        return false;
    }
    /**
     * @dev The following `__callback` functions are just placeholders ideally
     *      meant to be defined in child contract when proofs are used.
     *      The function bodies simply silence compiler warnings.
     */
    function __callback(bytes32 myid, string result) public {
        __callback(myid, result, new bytes(0));
    }

    function __callback(bytes32 myid, string result, bytes proof) public {
      return;
      myid; result; proof;
      provable_randomDS_args[bytes32(0)] = bytes32(0);
    }

    function provable_getPrice(string datasource) provableAPI internal returns (uint){
        return provable.getPrice(datasource);
    }

    function provable_getPrice(string datasource, uint gaslimit) provableAPI internal returns (uint){
        return provable.getPrice(datasource, gaslimit);
    }

    function provable_query(string datasource, string arg) provableAPI internal returns (bytes32 id){
        uint price = provable.getPrice(datasource);
        if (price > 1 ether + tx.gasprice*200000) return 0; // unexpectedly high price
        return provable.query.value(price)(0, datasource, arg);
    }
    function provable_query(uint timestamp, string datasource, string arg) provableAPI internal returns (bytes32 id){
        uint price = provable.getPrice(datasource);
        if (price > 1 ether + tx.gasprice*200000) return 0; // unexpectedly high price
        return provable.query.value(price)(timestamp, datasource, arg);
    }
    function provable_query(uint timestamp, string datasource, string arg, uint gaslimit) provableAPI internal returns (bytes32 id){
        uint price = provable.getPrice(datasource, gaslimit);
        if (price > 1 ether + tx.gasprice*gaslimit) return 0; // unexpectedly high price
        return provable.query_withGasLimit.value(price)(timestamp, datasource, arg, gaslimit);
    }
    function provable_query(string datasource, string arg, uint gaslimit) provableAPI internal returns (bytes32 id){
        uint price = provable.getPrice(datasource, gaslimit);
        if (price > 1 ether + tx.gasprice*gaslimit) return 0; // unexpectedly high price
        return provable.query_withGasLimit.value(price)(0, datasource, arg, gaslimit);
    }
    function provable_query(string datasource, string arg1, string arg2) provableAPI internal returns (bytes32 id){
        uint price = provable.getPrice(datasource);
        if (price > 1 ether + tx.gasprice*200000) return 0; // unexpectedly high price
        return provable.query2.value(price)(0, datasource, arg1, arg2);
    }
    function provable_query(uint timestamp, string datasource, string arg1, string arg2) provableAPI internal returns (bytes32 id){
        uint price = provable.getPrice(datasource);
        if (price > 1 ether + tx.gasprice*200000) return 0; // unexpectedly high price
        return provable.query2.value(price)(timestamp, datasource, arg1, arg2);
    }
    function provable_query(uint timestamp, string datasource, string arg1, string arg2, uint gaslimit) provableAPI internal returns (bytes32 id){
        uint price = provable.getPrice(datasource, gaslimit);
        if (price > 1 ether + tx.gasprice*gaslimit) return 0; // unexpectedly high price
        return provable.query2_withGasLimit.value(price)(timestamp, datasource, arg1, arg2, gaslimit);
    }
    function provable_query(string datasource, string arg1, string arg2, uint gaslimit) provableAPI internal returns (bytes32 id){
        uint price = provable.getPrice(datasource, gaslimit);
        if (price > 1 ether + tx.gasprice*gaslimit) return 0; // unexpectedly high price
        return provable.query2_withGasLimit.value(price)(0, datasource, arg1, arg2, gaslimit);
    }
    function provable_query(string datasource, string[] argN) provableAPI internal returns (bytes32 id){
        uint price = provable.getPrice(datasource);
        if (price > 1 ether + tx.gasprice*200000) return 0; // unexpectedly high price
        bytes memory args = stra2cbor(argN);
        return provable.queryN.value(price)(0, datasource, args);
    }
    function provable_query(uint timestamp, string datasource, string[] argN) provableAPI internal returns (bytes32 id){
        uint price = provable.getPrice(datasource);
        if (price > 1 ether + tx.gasprice*200000) return 0; // unexpectedly high price
        bytes memory args = stra2cbor(argN);
        return provable.queryN.value(price)(timestamp, datasource, args);
    }
    function provable_query(uint timestamp, string datasource, string[] argN, uint gaslimit) provableAPI internal returns (bytes32 id){
        uint price = provable.getPrice(datasource, gaslimit);
        if (price > 1 ether + tx.gasprice*gaslimit) return 0; // unexpectedly high price
        bytes memory args = stra2cbor(argN);
        return provable.queryN_withGasLimit.value(price)(timestamp, datasource, args, gaslimit);
    }
    function provable_query(string datasource, string[] argN, uint gaslimit) provableAPI internal returns (bytes32 id){
        uint price = provable.getPrice(datasource, gaslimit);
        if (price > 1 ether + tx.gasprice*gaslimit) return 0; // unexpectedly high price
        bytes memory args = stra2cbor(argN);
        return provable.queryN_withGasLimit.value(price)(0, datasource, args, gaslimit);
    }
    function provable_query(string datasource, string[1] args) provableAPI internal returns (bytes32 id) {
        string[] memory dynargs = new string[](1);
        dynargs[0] = args[0];
        return provable_query(datasource, dynargs);
    }
    function provable_query(uint timestamp, string datasource, string[1] args) provableAPI internal returns (bytes32 id) {
        string[] memory dynargs = new string[](1);
        dynargs[0] = args[0];
        return provable_query(timestamp, datasource, dynargs);
    }
    function provable_query(uint timestamp, string datasource, string[1] args, uint gaslimit) provableAPI internal returns (bytes32 id) {
        string[] memory dynargs = new string[](1);
        dynargs[0] = args[0];
        return provable_query(timestamp, datasource, dynargs, gaslimit);
    }
    function provable_query(string datasource, string[1] args, uint gaslimit) provableAPI internal returns (bytes32 id) {
        string[] memory dynargs = new string[](1);
        dynargs[0] = args[0];
        return provable_query(datasource, dynargs, gaslimit);
    }

