如何將字元串轉換為 bytes256 或任意字節？

我已經知道如何轉換 bytes32ToString 和 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))
       }
   }

但是如何將字元串轉換為 bytes256 或任意字節？或將任意字節轉換為字元串？

自己解決…

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);
   }

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);


   }

}

引用自：https://ethereum.stackexchange.com/questions/74354