Converting an int to a 2 byte hex value in C

Question

I need to convert an int to a 2 byte hex value to store in a char array, in C. How can I do this?

Answer 1

Figured out a quick way that I tested out and it works.

int value = 11;

array[0] = value >> 8;
array[1] = value & 0xff;

printf("%x%x", array[0], array[1]);

result is:

000B

which is 11 in hex.

Answer 2

unsigned int hex16 = ((unsigned int) input_int) & 0xFFFF;

input_int is the number you want to convert. hex16 will have the least significant 2 bytes of input_int. If you want to print it to the console, use %x as the format specifier instead of %d and it will be printed in hex format.

Answer 3

Normally I would recommend using the sprintf based solutions recommended by others. But when I wrote a tool that had to convert billions of items to hex, sprintf was too slow. For that application I used a 256 element array, which maps bytes to strings.

This is an incomplete solution for converting 1 byte, don't forget to add bounds checking, and make sure the array is static or global, recreating it for every check would kill performance.

static const char hexvals[][3]= {"00", "01", "02", ... "FD", "FE", "FF"};
const char *byteStr = hexvals[number];

Answer 4

you can use this it is simple and easy to convert

typedef union {
    struct hex{
            unsigned  char a;
            unsigned  char b;

    }hex_da;
    short int dec_val;
}hex2dec;

hex2dec value;
value.dec_val=10;

Now hex value is stored in hex_da structure access it for further use.

Answer 5

This function works like a charm.

void WORD2WBYTE(BYTE WBYTE[2], WORD Value) { 
    BYTE tmpByte[2]; 
    // Converts a value from word to word byte ----
    memcpy(tmpByte, (BYTE*) & Value, 2); 
    WBYTE[1] = tmpByte[0]; 
    WBYTE[0] = tmpByte[1]; 
} 

asumming the following:

typedef unsigned char   BYTE; 
typedef unsigned short  WORD;

Example of use:

we want to achieve this:

integer = 92
byte array in hex:
a[0] = 0x00;
a[1] = 0x5c;

unsigned char _byteHex[2];
WORD2WBYTE(_byteHex, 92);

Answer 6

Rather than sprintf, I would recommend using snprintf instead.

#include <stdio.h>

int main()
{
    char output[5];
    snprintf(output,5,"%04x",255);

    printf("%s\n",output);
    return 0;
}

Its a lot safer, and is available in pretty much every compiler.