ENH: add in-place modification for OCharStream

- enables partial overwriting of content
- make default construct zero-sized, add reserve_exact() method

STYLE: minor adjustments for Enum, IOstreamOption

applications/test/IStringStream/Make/files

@@ -1,3 +1,3 @@
-Test-IStringStream.C
+Test-IStringStream.cxx
 
 EXE = $(FOAM_USER_APPBIN)/Test-IStringStream

applications/test/OCharStream1/Test-OCharStream1.cxx

@@ -111,7 +111,10 @@ template<class BufType>
 void printInfo(const BufType& buf)
 {
     Info<< nl << "=========================" << endl;
-    buf.print(Info);
+    if constexpr (std::is_same_v<OCharStream, BufType>)
+    {
+        buf.print(Info);
+    }
     Info<< "addr: " << Foam::name(buf.list().cdata()) << nl;
     toString(Info, buf.list());
     Info<< nl << "=========================" << endl;
@@ -183,12 +186,25 @@ int main(int argc, char *argv[])
     printInfo(obuf);
 
     // Overwrite at some position
-    obuf.stdStream().rdbuf()->pubseekpos(0.60 * obuf.size());
-    obuf << "<" << nl << "OVERWRITE" << nl;
+    if (auto i = obuf.view().find("item5"); i != std::string::npos)
+    {
+        // obuf.seek(0.60 * obuf.size());
+        obuf.seek(i);
+        obuf << "<OVERWRITE>" << nl;
+    }
 
     Info<<"after overwrite" << nl;
     printInfo(obuf);
 
+    // Truncate
+    {
+        constexpr float fraction = 0.90;
+        Info<<"truncated at " << (100*fraction) << "% ["
+            << int(fraction*obuf.size()) << " chars]" << nl;
+        obuf.seek(fraction*obuf.size());
+        printInfo(obuf);
+    }
+
     Info<< "transfer contents to a List or ICharStream" << nl;
 
     // Reclaim data storage from OCharStream -> ICharStream

applications/test/OCharStream2/Make/files

@@ -0,0 +1,3 @@
+Test-OCharStream2.cxx
+
+EXE = $(FOAM_USER_APPBIN)/Test-OCharStream2

