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TableIterator Module Implementation Specifications

Client Specifications

Implementation Data Model

A TableIterator is an object that contains a reference to the Table that it is iterating, an index into the array of hash lists for the Table, and a reference to the current entry for the TableIterator. The more() method returns true when the array index is a valid index into the array of hash lists. The currentData() and currentKey() methods return data and keys accessed through the current entry reference.

The advance() method usually just replaces the current entry by the rest member of the current entry. However, when this value is null, the advance must proceed to the first entry on the next non-empty hash list of the table. This is accomplished by the protected method nextList(). This method is also used to initialize a TableIterator, after first setting its index to -1.

The currentData(), currentKey(), and advance() methods all call more() before doing anything else in order to check their preconditions. If this check fails then the program is terminated with an error message.

Instance Variables

Table table - the Table for this TableIterator
HashList currentEntry - the current entry for this TableIterator
int currentList - the index of the current list in the hash lists array for table

Private Method Specifications

void startNextList()
startNextList() advances the current position of this TableIterator to the start of the next non-empty hash list in table.

Private Method Algorithms

startNextList
Specification

increment currentList
while currentList < number of hash lists
    if table.hashLists[currentList] is not null
	set currentEntry to table.hashLists[currentList]
	break
    increment currentList

Public Method Algorithms

TableIterator
Client Specification

parameter: Table tbl

set table to tbl
set currentList to -1
call startNextList

more
Client Specification
```
return index < number of hash lists
```

advance
Client Specification

if more() is false
    terminate program with precondition violation error message
advance currentEntry to next entry in list
if currentEntry is null
    call startNextList

currentKey
Client Specification

if more() is false
    terminate program with precondition violation error message
return currentEntry.key

currentData
Client Specification

if more() is false
    terminate program with precondition violation error message
return currentEntry.data

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