Update wxMemoryInputStream::Peek to set last read count.

This aligns the memory stream's Peek with other streams' Peek impls by
making it set the last read count to 1 when it successfully peeks a
character, or 0 when it does not. While the formal docs do not link
Peek to LastCount directly, the in-source comments on the declaration
of both wxInputStream::Peek and wxInputStream::LastRead both indicate
that Peek will set the last read count.

src/common/mstream.cpp

@@ -112,10 +112,12 @@ char wxMemoryInputStream::Peek()
     if ( pos == m_length )
     {
         m_lasterror = wxSTREAM_READ_ERROR;
+        m_lastcount = 0;
 
         return 0;
     }
 
+    m_lastcount = 1;
     return buf[pos];
 }
 

tests/streams/bstream.h

@@ -253,9 +253,17 @@ protected:
         while (stream_in.IsOk())
         {
             char peekChar = stream_in.Peek();
+            size_t peekLastRead = stream_in.LastRead();
+
             char getChar = stream_in.GetC();
+
+            // Peek and GetC should retrieve the same 0 or 1 characters.
+            CPPUNIT_ASSERT_EQUAL(peekLastRead, stream_in.LastRead());
+
             if (stream_in.LastRead() == 1)
+            {
                 CPPUNIT_ASSERT_EQUAL(getChar, peekChar);
+            }
         }
     }