ENH: improved parallel transfer of strings

- support send/receive with embedded '\0' characters

applications/test/parallel/Test-parallel.C

@@ -120,6 +120,24 @@ void testMapDistribute()
 }
 
 
+// Print to Perr
+template<class T>
+Ostream& perrInfo(const T& data)
+{
+    Perr<< data;
+    return Perr;
+}
+
+
+// Print to Perr
+template<>
+Ostream& perrInfo(const string& data)
+{
+    Perr<< data << " (size: " << data.size() << ")";
+    return Perr;
+}
+
+
 template<class T>
 void testTransfer(const T& input)
 {
@@ -127,7 +145,8 @@ void testTransfer(const T& input)
 
     if (Pstream::master())
     {
-        Perr<<"test transfer (" << (typeid(T).name()) << "): " << data << nl << endl;
+        Perr<<"test transfer (" << (typeid(T).name()) << "): ";
+        perrInfo(data) << nl << endl;
     }
 
     if (Pstream::myProcNo() != Pstream::masterNo())
@@ -141,7 +160,7 @@ void testTransfer(const T& input)
         Perr<< "slave receiving from master " << Pstream::masterNo() << endl;
         IPstream fromMaster(Pstream::commsTypes::blocking, Pstream::masterNo());
         fromMaster >> data;
-        Perr<< data << endl;
+        perrInfo(data) << endl;
     }
     else
     {
@@ -155,7 +174,7 @@ void testTransfer(const T& input)
             Perr<< "master receiving from slave " << slave << endl;
             IPstream fromSlave(Pstream::commsTypes::blocking, slave);
             fromSlave >> data;
-            Perr<< data << endl;
+            perrInfo(data) << endl;
         }
 
         for
@@ -258,6 +277,15 @@ int main(int argc, char *argv[])
     testTransfer(scalar(3.14159));
     testTransfer(string("test   string"));
     testTransfer(string("  x "));
+
+    {
+        // Slightly roundabout way to construct with a nul in string
+        string str1("embedded. nul character in string");
+        str1[8] = '\0';
+
+        Info<< "len: " << str1.size() << endl;
+        testTransfer(str1);
+    }
     testTransfer(word("3.141 59"));  // bad word, but transfer doesn't care
 
     testTokenized(label(1234));

src/OpenFOAM/db/IOstreams/Pstreams/UIPstream.C

@@ -42,12 +42,12 @@ inline void Foam::UIPstream::checkEof()
 
 
 template<class T>
-inline void Foam::UIPstream::readFromBuffer(T& t)
+inline void Foam::UIPstream::readFromBuffer(T& val)
 {
     const size_t align = sizeof(T);
     externalBufPosition_ = align + ((externalBufPosition_ - 1) & ~(align - 1));
 
-    t = reinterpret_cast<T&>(externalBuf_[externalBufPosition_]);
+    val = reinterpret_cast<T&>(externalBuf_[externalBufPosition_]);
     externalBufPosition_ += sizeof(T);
     checkEof();
 }
@@ -67,10 +67,14 @@ inline void Foam::UIPstream::readFromBuffer
           + ((externalBufPosition_ - 1) & ~(align - 1));
     }
 
-    const char* bufPtr = &externalBuf_[externalBufPosition_];
-    char* dataPtr = reinterpret_cast<char*>(data);
-    size_t i = count;
-    while (i--) *dataPtr++ = *bufPtr++;
+    const char* const __restrict__ buf = &externalBuf_[externalBufPosition_];
+    char* const __restrict__ output = reinterpret_cast<char*>(data);
+
+    for (size_t i = 0; i < count; ++i)
+    {
+        output[i] = buf[i];
+    }
+
     externalBufPosition_ += count;
     checkEof();
 }
@@ -78,14 +82,15 @@ inline void Foam::UIPstream::readFromBuffer
 
 inline Foam::Istream& Foam::UIPstream::readStringFromBuffer(std::string& str)
 {
+    // Use std::string::assign() to copy content, including '\0'.
+    // Stripping (when desired) is the responsibility of the sending side.
+
     size_t len;
     readFromBuffer(len);
-    // Uses the underlying std::string::operator=()
-    // - no stripInvalid invoked (the sending side should have done that)
-    // - relies on trailing '\0' char (so cannot send anything with an embedded
-    //   nul char)
-    str = &externalBuf_[externalBufPosition_];
-    externalBufPosition_ += len + 1;
+
+    str.assign(&externalBuf_[externalBufPosition_], len);
+
+    externalBufPosition_ += len;
     checkEof();
 
     return *this;
@@ -276,7 +281,7 @@ Foam::Istream& Foam::UIPstream::read(token& t)
 Foam::Istream& Foam::UIPstream::read(char& c)
 {
     c = externalBuf_[externalBufPosition_];
-    externalBufPosition_++;
+    ++externalBufPosition_;
     checkEof();
     return *this;
 }

src/OpenFOAM/db/IOstreams/Pstreams/UIPstream.H

@@ -80,7 +80,7 @@ class UIPstream
 
         //- Read a T from the transfer buffer
         template<class T>
-        inline void readFromBuffer(T& t);
+        inline void readFromBuffer(T& val);
 
         //- Read count bytes of data from the transfer buffer
         //  using align byte alignment

src/OpenFOAM/db/IOstreams/Pstreams/UOPstream.C

@@ -109,7 +109,7 @@ inline void Foam::UOPstream::writeStringToBuffer(const std::string& str)
 {
     const size_t len = str.size();
     writeToBuffer(len);
-    writeToBuffer(str.c_str(), len + 1, 1);
+    writeToBuffer(str.data(), len, 1);
 }