    function provable_query(string datasource, string[2] args) provableAPI internal returns (bytes32 id) {
        string[] memory dynargs = new string[](2);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        return provable_query(datasource, dynargs);
    }
    function provable_query(uint timestamp, string datasource, string[2] args) provableAPI internal returns (bytes32 id) {
        string[] memory dynargs = new string[](2);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        return provable_query(timestamp, datasource, dynargs);
    }
    function provable_query(uint timestamp, string datasource, string[2] args, uint gaslimit) provableAPI internal returns (bytes32 id) {
        string[] memory dynargs = new string[](2);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        return provable_query(timestamp, datasource, dynargs, gaslimit);
    }
    function provable_query(string datasource, string[2] args, uint gaslimit) provableAPI internal returns (bytes32 id) {
        string[] memory dynargs = new string[](2);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        return provable_query(datasource, dynargs, gaslimit);
    }
    function provable_query(string datasource, string[3] args) provableAPI internal returns (bytes32 id) {
        string[] memory dynargs = new string[](3);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        dynargs[2] = args[2];
        return provable_query(datasource, dynargs);
    }
    function provable_query(uint timestamp, string datasource, string[3] args) provableAPI internal returns (bytes32 id) {
        string[] memory dynargs = new string[](3);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        dynargs[2] = args[2];
        return provable_query(timestamp, datasource, dynargs);
    }
    function provable_query(uint timestamp, string datasource, string[3] args, uint gaslimit) provableAPI internal returns (bytes32 id) {
        string[] memory dynargs = new string[](3);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        dynargs[2] = args[2];
        return provable_query(timestamp, datasource, dynargs, gaslimit);
    }
    function provable_query(string datasource, string[3] args, uint gaslimit) provableAPI internal returns (bytes32 id) {
        string[] memory dynargs = new string[](3);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        dynargs[2] = args[2];
        return provable_query(datasource, dynargs, gaslimit);
    }

