How to convert string to bytes256 or arbitrary bytes?

Question

I already know how to convert bytes32ToString and stringToBytes32:

 function bytes32ToString(bytes32 x) 
        public
        pure 
        returns (string memory) 
    {
        bytes memory bytesString = new bytes(32);
        uint charCount = 0;
        uint j = 0;
        for (j = 0; j < 32; j++) {
            byte char = byte(bytes32(uint(x) * 2 ** (8 * j)));
            if (char != 0) {
                bytesString[charCount] = char;
                charCount++;
            }
        }
        bytes memory bytesStringTrimmed = new bytes(charCount);
        for (j = 0; j < charCount; j++) {
            bytesStringTrimmed[j] = bytesString[j];
        }
        return string(bytesStringTrimmed);
    }

function stringToBytes32(string memory source) 
        public
        pure
        returns (bytes32 result) 
    {
        bytes memory tempEmptyStringTest = bytes(source);
        if (tempEmptyStringTest.length == 0) {
            return 0x0;
        }

        assembly {
            result := mload(add(source, 32))
        }
    }

But how to convert string to bytes256 or arbitrary bytes? or convert arbitrary bytes to string?

Answer 1

Solved on my own...

function substring(string memory str, uint startIndex, uint endIndex)
        public 
        pure 
        returns (string memory) 
    {
        bytes memory strBytes = bytes(str);
        bytes memory result = new bytes(endIndex-startIndex);
        for(uint i = startIndex; i < endIndex; i++) {
            result[i-startIndex] = strBytes[i];
        }
        return string(result);
    }

function stringToBytes256(string memory source) 
        public
        pure
        returns (byte[256] memory result) 
    {
        uint length = bytes(source).length;
        for(uint i=0;i<length/32;i++){
            bytes32 b32 = stringToBytes32(substring(source, i*8, i*8+32));
            for(uint j=0;j<32;j++){
                result[i*32+j] = b32[j];
            }
        }
        bytes32 b32 = stringToBytes32(substring(source, length/32*32, length));
        uint i=0;
        for(uint k=length/32*32; k<length; k++){
                result[k] = b32[i];
                i++;
        }
    }

function bytes256ToString(byte[256] memory x) public pure returns (string memory) {
        bytes memory bytesString = new bytes(256);
        uint charCount = 0;
        for (uint j = 0; j < 256; j++) {
            byte char = x[j];
            if (char != 0) {
                bytesString[charCount] = char;
                charCount++;
            }
        }
        bytes memory bytesStringTrimmed = new bytes(charCount);
        for (uint j = 0; j < charCount; j++) {
            bytesStringTrimmed[j] = bytesString[j];
        }
        return string(bytesStringTrimmed);
    }

Answer 2

public class byteString {

    /**
     * @param args
     */
    public static void main(String[] args) throws Exception {
        // TODO Auto-generated method stub
        String msg = "Hello";
        byte[] buff = new byte[1024];
        buff = msg.getBytes("UTF-8");
        System.out.println(buff);
        String m = new String(buff);
        System.out.println(m);


    }

}