Displaying Hex codes from buffer after reading from a file

Question

I'm trying to store the hex codes read from a file into a buffer and then display it on the console, so far it doesn't seem to work. This is my code:

using namespace std;

int main()
{
 ifstream file("Fishie.ch8",ios::binary);
 if (!file.is_open())
{
    cout << "Error";
}
else
{
    file.seekg(0, ios::end);
    streamoff size = file.tellg();
    file.seekg(0, ios::beg);
    char *buffer = new char[size];
    file.read(buffer, size);
    file.close();
    for (int i = 0; i < size; i++)
    {
        cout <<hex<< buffer[i] << " ";
    }
}
delete[] buffer;
cin.get();
}

The expected output should be this:

00 e0 a2 20 62 08 60 f8 70 08 61 10 40 20 12 0e
d1 08 f2 1e 71 08 41 30 12 08 12 10 00 00 00 00
00 00 00 00 00 18 3c 3c 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
3e 3f 3f 3b 39 38 38 38 00 00 80 c1 e7 ff 7e 3c
00 1f ff f9 c0 80 03 03 00 80 e0 f0 78 38 1c 1c
38 38 39 3b 3f 3f 3e 3c 78 fc fe cf 87 03 01 00
00 00 00 00 80 e3 ff 7f 1c 38 38 70 f0 e0 c0 00
3c 18 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

Instead the above output I get some strange looking symbols with lots of empty spaces. It looks like this: What could be the problem?

Klaus · Accepted Answer · 2018-07-30T14:36:56.220

3

As you buffer is char all elements will be printed as characters. What you want is the number converted to hex.

BTW: As you want a conversion to hexadecimal output, it is a question if you really want to read char from file or unsigned char.

As you find out, the signature for istream.read uses char you have to convert before to unsigned char and than to unsigned int like:

cout <<hex<< (unsigned int)(unsigned char) buffer[i] << " ";

For real c++ users you should write a fine static_cast ;)

This will print out the hex values. But if you have a CR you will see a 'a' instead of '0a', so you have to set your width and fill char before:

cout.width(2);
cout.fill('0');

for (int i = 0; i < size; i++)
{   
    cout <<hex<< (unsigned int)(unsigned char)buffer[i] << " ";
}

BTW: delete[] buffer; is in wrong scope and must be shifted in the scope where it was defined.

edited Jul 30 '18 at 14:36

answered Jul 30 '18 at 14:09

Klaus

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You will need to `#include ` for this to work. – Sailanarmo Jul 30 '18 at 14:13
@Sailanarmo: and and – Klaus Jul 30 '18 at 14:16
@Klaus your solution works so far but there is a problem instead of `e0` I get `ffffffe0` and it happens to other values that are alphanumeric. – Kulten Jul 30 '18 at 14:23
1

@Kulten: That is what I expect by conversion from `char` to `unsigned int`. So make your buffer `unsigned char` as already written in my answer ;) ! – Klaus Jul 30 '18 at 14:25
@Klaus thank for you taking the time to help me, when I change `char` to `unsigned char` I get an error at the line `file.read(buffer, size);` saying `note: Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast`. – Kulten Jul 30 '18 at 14:28
@Kulten: OK, than do a double conversion, see edit of my answer! – Klaus Jul 30 '18 at 14:37
@Klaus was just about to comment that I fixed it by a double conversion lol, I did not see your prior comment or edit. Thank you so much. – Kulten Jul 30 '18 at 14:47

Displaying Hex codes from buffer after reading from a file

1 Answers1