OS-11

object_Author.java

package io.mappedbus.sample.object;

import io.mappedbus.MappedBusWriter;

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Author {

    public static void main(String[] args) {
        Author author = new Author();
        author.run();
    }

    public void run() {

        try {
            MappedBusWriter writer = new MappedBusWriter("messages", 2000000L, 100);
            writer.open();

            BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
            String title = reader.readLine();

            BookToSell bookToSell = null;


            while (title.length() > 0) {
                bookToSell = new BookToSell(new Book(title));
                writer.write(bookToSell);
                title = reader.readLine();
            }

        } catch(Exception e) {
            e.printStackTrace();
        }
    }
}

object_Book.java

package io.mappedbus.sample.object;

public class Book {

    private String title;

    public Book(String title) {
        this.title = title;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }
}

object_BookShop.java

package io.mappedbus.sample.object;

import io.mappedbus.MappedBusMessage;
import io.mappedbus.MappedBusReader;

import java.io.File;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.concurrent.Semaphore;

public class BookShop {

    private static final int SHOP_CAPACITY = 10;
    private static final Semaphore SEMAPHORE = new Semaphore(1, true);
    private static ArrayList<Book> books;

    public static void main(String[] args) {
        BookShop server = new BookShop();
        server.books = new ArrayList<>(SHOP_CAPACITY);
        server.run();
    }

    public void run() {

        books.add(new Book("Biased"));
        books.add(new Book("Never again"));
        books.add(new Book("Never again II"));

        try {

            PrintWriter writer = new PrintWriter("messages", "UTF-8");
            writer.close();

            MappedBusReader reader = new MappedBusReader("messages", 2000000L, 100);
            reader.open();

            DemandedBook demandedBook = new DemandedBook();
            BookToSell bookToSell = new BookToSell();
            MappedBusMessage message = null;

            while (true) {
                if (reader.next()) {
                    int type = reader.readType();

                    switch (type) {
                        case DemandedBook.TYPE:
                            message = demandedBook;
                            reader.readMessage(message);

                            String bookTitle = ((DemandedBook) message).getTitle();
                            new Thread(new BookSeller(bookTitle)).start();
                            break;

                        case BookToSell.TYPE:
                            message = bookToSell;
                            reader.readMessage(message);

                            Book book = ((BookToSell) message).getBook();
                            new Thread(new BookAdder(book)).start();
                            break;

                        default:
                            throw new RuntimeException("Unknown type: " + type);
                    }
                }
            }
        } catch(Exception e) {
            e.printStackTrace();
        }
    }

    class BookAdder implements Runnable {

        Book book;

        public BookAdder(Book book) {
            this.book = book;
        }

        @Override
        public void run() {
            try {

                System.out.println(String.format("Author is trying to sell their book entitled as \"%s\"...", book.getTitle()));
                BookShop.SEMAPHORE.acquire();

                if (BookShop.books.size() == SHOP_CAPACITY) {
                    System.out.println("All bookshelves are full. Please, try to add \"" + book.getTitle() + "\" again later...");
                } else {
                    BookShop.books.add(book);
                    System.out.println("The book \"" + book.getTitle() + "\" has been successfully added to the range of the book store!");
                }

                BookShop.SEMAPHORE.release();
                System.out.println("Author left the book store.\n");

            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

    class BookSeller implements Runnable {

        String bookTitle;

        public BookSeller(String bookTitle) {
            this.bookTitle = bookTitle;
        }

        @Override
        public void run() {
            try {

                System.out.println(String.format("Customer is looking for \"%s\"...", bookTitle));
                BookShop.SEMAPHORE.acquire();

                Book book = null;

                for (Book bookFromShop : books) {
                    if (bookFromShop.getTitle().equals(bookTitle)) {
                        book = bookFromShop;
                        break;
                    }
                }

                if (book == null) {
                    System.out.println("There's no such book as \"" + bookTitle + "\" in the range available.");
                } else {
                    System.out.println("There's a book entitled as \"" + bookTitle + "\". Selling it to the customer...");
                    books.remove(book);
                    System.out.println("The book \"" + book.getTitle() + "\" has been sold.");
                }

                BookShop.SEMAPHORE.release();
                System.out.println("Customer left the book store.\n");

            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

object_BookToSell.java

package io.mappedbus.sample.object;

import io.mappedbus.MappedBusMessage;
import io.mappedbus.MemoryMappedFile;

public class BookToSell implements MappedBusMessage {

    public static final int TYPE = 2;

    private Book book;

    public BookToSell() {
        this.book = new Book("Untitled Book");
    }

    public BookToSell(Book book) {
        this.book = book;
    }

    public int type() {
        return TYPE;
    }

    public Book getBook() {
        return book;
    }

    public void setBook(Book book) {
        this.book = book;
    }

    @Override
    public String toString() {
        return book.getTitle();
    }

    @Override
    public void write(MemoryMappedFile mem, long pos) {
        String title = book.getTitle();

        mem.putInt(pos, title.length());
        for (int i = 0; i < title.length(); i++)
            mem.putByte(pos + 4 + i, (byte) title.charAt(i));
    }

    @Override
    public void read(MemoryMappedFile mem, long pos) {
        int length = mem.getInt(pos);
        byte[] bytes = new byte[length];

        for (int i = 0; i < length; i++) {
            bytes[i] = mem.getByte(pos + 4 + i);
        }

        String title = new String(bytes);
        book = new Book(title);
    }
}

object_Customer.java

package io.mappedbus.sample.object;

import io.mappedbus.MappedBusWriter;

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Customer {

    public static void main(String[] args) {
        Customer customer = new Customer();
        customer.run();
    }

    public void run() {

        try {
            MappedBusWriter writer = new MappedBusWriter("messages", 2000000L, 100);
            writer.open();

            DemandedBook demandedBook = new DemandedBook();

            BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
            String title = reader.readLine();

            while (title.length() > 0) {
                demandedBook.setTitle(title);
                writer.write(demandedBook);
                title = reader.readLine();
            }

        } catch(Exception e) {
            e.printStackTrace();
        }
    }

}

object_DemandedBook.java

package io.mappedbus.sample.object;

import io.mappedbus.MappedBusMessage;
import io.mappedbus.MemoryMappedFile;

public class DemandedBook implements MappedBusMessage {

    public static final int TYPE = 1;

    private String title;

    public DemandedBook() {
        this.title = "Untitled Book";
    }

    public DemandedBook(String title) {
        this.title = title;
    }

    public int type() {
        return TYPE;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    @Override
    public String toString() {
        return title;
    }

    @Override
    public void write(MemoryMappedFile mem, long pos) {
        mem.putInt(pos, title.length());
        for (int i = 0; i < title.length(); i++)
            mem.putByte(pos + 4 + i, (byte) title.charAt(i));
    }

    @Override
    public void read(MemoryMappedFile mem, long pos) {
        int length = mem.getInt(pos);
        byte[] bytes = new byte[length];

        for (int i = 0; i < length; i++) {
            bytes[i] = mem.getByte(pos + 4 + i);
        }

        title = new String(bytes);
    }
}