固定大小位元組陣列之間的轉換

固定大小位元組陣列，我們可以通過bytes1~32來進行宣告，固定大小位元組陣列的長度不可變，內容不可修改。

pragma solidity ^0.4.4;
contract Test {

  bytes5 public g = 0x6869736565; //hisee
  
  function getBytesLength() constant returns (uint) {
    return g.length;
  }

  function gTobytes2() constant returns (bytes2) {
    return bytes2(g);
  }
  function gTobytes10() constant returns (bytes10) {
    return bytes10(g);
  }
}
 

說明：轉長的位元組陣列，後面填0。轉短的位元組陣列，截斷後面的。

固定大小位元組陣列轉動態大小位元組陣列

pragma solidity ^0.4.4;
contract Test {

  bytes5 public b = 0x6869736565; //hisee


  function jingZhuanDong() constant returns (bytes) {
    bytes memory b1 = new bytes(b.length);
    for(uint i=0;i<b.length;i++){
      b1[i] = b[i];
    }
    return b1;
  }
}
 

固定大小位元組陣列不能直接轉換為string

動態大小位元組陣列轉string

pragma solidity ^0.4.4;
contract Test {

  bytes5 public b = 0x6869736565; //hisee
  bytes names = new bytes(2);
  bytes name = new bytes(b.length);

  function Test() {
    names[0]=0x68;
    names[1]=0x69;
    for(uint i=0;i<b.length;i++){
      name[i] = b[i];
    }
  }

  function namesToString() constant returns (string) {
    return string(names);
  }

  function nameToString() constant returns (string) {
    return string(name);
  }
}
 

本身就是動態大小位元組陣列

固定大小位元組陣列轉string，需先轉動態位元組陣列後再轉string

pragma solidity ^0.4.4;
contract Test {

  bytes5 public b = 0x6869736565; //hisee

  function bytes32ToString(bytes32 x) constant returns (string) {
    bytes memory bytesString = new bytes(32);
    uint charCount = 0;
    for(uint i=0;i<32;i++){
      byte char = byte(bytes32(uint(x)*2**(8*i)));//左移2的（8*i)次方,下同
   //   byte char = byte(bytes32(uint(x) << (8*i)));
      if(char!=0){
        bytesString[charCount] = char;
        charCount++;
      }
    }
    bytes memory bytesStringTrimmed = new bytes(charCount);
    for(i=0;i<charCount;i++){
      bytesStringTrimmed[i] = bytesString[i];
    }
    return string(bytesStringTrimmed);
  }

}