From 57eb631654fc0db12da790356bd471f9c67902e0 Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Fri, 24 Jun 2005 19:50:14 +0000
Subject: [PATCH] From Colin McDonald,     "On fixing the pointer access I
 discovered that reading osga archives     containing ive files went into a
 cpu loop.  This turned out to be a     problem with proxy_streambuf on
 Solaris.  Public methods in the Solaris     streambuf standard library
 implementation rely on the gptr() being set,     which proxy_streambuf was
 not doing.  So I have modified     proxy_streambuf to set the input sequence
 pointers, and have also     aligned it more with the standard library
 streambuf implementation     where all input is through underflow(), not
 uflow() which merely calls     underflow() and advances the pointer."

From Robert Osfield, change from using pointer cast and assignment to using
    a templated _write and _read method to avoid pointer aliasing to 2/4/8
    byte boundaries that some computer system may produce.  These changes
    where inspried by Colin McDonalds change to using memcpy, these
    changes weren't merged as memcpy is not as clear in naming as _read,
    _write and memcpy will incurr a function call just for copy a
    uint.
---
 src/osgPlugins/osga/OSGA_Archive.cpp | 67 +++++++++++++++-------------
 src/osgPlugins/osga/OSGA_Archive.h   | 12 +++++
 2 files changed, 47 insertions(+), 32 deletions(-)

diff --git a/src/osgPlugins/osga/OSGA_Archive.cpp b/src/osgPlugins/osga/OSGA_Archive.cpp
index 3bfb00263..97fedd1d3 100644
--- a/src/osgPlugins/osga/OSGA_Archive.cpp
+++ b/src/osgPlugins/osga/OSGA_Archive.cpp
@@ -83,7 +83,8 @@ OSGA_Archive::IndexBlock* OSGA_Archive::IndexBlock::read(std::istream& in, bool
                 ptr += sizeof(size_type);
 
                 osg::swapBytes(ptr,sizeof(unsigned int)); 
-                unsigned int filename_size = *(reinterpret_cast<unsigned int*>(ptr));
+                unsigned int filename_size; // = *(reinterpret_cast<unsigned int*>(ptr));
+                _read(ptr, filename_size);
                 ptr += sizeof(unsigned int);
                 ptr += filename_size;
 
@@ -113,7 +114,8 @@ std::string OSGA_Archive::IndexBlock::getFirstFileName() const
         ptr += sizeof(pos_type);
         ptr += sizeof(size_type);
 
-        unsigned int filename_size = *(reinterpret_cast<unsigned int*>(ptr));
+        unsigned int filename_size; // = *(reinterpret_cast<unsigned int*>(ptr));
+        _read(ptr, filename_size);
         ptr += sizeof(unsigned int);
 
         return std::string(ptr, ptr+filename_size);
@@ -134,13 +136,16 @@ bool OSGA_Archive::IndexBlock::getFileReferences(FileNamePositionMap& indexMap)
     char* end_ptr = _data + _offsetOfNextAvailableSpace;
     while (ptr<end_ptr)
     {
-        pos_type position = *(reinterpret_cast<pos_type*>(ptr)); 
+        pos_type position; // = *(reinterpret_cast<pos_type*>(ptr)); 
+        _read(ptr, position);
         ptr += sizeof(pos_type);
         
-        size_type size = *(reinterpret_cast<size_type*>(ptr)); 
+        size_type size; // = *(reinterpret_cast<size_type*>(ptr)); 
+        _read(ptr, size);
         ptr += sizeof(size_type);
 
-        unsigned int filename_size = *(reinterpret_cast<unsigned int*>(ptr));
+        unsigned int filename_size; // = *(reinterpret_cast<unsigned int*>(ptr));
+        _read(ptr, filename_size);
         ptr += sizeof(unsigned int);
         
         std::string filename(ptr, ptr+filename_size);
@@ -184,13 +189,16 @@ bool OSGA_Archive::IndexBlock::addFileReference(pos_type position, size_type siz
     {
         char* ptr = _data+_offsetOfNextAvailableSpace;
         
-        *(reinterpret_cast<pos_type*>(ptr)) = position; 
+        //*(reinterpret_cast<pos_type*>(ptr)) = position; 
+        _write(ptr, position);
         ptr += sizeof(pos_type);
         
-        *(reinterpret_cast<size_type*>(ptr)) = size; 
+        //*(reinterpret_cast<size_type*>(ptr)) = size; 
+        _write(ptr, size);
         ptr += sizeof(size_type);
         
-        *(reinterpret_cast<unsigned int*>(ptr)) = filename.size();
+        //*(reinterpret_cast<unsigned int*>(ptr)) = filename.size();
+        _write(ptr, static_cast<unsigned int>(filename.size()));
         ptr += sizeof(unsigned int);
         
         for(unsigned int i=0;i<filename.size();++i, ++ptr)
@@ -478,41 +486,36 @@ class proxy_streambuf : public std::streambuf
    
       proxy_streambuf(std::streambuf* streambuf, unsigned int numChars):
         _streambuf(streambuf),
-        _numChars(numChars),
-        value_peeked(false),
-        peek_value(0) {}
+        _numChars(numChars) {
+            setg(&oneChar, (&oneChar)+1, (&oneChar)+1);
+    }
    
       /// Destructor deallocates no buffer space.
       virtual ~proxy_streambuf()  {}
 
       std::streambuf* _streambuf;
-      unsigned int _numChars;
-      
-      bool value_peeked;
-      int_type peek_value;
 
     protected:
 
-      virtual int_type uflow ()
+      unsigned int _numChars;      
+      char_type oneChar;
+      
+      virtual int_type underflow()
       {
-         if (_numChars==0) return -1;
-         
+     if ( gptr() == &oneChar ) return traits_type::to_int_type(oneChar);
+        
+         if ( _numChars==0 ) return traits_type::eof();         
          --_numChars;
 
-         int_type val = value_peeked ? peek_value : _streambuf->sbumpc();
-         value_peeked = false;
-                  
-         return val;
-      }
-
-      virtual int_type 
-      underflow()
-      {
-        if (value_peeked) return peek_value;
-
-        value_peeked = true;
-        peek_value = _streambuf->sbumpc();
-        return peek_value;
+           int_type next_value = _streambuf->sbumpc();
+     
+         if ( !traits_type::eq_int_type(next_value,traits_type::eof()) )
+     {
+       setg(&oneChar, &oneChar, (&oneChar)+1);
+            oneChar = traits_type::to_char_type(next_value);
+     }
+    
+         return next_value;
       }
 };
 
diff --git a/src/osgPlugins/osga/OSGA_Archive.h b/src/osgPlugins/osga/OSGA_Archive.h
index 8a73db6b6..f00e1c6ca 100644
--- a/src/osgPlugins/osga/OSGA_Archive.h
+++ b/src/osgPlugins/osga/OSGA_Archive.h
@@ -210,6 +210,18 @@ class OSGA_Archive : public osgDB::Archive
         std::string         _masterFileName;
         IndexBlockList      _indexBlockList;
         FileNamePositionMap _indexMap;
+        
 
+        template <typename T>
+        static inline void _write(char* ptr, const T& value)
+        {
+            std::copy(reinterpret_cast<const char*>(&value),reinterpret_cast<const char*>(&value)+sizeof(value),ptr);
+        }
+        
+        template <typename T>
+        static inline void _read(char* ptr, T& value)
+        {
+            std::copy(ptr,ptr+sizeof(value),reinterpret_cast<char*>(&value));
+        }
 
 };