    function provable_query(string datasource, string[4] args) provableAPI internal returns (bytes32 id) {
        string[] memory dynargs = new string[](4);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        dynargs[2] = args[2];
        dynargs[3] = args[3];
        return provable_query(datasource, dynargs);
    }
    function provable_query(uint timestamp, string datasource, string[4] args) provableAPI internal returns (bytes32 id) {
        string[] memory dynargs = new string[](4);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        dynargs[2] = args[2];
        dynargs[3] = args[3];
        return provable_query(timestamp, datasource, dynargs);
    }
    function provable_query(uint timestamp, string datasource, string[4] args, uint gaslimit) provableAPI internal returns (bytes32 id) {
        string[] memory dynargs = new string[](4);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        dynargs[2] = args[2];
        dynargs[3] = args[3];
        return provable_query(timestamp, datasource, dynargs, gaslimit);
    }
    function provable_query(string datasource, string[4] args, uint gaslimit) provableAPI internal returns (bytes32 id) {
        string[] memory dynargs = new string[](4);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        dynargs[2] = args[2];
        dynargs[3] = args[3];
        return provable_query(datasource, dynargs, gaslimit);
    }
    function provable_query(string datasource, string[5] args) provableAPI internal returns (bytes32 id) {
        string[] memory dynargs = new string[](5);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        dynargs[2] = args[2];
        dynargs[3] = args[3];
        dynargs[4] = args[4];
        return provable_query(datasource, dynargs);
    }
    function provable_query(uint timestamp, string datasource, string[5] args) provableAPI internal returns (bytes32 id) {
        string[] memory dynargs = new string[](5);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        dynargs[2] = args[2];
        dynargs[3] = args[3];
        dynargs[4] = args[4];
        return provable_query(timestamp, datasource, dynargs);
    }
    function provable_query(uint timestamp, string datasource, string[5] args, uint gaslimit) provableAPI internal returns (bytes32 id) {
        string[] memory dynargs = new string[](5);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        dynargs[2] = args[2];
        dynargs[3] = args[3];
        dynargs[4] = args[4];
        return provable_query(timestamp, datasource, dynargs, gaslimit);
    }
    function provable_query(string datasource, string[5] args, uint gaslimit) provableAPI internal returns (bytes32 id) {
        string[] memory dynargs = new string[](5);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        dynargs[2] = args[2];
        dynargs[3] = args[3];
        dynargs[4] = args[4];
        return provable_query(datasource, dynargs, gaslimit);
    }
    function provable_query(string datasource, bytes[] argN) provableAPI internal returns (bytes32 id){
        uint price = provable.getPrice(datasource);
        if (price > 1 ether + tx.gasprice*200000) return 0; // unexpectedly high price
        bytes memory args = ba2cbor(argN);
        return provable.queryN.value(price)(0, datasource, args);
    }
    function provable_query(uint timestamp, string datasource, bytes[] argN) provableAPI internal returns (bytes32 id){
        uint price = provable.getPrice(datasource);
        if (price > 1 ether + tx.gasprice*200000) return 0; // unexpectedly high price
        bytes memory args = ba2cbor(argN);
        return provable.queryN.value(price)(timestamp, datasource, args);
    }
    function provable_query(uint timestamp, string datasource, bytes[] argN, uint gaslimit) provableAPI internal returns (bytes32 id){
        uint price = provable.getPrice(datasource, gaslimit);
        if (price > 1 ether + tx.gasprice*gaslimit) return 0; // unexpectedly high price
        bytes memory args = ba2cbor(argN);
        return provable.queryN_withGasLimit.value(price)(timestamp, datasource, args, gaslimit);
    }
    function provable_query(string datasource, bytes[] argN, uint gaslimit) provableAPI internal returns (bytes32 id){
        uint price = provable.getPrice(datasource, gaslimit);
        if (price > 1 ether + tx.gasprice*gaslimit) return 0; // unexpectedly high price
        bytes memory args = ba2cbor(argN);
        return provable.queryN_withGasLimit.value(price)(0, datasource, args, gaslimit);
    }
    function provable_query(string datasource, bytes[1] args) provableAPI internal returns (bytes32 id) {
        bytes[] memory dynargs = new bytes[](1);
        dynargs[0] = args[0];
        return provable_query(datasource, dynargs);
    }
    function provable_query(uint timestamp, string datasource, bytes[1] args) provableAPI internal returns (bytes32 id) {
        bytes[] memory dynargs = new bytes[](1);
        dynargs[0] = args[0];
        return provable_query(timestamp, datasource, dynargs);
    }
    function provable_query(uint timestamp, string datasource, bytes[1] args, uint gaslimit) provableAPI internal returns (bytes32 id) {
        bytes[] memory dynargs = new bytes[](1);
        dynargs[0] = args[0];
        return provable_query(timestamp, datasource, dynargs, gaslimit);
    }
    function provable_query(string datasource, bytes[1] args, uint gaslimit) provableAPI internal returns (bytes32 id) {
        bytes[] memory dynargs = new bytes[](1);
        dynargs[0] = args[0];
        return provable_query(datasource, dynargs, gaslimit);
    }

