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DynamicLibrary.h
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1 //===-- llvm/Support/DynamicLibrary.h - Portable Dynamic Library -*- C++ -*-===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file declares the sys::DynamicLibrary class.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_SYSTEM_DYNAMICLIBRARY_H
15 #define LLVM_SYSTEM_DYNAMICLIBRARY_H
16 
17 #include <string>
18 
19 namespace llvm {
20 
21 class StringRef;
22 
23 namespace sys {
24 
25  /// This class provides a portable interface to dynamic libraries which also
26  /// might be known as shared libraries, shared objects, dynamic shared
27  /// objects, or dynamic link libraries. Regardless of the terminology or the
28  /// operating system interface, this class provides a portable interface that
29  /// allows dynamic libraries to be loaded and searched for externally
30  /// defined symbols. This is typically used to provide "plug-in" support.
31  /// It also allows for symbols to be defined which don't live in any library,
32  /// but rather the main program itself, useful on Windows where the main
33  /// executable cannot be searched.
34  ///
35  /// Note: there is currently no interface for temporarily loading a library,
36  /// or for unloading libraries when the LLVM library is unloaded.
38  // Placeholder whose address represents an invalid library.
39  // We use this instead of NULL or a pointer-int pair because the OS library
40  // might define 0 or 1 to be "special" handles, such as "search all".
41  static char Invalid;
42 
43  // Opaque data used to interface with OS-specific dynamic library handling.
44  void *Data;
45 
46  explicit DynamicLibrary(void *data = &Invalid) : Data(data) {}
47  public:
48  /// Returns true if the object refers to a valid library.
49  bool isValid() { return Data != &Invalid; }
50 
51  /// Searches through the library for the symbol \p symbolName. If it is
52  /// found, the address of that symbol is returned. If not, NULL is returned.
53  /// Note that NULL will also be returned if the library failed to load.
54  /// Use isValid() to distinguish these cases if it is important.
55  /// Note that this will \e not search symbols explicitly registered by
56  /// AddSymbol().
57  void *getAddressOfSymbol(const char *symbolName);
58 
59  /// This function permanently loads the dynamic library at the given path.
60  /// The library will only be unloaded when the program terminates.
61  /// This returns a valid DynamicLibrary instance on success and an invalid
62  /// instance on failure (see isValid()). \p *errMsg will only be modified
63  /// if the library fails to load.
64  ///
65  /// It is safe to call this function multiple times for the same library.
66  /// @brief Open a dynamic library permanently.
67  static DynamicLibrary getPermanentLibrary(const char *filename,
68  std::string *errMsg = 0);
69 
70  /// This function permanently loads the dynamic library at the given path.
71  /// Use this instead of getPermanentLibrary() when you won't need to get
72  /// symbols from the library itself.
73  ///
74  /// It is safe to call this function multiple times for the same library.
75  static bool LoadLibraryPermanently(const char *Filename,
76  std::string *ErrMsg = 0) {
77  return !getPermanentLibrary(Filename, ErrMsg).isValid();
78  }
79 
80  /// This function will search through all previously loaded dynamic
81  /// libraries for the symbol \p symbolName. If it is found, the address of
82  /// that symbol is returned. If not, null is returned. Note that this will
83  /// search permanently loaded libraries (getPermanentLibrary()) as well
84  /// as explicitly registered symbols (AddSymbol()).
85  /// @throws std::string on error.
86  /// @brief Search through libraries for address of a symbol
87  static void *SearchForAddressOfSymbol(const char *symbolName);
88 
89  /// @brief Convenience function for C++ophiles.
90  static void *SearchForAddressOfSymbol(const std::string &symbolName) {
91  return SearchForAddressOfSymbol(symbolName.c_str());
92  }
93 
94  /// This functions permanently adds the symbol \p symbolName with the
95  /// value \p symbolValue. These symbols are searched before any
96  /// libraries.
97  /// @brief Add searchable symbol/value pair.
98  static void AddSymbol(StringRef symbolName, void *symbolValue);
99  };
100 
101 } // End sys namespace
102 } // End llvm namespace
103 
104 #endif // LLVM_SYSTEM_DYNAMIC_LIBRARY_H
static void * SearchForAddressOfSymbol(const char *symbolName)
Search through libraries for address of a symbol.
static void * SearchForAddressOfSymbol(const std::string &symbolName)
Convenience function for C++ophiles.
void * getAddressOfSymbol(const char *symbolName)
static void AddSymbol(StringRef symbolName, void *symbolValue)
Add searchable symbol/value pair.
static bool LoadLibraryPermanently(const char *Filename, std::string *ErrMsg=0)
bool isValid()
Returns true if the object refers to a valid library.
static DynamicLibrary getPermanentLibrary(const char *filename, std::string *errMsg=0)
Open a dynamic library permanently.
const StringRef filename(StringRef path)
Get filename.
Definition: Path.cpp:467