ENH: PtrList, PtrDynList, HashPtrTable try_emplace() method

- naming like std::map::try_emplace(), it behaves like emplace_set()
  if there is no element at the given location otherwise a no-op

ENH: reuse existing HashPtrTable 'slot' when setting pointers

- avoids extra HashTable operations

applications/test/Dictionary/Test-Dictionary.C

@@ -55,10 +55,7 @@ public:
         i_(i)
     {}
 
-    const word& keyword() const
-    {
-        return keyword_;
-    }
+    word& keyword() const noexcept { return keyword_; }
 
     friend Ostream& operator<<(Ostream& os, const ent& e)
     {
@@ -74,28 +71,27 @@ class Scalar
 
 public:
 
-    Scalar()
-    :
-        data_(0)
-    {}
+    static bool verbose;
 
-    Scalar(scalar val)
-    :
-        data_(val)
-    {}
+    constexpr Scalar() noexcept : data_(0) {}
+    Scalar(scalar val) noexcept : data_(val) {}
 
     ~Scalar()
     {
-        Info<<"delete Scalar: " << data_ << endl;
+        if (verbose) Info<< "delete Scalar: " << data_ << endl;
     }
 
-    friend Ostream& operator<<(Ostream& os, const Scalar& val)
+    scalar value() const noexcept { return data_; }
+    scalar& value() noexcept { return data_; }
+
+    friend Ostream& operator<<(Ostream& os, const Scalar& item)
     {
-        os  << val.data_;
+        os  << item.value();
         return os;
     }
 };
 
+bool Scalar::verbose = true;
 
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

applications/test/HashPtrTable/Test-HashPtrTable.C

@@ -44,38 +44,28 @@ class Scalar
 
 public:
 
-    Scalar()
-    :
-        data_(0)
-    {}
+    static bool verbose;
 
-    Scalar(scalar val)
-    :
-        data_(val)
-    {}
+    constexpr Scalar() noexcept : data_(0) {}
+    Scalar(scalar val) noexcept : data_(val) {}
 
     ~Scalar()
     {
-        Info<<"delete Scalar: " << data_ << endl;
+        if (verbose) Info<< "delete Scalar: " << data_ << endl;
     }
 
-    const scalar& value() const
-    {
-        return data_;
-    }
+    const scalar& value() const noexcept { return data_; }
+    scalar& value() noexcept { return data_; }
 
-    scalar& value()
+    friend Ostream& operator<<(Ostream& os, const Scalar& item)
     {
-        return data_;
-    }
-
-    friend Ostream& operator<<(Ostream& os, const Scalar& val)
-    {
-        os  << val.data_;
+        os  << item.value();
         return os;
     }
 };
 
+bool Scalar::verbose = true;
+
 
 template<class T>
 void printTable(const HashPtrTable<T>& table)
@@ -129,6 +119,9 @@ int main()
     myTable.set("natlog", new double(2.718282));
     myTable.insert("sqrt2", autoPtr<double>::New(1.414214));
     myTable.insert("euler", autoPtr<double>::New(0.577216));
+    myTable.set("def_0", nullptr);
+    myTable.emplace_set("def_1", 123);
+    myTable.emplace_set("def_2", 456);
 
     HashTable<std::unique_ptr<double>> myTable1;
 
@@ -146,6 +139,14 @@ int main()
     Info<< "Initial table" << nl;
     printTable(myTable);
 
+    myTable.try_emplace("def_0", 1000);  // was nullptr, now value
+    myTable.try_emplace("def_1", 1001);  // no-op
+    myTable.try_emplace("def_2", 1002);  // no-op;
+    myTable.try_emplace("def_3", 1003);  // was non-existent, now value
+
+    Info<< "after try_emplace" << nl;
+    printTable(myTable);
+
     Info<< "print" << nl;
     Info<< myTable2 << nl;
 

applications/test/ISLList/Test-ISLList.C

@@ -46,26 +46,27 @@ class Scalar
 {
 public:
 
+    // static bool verbose;
+
     scalar data_;
 
-    Scalar()
-    :
-        data_(0)
-    {}
+    Scalar() : data_(0) {}
+    Scalar(scalar val) : data_(val) {}
 
-    Scalar(scalar s)
-    :
-        data_(s)
-    {}
+    // ~Scalar() {}
 
-    friend Ostream& operator<<(Ostream& os, const Scalar& s)
+    scalar value() const noexcept { return data_; }
+    scalar& value() noexcept { return data_; }
+
+    friend Ostream& operator<<(Ostream& os, const Scalar& item)
     {
-        os  << s.data_;
+        os  << item.value();
         return os;
     }
-
 };
 
+// bool Scalar::verbose = true;
+
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 //  Main program:

applications/test/PtrList/Test-PtrList.C

@@ -49,15 +49,8 @@ public:
 
     static bool verbose;
 
