从文本文件读取十六进制

Question

I am new to C and would like to ask the following question which I have struggled for a period of time. :( Please help!

I want to read a plaintext file, passout.txt which contains a string of hexadecimal like:

A1B2C3D4E5403E9D501B223AD45523D6

and put them into an array like :

{A1, B2, C3, D4, E5, 40, 3E, 9D, 50, 1B, 22, 3A, D4, 55, 23, D6}

However, my current output is only :

{D4, 55, 23, D6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}

Only the last four hexidecimals can be retrieved only! I really don't know what mistakes I have made and I couldn't find any related solution from the web! Therefore, would anybody please help?

Here's my code!

#include <stdio.h>
#include <string.h>
#include <openssl/aes.h>

#define AES_BLOCK_SIZE 16

void main()
{
    FILE *ifp;
    int i, rv;
    unsigned char in[AES_BLOCK_SIZE] = {0};

    ifp = fopen("passout.txt", "r");

    // loop and read the input file
    for(i = 0; i < AES_BLOCK_SIZE; i++)
    {
        rv = fscanf(ifp, "%X", &in[i]);
        if(rv != 1)
            i = AES_BLOCK_SIZE;
    }

    printf("Print result: \n");
    for(i=0; i < AES_BLOCK_SIZE; i++)
        printf("%X ",*(in+i));
    printf("\n");   

    fclose(ifp);
}

Answer 1

rv = fscanf(ifp, "%X", &in[i]);

change to

rv = fscanf(ifp, "%2hhX", &in[i]);

---

for before C99

unsigned X;
rv = fscanf(ifp, "%2X", &X);
if(rv != 1)
    break;
in[i] = (unsigned char)X;

Answer 2

Your approach fails since the output format of sscanf is one number.

Your approach fails since the output format of sscanf is one number.You need to copy pairs of hex digits to a buffer and convert each pair to a byte. This allows to convert any length of hex string.