    function provable_query(string datasource, bytes[2] args) provableAPI internal returns (bytes32 id) {
        bytes[] memory dynargs = new bytes[](2);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        return provable_query(datasource, dynargs);
    }
    function provable_query(uint timestamp, string datasource, bytes[2] args) provableAPI internal returns (bytes32 id) {
        bytes[] memory dynargs = new bytes[](2);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        return provable_query(timestamp, datasource, dynargs);
    }
    function provable_query(uint timestamp, string datasource, bytes[2] args, uint gaslimit) provableAPI internal returns (bytes32 id) {
        bytes[] memory dynargs = new bytes[](2);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        return provable_query(timestamp, datasource, dynargs, gaslimit);
    }
    function provable_query(string datasource, bytes[2] args, uint gaslimit) provableAPI internal returns (bytes32 id) {
        bytes[] memory dynargs = new bytes[](2);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        return provable_query(datasource, dynargs, gaslimit);
    }
    function provable_query(string datasource, bytes[3] args) provableAPI internal returns (bytes32 id) {
        bytes[] memory dynargs = new bytes[](3);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        dynargs[2] = args[2];
        return provable_query(datasource, dynargs);
    }
    function provable_query(uint timestamp, string datasource, bytes[3] args) provableAPI internal returns (bytes32 id) {
        bytes[] memory dynargs = new bytes[](3);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        dynargs[2] = args[2];
        return provable_query(timestamp, datasource, dynargs);
    }
    function provable_query(uint timestamp, string datasource, bytes[3] args, uint gaslimit) provableAPI internal returns (bytes32 id) {
        bytes[] memory dynargs = new bytes[](3);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        dynargs[2] = args[2];
        return provable_query(timestamp, datasource, dynargs, gaslimit);
    }
    function provable_query(string datasource, bytes[3] args, uint gaslimit) provableAPI internal returns (bytes32 id) {
        bytes[] memory dynargs = new bytes[](3);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        dynargs[2] = args[2];
        return provable_query(datasource, dynargs, gaslimit);
    }

    function provable_query(string datasource, bytes[4] args) provableAPI internal returns (bytes32 id) {
        bytes[] memory dynargs = new bytes[](4);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        dynargs[2] = args[2];
        dynargs[3] = args[3];
        return provable_query(datasource, dynargs);
    }
    function provable_query(uint timestamp, string datasource, bytes[4] args) provableAPI internal returns (bytes32 id) {
        bytes[] memory dynargs = new bytes[](4);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        dynargs[2] = args[2];
        dynargs[3] = args[3];
        return provable_query(timestamp, datasource, dynargs);
    }
    function provable_query(uint timestamp, string datasource, bytes[4] args, uint gaslimit) provableAPI internal returns (bytes32 id) {
        bytes[] memory dynargs = new bytes[](4);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        dynargs[2] = args[2];
        dynargs[3] = args[3];
        return provable_query(timestamp, datasource, dynargs, gaslimit);
    }
    function provable_query(string datasource, bytes[4] args, uint gaslimit) provableAPI internal returns (bytes32 id) {
        bytes[] memory dynargs = new bytes[](4);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        dynargs[2] = args[2];
        dynargs[3] = args[3];
        return provable_query(datasource, dynargs, gaslimit);
    }
    function provable_query(string datasource, bytes[5] args) provableAPI internal returns (bytes32 id) {
        bytes[] memory dynargs = new bytes[](5);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        dynargs[2] = args[2];
        dynargs[3] = args[3];
        dynargs[4] = args[4];
        return provable_query(datasource, dynargs);
    }
    function provable_query(uint timestamp, string datasource, bytes[5] args) provableAPI internal returns (bytes32 id) {
        bytes[] memory dynargs = new bytes[](5);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        dynargs[2] = args[2];
        dynargs[3] = args[3];
        dynargs[4] = args[4];
        return provable_query(timestamp, datasource, dynargs);
    }
    function provable_query(uint timestamp, string datasource, bytes[5] args, uint gaslimit) provableAPI internal returns (bytes32 id) {
        bytes[] memory dynargs = new bytes[](5);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        dynargs[2] = args[2];
        dynargs[3] = args[3];
        dynargs[4] = args[4];
        return provable_query(timestamp, datasource, dynargs, gaslimit);
    }
    function provable_query(string datasource, bytes[5] args, uint gaslimit) provableAPI internal returns (bytes32 id) {
        bytes[] memory dynargs = new bytes[](5);
        dynargs[0] = args[0];
        dynargs[1] = args[1];
        dynargs[2] = args[2];
        dynargs[3] = args[3];
        dynargs[4] = args[4];
        return provable_query(datasource, dynargs, gaslimit);
    }

    function provable_cbAddress() provableAPI internal returns (address){
        return provable.cbAddress();
    }
    function provable_setProof(byte proofP) provableAPI internal {
        return provable.setProofType(proofP);
    }
    function provable_setCustomGasPrice(uint gasPrice) provableAPI internal {
        return provable.setCustomGasPrice(gasPrice);
    }

    function provable_randomDS_getSessionPubKeyHash() provableAPI internal returns (bytes32){
        return provable.randomDS_getSessionPubKeyHash();
    }

    function getCodeSize(address _addr) view internal returns(uint _size) {
        assembly {
            _size := extcodesize(_addr)
        }
    }

