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Hex to ASCII showing a different result to correct the implementation of PHP

 2 years ago
source link: https://www.codesd.com/item/hex-to-ascii-showing-a-different-result-to-correct-the-implementation-of-php.html
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Hex to ASCII showing a different result to correct the implementation of PHP

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I needed a method that would convert hex to ascii, and most seem to be a variation of the following:

public String hexToAscii(String hex) {
    StringBuilder sb = new StringBuilder();
    StringBuilder temp = new StringBuilder();
    for(int i = 0; i < hex.length() - 1; i += 2){
        String output = hex.substring(i, (i + 2));
        int decimal = Integer.parseInt(output, 16);
        sb.append((char)decimal);
        temp.append(decimal);
    }
    return sb.toString();
}

The idea is to look at

hexToAscii("51d37bdd871c9e1f4d5541be67a6ab625e32028744d7d4609d0c37747b40cd2d");

If I print the result out, I get

-Í@{t7?`Ô×D?2^b«¦g¾AUM??Ý{ÓQ.

This is not the result I am needing though. A friend got the correct result in PHP which was the string reverse of the following:

QÓ{݇žMUA¾g¦«b^2‡D×Ô`7t{@Í-

There are clearly characters that his hexToAscii function is encoding whereas mine is not. Not really sure why this is the case, but how can I implement this version in Java?

Assuming your input string is in, I would use a method like this

public static byte[] decode(String in) {
  if (in != null) {
    in = in.trim();
    List<Byte> bytes = new ArrayList<Byte>();
    char[] chArr = in.toCharArray();

    int t = 0;
    while (t + 1 < chArr.length) {
      String token = "" + chArr[t] + chArr[t + 1];
      // This subtracts 128 from the byte value.
      int b = Byte.MIN_VALUE
          + Integer.valueOf(token, 16);
      bytes.add((byte) b);
      t += 2;
    }
    byte[] out = new byte[bytes.size()];
    for (int i = 0; i < bytes.size(); ++i) {
      out[i] = bytes.get(i);
    }
    return out;
  }
  return new byte[] {};
}

And then you could use it like this

new String(decode("51d37bdd871c9e1f4d5541be67a6ab625e"
  +"32028744d7d4609d0c37747b40cd2d"))

report

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