Convert char array to hex array

Question

Input:

char arr1[9] = "+100-200"  // (+ is 2B, - is 2D, 1 is 31 and 2 is 32)

Output:

unsigned int arr2[4]= [0x2B31,0x3030,0x2D32,0x3030]

How can I do this?

Cast to unsigned char for safety. An unsigned char is a small integer in the range 0-0xFF. Two of them can be combined to mkae a 16-bit integer in the range 0-0xFFFF simply by bit shifting and logical or-ing — Malcolm McLean
– Malcolm McLean, Commented Feb 5, 2017 at 12:54
@MalcolmMcLean: to accomodate 16-bit ints, it would be safer to cast the result to (unsigned int) before shifting. The specific values in the example would not pose a problem, but the code should be as generic and portable as possible. — chqrlie
– chqrlie, Commented Feb 5, 2017 at 12:57

chqrlie · Accepted Answer · 2017-02-05 13:07:17Z

1

Your question seems inconsistent: 0 should convert to 0x30, its ASCII value.

Why this modification, the code is quite straightforward:

char arr1[8] = "+100-200";
unsigned int arr2[4];

for (int i = 0; i < 8; i += 2) {
    arr2[i / 2] = ((unsigned int)(unsigned char)arr1[i] << 8) |
                   (unsigned int)(unsigned char)arr1[i + 1];
}

for (int i = 0; i < 4; i++) {
    printf("0x%04X ", arr2[i]);
}
printf("\n");

Output:

0x2B31 0x3030 0x2D32 0x3030

edited Feb 5, 2017 at 13:07

answered Feb 5, 2017 at 12:54

chqrlie

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1 Comment

AM_87 Over a year ago

Thanks all for the help, I have edited the original post to make the question clear.

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