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);
        }
        _buf.capacity = capacity; // Allocate space for the buffer data
        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 _max) {
        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 memory _data) internal pure returns (buffer memory _buffer) {
        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 {
            let bufptr := mload(_buf) // Memory address of the buffer data
            let buflen := mload(bufptr) // Length of existing buffer data
            dest := add(add(bufptr, buflen), 32) // Start address = buffer address + buffer length + sizeof(buffer length)
            mstore(bufptr, add(buflen, mload(_data))) // Update buffer length
            src := add(_data, 32)
        }
        for(; len >= 32; len -= 32) { // Copy word-length chunks while possible
            assembly {
                mstore(dest, mload(src))
            }
            dest += 32;
            src += 32;
        }
        uint mask = 256 ** (32 - len) - 1; // Copy remaining bytes
        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 {
            let bufptr := mload(_buf) // Memory address of the buffer data
            let buflen := mload(bufptr) // Length of existing buffer data
            let dest := add(add(bufptr, buflen), 32) // Address = buffer address + buffer length + sizeof(buffer length)
            mstore8(dest, _data)
            mstore(bufptr, add(buflen, 1)) // Update buffer length
        }
    }
    /**
      *
      * @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 _buffer) {
        if (_len + _buf.buf.length > _buf.capacity) {
            resize(_buf, max(_buf.capacity, _len) * 2);
        }
        uint mask = 256 ** _len - 1;
        assembly {
            let bufptr := mload(_buf) // Memory address of the buffer data
            let buflen := mload(bufptr) // Length of existing buffer data
            let dest := add(add(bufptr, buflen), _len) // Address = buffer address + buffer length + sizeof(buffer length) + len
            mstore(dest, or(and(mload(dest), not(mask)), _data))
            mstore(bufptr, add(buflen, _len)) // Update buffer length
        }
        return _buf;
    }
}
function appendInt(buffer memory _buf, uint _data, uint _len) internal pure returns (buffer memory _buffer) {
    if (_len + _buf.buf.length > _buf.capacity) {
        resize(_buf, max(_buf.capacity, _len) * 2);
    }
    uint mask = 256 ** _len - 1;
    assembly {
        let bufptr := mload(_buf) // Memory address of the buffer data
        let buflen := mload(bufptr) // Length of existing buffer data
        let dest := add(add(bufptr, buflen), _len) // Address = buffer address + buffer length + sizeof(buffer length) + len
        mstore(dest, or(and(mload(dest), not(mask)), _data))
        mstore(bufptr, add(buflen, _len)) // Update buffer length
    }
    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.
 *
 */