package simpledb.file;
   
   /**
    * A reference to a disk block.
    * A Block object consists of a filename and a block number.
    * It does not hold the contents of the block;
    * instead, that is the job of a {@link Page} object.
    * @author Edward Sciore
    */
  public class Block {
     private String filename;
     private int blknum;
     
     /**
      * Constructs a block reference 
      * for the specified filename and block number.
      * @param filename the name of the file
      * @param blknum the block number
      */
     public Block(String filename, int blknum) {
        this.filename = filename;
        this.blknum   = blknum;
     }
     
     /**
      * Returns the name of the file where the block lives.
      * @return the filename
      */
     public String fileName() {
        return filename;
     }
     
     /**
      * Returns the location of the block within the file.
      * @return the block number
      */
     public int number() {
        return blknum;
     }
     
     public boolean equals(Object obj) {
        Block blk = (Block) obj;
        return filename.equals(blk.filename) && blknum == blk.blknum;
     }
     
     public String toString() {
        return "[file " + filename + ", block " + blknum + "]";
     }
     
     public int hashCode() {
        return toString().hashCode();
     }
  }