C_and_CPP(#1Gw0vUeU)

ptt.c

#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>

#include <stdlib.h>
#include <stddef.h>

#define READ_BUFFER_SIZE 10

enum FileState
{
    FILE_STATE_UNOPENED, 
    FILE_STATE_READING,
    FILE_STATE_ENDREAD,
};

struct File
{
    int descriptor;
    enum FileState state;
};

void open_file( char const * name, 
                struct File * file ) {

    file->descriptor = open( name, O_RDONLY );
    file->state = FILE_STATE_READING;
}

void read_file( struct File * file,
                char * buffer, size_t size ) {

    if( file->state != FILE_STATE_READING )
        return;

    int read_bytes = read( file->descriptor, 
                           buffer, size-1 );

    if( !read_bytes ) {
        file->state = FILE_STATE_ENDREAD;
        close( file->descriptor );
    }
    buffer[ read_bytes ] = '\0';
}

void close_file( struct File * file ) {
    if( file->state != FILE_STATE_ENDREAD )
        return;
    
    file->state = FILE_STATE_UNOPENED; 
    close( file->descriptor );
}

int main() {
    
    struct File file; 
    char read_buffer[ READ_BUFFER_SIZE ];
    
    open_file( "input.txt", &file );

    while( read_file(&file, read_buffer, READ_BUFFER_SIZE), 
           file.state != FILE_STATE_ENDREAD ) {

        puts( read_buffer );

    }

    close_file( &file );
    
    return EXIT_SUCCESS;
}