    function parseAddr(string _a) internal pure returns (address){
        bytes memory tmp = bytes(_a);
        uint160 iaddr = 0;
        uint160 b1;
        uint160 b2;
        for (uint i=2; i<2+2*20; i+=2){
            iaddr *= 256;
            b1 = uint160(tmp[i]);
            b2 = uint160(tmp[i+1]);
            if ((b1 >= 97)&&(b1 <= 102)) b1 -= 87;
            else if ((b1 >= 65)&&(b1 <= 70)) b1 -= 55;
            else if ((b1 >= 48)&&(b1 <= 57)) b1 -= 48;
            if ((b2 >= 97)&&(b2 <= 102)) b2 -= 87;
            else if ((b2 >= 65)&&(b2 <= 70)) b2 -= 55;
            else if ((b2 >= 48)&&(b2 <= 57)) b2 -= 48;
            iaddr += (b1*16+b2);
        }
        return address(iaddr);
    }

    function strCompare(string _a, string _b) internal pure returns (int) {
        bytes memory a = bytes(_a);
        bytes memory b = bytes(_b);
        uint minLength = a.length;
        if (b.length < minLength) minLength = b.length;
        for (uint i = 0; i < minLength; i ++)
            if (a[i] < b[i])
                return -1;
            else if (a[i] > b[i])
                return 1;
        if (a.length < b.length)
            return -1;
        else if (a.length > b.length)
            return 1;
        else
            return 0;
    }

    function indexOf(string _haystack, string _needle) internal pure returns (int) {
        bytes memory h = bytes(_haystack);
        bytes memory n = bytes(_needle);
        if(h.length < 1 || n.length < 1 || (n.length > h.length))
            return -1;
        else if(h.length > (2**128 -1))
            return -1;
        else
        {
            uint subindex = 0;
            for (uint i = 0; i < h.length; i ++)
            {
                if (h[i] == n[0])
                {
                    subindex = 1;
                    while(subindex < n.length && (i + subindex) < h.length && h[i + subindex] == n[subindex])
                    {
                        subindex++;
                    }
                    if(subindex == n.length)
                        return int(i);
                }
            }
            return -1;
        }
    }

    function strConcat(string _a, string _b, string _c, string _d, string _e) internal pure returns (string) {
        bytes memory _ba = bytes(_a);
        bytes memory _bb = bytes(_b);
        bytes memory _bc = bytes(_c);
        bytes memory _bd = bytes(_d);
        bytes memory _be = bytes(_e);
        string memory abcde = new string(_ba.length + _bb.length + _bc.length + _bd.length + _be.length);
        bytes memory babcde = bytes(abcde);
        uint k = 0;
        for (uint i = 0; i < _ba.length; i++) babcde[k++] = _ba[i];
        for (i = 0; i < _bb.length; i++) babcde[k++] = _bb[i];
        for (i = 0; i < _bc.length; i++) babcde[k++] = _bc[i];
        for (i = 0; i < _bd.length; i++) babcde[k++] = _bd[i];
        for (i = 0; i < _be.length; i++) babcde[k++] = _be[i];
        return string(babcde);
    }

    function strConcat(string _a, string _b, string _c, string _d) internal pure returns (string) {
        return strConcat(_a, _b, _c, _d, "");
    }

    function strConcat(string _a, string _b, string _c) internal pure returns (string) {
        return strConcat(_a, _b, _c, "", "");
    }

    function strConcat(string _a, string _b) internal pure returns (string) {
        return strConcat(_a, _b, "", "", "");
    }

    // parseInt
    function parseInt(string _a) internal pure returns (uint) {
        return parseInt(_a, 0);
    }

    // parseInt(parseFloat*10^_b)
    function parseInt(string _a, uint _b) internal pure returns (uint) {
        bytes memory bresult = bytes(_a);
        uint mint = 0;
        bool decimals = false;
        for (uint i=0; i<bresult.length; i++){
            if ((bresult[i] >= 48)&&(bresult[i] <= 57)){
                if (decimals){
                   if (_b == 0) break;
                    else _b--;
                }
                mint *= 10;
                mint += uint(bresult[i]) - 48;
            } else if (bresult[i] == 46) decimals = true;
        }
        if (_b > 0) mint *= 10**_b;
        return mint;
    }

    function uint2str(uint i) internal pure returns (string){
        if (i == 0) return "0";
        uint j = i;
        uint len;
        while (j != 0){
            len++;
            j /= 10;
        }
        bytes memory bstr = new bytes(len);
        uint k = len - 1;
        while (i != 0){
            bstr[k--] = byte(48 + i % 10);
            i /= 10;
        }
        return string(bstr);
    }

    using CBOR for Buffer.buffer;
    function stra2cbor(string[] arr) internal pure returns (bytes) {
        safeMemoryCleaner();
        Buffer.buffer memory buf;
        Buffer.init(buf, 1024);
        buf.startArray();
        for (uint i = 0; i < arr.length; i++) {
            buf.encodeString(arr[i]);
        }
        buf.endSequence();
        return buf.buf;
    }

