DEFEATURE: remove OStringStream::count() method (issue #3281)

- as seen in #3201, using count() based on the ostringstream tellp
  is not reliable since it is not updated with reset or copying.

STYLE: minor changes to string/char/span streams

- update docs to only mention string_view
- use auto return, without extra trailing 'decltype'

ENH: add IOstream size check helper methods

  * checkNativeSizes() : test only
  * fatalCheckNativeSizes() : an assert with FatalIOError

applications/test/ICharStream1/Test-ICharStream1.cxx

@@ -89,12 +89,6 @@ Ostream& printView(Ostream& os, std::string_view s)
 }
 
 
-Ostream& printView(Ostream& os, stdFoam::span<char> s)
-{
-    return printView(os, s.begin(), s.end());
-}
-
-
 Ostream& printView(Ostream& os, const UList<char>& list)
 {
     return printView(os, list.begin(), list.end());

applications/test/OCharStream1/Test-OCharStream1.cxx

@@ -89,12 +89,6 @@ Ostream& printView(Ostream& os, std::string_view s)
 }
 
 
-Ostream& printView(Ostream& os, stdFoam::span<char> s)
-{
-    return printView(os, s.begin(), s.end());
-}
-
-
 Ostream& printView(Ostream& os, const UList<char>& list)
 {
     return printView(os, list.begin(), list.end());

applications/test/OCountStream/Test-OCountStream.cxx

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2017-2023 OpenCFD Ltd.
+    Copyright (C) 2017-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -65,7 +65,6 @@ int main(int argc, char *argv[])
 
     OCountStream cnt;
     OCharStream cstr;
-    OStringStream sstr;
     ocountstream plain;
 
     generateOutput(cstr);
@@ -77,7 +76,6 @@ int main(int argc, char *argv[])
 
     Info<< "counter state: " << (cnt.stdStream().rdstate()) << nl
         << "via char-stream: " << label(cstr.view().size()) << " chars" << nl
-        << "via string-stream: " << label(sstr.count()) << " chars" << nl
         << "via ocountstream: " << plain.count() << " chars" << endl;
 
     fileName outputName;

applications/test/SpanStream1/Test-SpanStream1.cxx

@@ -91,12 +91,6 @@ Ostream& printView(Ostream& os, std::string_view s)
 }
 
 
-Ostream& printView(Ostream& os, stdFoam::span<char> s)
-{
-    return printView(os, s.begin(), s.end());
-}
-
-
 Ostream& printView(Ostream& os, const UList<char>& list)
 {
     return printView(os, list.begin(), list.end());

src/OpenFOAM/db/IOstreams/IOstreams/IOstream.C

@@ -71,6 +71,26 @@ bool Foam::IOstream::fatalCheck(const char* operation) const
 }
 
 
+bool Foam::IOstream::fatalCheckNativeSizes(const char* operation) const
+{
+    const bool ok = this->checkNativeSizes();
+
+    if (!ok)
+    {
+        FatalIOErrorInFunction(*this)
+            << "Error in stream: " << relativeName()
+            << " for operation " << operation << nl
+            << "Expecting (label=" << (8*sizeof(label))
+            << ";scalar=" << (8*sizeof(scalar))
+            << ") found (label=" << (8*this->labelByteSize())
+            << ";scalar=" << (8*this->scalarByteSize()) << ')' << nl
+            << exit(FatalIOError);
+    }
+
+    return ok;
+}
+
+
 void Foam::IOstream::print(Ostream& os) const
 {
     os  << "IOstream: " << "Version "  << version() << ", format "

src/OpenFOAM/db/IOstreams/IOstreams/IOstream.H

@@ -297,7 +297,7 @@ public:
         }
 
 
-        //- Check if the label byte-size associated with the stream
+        //- Test if the label byte-size associated with the stream
         //- is the same as the given type
         template<class T = label>
         std::enable_if_t<std::is_integral_v<T>, bool>
@@ -306,7 +306,7 @@ public:
             return sizeofLabel_ == sizeof(T);
         }
 
