Method readPageData

src/java/simpledb/storage/LogFile.java:252–290

(RandomAccessFile raf)

    }

    Page readPageData(RandomAccessFile raf) throws IOException {
        PageId pid;
        Page newPage = null;

        String pageClassName = raf.readUTF();
        String idClassName = raf.readUTF();

        try {
            Class<?> idClass = Class.forName(idClassName);
            Class<?> pageClass = Class.forName(pageClassName);

            Constructor<?>[] idConsts = idClass.getDeclaredConstructors();
            int numIdArgs = raf.readInt();
            Object[] idArgs = new Object[numIdArgs];
            for (int i = 0; i<numIdArgs;i++) {
                idArgs[i] = raf.readInt();
            }
            pid = (PageId)idConsts[0].newInstance(idArgs);

            Constructor<?>[] pageConsts = pageClass.getDeclaredConstructors();
            int pageSize = raf.readInt();

            byte[] pageData = new byte[pageSize];
            raf.read(pageData); //read before image

            Object[] pageArgs = new Object[2];
            pageArgs[0] = pid;
            pageArgs[1] = pageData;

            newPage = (Page)pageConsts[0].newInstance(pageArgs);

            //            Debug.log("READ PAGE OF TYPE " + pageClassName + ", table = " + newPage.getId().getTableId() + ", page = " + newPage.getId().pageno());
        } catch (ClassNotFoundException | InvocationTargetException | IllegalAccessException | InstantiationException e){
            e.printStackTrace();
            throw new IOException();
        }
        return newPage;

    }

    /** Write a BEGIN record for the specified transaction
        @param tid The transaction that is beginning