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Angel Angel
Asked: 2020-12-06 19:18:11 +0800 CST 2020-12-06 19:18:11 +0800 CST

Why does char, hex show ffffff?

  • 772

I have a char[] , named buffer , the data is stored using an ifstream in mode binary mode,

void File::mostrarBuffer(){
  for (int a = 0; a < std::strlen(buffer); a++){
    std::cout << std::hex << ((int)buffer[a]) << std::endl;
  }

  std::cout <<  "==="  << std::endl;

  for (int a = 0; a < std::strlen(buffer); a++){
    std::cout <<  buffer[a] << std::endl;
  }

  char charTest = '\211';

  std::cout <<  "==="  << std::endl;

  std::cout << std::hex << (int)charTest  << std::endl;
  std::cout << std::hex << (int)buffer[0] << std::endl;
}

The shell displays the following:

ffffff89
50
4e
47
===
\211
P
N
G
===
ffffff89
ffffff89

File part in hexdump (" little-endian"):

0000000 5089 474e 0a0d 0a1a 0000 0d00 4849 5244

Why does it print ffffff89and not 89, and only on the first element of the char []?

c++

1 Answers

  1. Best Answer

    Jonathan Wood https://stackoverflow.com/users/522663/jonathan-wood

    Because your char is signed, try to cast to unsigned.

    this way works for me: 

     std::cout << std::hex << ((unsigned int)(unsigned char)buffer[a]) 
           << std::endl;
    • 4