-        //- Check if the scalar byte-size associated with the stream
+        //- Test if the scalar byte-size associated with the stream
         //- is the same as the given type
         template<class T = scalar>
         std::enable_if_t<std::is_floating_point_v<T>, bool>
@@ -315,6 +315,22 @@ public:
             return sizeofScalar_ == sizeof(T);
         }
 
+        //- Test if the label/scalar byte-size associated with the stream
+        //- are the native label/scalar sizes
+        bool checkNativeSizes() const noexcept
+        {
+            return
+            (
+                sizeofLabel_ == sizeof(label)
+             && sizeofScalar_ == sizeof(scalar)
+            );
+        }
+
+        //- Assert that the label/scalar byte-size associated with the stream
+        //- are the native label/scalar sizes.
+        //  Generate a FatalIOError for any mismatch.
+        bool fatalCheckNativeSizes(const char* operation) const;
+
 
     // Stream State Functions
 

src/OpenFOAM/db/IOstreams/StringStreams/StringStream.H

@@ -215,9 +215,6 @@ public:
 
     // Member Functions
 
-        //- The number of bytes outputted
-        std::streamsize count() { return stream_.tellp(); }
-
         //- Get the string.
         //- As Foam::string instead of std::string (may change in future)
         Foam::string str() const { return Foam::string(stream_.str()); }

src/OpenFOAM/db/IOstreams/memory/ICharStream.H

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2017-2024 OpenCFD Ltd.
+    Copyright (C) 2017-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -141,8 +141,8 @@ public:
             );
         }
 
-        //- A string_view (c++17) or span view (older c++) of buffer contents
+        //- A string_view of buffer contents
-        auto view() const -> decltype(buffer_type::view())
+        auto view() const
         {
             return buffer_type::view();
         }
@@ -290,15 +290,15 @@ public:
         //- Span of the input characters (is modifiable!)
         UList<char> list() const { return stream_.list(); }
 
-        //- A string_view (c++17) or span view (older c++) of buffer contents
+        //- A string_view of buffer contents
-        auto view() const -> decltype(stream_.view())
+        auto view() const
         {
             return stream_.view();
         }
 
         //- For IStringStream compatibility, return the buffer as string copy.
         //  Use sparingly - it creates a full copy!!
-        auto str() const -> decltype(stream_.str())
+        auto str() const
         {
             return stream_.str();
         }

src/OpenFOAM/db/IOstreams/memory/ISpanStream.H

@@ -169,8 +169,8 @@ public:
             );
         }
 
-        //- A string_view (c++17) or span view (older c++) of buffer contents
+        //- A string_view of buffer contents
-        auto view() const -> decltype(buffer_type::view())
+        auto view() const
         {
             return buffer_type::view();
         }
@@ -351,15 +351,15 @@ public:
         //- Span of the current input characters (is modifiable!)
         UList<char> list() const { return stream_.list(); }
 
-        //- A string_view (c++17) or span view (older c++) of buffer contents
+        //- A string_view of buffer contents
-        auto view() const -> decltype(stream_.view())
+        auto view() const
         {
             return stream_.view();
         }
 
         //- For IStringStream compatibility, return the buffer as string copy.
         //  Use sparingly - it creates a full copy!!
-        auto str() const -> decltype(stream_.str())
+        auto str() const
         {
             return stream_.str();
         }

src/OpenFOAM/db/IOstreams/memory/OCharStream.H

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2017-2024 OpenCFD Ltd.
+    Copyright (C) 2017-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -147,8 +147,8 @@ public:
             );
         }
 
-        //- A string_view (c++17) or span view (older c++) of buffer contents
+        //- A string_view of buffer contents
-        auto view() const -> decltype(buffer_type::view())
+        auto view() const
         {
             return buffer_type::view();
         }
@@ -273,15 +273,15 @@ public:
         //- Span of the current output characters (is modifiable!)
         UList<char> list() const { return stream_.list(); }
 
