lookup function in OpenFOAM

The lookup function in OpenFOAM

The lookup function is defined in dictionary.H and dictionary.C:

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ITstream& lookup
(
 const word&,
 bool recursive=false,
    bool patternMatch=true
) const;

Foam::ITstream& Foam::dictionary::lookup
(
    const word& keyword,
    bool recursive,
    bool patternMatch
) const
{
    return lookupEntry(keyword, recursive, patternMatch).stream();
}

The return of this function will call:

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const Foam::entry& Foam::dictionary::lookupEntry
(
    const word& keyword,
    bool recursive,
    bool patternMatch
) const
{
    const entry* entryPtr = lookupEntryPtr(keyword, recursive, patternMatch);

    ......

    return *entryPtr;
}

The looupEntry function will call:

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Foam::entry* Foam::dictionary::lookupEntryPtr
(
    const word& keyword,
    bool recursive, // false
    bool patternMatch // true
)
{
    HashTable<entry*>::iterator iter = hashedEntries_.find(keyword);

    ......

    return iter();
}

The hashedEntries_ is defined as:

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//- HashTable of the entries held on the DL-list for quick lookup
HashTable<entry*> hashedEntries_;

Here the find function defined in the HashTable is used:

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//- Find and return an iterator set at the hashedEntry
//  If not found iterator = end()
iterator find(const Key&);

The returned iter() call the operator() of class iterator which is a class defined in HashTable class.

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template<class T, class Key, class Hash>
inline T&
Foam::HashTable<T, Key, Hash>::iterator::operator()()
{
    return this->object();
}

The object function is defined inside the iterator class in HashTableI.H:

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template<class T, class Key, class Hash>
inline T&
Foam::HashTable<T, Key, Hash>::iteratorBase::object()
{
    return entryPtr_->obj_;
}

The entryPtr_ is an object with a type of hashedEntry*:

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//- Current element
hashedEntry* entryPtr_;

The hashedEntry is a struct defined in HashTable class:

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struct hashedEntry
{
    ......
 
    //- The data object
    T obj_;
    
    ......
};