OW_dlSharedLibrary.cpp

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#include "OW_config.h"
#if defined(OW_USE_DL)
#include "OW_dlSharedLibrary.hpp"
#include "OW_Format.hpp"
#include "OW_Mutex.hpp"
#include "OW_MutexLock.hpp"
#include <dlfcn.h>

#include "OW_Types.hpp"

#if defined(OW_USE_FAKE_LIBS)

#include "OW_FileSystem.hpp"
#include "OW_File.hpp"
#include "OW_Array.hpp"

#define OW_FAKELIB_HEADING "FAKE"
#define OW_FAKELIB_HEADING_LENGTH 4

// NOTE: To make a fake library, create a text file with all functions that
// should be contained, in a list like:
// FAKE=true
// library_function1=some_unique_global_function_name
// library_function2=some_other_unique_global_function_name
// library_function3=some_final_unique_global_function_name
// ...
//
// The first entry MUST begin with FAKE, and there can be NO characters before
// this entry.
//
// Most dynamic libraries in openwbem are expected to have a getOWVersion
// function, so...
extern "C" const char* getOWVersion()
{ 
   return OW_VERSION;
}
// Now a line should be in your fake library which says:
// getOWVersion=getOWVersion
#endif

#include <iostream>

namespace OW_NAMESPACE
{

// static
bool dlSharedLibrary::s_call_dlclose = true;

Mutex dlSharedLibrary_guard;

dlSharedLibrary::dlSharedLibrary(void * libhandle, const String& libName)
   : SharedLibrary(), m_libhandle( libhandle ), m_libName(libName)
{
#if defined(OW_USE_FAKE_LIBS)
   // Find out if it is a fake library.
   m_fakeLibrary = dlSharedLibrary::isFakeLibrary(libName);

   if ( m_fakeLibrary )
   {
      initializeSymbolMap();
   }
#endif /* defined(OW_USE_FAKE_LIBS) */
}
  
dlSharedLibrary::~dlSharedLibrary()
{
#if !defined(OW_VALGRIND_SUPPORT) // dlclose()ing shared libs make it impossible to see where memory leaks occurred with valgrind.
   if (s_call_dlclose)
   {
      dlclose( m_libhandle );
   }
#endif
}
bool dlSharedLibrary::doGetFunctionPointer(const String& functionName,
      void** fp) const
{
   MutexLock l(dlSharedLibrary_guard);
#if defined(OW_USE_FAKE_LIBS)
   String realFunctionName = functionName;
   // If this is a fake library, extract convert the requested function
   // name into the proper function name for the main executable.
   if ( m_fakeLibrary )
   {
      Map<String,String>::const_iterator symIter = m_symbolMap.find(functionName);
      if ( symIter == m_symbolMap.end() )
      {
         return false;
      }
      realFunctionName = symIter->second;
   }
   *fp = dlsym( m_libhandle, realFunctionName.c_str() );
#else
   *fp = dlsym( m_libhandle, functionName.c_str() );
#endif /* defined(OW_USE_FAKE_LIBS) */
     
   if (!*fp)
   {
      return false;
   }
   return true;
}

bool dlSharedLibrary::isFakeLibrary(const String& library_path)
{
#if defined(OW_USE_FAKE_LIBS)
  if ( FileSystem::canRead(library_path) )
  {
    // Read the beginning of the file and see if it
    // contains the fake library heading.
    File libfile = FileSystem::openFile(library_path);

    if ( libfile )
    {
      char buffer[(OW_FAKELIB_HEADING_LENGTH) + 1];
      size_t num_read = libfile.read(buffer,(OW_FAKELIB_HEADING_LENGTH));
      if ( num_read == (OW_FAKELIB_HEADING_LENGTH) )
      {
   // Null terminate it.
   buffer[OW_FAKELIB_HEADING_LENGTH] = '\0';
   if ( String(OW_FAKELIB_HEADING) == buffer )
   {
     // Yes, it's a fake library.
     return true;
   }
      }
    }
  }  
#endif
  return false;
}

#if defined(OW_USE_FAKE_LIBS)
void dlSharedLibrary::initializeSymbolMap()
{
   if ( ! m_fakeLibrary )
   {
      return;
   }
   // Read the contents of the file to find out what the function names
   // (normally available from dlsym) are mapped to functions in the main
   // program. 
   StringArray lines = FileSystem::getFileLines(m_libName);

   for ( StringArray::const_iterator iter = lines.begin();
      iter != lines.end();
      ++iter )
   {
      // Skip commented lines.  
      if ( iter->startsWith('#') )
      {
         continue;
      }
      StringArray current_line = iter->tokenize("=");
      // Skip invalid lines.
      if ( current_line.size() != 2 )
      {
         continue;
      }
      // Add the data into the map.
      String option = String(current_line[0]).trim();
      String value = String(current_line[1]).trim();
      m_symbolMap[option] = value;
   }      
}
#endif /* defined(OW_USE_FAKE_LIBS) */

} // end namespace OW_NAMESPACE

#endif

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