-        //- A string_view (c++17) or span view (older c++) of buffer contents
+        //- A string_view of buffer contents
-        auto view() const -> decltype(stream_.view())
+        auto view() const
         {
             return stream_.view();
         }
 
         //- For OStringStream compatibility, return the buffer as string copy.
         //  Use sparingly - it creates a full copy!!
-        auto str() const -> decltype(stream_.str())
+        auto str() const
         {
             return stream_.str();
         }

src/OpenFOAM/db/IOstreams/memory/OSpanStream.H

@@ -162,8 +162,8 @@ public:
             );
         }
 
-        //- A string_view (c++17) or span view (older c++) of buffer contents
+        //- A string_view of buffer contents
-        auto view() const -> decltype(buffer_type::view())
+        auto view() const
         {
             return buffer_type::view();
         }
@@ -305,15 +305,15 @@ public:
         //- Span of the current output characters (is modifiable!)
         UList<char> list() const { return stream_.list(); }
 
-        //- A string_view (c++17) or span view (older c++) of buffer contents
+        //- A string_view of buffer contents
-        auto view() const -> decltype(stream_.view())
+        auto view() const
         {
             return stream_.view();
         }
 
         //- For OStringStream compatibility, return buffer as string copy.
         //  Use sparingly - it creates a full copy!!
-        auto str() const -> decltype(stream_.str())
+        auto str() const
         {
             return stream_.str();
         }

src/dynamicMesh/meshCut/wallLayerCells/wallNormalInfo/wallNormalInfo.C

@@ -64,9 +64,9 @@ Foam::Istream& Foam::operator>>
     {
         is >> rhs.normal_;
     }
-    else if (!is.checkLabelSize<>() || !is.checkScalarSize<>())
+    else if (!is.checkScalarSize<>())
     {
-        // Non-native label or scalar size
+        // Non-native scalar size
         is.beginRawRead();
 
         readRawScalar(is, rhs.normal_.data(), vector::nComponents);

src/functionObjects/utilities/foamReport/substitutionModels/dictionaryValue/dictionaryValue.C

@@ -5,7 +5,7 @@
     \  /    A nd           | www.openfoam.com
      \/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2024 OpenCFD Ltd.
+    Copyright (C) 2024-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -53,7 +53,7 @@ bool Foam::substitutionModels::dictionaryValue::processDict
 {
     const string& lookup = entries_[key];
 
-    OStringStream oss;
+    OCharStream oss;
     if (lookup.empty())
     {
         // Add complete dictionary
@@ -216,4 +216,4 @@ Foam::wordList Foam::substitutionModels::dictionaryValue::keys() const
 }
 
 
-// ************************************************************************* //
+// ************************************************************************* //

src/functionObjects/utilities/foamReport/substitutionModels/fileRegEx/fileRegEx.C

@@ -5,7 +5,7 @@
     \  /    A nd           | www.openfoam.com
      \/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2024 OpenCFD Ltd.
+    Copyright (C) 2024-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -124,15 +124,15 @@ bool Foam::substitutionModels::fileRegEx::apply
 
     Info<< "Cached " << lines.size() << " lines" << endl;
 
-    OStringStream oss;
+    OCharStream oss;
-    regExp re(entries_[key].c_str());
+    const regExp re(entries_[key].c_str());
 
     for (const string& data : lines)
     {
         regExp::results_type match;
         if (re.match(data, match))
         {
-            oss.reset();
+            oss.rewind();
 
             for (size_t i = 1; i < match.size(); ++i)
             {
@@ -160,4 +160,4 @@ Foam::wordList Foam::substitutionModels::fileRegEx::keys() const
 }
 
 
-// ************************************************************************* //
+// ************************************************************************* //