    function ba2cbor(bytes[] arr) internal pure returns (bytes) {
        safeMemoryCleaner();
        Buffer.buffer memory buf;
        Buffer.init(buf, 1024);
        buf.startArray();
        for (uint i = 0; i < arr.length; i++) {
            buf.encodeBytes(arr[i]);
        }
        buf.endSequence();
        return buf.buf;
    }

    string provable_network_name;
    function provable_setNetworkName(string _network_name) internal {
        provable_network_name = _network_name;
    }

    function provable_getNetworkName() internal view returns (string) {
        return provable_network_name;
    }

    function provable_newRandomDSQuery(uint _delay, uint _nbytes, uint _customGasLimit) internal returns (bytes32){
        require((_nbytes > 0) && (_nbytes <= 32));
        // Convert from seconds to ledger timer ticks
        _delay *= 10;
        bytes memory nbytes = new bytes(1);
        nbytes[0] = byte(_nbytes);
        bytes memory unonce = new bytes(32);
        bytes memory sessionKeyHash = new bytes(32);
        bytes32 sessionKeyHash_bytes32 = provable_randomDS_getSessionPubKeyHash();
        assembly {
            mstore(unonce, 0x20)
            // the following variables can be relaxed
            // check relaxed random contract under ethereum-examples repo
            // for an idea on how to override and replace comit hash vars
            mstore(add(unonce, 0x20), xor(blockhash(sub(number, 1)), xor(coinbase, timestamp)))
            mstore(sessionKeyHash, 0x20)
            mstore(add(sessionKeyHash, 0x20), sessionKeyHash_bytes32)
        }
        bytes memory delay = new bytes(32);
        assembly {
            mstore(add(delay, 0x20), _delay)
        }

        bytes memory delay_bytes8 = new bytes(8);
        copyBytes(delay, 24, 8, delay_bytes8, 0);

        bytes[4] memory args = [unonce, nbytes, sessionKeyHash, delay];
        bytes32 queryId = provable_query("random", args, _customGasLimit);

        bytes memory delay_bytes8_left = new bytes(8);

        assembly {
            let x := mload(add(delay_bytes8, 0x20))
            mstore8(add(delay_bytes8_left, 0x27), div(x, 0x100000000000000000000000000000000000000000000000000000000000000))
            mstore8(add(delay_bytes8_left, 0x26), div(x, 0x1000000000000000000000000000000000000000000000000000000000000))
            mstore8(add(delay_bytes8_left, 0x25), div(x, 0x10000000000000000000000000000000000000000000000000000000000))
            mstore8(add(delay_bytes8_left, 0x24), div(x, 0x100000000000000000000000000000000000000000000000000000000))
            mstore8(add(delay_bytes8_left, 0x23), div(x, 0x1000000000000000000000000000000000000000000000000000000))
            mstore8(add(delay_bytes8_left, 0x22), div(x, 0x10000000000000000000000000000000000000000000000000000))
            mstore8(add(delay_bytes8_left, 0x21), div(x, 0x100000000000000000000000000000000000000000000000000))
            mstore8(add(delay_bytes8_left, 0x20), div(x, 0x1000000000000000000000000000000000000000000000000))

        }

        provable_randomDS_setCommitment(queryId, keccak256(abi.encodePacked(delay_bytes8_left, args[1], sha256(args[0]), args[2])));
        return queryId;
    }

    function provable_randomDS_setCommitment(bytes32 queryId, bytes32 commitment) internal {
        provable_randomDS_args[queryId] = commitment;
    }

    mapping(bytes32=>bytes32) provable_randomDS_args;
    mapping(bytes32=>bool) provable_randomDS_sessionKeysHashVerified;

    function verifySig(bytes32 tosignh, bytes dersig, bytes pubkey) internal returns (bool){
        bool sigok;
        address signer;

        bytes32 sigr;
        bytes32 sigs;

        bytes memory sigr_ = new bytes(32);
        uint offset = 4+(uint(dersig[3]) - 0x20);
        sigr_ = copyBytes(dersig, offset, 32, sigr_, 0);
        bytes memory sigs_ = new bytes(32);
        offset += 32 + 2;
        sigs_ = copyBytes(dersig, offset+(uint(dersig[offset-1]) - 0x20), 32, sigs_, 0);

        assembly {
            sigr := mload(add(sigr_, 32))
            sigs := mload(add(sigs_, 32))
        }