applications/test/OCharStream2/Make/options

@@ -0,0 +1,2 @@
+/* EXE_INC = */
+/* EXE_LIBS = */

applications/test/OCharStream2/Test-OCharStream2.cxx

@@ -0,0 +1,404 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2025 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+Description
+
+\*---------------------------------------------------------------------------*/
+
+#include "SpanStream.H"
+#include "wordList.H"
+#include "IOstreams.H"
+#include "argList.H"
+
+#include <cctype>
+#include <cstdio>
+#include <limits>
+#include <iomanip>
+
+using namespace Foam;
+
+Ostream& printString(Ostream& os, const char* first, const char* last)
+{
+    os << '"';
+    for (; first != last; (void)++first)
+    {
+        os << *first;
+    }
+    os << '"';
+
+    return os;
+}
+
+
+Ostream& printView(Ostream& os, const char* first, const char* last)
+{
+    char buf[4];
+    os << label(last-first) << '(';
+
+    for (; first != last; (void)++first)
+    {
+        const char c = *first;
+
+        if (isprint(c))
+        {
+            os << c;
+        }
+        else if (c == '\t')
+        {
+            os << "\\t";
+        }
+        else if (c == '\n')
+        {
+            os << "\\n";
+        }
+        else
+        {
+            ::snprintf(buf, 4, "%02X", c);
+            os << "\\x" << buf;
+        }
+    }
+    os << ')';
+
+    return os;
+}
+
+
+Ostream& printView(Ostream& os, std::string_view s)
+{
+    return printView(os, s.begin(), s.end());
+}
+
+
+Ostream& printView(Ostream& os, const UList<char>& list)
+{
+    return printView(os, list.begin(), list.end());
+}
+
+
+Ostream& writeList(Ostream& os, const UList<char>& list)
+{
+    return printView(os, list);
+}
+
+
+Ostream& toString(Ostream& os, const UList<char>& list)
+{
+    return printString(os, list.begin(), list.end());
+}
+
+
+Ostream& toString(Ostream& os, std::string_view s)
+{
+    return printString(os, s.begin(), s.end());
+}
+
+
+template<class BufType>
+void printInfo(const BufType& buf)
+{
+    Info<< nl << "=========================" << endl;
+    if constexpr (std::is_same_v<OCharStream, BufType>)
+    {
+        buf.print(Info);
+    }
+    Info<< "addr: " << Foam::name(buf.view().data()) << nl;
+    toString(Info, buf.view());
+    Info<< nl << "=========================" << endl;
+}
+
+
+template<class IntType>
+void leftpad(std::ostream& os, IntType val, char fillch = ' ')
+{
+    // set fill char and width
+    os.setf(std::ios_base::left, std::ios_base::adjustfield);
+    fillch = os.fill(fillch);
+    os.width(std::numeric_limits<IntType>::digits10+1);
+    os  << val;
+    // restore fill char
+    os.fill(fillch);
+}
+
+
+template<class IntType>
+void rightpad(std::ostream& os, IntType val, char fillch = ' ')
+{
+    // set fill char and width
+    os.setf(std::ios_base::right, std::ios_base::adjustfield);
+    fillch = os.fill(fillch);
+    os.width(std::numeric_limits<IntType>::digits10+1);
+    os  << val;
+    // restore fill char
+    os.fill(fillch);
+}
+
+
+// Left-padded value with trailing comment slashes
+template<class IntType>
+void leftpad(ocharstream& os, IntType val)
+{
+    const auto beg = os.tellp();
+    os << val;
+    int count = (std::numeric_limits<IntType>::digits10+1) - (os.tellp() - beg);
+
+    // With two spaces before comments
+    if (count > 0) { os << ' '; --count; }
+    if (count > 0) { os << ' '; --count; }
+    for (const char c = (count >= 2 ? '/' : ' '); count > 0; --count)
+    {
+        os << c;
+    }
+}
+
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+// Main program:
+
+int main(int argc, char *argv[])
+{
+    argList::noParallel();
+    argList::addBoolOption("fake-zerosize", "Fake overwriting with zero data");
+    argList::addBoolOption("dict-format", "Format as dictionary entry");
+
+    #include "setRootCase.H"
+
+    const bool optFakeZerosize = args.found("fake-zerosize");
+    const bool isDictFormat = args.found("dict-format");
+
+    // const constexpr int width = (std::numeric_limits<label>::digits10+1);
+
+    ocharstream labelbuf{charList(32)};
+
+    // Some value
+    labelbuf.rewind();
+    rightpad(labelbuf, label(10));
+
+    printInfo(labelbuf);
+
+    OCharStream obuf{charList(32)};
+
+    printInfo(obuf);
+
+    // Fill with some content
+    for (int i = 0; i < 26; ++i)
+    {
+        obuf<< char('A' + i);
+    }
+
+    // Change letter 'O' to '_'
+    if (auto i = obuf.view().find('O'); i != std::string::npos)
+    {
+        obuf.overwrite(i, '_');
+    }
+
+    printInfo(obuf);
+
+    obuf.overwrite(4, labelbuf.view());
+    printInfo(obuf);
+
+    obuf.overwrite(20, "####");
+    printInfo(obuf);
+
+    Info<< "operation Ignored..." << nl;
+    obuf.overwrite(45, "????");
+    printInfo(obuf);
+
+    // Update with new value
+    {
+        labelbuf.rewind();
+        rightpad(labelbuf, label(200), '.');
+        obuf.overwrite(4, labelbuf.view());
+
+        printInfo(obuf);
+    }
+
+    // With yet another value (non-fixed width)
+    {
+        labelbuf.rewind();
+        labelbuf << label(15);
+        obuf.overwrite(4, labelbuf.view());
+
+        printInfo(obuf);
+    }
+
+    // Slightly harder test
+    {
+        std::string chars(26, '?');
+
+        for (int i = 0; i < 26; ++i)
+        {
+            chars[i] = char('A' + i);
+        }
+
+        auto& os = obuf;
+        os.rewind();
+
+        const word procName("processor0");
+
+        // Write as primitiveEntry or commented content
+        // // constexpr bool isDictFormat = true;
+
+        // if constexpr (isDictFormat)
+        if (isDictFormat)
+        {
+            // Like writeKeyword() with compoundToken
+            os << nl << procName << ' ' << word("List<char>") << nl;
+        }
+        else
+        {
+            // Human-readable comments
+            os << nl << "// " << procName << nl;
+        }
+
+        // This is the code we want to have, but assume we don't know
+        // the size or data beforehand.
+        //
+        // if (str && len > 0)
+        // {
+        //     // Special treatment for char data (binary I/O only)
+        //     const auto oldFmt = os.format(IOstreamOption::BINARY);
+        //
+        //     os << label(len) << nl;
+        //     os.write(str, len);
+        //     os << nl;
+        //
+        //     os.format(oldFmt);
+        // }
+        // else
+        // {
+        //     os << label(0) << nl;
+        // }
+
+        // Position before writing the label
+        const auto labelBegin = os.tellp();
+
+        // Replace: os << label(len) << nl;
+        // with a fixed-length version
+        {
+            labelbuf.rewind();
+            rightpad(labelbuf, 0);
+
+            os.append(labelbuf.view());
+            os << nl;
+        }
+
+        constexpr bool testUnknown = true;
+
+        label dataCount = 0;
+
+        if constexpr (testUnknown)
+        {
+            // Pretend we don't know the number of characters a priori
+
+            const auto oldFmt = os.format(IOstreamOption::BINARY);
+
+            const auto lineNumber = os.lineNumber();
+
+            // count is unknown but irrelevant for serial
+            os.beginRawWrite(0);
+
+            // Position before raw binary data
+            const auto dataBegin = os.tellp();
+
+            // Some type of output, streaming etc
+            os.writeRaw(chars.data(), chars.size());
+
+            // How many chars of binary data written?
+            dataCount = (os.tellp() - dataBegin);
+
+            os.endRawWrite();
+            os.lineNumber() = lineNumber;
+            os << nl;
+
+            os.format(oldFmt);
+        }
+        else
+        {
+            // If we had all data collected a priori
+
+            dataCount = chars.size();
+
+            const auto oldFmt = os.format(IOstreamOption::BINARY);
+
+            if (dataCount > 0)
+            {
+                os.write(chars.data(), chars.size());
+                os << nl;
+            }
+            os.format(oldFmt);
+        }
+
+        if (optFakeZerosize)
+        {
+            dataCount = 0;  // fake zero-size
+        }
+
+        printInfo(os);
+
+        // Update the data count with the correct value
+
+        if (dataCount > 0)
+        {
+            labelbuf.rewind();
+            leftpad(labelbuf, label(dataCount));
+
+            os.overwrite(labelBegin, labelbuf.view());
+        }
+        else
+        {
+            os.seek(int64_t(labelBegin)-1);
+
+            // if constexpr (isDictFormat)
+            if (isDictFormat)
+            {
+                os << ' ' << label(0);
+            }
+            else
+            {
+                os << nl << label(0) << nl;
+            }
+        }
+
+        // if constexpr (isDictFormat)
+        if (isDictFormat)
+        {
+            os.endEntry();
+        }
+
+        printInfo(os);
+
+        Info<< "view: " << os.view(4, 8) << nl;
+        Info<< "view: " << os.view(32) << nl;
+        // Ignores out-of-range
+        Info<< "view: " << os.view(1000) << nl;
+    }
+
+    Info<< "\nEnd\n" << endl;
+
+    return 0;
+}
+
+
+// ************************************************************************* //

applications/test/OStringStream/Make/files

@@ -1,3 +1,3 @@
-Test-OStringStream.C
+Test-OStringStream.cxx
 
 EXE = $(FOAM_USER_APPBIN)/Test-OStringStream

applications/test/sha1/Make/files

@@ -1,3 +1,3 @@
-Test-SHA1.C
+Test-SHA1.cxx
 
 EXE = $(FOAM_USER_APPBIN)/Test-SHA1

applications/test/sha1/Test-SHA1.cxx

@@ -64,6 +64,10 @@ int main(int argc, char * argv[])
     osha<< str;
     Info<< osha.digest() << " : output << to empty" << nl;
 
+    osha.reset();
+    osha<< std::string_view(str);
+    Info<< osha.digest() << " : << string_view [ not quite right !]" << nl;
+
     sha.clear();
     sha.append(str);
     shaDig = sha;