//===-- llvm/System/DynamicLibrary.h - Portable Dynamic Library -*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file declares the sys::DynamicLibrary class.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_SYSTEM_DYNAMIC_LIBRARY_H
#define LLVM_SYSTEM_DYNAMIC_LIBRARY_H

#include <string>

namespace llvm {
namespace sys {

  /// This class provides a portable interface to dynamic libraries which also
  /// might be known as shared libraries, shared objects, dynamic shared
  /// objects, or dynamic link libraries. Regardless of the terminology or the
  /// operating system interface, this class provides a portable interface that
  /// allows dynamic libraries to be loaded and searched for externally
  /// defined symbols. This is typically used to provide "plug-in" support.
  /// It also allows for symbols to be defined which don't live in any library,
  /// but rather the main program itself, useful on Windows where the main
  /// executable cannot be searched.
  class DynamicLibrary {
    DynamicLibrary(); // DO NOT IMPLEMENT
  public:
    /// This function allows a library to be loaded without instantiating a
    /// DynamicLibrary object. Consequently, it is marked as being permanent
    /// and will only be unloaded when the program terminates.  This returns
    /// false on success or returns true and fills in *ErrMsg on failure.
    /// @brief Open a dynamic library permanently.
    ///
    /// NOTE: This function is not thread safe.
    ///
    static bool LoadLibraryPermanently(const char *filename,
                                       std::string *ErrMsg = 0);

    /// This function will search through all previously loaded dynamic
    /// libraries for the symbol \p symbolName. If it is found, the addressof
    /// that symbol is returned. If not, null is returned. Note that this will
    /// search permanently loaded libraries (LoadLibraryPermanently) as well
    /// as ephemerally loaded libraries (constructors).
    /// @throws std::string on error.
    /// @brief Search through libraries for address of a symbol
    ///
    /// NOTE: This function is not thread safe.
    ///
    static void *SearchForAddressOfSymbol(const char *symbolName);

    /// @brief Convenience function for C++ophiles.
    ///
    /// NOTE: This function is not thread safe.
    ///
    static void *SearchForAddressOfSymbol(const std::string &symbolName) {
      return SearchForAddressOfSymbol(symbolName.c_str());
    }

    /// This functions permanently adds the symbol \p symbolName with the
    /// value \p symbolValue.  These symbols are searched before any
    /// libraries.
    /// @brief Add searchable symbol/value pair.
    ///
    /// NOTE: This function is not thread safe.
    ///
    static void AddSymbol(const char *symbolName, void *symbolValue);

    /// @brief Convenience function for C++ophiles.
    ///
    /// NOTE: This function is not thread safe.
    ///
    static void AddSymbol(const std::string &symbolName, void *symbolValue) {
      AddSymbol(symbolName.c_str(), symbolValue);
    }
  };

} // End sys namespace
} // End llvm namespace

#endif // LLVM_SYSTEM_DYNAMIC_LIBRARY_H