Combine BytesX and BytesY to create BytesZ?

Question

I am working on a Solidity Smart Contract (^0.5.10) where I want to return an array of Ratings elements.

struct Ratings {
    address restaurant
    uint8 score
};

Since returning Rating[], string[], and bytes[] from functions is still experimental, I was attempting to compress the struct into a byte22[] and return that in a serialized format. But I don't know how to combine byteX objects into another byteX object.

I have 3 variables like so:

bytes20 address_string = BytesUtils.toBytes(restaurant.experience);
bytes1 separator = bytes1(";");
bytes1 rating = BytesUtils.toBytes(review.rating);

How can I combine them to create a byte22?

Answer 1

The following code can help your purpose.

pragma solidity 0.5.1;

contract A {

    bytes private finalBytes;


    function setBytesCombined() external {
        bytes20 address_string = toBytes(msg.sender);

        bytes1 separator = bytes1(";");

        // Combining.......
        string memory combinedStringEmpty = new string(address_string.length + separator.length);

        bytes memory combinedBytes = bytes(combinedStringEmpty);

        uint iter = 0;

        for (uint i = 0; i < address_string.length; i++) {
            combinedBytes[iter++] = address_string[i];
        }

        for (uint i = 0; i < separator.length; i++) {
            combinedBytes[iter++] = separator[i];
        }

        finalBytes = bytes(combinedBytes);
    }

    function getBytesCombined() public view returns(bytes memory) {
        return finalBytes;
    }

    function toBytes(address a) internal pure returns (bytes20 b) {
        return bytes20(uint160(a));
    }
}