#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

int hex_char_to_int(char c) {
    if (c >= '0' && c <= '9') return c - '0';
    if (c >= 'A' && c <= 'F') return c - 'A' + 10;
    if (c >= 'a' && c <= 'f') return c - 'a' + 10;
    return -1;
}

int main() {
    // Extract EXI data starting from offset 0x0052 (after "80 98 02")
    // The complete EXI data from the hex dump
    const char* hex_string = "8098021050908c0c0c0e0c50d10032018600a01881ae0601860c806140c801030800006100001881980600";
    
    size_t hex_len = strlen(hex_string);
    if (hex_len % 2 != 0) {
        printf("Error: Hex string length must be even\n");
        return -1;
    }
    
    size_t binary_len = hex_len / 2;
    unsigned char* binary_data = malloc(binary_len);
    
    if (!binary_data) {
        printf("Memory allocation failed\n");
        return -1;
    }
    
    // Convert hex string to binary
    for (size_t i = 0; i < binary_len; i++) {
        int high = hex_char_to_int(hex_string[i * 2]);
        int low = hex_char_to_int(hex_string[i * 2 + 1]);
        
        if (high == -1 || low == -1) {
            printf("Invalid hex character at position %zu\n", i * 2);
            free(binary_data);
            return -1;
        }
        
        binary_data[i] = (high << 4) | low;
    }
    
    // Write to file
    FILE* file = fopen("test2.exi", "wb");
    if (!file) {
        printf("Cannot create output file\n");
        free(binary_data);
        return -1;
    }
    
    size_t written = fwrite(binary_data, 1, binary_len, file);
    fclose(file);
    free(binary_data);
    
    if (written != binary_len) {
        printf("Write error\n");
        return -1;
    }
    
    printf("Successfully created test2.exi with %zu bytes\n", binary_len);
    
    // Show first few bytes for verification
    printf("First 16 bytes: ");
    FILE* verify = fopen("test2.exi", "rb");
    if (verify) {
        for (int i = 0; i < 16 && i < binary_len; i++) {
            int c = fgetc(verify);
            printf("%02X ", c);
        }
        fclose(verify);
    }
    printf("\n");
    
    return 0;
}