/*
 * iohelper.c
 * 
 * Alexander Occhipinti
 * Student ID: 29994705
 * Created: 10 Sep 2020
 * Last Modified: 10 Sep 2020
 * 
 * iohelper is a small, simple library containing light wrapper functions to Linux system calls.
 * The functions in iohelper are similar to what would normally be provided in C's stdio.h library.
 *  
*/

#include <unistd.h>
#include <sys/file.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include "iohelper.h"

/*
 * Prints a given string to stdout. Returns nothing.
*/
void to_stdout(char *string) {
    write(1, string, strlen(string));
}

/*
 * Prints a given string to stderr. Returns nothing.
*/
void to_stderr(char *string) {
    write(2, string, strlen(string));
}

/*
 * Given a file path and open() flags, open a file
 * Catches openning errors, prints an error to stderr when an error occurs and exits 
 * Returns a file descriptor of the open file. Needs to be closed afterwards.
*/
int open_file(char *path, int flags){
        // Read the input file
    int fd;
    if ((fd = open(path, flags, NEW_FILE_PERMS)) < 0){
        int error = errno;
        to_stderr(path);
        to_stderr(" could not be opened: ");
        to_stderr(strerror(error));
        to_stderr("\n");
        // Exit as error 2 if the file exists and can not be overwriten
        if (errno == EEXIST) exit(2);
        exit(1); // Exit with 1 otherwise
    }
    return fd;
}

/*
 * Given a source file descriptor open for reading, 
 * put all of its contents in the destination file descriptor open for writing.
 * 
 * Useful for transferring data between files or stdin/stdout/stderr
*/
void file_into_file(int source_fd, int dest_fd){
    int bytes_read;
    char buffer[FILE_BUF_SIZE];
    while ((bytes_read = read(source_fd, buffer, FILE_BUF_SIZE))) {
        write(dest_fd, buffer, bytes_read);
    }

}