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TableIterator Module Implementation Specifications

Client Specifications

Implementation Data Model

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

The advance() function usually just replaces the current entry pointer by the next 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 private function nextList(). This function is also used to initialize a TableIterator, after first setting its index to -1.

The currentData(), currentKey(), and advance() functions 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.

Private Importing Information

Source code for the TableIterator module is in Table.C and header information is in Table.h. Importing information is covered in Table Module Implementation Specifications.

Private Data Type Implementations

The following type is declared in Table.C.

TableIteratorNode - A TableIteratorNode is a typedeffed struct with the following members:
- Table table - the table that the iterator is iterating through
- int currentList - the index of the current hash list
- HashList currentEntry - a reference to the current iterator entry

Public Data Type Implementations

The following type is declared in Table.h.

TableIterator - TableIterator is typedeffed as a pointer to a TableIteratorNode.

Private Function Specifications

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

Private Function Algorithms

findNextList
Specification

parameter: TableIterator iter

increment iter->currentList
while iter->currentList < number of hash lists
    if iter->table->hashLists[iter->currentList] is not null
	break
    increment iter->currentList

Public Function Algorithms

iteratorFor
Client Specification

parameter: Table tbl

allocate a TableIteratorNode with malloc
set the table member to tbl
set the currentList member to -1
call startNextList with pointer to node as parameter

freeTableIterator
Client Specification

parameter: TableIterator iter

free iter

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

advance
Client Specification

parameter: TableIterator iter

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

currentKey
Client Specification

parameter: TableIterator iter

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

currentData
Client Specification

parameter: TableIterator iter

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

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