ACE  6.1.2
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Public Member Functions | Private Member Functions | Private Attributes | Static Private Attributes
ACE_DLL_Handle Class Reference

Provides an abstract interface for handling various DLL operations. More...

#include <DLL_Manager.h>

List of all members.

Public Member Functions

 ACE_DLL_Handle (void)
 Default construtor.
 ~ACE_DLL_Handle (void)
const ACE_TCHARdll_name () const
 Returns the name of the shared library (without prefixes or suffixes).
int open (const ACE_TCHAR *dll_name, int open_mode, ACE_SHLIB_HANDLE handle)
int close (int unload=0)
sig_atomic_t refcount (void) const
 Return the current refcount.
void * symbol (const ACE_TCHAR *symbol_name, int ignore_errors=0)
ACE_SHLIB_HANDLE get_handle (int become_owner=0)

Private Member Functions

auto_ptr< ACE_TStringerror (void)
void get_dll_names (const ACE_TCHAR *dll_name, ACE_Array< ACE_TString > &try_names)
 ACE_DLL_Handle (const ACE_DLL_Handle &)
 Disallow copying and assignment since we don't handle them.
void operator= (const ACE_DLL_Handle &)

Private Attributes

sig_atomic_t refcount_
 Name of the shared library.
 Handle to the actual library loaded by the OS.

Static Private Attributes

static sig_atomic_t open_called_ = 0

Detailed Description

Provides an abstract interface for handling various DLL operations.

This class is an wrapper over the various methods for utilizing a dynamically linked library (DLL), which is called a shared library on some platforms. It is refcounted and managed by ACE_DLL_Manager, so there will only be a single instance of this class for each dll loaded, no matter how many instances of ACE_DLL an application has open. Operations open(), close(), and symbol() have been implemented to help opening/closing and extracting symbol information from a DLL, respectively.

Most of this class came from the original ACE_DLL class. ACE_DLL is now just an interface that passed all it's calls either directly or via ACE_DLL_Manager to this class for execution.

Constructor & Destructor Documentation

Default construtor.


Disallow copying and assignment since we don't handle them.

Member Function Documentation

int ACE_DLL_Handle::close ( int  unload = 0)

Call to close the DLL object. If unload = 0, it only decrements the refcount, but if unload = 1, then it will actually unload the library when the refcount == 0;

const ACE_TCHAR * ACE_DLL_Handle::dll_name ( void  ) const

Returns the name of the shared library (without prefixes or suffixes).

Returns a pointer to a string explaining why <symbol> or <open> failed. This is used internal to print out the error to the log, but since this object is shared, we can't store or return the error to the caller.

void ACE_DLL_Handle::get_dll_names ( const ACE_TCHAR dll_name,
ACE_Array< ACE_TString > &  try_names 

Builds array of DLL names to try to dlopen, based on platform and configured DLL prefixes/suffixes. Returns the array of names to try in try_names.

ACE_SHLIB_HANDLE ACE_DLL_Handle::get_handle ( int  become_owner = 0)

Return the handle to the caller. If become_owner is non-0 then caller assumes ownership of the handle so we decrement the retcount.

int ACE_DLL_Handle::open ( const ACE_TCHAR dll_name,
int  open_mode,

This method opens and dynamically links a library/DLL.

dll_nameThe filename or path of the DLL to load. ACE will attempt to apply the platform's standard library/DLL prefixes and suffixes, allowing a simple, unadorned name to be passed regardless of platform. The set of name transforms is listed below. A decorator is a platform's name designator for a debug vs release build. For example, on Windows it is usually "d".
  • Name + decorator + suffix
  • Name + suffix
  • Prefix + name + decorator + suffix
  • Prefix + name + suffix
  • Name Note that the transforms with decorator will be avoided if ACE is built with the ACE_DISABLE_DEBUG_DLL_CHECK config macro.
There is another mode for locating library/DLL files that was used in old versions of ACE. The alternate method builds more combinations of pathname by combining the names transforms above with locations listed in the platform's standard "path" locations (e.g., LD_LIBRARY_PATH). It can be enabled by building ACE with the ACE_MUST_HELP_DLOPEN_SEARCH_PATH config macro. Use of this option is discouraged since it avoids the standard platform search options and security mechanisms.
open_modeFlags to alter the actions taken when loading the DLL. The possible values are:
  • RTLD_LAZY (this the default): loads identifier symbols but not the symbols for functions, which are loaded dynamically on demand.
  • RTLD_NOW: performs all necessary relocations when dll_name is first loaded
  • RTLD_GLOBAL: makes symbols available for relocation processing of any other DLLs.
handleIf a value other than ACE_INVALID_HANDLE is supplied, this object is assigned the specified handle instead of attempting to open the specified dll_name.
Return values:
-1On failure
0On success.
void ACE_DLL_Handle::operator= ( const ACE_DLL_Handle )

Return the current refcount.

void * ACE_DLL_Handle::symbol ( const ACE_TCHAR symbol_name,
int  ignore_errors = 0 

If symbol_name is in the symbol table of the DLL a pointer to the symbol_name is returned. Otherwise, returns 0. Set the ignore_errors flag to supress logging errors if symbol_name isn't found. This is nice if you just want to probe a dll to see what's available, since missing functions in that case aren't really errors.

Member Data Documentation

Name of the shared library.

Handle to the actual library loaded by the OS.

Keeps track of whether or not open() has ever been called. This helps get around problem on Linux, and perhaps other OS's, that seg-fault if dlerror() is called before the ld library has been initialized by a call to dlopen().

Keep track of how many ACE_DLL objects have a reference to this dll.

The documentation for this class was generated from the following files: