ENH: stringOps removeComments and inplaceRemoveComments

- useful for manual handling of string with comments

applications/test/string/Test-string.C

@@ -44,6 +44,20 @@ Description
 
 using namespace Foam;
 
+void testCommentStripping(const std::string& s)
+{
+    Info<< "input" << nl
+        << "========" << nl
+        << s << nl
+        << "========" << nl;
+
+    Info<< "output" << nl
+        << "========" << nl
+        << stringOps::removeComments(s) << nl
+        << "========" << nl << nl;
+}
+
+
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 // Main program:
 
@@ -158,6 +172,35 @@ int main(int argc, char *argv[])
     Info<<"trimRight: " << stringOps::trimRight(test) << endl;
     Info<<"trim: " << stringOps::trim(test) << endl;
 
+    // Test comment stripping
+    {
+        Info<< nl << "Test comment stripping" << nl;
+        testCommentStripping
+        (
+            "/String without comments/"
+        );
+        testCommentStripping
+        (
+            "Removed some/* C-comments */ / C comments"
+        );
+        testCommentStripping
+        (
+            "Removed some//C++ comments\n / C++ comments"
+        );
+        testCommentStripping
+        (
+            "Partly degenerate C comment </*/ C-comment..."
+        );
+        testCommentStripping
+        (
+            "Truncated C comment </* C-comment..."
+        );
+        testCommentStripping
+        (
+            "Truncated C++ comment <// C++ comment..."
+        );
+    }
+
     if (false)
     {
         Info<<"test move construct - string size:" << test.size() << nl;

src/OpenFOAM/primitives/strings/stringOps/stringOps.C

@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
-    \\  /    A nd           | Copyright (C) 2017-2018 OpenCFD Ltd.
+    \\  /    A nd           | Copyright (C) 2017-2019 OpenCFD Ltd.
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
                             | Copyright (C) 2011-2016 OpenFOAM Foundation
@@ -1104,6 +1104,90 @@ void Foam::stringOps::inplaceTrim(std::string& s)
 }
 
 
+Foam::string Foam::stringOps::removeComments(const string& original)
+{
+    string s(original);
+    inplaceRemoveComments(s);
+    return s;
+}
+
+
+void Foam::stringOps::inplaceRemoveComments(std::string& s)
+{
+    const auto len = s.length();
+
+    if (len < 2)
+    {
+        return;
+    }
+
+    std::string::size_type n = 0;
+
+    for (std::string::size_type i = 0; i < len; ++i)
+    {
+        char c = s[i];
+
+        if (n != i)
+        {
+            s[n] = c;
+        }
+        ++n;
+
+        // The start of a C/C++ comment?
+        if (c == '/')
+        {
+            ++i;
+
+            if (i == len)
+            {
+                // No further characters
+                break;
+            }
+
+            c = s[i];
+
+            if (c == '/')
+            {
+                // C++ comment - search for end-of-line
+                --n;
+                i = s.find('\n', ++i);
+
+                if (i == std::string::npos)
+                {
+                    // Trucated - done
+                    break;
+                }
+            }
+            else if (c == '*')
+            {
+                // C comment - search for '*/'
+                --n;
+                i = s.find("*/", ++i, 2);
+
+                if (i == std::string::npos)
+                {
+                    // Trucated - done
+                    break;
+                }
+
+                ++i;
+            }
+            else
+            {
+                // Not a C/C++ comment
+                if (n != i)
+                {
+                    s[n] = c;
+                }
+                ++n;
+            }
+        }
+    }
+
+    s.resize(n);
+}
+
+
 Foam::string Foam::stringOps::lower(const string& original)
 {
     string s(original);

src/OpenFOAM/primitives/strings/stringOps/stringOps.H

@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
-    \\  /    A nd           | Copyright (C) 2016-2018 OpenCFD Ltd.
+    \\  /    A nd           | Copyright (C) 2016-2019 OpenCFD Ltd.
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
                             | Copyright (C) 2011-2012 OpenFOAM Foundation
@@ -351,6 +351,13 @@ namespace stringOps
     void inplaceTrim(std::string& s);
 
 
+    //- Return string with C/C++ comments removed
+    string removeComments(const string& original);
+
+    //- Remove C/C++ comments inplace
+    void inplaceRemoveComments(std::string& s);
+
+
     //- Return string transformed with std::tolower on each character
     string lower(const string& original);