How to convert char array to a byte array in C program

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how can I convert a hex char array to a byte array?

for eg

data[]="600ffe422b4e00731a59557a5cca46cc183944191006324a447bdb2d98d4b408

"

how can I convert this array to a byte array strictly in c language

What I have tried:

.....................................................................................

Posted 23-Mar-20 20:29pm

Asish6542165

Updated 23-Mar-20 21:05pm

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phil.o · Accepted Answer · 2020-03-23T20:34:00

Solution 1

Here you can find an example implementation for C:
c - How to turn a hex string into an unsigned char array? - Stack Overflow[^]

Posted 23-Mar-20 20:34pm

phil.o

Comments

Rick York 24-Mar-20 2:54am

Hopefully he is able to figure out how to peel off one character at a time into a temporary string and convert that.

CPallini 24-Mar-20 3:01am

5.

Asish6542165 26-Mar-20 9:06am

thanks

OriginalGriff · Accepted Answer · 2020-03-23T21:06:00

Oh come on - is there anything you do know how to do for yourself? OK, Hashes can get a little complex, but this is a trivial task that shouldn't be beyond the average beginner after the second week of his course...

Allocate a new array of bytes: in the char array is n chars, then the length should be (n - 1) / 2 + 1 bytes.
Write a function that accepts a hex char, and returns a byte. That's pretty trivial, the simplest solution (though not the best) is a basic switch :

C++

unsigned char FromHex(char c)
   {
   switch(c)
      {
      case '0': return 0;
      case '1': return 1;
      case '2': return 2;
      case '3': return 3;
      case '4': return 4;
      case '5': return 5;
      case '6': return 6;
      case '7': return 7;
      case '8': return 8;
      case '9': return 9;
      case 'a': return 10;
      case 'b': return 11;
      case 'c': return 12;
      case 'd': return 13;
      case 'e': return 14;
      case 'f': return 15;
      }
   // Report a problem here!
   ...
   return -1;
   }

Then loop through your char array in pairs.
Use the FromHex function to convert each character to binary, and use the Left Shift operator << to move the first result to the high byte, and binary OR iot with teh low byte:

C++

b1 = FromHex(InputData[i++];
b2 = FromHex(INputData[i++};
b = (b1 << 4) | b2;

Then insert that byte into your output array.

30 seconds of actual thinking would have got you that: so why did you ask us?