-    constexpr Scalar() noexcept
-    :
-        data_(0)
-    {}
-
-    Scalar(scalar val) noexcept
-    :
-        data_(val)
-    {}
+    constexpr Scalar() noexcept : data_(0) {}
+    Scalar(scalar val) noexcept : data_(val) {}
 
     ~Scalar()
     {
@@ -67,10 +60,7 @@ public:
     scalar value() const noexcept { return data_; }
     scalar& value() noexcept { return data_; }
 
-    autoPtr<Scalar> clone() const
-    {
-        return autoPtr<Scalar>::New(data_);
-    }
+    autoPtr<Scalar> clone() const { return autoPtr<Scalar>::New(data_); }
 
     friend Ostream& operator<<(Ostream& os, const Scalar& item)
     {
@@ -361,15 +351,19 @@ int main(int argc, char *argv[])
         list2.emplace(i, (10 + 1.3*i));
     }
 
-    #if 0
     list2.release(5);
     list2.release(10);
 
-    forAll(list2, i)
     {
-        list2.try_emplace(i, (50 + 1.3*i));
+        // Memory error (with fulldebug): const label len = (list2.size()+2);
+        const label len = list2.size();
+        Info<< "try_emplace " << len << " values" << nl;
+
+        for (label i = 0; i < len; ++i)
+        {
+            list2.try_emplace(i, (50 + 1.3*i));
+        }
     }
-    #endif
 
     PtrList<Scalar> listApp;
     for (label i = 0; i < 5; ++i)

applications/test/PtrListDictionary/Test-PtrListDictionary.C

@@ -45,28 +45,29 @@ class Scalar
 
 public:
 
-    Scalar()
-    :
-        data_(0)
-    {}
+    static bool verbose;
 
-    Scalar(scalar val)
-    :
-        data_(val)
-    {}
+    constexpr Scalar() noexcept : data_(0) {}
+    Scalar(scalar val) noexcept : data_(val) {}
 
     ~Scalar()
     {
-        Info<<"delete Scalar: " << data_ << endl;
+        if (verbose) Info<< "delete Scalar: " << data_ << endl;
     }
 
-    friend Ostream& operator<<(Ostream& os, const Scalar& val)
+    const scalar& value() const noexcept { return data_; }
+    scalar& value() noexcept { return data_; }
+
+    autoPtr<Scalar> clone() const { return autoPtr<Scalar>::New(data_); }
+
+    friend Ostream& operator<<(Ostream& os, const Scalar& item)
     {
-        os  << val.data_;
+        os  << item.value();
         return os;
     }
 };
 
+bool Scalar::verbose = true;
 
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

src/OpenFOAM/containers/HashTables/HashPtrTable/HashPtrTable.H

@@ -78,6 +78,14 @@ class HashPtrTable
         template<class INew>
         void read(const dictionary& dict, const INew& inew);
 
+        //- Implementation for emplace_set and try_emplace
+        template<class... Args>
+        inline T& emplaceImpl
+        (
+            const bool overwrite,
+            const Key& key,
+            Args&&... args
+        );
 
 public:
 
@@ -233,6 +241,14 @@ public:
         template<class... Args>
         inline T& emplace_set(const Key& key, Args&&... args);
 
+        //- Like emplace_set() but will not overwrite an occupied (non-null)
+        //- location.
+        //  \param key - the location to set (unless already defined)
+        //  \param args arguments to forward to the constructor of the element
+        //  \return reference to the existing or the new element.
+        template<class... Args>
+        inline T& try_emplace(const Key& key, Args&&... args);
+
         //- No insert() with raw pointers (potential memory leaks).
         //- Use insert() with autoPtr or set()
         inline bool insert(const Key&, T*) = delete;

