iterator
Class OBuf

java.lang.Object
  iterator.OBuf

All Implemented Interfaces:

GlobalConst

public class OBuf

extends java.lang.Object

implements GlobalConst

O_buf::Put takes tuples and stores them on the buffer pages that were passed to O_buf::init. O_buf::flush inserts them enmass into a temporary HeapFile.

Field Summary

Fields inherited from interface global.GlobalConst

INVALID_PAGE, MAX_NAME, MAX_SPACE, MAXATTRNAME, MAXFILENAME, MAXINDEXNAME, MINIBASE_BUFFER_POOL_SIZE, MINIBASE_DB_SIZE, MINIBASE_DEFAULT_SHAREDMEM_SIZE, MINIBASE_MAX_TRANSACTIONS, MINIBASE_MAXARRSIZE, MINIBASE_PAGESIZE, NUMBUF

Constructor Summary

OBuf()
fault constructor no args -- use init to initialize

Method Summary

long	flush() returns the # of tuples written.
void	init(byte[][] bufs, int n_pages, int tSize, Heapfile temp_fd, boolean buffer) O_buf is an output buffer.
Tuple	Put(Tuple buf) Writes a tuple to the output buffer

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

OBuf

public OBuf()

fault constructor no args -- use init to initialize

Method Detail

init

public void init(byte[][] bufs,
                 int n_pages,
                 int tSize,
                 Heapfile temp_fd,
                 boolean buffer)

O_buf is an output buffer. It takes as input:

Parameters:

bufs - temporary buffer to pages.(EACH ELEMENT IS A SINGLE BUFFER PAGE).

n_pages - the number of pages

tSize - tuple size

temp_fd - fd of a HeapFile

buffer - true => it is used as a buffer => if it is flushed, print a nasty message. it is false by default.

Put

public Tuple Put(Tuple buf)
          throws java.io.IOException,
                 java.lang.Exception

Writes a tuple to the output buffer

Parameters:

buf - the tuple written to buffer

Returns:

the position of tuple which is in buffer

Throws:

java.io.IOException - some I/O fault

java.lang.Exception - other exceptions

flush

public long flush()
           throws java.io.IOException,
                  java.lang.Exception

returns the # of tuples written.

Returns:

the numbers of tuples written

Throws:

java.io.IOException - some I/O fault

java.lang.Exception - other exceptions