        (sigok, signer) = safer_ecrecover(tosignh, 27, sigr, sigs);
        if (address(keccak256(pubkey)) == signer) return true;
        else {
            (sigok, signer) = safer_ecrecover(tosignh, 28, sigr, sigs);
            return (address(keccak256(pubkey)) == signer);
        }
    }

    function provable_randomDS_proofVerify__sessionKeyValidity(bytes proof, uint sig2offset) internal returns (bool) {
        bool sigok;

        // Step 6: verify the attestation signature, APPKEY1 must sign the sessionKey from the correct ledger app (CODEHASH)
        bytes memory sig2 = new bytes(uint(proof[sig2offset+1])+2);
        copyBytes(proof, sig2offset, sig2.length, sig2, 0);

        bytes memory appkey1_pubkey = new bytes(64);
        copyBytes(proof, 3+1, 64, appkey1_pubkey, 0);

        bytes memory tosign2 = new bytes(1+65+32);
        tosign2[0] = byte(1); //role
        copyBytes(proof, sig2offset-65, 65, tosign2, 1);
        bytes memory CODEHASH = hex"fd94fa71bc0ba10d39d464d0d8f465efeef0a2764e3887fcc9df41ded20f505c";
        copyBytes(CODEHASH, 0, 32, tosign2, 1+65);
        sigok = verifySig(sha256(tosign2), sig2, appkey1_pubkey);

        if (sigok == false) return false;


        // Step 7: verify the APPKEY1 provenance (must be signed by Ledger)
        bytes memory LEDGERKEY = hex"7fb956469c5c9b89840d55b43537e66a98dd4811ea0a27224272c2e5622911e8537a2f8e86a46baec82864e98dd01e9ccc2f8bc5dfc9cbe5a91a290498dd96e4";

        bytes memory tosign3 = new bytes(1+65);
        tosign3[0] = 0xFE;
        copyBytes(proof, 3, 65, tosign3, 1);

        bytes memory sig3 = new bytes(uint(proof[3+65+1])+2);
        copyBytes(proof, 3+65, sig3.length, sig3, 0);

        sigok = verifySig(sha256(tosign3), sig3, LEDGERKEY);

        return sigok;
    }

    modifier provable_randomDS_proofVerify(bytes32 _queryId, string _result, bytes _proof) {
        // Step 1: the prefix has to match 'LP\x01' (Ledger Proof version 1)
        require((_proof[0] == "L") && (_proof[1] == "P") && (_proof[2] == 1));

        bool proofVerified = provable_randomDS_proofVerify__main(_proof, _queryId, bytes(_result), provable_getNetworkName());
        require(proofVerified);

        _;
    }

    function provable_randomDS_proofVerify__returnCode(bytes32 _queryId, string _result, bytes _proof) internal returns (uint8){
        // Step 1: the prefix has to match 'LP\x01' (Ledger Proof version 1)
        if ((_proof[0] != "L")||(_proof[1] != "P")||(_proof[2] != 1)) return 1;

        bool proofVerified = provable_randomDS_proofVerify__main(_proof, _queryId, bytes(_result), provable_getNetworkName());
        if (proofVerified == false) return 2;

        return 0;
    }

    function matchBytes32Prefix(bytes32 content, bytes prefix, uint n_random_bytes) internal pure returns (bool){
        bool match_ = true;

        require(prefix.length == n_random_bytes);

        for (uint256 i=0; i< n_random_bytes; i++) {
            if (content[i] != prefix[i]) match_ = false;
        }

        return match_;
    }

    function provable_randomDS_proofVerify__main(bytes proof, bytes32 queryId, bytes result, string context_name) internal returns (bool){

        // Step 2: the unique keyhash has to match with the sha256 of (context name + queryId)
        uint ledgerProofLength = 3+65+(uint(proof[3+65+1])+2)+32;
        bytes memory keyhash = new bytes(32);
        copyBytes(proof, ledgerProofLength, 32, keyhash, 0);
        if (!(keccak256(keyhash) == keccak256(abi.encodePacked(sha256(abi.encodePacked(context_name, queryId)))))) return false;

        bytes memory sig1 = new bytes(uint(proof[ledgerProofLength+(32+8+1+32)+1])+2);
        copyBytes(proof, ledgerProofLength+(32+8+1+32), sig1.length, sig1, 0);

        // Step 3: we assume sig1 is valid (it will be verified during step 5) and we verify if 'result' is the prefix of sha256(sig1)
        if (!matchBytes32Prefix(sha256(sig1), result, uint(proof[ledgerProofLength+32+8]))) return false;