src/OpenFOAM/containers/HashTables/HashPtrTable/HashPtrTableI.H

@@ -74,6 +74,42 @@ inline bool Foam::HashPtrTable<T, Key, Hash>::emplace
 }
 
 
+template<class T, class Key, class Hash>
+template<class... Args>
+inline T& Foam::HashPtrTable<T, Key, Hash>::emplaceImpl
+(
+    const bool overwrite,
+    const Key& key,
+    Args&&... args
+)
+{
+    T* ptr = nullptr;
+
+    // Replace existing entry unconditionally (overwrite = true)
+    // or only if nullptr (overwrite = false)
+    iterator iter(this->find(key));
+    if (iter.good())
+    {
+        ptr = iter.val();
+
+        if (overwrite || !ptr)
+        {
+            // Overwrite existing or replace nullptr
+            delete ptr;
+            ptr = new T(std::forward<Args>(args)...);
+            iter.val() = ptr;
+        }
+    }
+    else
+    {
+        ptr = new T(std::forward<Args>(args)...);
+        this->parent_type::set(key, ptr);
+    }
+
+    return *ptr;
+}
+
+
 template<class T, class Key, class Hash>
 template<class... Args>
 inline T& Foam::HashPtrTable<T, Key, Hash>::emplace_set
@@ -82,9 +118,21 @@ inline T& Foam::HashPtrTable<T, Key, Hash>::emplace_set
     Args&&... args
 )
 {
-    T* ptr = new T(std::forward<Args>(args)...);
-    (void)this->set(key, ptr);
-    return *ptr;
+    // overwrite = true
+    return this->emplaceImpl(true, key, std::forward<Args>(args)...);
+}
+
+
+template<class T, class Key, class Hash>
+template<class... Args>
+inline T& Foam::HashPtrTable<T, Key, Hash>::try_emplace
+(
+    const Key& key,
+    Args&&... args
+)
+{
+    // overwrite = false
+    return this->emplaceImpl(false, key, std::forward<Args>(args)...);
 }
 
 
@@ -129,16 +177,20 @@ inline bool Foam::HashPtrTable<T, Key, Hash>::set
     T* ptr
 )
 {
-    const T* old = this->get(key);
-
-    const bool ok = this->parent_type::set(key, ptr);
-
-    if (ok && old != ptr)
+    // Replace existing entry unconditionally
+    iterator iter(this->find(key));
+    if (iter.good())
     {
-        delete const_cast<T*>(old);
+        if (iter.val() != ptr)
+        {
+            delete iter.val();
+            iter.val() = ptr;
+        }
+        return true;
     }
 
-    return ok;
+    // Or add new entry
+    return this->parent_type::set(key, ptr);
 }
 
 

src/OpenFOAM/containers/PtrLists/PtrDynList/PtrDynList.H

@@ -190,6 +190,13 @@ public:
         template<class... Args>
         inline T& emplace(const label i, Args&&... args);
 
+        //- Like emplace_set() but will not overwrite an occupied location.
+        //  \param i - the location to set (unless already defined)
+        //  \param args arguments to forward to the constructor of the element
+        //  \return reference to the existing or the new list element.
+        template<class... Args>
+        inline T& try_emplace(const label i, Args&&... args);
+
         //- Set element to given pointer and return old element (can be null).
         //- Auto-sizes list as required.
         inline autoPtr<T> set(const label i, T* ptr);

src/OpenFOAM/containers/PtrLists/PtrDynList/PtrDynListI.H

@@ -399,7 +399,7 @@ inline T& Foam::PtrDynList<T, SizeMin>::emplace_set
     {
         resize(i+1);
     }
-    return this->PtrList<T>::emplace_set(i, std::forward<Args>(args)...);
+    return PtrList<T>::emplace_set(i, std::forward<Args>(args)...);
 }
 
 
@@ -415,6 +415,22 @@ inline T& Foam::PtrDynList<T, SizeMin>::emplace
 }
 
 
+template<class T, int SizeMin>
+template<class... Args>
+inline T& Foam::PtrDynList<T, SizeMin>::try_emplace
+(
+    const label i,
+    Args&&... args
+)
+{
+    if (i >= this->size())
+    {
+        resize(i+1);
+    }
+    return PtrList<T>::try_emplace(i, std::forward<Args>(args)...);
+}
+
+
 template<class T, int SizeMin>
 inline Foam::autoPtr<T> Foam::PtrDynList<T, SizeMin>::set
 (

src/OpenFOAM/containers/PtrLists/PtrList/PtrList.H

@@ -187,6 +187,14 @@ public:
         template<class... Args>
         inline T& emplace(const label i, Args&&... args);
 
+        //- Like emplace_set() but will not overwrite an occupied (non-null)
+        //- location.
+        //  \param i - the location to set (unless already defined)
+        //  \param args arguments to forward to the constructor of the element
+        //  \return reference to the existing or the new list element.
+        template<class... Args>
+        inline T& try_emplace(const label i, Args&&... args);
+
         //- Set element to given pointer and return old element (can be null)
         //  No-op if the new pointer value is identical to the current content.
         inline autoPtr<T> set(const label i, T* ptr);

src/OpenFOAM/containers/PtrLists/PtrList/PtrListI.H

@@ -195,6 +195,19 @@ inline T& Foam::PtrList<T>::emplace(const label i, Args&&... args)
 }
 
 
+template<class T>
+template<class... Args>
+inline T& Foam::PtrList<T>::try_emplace(const label i, Args&&... args)
+{
+    T* ptr = UPtrList<T>::get(i);
+    if (ptr)
+    {
+        return *ptr;
+    }
+    return this->emplace_set(i, std::forward<Args>(args)...);
+}
+
+
 template<class T>
 inline Foam::autoPtr<T> Foam::PtrList<T>::set(const label i, T* ptr)
 {