#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

int main(int argc, char *argv[]) {
    if (argc != 2) {
        printf("Usage: %s <file>\n", argv[0]);
        return 1;
    }

    FILE *file = fopen(argv[1], "r");

    if (file == NULL) {
        fprintf(stderr, "Failed to open file: %s\n", strerror(errno));
        return 1;
    }

    fseek(file, 0, SEEK_END);
    size_t filesize = ftell(file);
    fseek(file, 0, 0);

    char buffer[filesize + 1];
    fread(buffer, 1, filesize, file);
    buffer[filesize] = '\0';

    static int width = 0x10;
    size_t offset = 0;
    while (offset < filesize) {
        printf("%08lx: ", offset);

        // print hex chars
        for (int c = 0; c < 0x10; c++) {
            if (offset + c >= filesize)
                printf("  ");
            else {
                if ((buffer[offset + c] & 0xff) < 0x10)
                    printf("0");
                printf("%x", buffer[offset + c] & 0xff);
            }
            
            if (c % 2 != 0)
                printf(" ");
        }

        printf(" ");

        // print ASCII chars
        for (int o = 0; o < 0x10 && offset + o < filesize; o++) {
            char c = buffer[offset + o];
            if (c > 31)
                printf("%c", c);
            else
                printf(".");
        }

        printf("\n");
        offset += 0x10;
    }

    return 0;
}