Binary include for bin86/as86

#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

void printUsageHelp()
{
    printf("as86 binary includer\n\n");
    printf("\t Usage: as86_binin assembler_binary as86_symbol_file label_name include_file\n\n");
    printf("as86_binin replaces the content of the 'assembler_binary' starting from the offset of the label 'label_name' found in 'as86_symbol_file' with the content of 'include_file'. Make sure you created enough space in the binary, i.e. by using .SPACE\n");
}

int main(int argc, char* argv[]) {
    if (argc != 5) {
        printUsageHelp();
        return 1;
    }

    int bin_desc, symbol_desc, inc_desc;

    if ((bin_desc = open(argv[1], O_RDWR)) == -1)
    {
        printf("Could not open binary file '%s'\n", argv[1]);
        return 1;
    }
    if ((symbol_desc = open(argv[2], O_RDONLY)) == -1)
    {
        close(bin_desc);
        printf("Could not open symbol file '%s'\n", argv[2]);
        return 1;
    }
    if((inc_desc = open(argv[4], O_RDONLY)) == -1)
    {
        close(bin_desc);
        close(symbol_desc);
        printf("Could not open include file '%s'\n", argv[4]);
        return 1;
    }

    long size = lseek(symbol_desc, 0, SEEK_END);
    lseek(symbol_desc, 0, SEEK_SET);

    char *buffer = (char*)malloc(size + 1);
    read(symbol_desc, buffer, size);
    buffer[size + 1] = 0;

    int search_lenght = strlen(argv[3]);
    char *pattern = (char*)malloc(search_lenght + 2);
    pattern[0] = ' ';
    strcpy(pattern + 1, argv[3]);

    char* hex_string = strstr(buffer, pattern);

    if (hex_string == 0 || hex_string < buffer + 14) {
        printf("Incompatible symbol file '%s'\n", argv[2]);

        free(buffer);
        free(pattern);

        close(bin_desc);
        close(symbol_desc);
        close(inc_desc);

        return 1;
    }

    hex_string -= 14; // hex number sequence is 14 chars in front of the symbol name with whitespace (simply the file format)

    long bin_offset = strtol(hex_string, 0, 16);

    free(buffer);
    free(pattern);
    close(symbol_desc);


    size = lseek(inc_desc, 0, SEEK_END);
    lseek(inc_desc, 0, SEEK_SET);

    buffer = (char*)malloc(size);

    lseek(bin_desc, bin_offset, SEEK_SET);

    if (read(inc_desc, buffer, size) == -1)
    {
        printf("Could read from include file '%s'\n", argv[4]);

        free(buffer);

        close(bin_desc);
        close(inc_desc);

        return 1;
    }
    if (write(bin_desc, buffer, size) == -1)
    {
        printf("Could not write to binary file '%s'\n", argv[1]);

        free(buffer);

        close(bin_desc);
        close(inc_desc);

        return 1;
    }

    free(buffer);

    close(bin_desc);
    close(inc_desc);

    return 0;
}