如何添加2个四位十六进制以构成ASCII字符字节

Question

I have a binary file from a source, from which i have to retrive data so that it is read in human readable form. I have retrived the data and have it in the 4 bit hexa. For eg the file size is 256 byte and i am retrieving it in hexa and getting 512 4 bit hexa values. Now, to make it human readable ASCII chars, i have to add two 4 bit hexa to make a byte. The way i am retrieving the data in Hex format is

byte = read_buffer[i];

// Convert the Most Significant nibble for first byte
write_buffer_hex[(i + 1) * 2 + 0] = hex_chars[(byte >> 4)];

// Convert the Least Significant nibble for the first byte
write_buffer_hex[(i + 1) * 2 + 1] = hex_chars[byte & 0x0f];

Now, my question is how should i add these two hex values to have a ASCII value. The way i am doing now is to just add these two, but is it the correct way ??. Thank you

Answer 1

I agree with John, it may be easier to output it directly in the hexadecimal basis like so:

printf("%x", byte);

or with C++'s IOstream library:

cout << hex << byte;

Answer 2

Use a lookup table:

static char const alphabet[] = "0123456789ABCDEF";

// Loop:

output[cursor++] = alphabet[byte % 16];
output[cursor++] = alphabet[byte / 16];

You can index directly into the string, too:

output[cursor++] = "0123456789ABCDEF"[byte % 16];