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_DYNAMIC_LIBRARY_H 15 #define LLVM_SYSTEM_DYNAMIC_LIBRARY_H 16 17 #include <string> 18 19 namespace llvm { 20 namespace sys { 21 22 /// This class provides a portable interface to dynamic libraries which also 23 /// might be known as shared libraries, shared objects, dynamic shared 24 /// objects, or dynamic link libraries. Regardless of the terminology or the 25 /// operating system interface, this class provides a portable interface that 26 /// allows dynamic libraries to be loaded and searched for externally 27 /// defined symbols. This is typically used to provide "plug-in" support. 28 /// It also allows for symbols to be defined which don't live in any library, 29 /// but rather the main program itself, useful on Windows where the main 30 /// executable cannot be searched. 31 /// 32 /// Note: there is currently no interface for temporarily loading a library, 33 /// or for unloading libraries when the LLVM library is unloaded. 34 class DynamicLibrary { 35 // Placeholder whose address represents an invalid library. 36 // We use this instead of NULL or a pointer-int pair because the OS library 37 // might define 0 or 1 to be "special" handles, such as "search all". 38 static char Invalid; 39 40 // Opaque data used to interface with OS-specific dynamic library handling. 41 void *Data; 42 43 explicit DynamicLibrary(void *data = &Invalid) : Data(data) {} 44 public: 45 /// Returns true if the object refers to a valid library. 46 bool isValid() { return Data != &Invalid; } 47 48 /// Searches through the library for the symbol \p symbolName. If it is 49 /// found, the address of that symbol is returned. If not, NULL is returned. 50 /// Note that NULL will also be returned if the library failed to load. 51 /// Use isValid() to distinguish these cases if it is important. 52 /// Note that this will \e not search symbols explicitly registered by 53 /// AddSymbol(). 54 void *getAddressOfSymbol(const char *symbolName); 55 56 /// This function permanently loads the dynamic library at the given path. 57 /// The library will only be unloaded when the program terminates. 58 /// This returns a valid DynamicLibrary instance on success and an invalid 59 /// instance on failure (see isValid()). \p *errMsg will only be modified 60 /// if the library fails to load. 61 /// 62 /// It is safe to call this function multiple times for the same library. 63 /// @brief Open a dynamic library permanently. 64 static DynamicLibrary getPermanentLibrary(const char *filename, 65 std::string *errMsg = 0); 66 67 /// This function permanently loads the dynamic library at the given path. 68 /// Use this instead of getPermanentLibrary() when you won't need to get 69 /// symbols from the library itself. 70 /// 71 /// It is safe to call this function multiple times for the same library. 72 static bool LoadLibraryPermanently(const char *Filename, 73 std::string *ErrMsg = 0) { 74 return !getPermanentLibrary(Filename, ErrMsg).isValid(); 75 } 76 77 /// This function will search through all previously loaded dynamic 78 /// libraries for the symbol \p symbolName. If it is found, the address of 79 /// that symbol is returned. If not, null is returned. Note that this will 80 /// search permanently loaded libraries (getPermanentLibrary()) as well 81 /// as explicitly registered symbols (AddSymbol()). 82 /// @throws std::string on error. 83 /// @brief Search through libraries for address of a symbol 84 static void *SearchForAddressOfSymbol(const char *symbolName); 85 86 /// @brief Convenience function for C++ophiles. 87 static void *SearchForAddressOfSymbol(const std::string &symbolName) { 88 return SearchForAddressOfSymbol(symbolName.c_str()); 89 } 90 91 /// This functions permanently adds the symbol \p symbolName with the 92 /// value \p symbolValue. These symbols are searched before any 93 /// libraries. 94 /// @brief Add searchable symbol/value pair. 95 static void AddSymbol(StringRef symbolName, void *symbolValue); 96 }; 97 98 } // End sys namespace 99 } // End llvm namespace 100 101 #endif // LLVM_SYSTEM_DYNAMIC_LIBRARY_H 102