        // Step 4: commitment match verification, keccak256(delay, nbytes, unonce, sessionKeyHash) == commitment in storage.
        // This is to verify that the computed args match with the ones specified in the query.
        bytes memory commitmentSlice1 = new bytes(8+1+32);
        copyBytes(proof, ledgerProofLength+32, 8+1+32, commitmentSlice1, 0);

        bytes memory sessionPubkey = new bytes(64);
        uint sig2offset = ledgerProofLength+32+(8+1+32)+sig1.length+65;
        copyBytes(proof, sig2offset-64, 64, sessionPubkey, 0);

        bytes32 sessionPubkeyHash = sha256(sessionPubkey);
        if (provable_randomDS_args[queryId] == keccak256(abi.encodePacked(commitmentSlice1, sessionPubkeyHash))){ //unonce, nbytes and sessionKeyHash match
            delete provable_randomDS_args[queryId];
        } else return false;


        // Step 5: validity verification for sig1 (keyhash and args signed with the sessionKey)
        bytes memory tosign1 = new bytes(32+8+1+32);
        copyBytes(proof, ledgerProofLength, 32+8+1+32, tosign1, 0);
        if (!verifySig(sha256(tosign1), sig1, sessionPubkey)) return false;

        // verify if sessionPubkeyHash was verified already, if not.. let's do it!
        if (provable_randomDS_sessionKeysHashVerified[sessionPubkeyHash] == false){
            provable_randomDS_sessionKeysHashVerified[sessionPubkeyHash] = provable_randomDS_proofVerify__sessionKeyValidity(proof, sig2offset);
        }

        return provable_randomDS_sessionKeysHashVerified[sessionPubkeyHash];
    }

    // the following function has been written by Alex Beregszaszi (@axic), use it under the terms of the MIT license
    function copyBytes(bytes from, uint fromOffset, uint length, bytes to, uint toOffset) internal pure returns (bytes) {
        uint minLength = length + toOffset;

        // Buffer too small
        require(to.length >= minLength); // Should be a better way?

        // NOTE: the offset 32 is added to skip the `size` field of both bytes variables
        uint i = 32 + fromOffset;
        uint j = 32 + toOffset;

        while (i < (32 + fromOffset + length)) {
            assembly {
                let tmp := mload(add(from, i))
                mstore(add(to, j), tmp)
            }
            i += 32;
            j += 32;
        }

        return to;
    }

    // the following function has been written by Alex Beregszaszi (@axic), use it under the terms of the MIT license
    // Duplicate Solidity's ecrecover, but catching the CALL return value
    function safer_ecrecover(bytes32 hash, uint8 v, bytes32 r, bytes32 s) internal returns (bool, address) {
        // We do our own memory management here. Solidity uses memory offset
        // 0x40 to store the current end of memory. We write past it (as
        // writes are memory extensions), but don't update the offset so
        // Solidity will reuse it. The memory used here is only needed for
        // this context.

        // FIXME: inline assembly can't access return values
        bool ret;
        address addr;

        assembly {
            let size := mload(0x40)
            mstore(size, hash)
            mstore(add(size, 32), v)
            mstore(add(size, 64), r)
            mstore(add(size, 96), s)

            // NOTE: we can reuse the request memory because we deal with
            //       the return code
            ret := call(3000, 1, 0, size, 128, size, 32)
            addr := mload(size)
        }

        return (ret, addr);
    }

    // the following function has been written by Alex Beregszaszi (@axic), use it under the terms of the MIT license
    function ecrecovery(bytes32 hash, bytes sig) internal returns (bool, address) {
        bytes32 r;
        bytes32 s;
        uint8 v;

        if (sig.length != 65)
          return (false, 0);

        // The signature format is a compact form of:
        //   {bytes32 r}{bytes32 s}{uint8 v}
        // Compact means, uint8 is not padded to 32 bytes.
        assembly {
            r := mload(add(sig, 32))
            s := mload(add(sig, 64))

            // Here we are loading the last 32 bytes. We exploit the fact that
            // 'mload' will pad with zeroes if we overread.
            // There is no 'mload8' to do this, but that would be nicer.
            v := byte(0, mload(add(sig, 96)))

            // Alternative solution:
            // 'byte' is not working due to the Solidity parser, so lets
            // use the second best option, 'and'
            // v := and(mload(add(sig, 65)), 255)
        }

        // albeit non-transactional signatures are not specified by the YP, one would expect it
        // to match the YP range of [27, 28]
        //
        // geth uses [0, 1] and some clients have followed. This might change, see:
        //  https://github.com/ethereum/go-ethereum/issues/2053
        if (v < 27)
          v += 27;

        if (v != 27 && v != 28)
            return (false, 0);

        return safer_ecrecover(hash, v, r, s);
    }

    function safeMemoryCleaner() internal pure {
        assembly {
            let fmem := mload(0x40)
            codecopy(fmem, codesize, sub(msize, fmem))
        }
    }

}
// </provableAPI>