Answered: ent and demonstrate a disk-based buffer…

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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Implement and demonstrate a disk-based buffer pool class based on the LRU buffer pool replacement strategy. Disk blocks are numbered consecutively from the beginning of the file with the first block numbered as 0. Assume that blocks are 4096 bytes in size. Use the supplied C++ files to implement your LRU Buffer Pool based on the instructions below.

Implement a BufferBlock class using the supplied BufferBlockADT.h

Your Buffer Block must inherit BufferBlockADT or you will not get credit for your work.
All BufferBlockADT virtual functions must be implemented in BufferBlock

Block Size: 4096 bytes
Add an instance variable to your buffer block implementation to store the block id; i.e., “int blockID.”

Implement a Buffer Pool by inheriting BufferPoolADT (BufferPoolADT.h) – implement all of BufferPoolADT’s functions

Your buffer pool should consist of 5 buffer blocks
Your buffer pool should manage the buffers using the LRU strategy
Your buffer pool should be named LRUBufferPool and the file containing the LRUBufferPool class should be named LRUBufferPool.h

Use the provided main.cpp and the included test file mydatafile.txt to test your program.

/* Assuming you initialize your buffer pool with blocks 0-4 and
* open the test file as a binary file, your output for the first
* three tests (file position 5030, 16500, and 24640) should look
* like the following:
*/

My data for block 1 is: "ment all o"
My buffer block order from most recently used to LRU is:
1, 0, 2, 3, 4,

My data for block 4 is: "e for the "
My buffer block order from most recently used to LRU is:
4, 1, 0, 2, 3,

My data for block 6 is: "ent a Buff"
My buffer block order from most recently used to LRU is:
6, 4, 1, 0, 2,

E#include "constants.h"
#include "LRUBufferPool.h"
using namespace std;
Bint main() {
//initialize buffer pool
LRUBufferPool* bp = new LRUBufferPool("mydatafile.txt", POOL_SIZE, BLOCKSIZE);
//get data from the buffer
char* data = new char[10];
bp->getBytes (data, 10, 5030);
printchars(data, 10, 5030/BLOCKSIZE);
bp->printBufferBlockorder ();
/*Output should be something like the following:
My data for block 1 is: "ment all o"
My buffer block order from most recently used to LRU is:
1, 0, 2, 3, 4,
//re-initialize the char array and get the next block of data
initializecharArray(10, data);
bp->getBytes (data, 10, 16500);
printchars (data, 10, 16500/BLOCKSIZE);
bp->printBufferBlockorder ();
/*Output should be something like the following:
My data for block 4 is: "e for the
My buffer block order from most recently used to LRU is:
4, 1, 0, 2, 3,
*/
//re-initialize the char array and get the next block of data
initializecharArray(10, data);
bp->getBytes (data, 10, 24640);
printchars(data, 10, 24640/BLOCKSIZE);
bp- >printBufferBlockorder();
/*Output should be something like the following:
My data for block 6 is: "ent a Buff"
My buffer block order from most recently used to LRU is:
6, 4, 1, 0, 2,
* /
//re-initialize the char array and get the next block of data
initializecharArray(10, data);
bp->getBytes(data, 10, 28700);
printchars (data, 10, 28700/BLOCKSIZE);
bp->printBufferBlockOrder ();
//re-initialize the char array and get the next block of data
initializecharArray(10, data);
bp->getBytes(data, 10, 16600);
printchars(data, 10, 16600/BLOCKSIZE);
bp->printBufferBlockOrder ();
//close program
cout <« endl << endl;
system("pause");
return 0;

#ifndef BUFFERPOOLADT H
#define BUFFERPOOLADT H
tinclude <string>
using namespace std;
// ADT for buffer pools using the message-passing style
class BufferPoolADT {
private:
//The buffer pool consists of X number of buffer blocks
public:
//Constructor gets the filename of the file to be buffered,
//opens the file, and instantiates poolSize buffer blocks by
//reading the file and filling the blocks in order.
//is done the buffer pool blocks should be full with the beginning
//contents of the input file.
BufferPoolADT() {}
When the constructor
4096) {}
BufferPoolADT (string filename, int poolSize
virtual ~BufferPoolADT() {}
5, int blockSize
// Copy "sz." bytes from position "pos" of the buffered
//
virtual void getBytes(char* space, int sz,
storage to "space".
int pos)
0;
// Print the order of the buffer blocks using the block id
//
numbers.
virtual void printBufferBlockOrder()
0;
// Get the block id number of the least recently used
//
buffer block.
virtual int getLRUBlockID()
};
0;
tendif
/* BUFFERPOOLADT.H */

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