ENH: add basic support for file extensions to word

- when a plain word is used as a directory-local name for file.
  We don't have a full blown fileName, but still want to check/remove
  extensions etc.

src/OpenFOAM/primitives/strings/string/string.C

@@ -25,6 +25,8 @@ License
 
 #include "string.H"
 #include "stringOps.H"
+#include "word.H"
+#include "wordRe.H"
 
 /* * * * * * * * * * * * * * * Static Member Data  * * * * * * * * * * * * * */
 
@@ -33,13 +35,75 @@ int Foam::string::debug(Foam::debug::debugSwitch(string::typeName, 0));
 const Foam::string Foam::string::null;
 
 
+// * * * * * * * * * * * * Protected Member Functions  * * * * * * * * * * * //
+
+Foam::word Foam::string::ext() const
+{
+    const size_type i = find_ext();
+
+    if (i == npos)
+    {
+        return word::null;
+    }
+    else
+    {
+        return substr(i+1, npos);
+    }
+}
+
+
+bool Foam::string::ext(const Foam::word& ending)
+{
+    if (!ending.empty() && !empty() && operator[](size()-1) != '/')
+    {
+        append(1u, '.');
+        append(ending);
+
+        return true;
+    }
+
+    return false;
+}
+
+
+bool Foam::string::hasExt(const word& ending) const
+{
+    size_type i = find_ext();
+    if (i == npos)
+    {
+        return false;
+    }
+
+    ++i; // Compare *after* the dot
+    return
+    (
+        // Lengths must match
+        ((size() - i) == ending.size())
+     && !compare(i, npos, ending)
+    );
+}
+
+
+bool Foam::string::hasExt(const wordRe& ending) const
+{
+    const size_type i = find_ext();
+    if (i == npos)
+    {
+        return false;
+    }
+
+    const std::string end = substr(i+1, npos);  // Compare *after* the dot
+    return ending.match(end);
+}
+
+
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
 Foam::string::size_type Foam::string::count(const char c) const
 {
     size_type cCount = 0;
 
-    for (const_iterator iter = begin(); iter != end(); ++iter)
+    for (const_iterator iter = cbegin(); iter != cend(); ++iter)
     {
         if (*iter == c)
         {

src/OpenFOAM/primitives/strings/string/string.H

@@ -58,6 +58,8 @@ namespace Foam
 {
 
 // Forward declaration of classes
+class word;
+class wordRe;
 class Istream;
 class Ostream;
 
@@ -76,6 +78,37 @@ class string
 :
     public std::string
 {
+protected:
+
+    // Protected Member Functions
+
+        //- Find position of a file extension dot, return npos on failure.
+        //  A wrapped version of find_last_of("./") with additional logic.
+        inline size_type find_ext() const;
+
+        //- Return file name extension (part after last .)
+        word ext() const;
+
+        //- Append a '.' and the ending.
+        //  The '.' and ending will not be added when the ending is empty,
+        //  or when the object was or ended with a '/'.
+        //
+        //  \return True if append occurred.
+        bool ext(const word& ending);
+
+        //- Return true if it has an extension or simply ends with a '.'
+        inline bool hasExt() const;
+
+        //- Return true if the extension is the same as the given ending.
+        bool hasExt(const word& ending) const;
+
+        //- Return true if the extension matches the given ending.
+        bool hasExt(const wordRe& ending) const;
+
+        //- Remove extension, returning true if string changed.
+        inline bool removeExt();
+
+
 public:
 
     // Static data members

src/OpenFOAM/primitives/strings/string/stringI.H

@@ -3,7 +3,7 @@
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
     \\  /    A nd           | Copyright (C) 2011-2015 OpenFOAM Foundation
-     \\/     M anipulation  |
+     \\/     M anipulation  | Copyright (C) 2017 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -25,6 +25,45 @@ License
 
 #include <iostream>
 
+// * * * * * * * * * * * * Protected Member Functions  * * * * * * * * * * * //
+
+inline std::string::size_type Foam::string::find_ext() const
+{
+    const size_type i = find_last_of("./");
+
+    if (i == npos || i == 0 || operator[](i) == '/')
+    {
+        return npos;
+    }
+    else
+    {
+        return i;
+    }
+}
+
+
+inline bool Foam::string::hasExt() const
+{
+    return (find_ext() != npos);
+}
+
+
+inline bool Foam::string::removeExt()
+{
+    const size_type i = find_ext();
+
+    if (i == npos)
+    {
+        return false;
+    }
+    else
+    {
+        this->resize(i);
+        return true;
+    }
+}
+
+
 // * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
 inline Foam::string::string()