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102 lines
4.5 KiB
C++
102 lines
4.5 KiB
C++
//===-- llvm/Support/DynamicLibrary.h - Portable Dynamic Library -*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file declares the sys::DynamicLibrary class.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_SYSTEM_DYNAMIC_LIBRARY_H
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#define LLVM_SYSTEM_DYNAMIC_LIBRARY_H
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#include <string>
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namespace llvm {
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namespace sys {
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/// This class provides a portable interface to dynamic libraries which also
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/// might be known as shared libraries, shared objects, dynamic shared
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/// objects, or dynamic link libraries. Regardless of the terminology or the
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/// operating system interface, this class provides a portable interface that
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/// allows dynamic libraries to be loaded and searched for externally
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/// defined symbols. This is typically used to provide "plug-in" support.
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/// It also allows for symbols to be defined which don't live in any library,
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/// but rather the main program itself, useful on Windows where the main
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/// executable cannot be searched.
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///
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/// Note: there is currently no interface for temporarily loading a library,
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/// or for unloading libraries when the LLVM library is unloaded.
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class DynamicLibrary {
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// Placeholder whose address represents an invalid library.
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// We use this instead of NULL or a pointer-int pair because the OS library
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// might define 0 or 1 to be "special" handles, such as "search all".
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static char Invalid;
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// Opaque data used to interface with OS-specific dynamic library handling.
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void *Data;
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explicit DynamicLibrary(void *data = &Invalid) : Data(data) {}
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public:
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/// Returns true if the object refers to a valid library.
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bool isValid() { return Data != &Invalid; }
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/// Searches through the library for the symbol \p symbolName. If it is
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/// found, the address of that symbol is returned. If not, NULL is returned.
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/// Note that NULL will also be returned if the library failed to load.
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/// Use isValid() to distinguish these cases if it is important.
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/// Note that this will \e not search symbols explicitly registered by
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/// AddSymbol().
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void *getAddressOfSymbol(const char *symbolName);
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/// This function permanently loads the dynamic library at the given path.
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/// The library will only be unloaded when the program terminates.
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/// This returns a valid DynamicLibrary instance on success and an invalid
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/// instance on failure (see isValid()). \p *errMsg will only be modified
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/// if the library fails to load.
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///
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/// It is safe to call this function multiple times for the same library.
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/// @brief Open a dynamic library permanently.
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static DynamicLibrary getPermanentLibrary(const char *filename,
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std::string *errMsg = 0);
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/// This function permanently loads the dynamic library at the given path.
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/// Use this instead of getPermanentLibrary() when you won't need to get
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/// symbols from the library itself.
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///
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/// It is safe to call this function multiple times for the same library.
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static bool LoadLibraryPermanently(const char *Filename,
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std::string *ErrMsg = 0) {
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return !getPermanentLibrary(Filename, ErrMsg).isValid();
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}
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/// This function will search through all previously loaded dynamic
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/// libraries for the symbol \p symbolName. If it is found, the address of
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/// that symbol is returned. If not, null is returned. Note that this will
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/// search permanently loaded libraries (getPermanentLibrary()) as well
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/// as explicitly registered symbols (AddSymbol()).
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/// @throws std::string on error.
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/// @brief Search through libraries for address of a symbol
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static void *SearchForAddressOfSymbol(const char *symbolName);
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/// @brief Convenience function for C++ophiles.
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static void *SearchForAddressOfSymbol(const std::string &symbolName) {
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return SearchForAddressOfSymbol(symbolName.c_str());
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}
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/// This functions permanently adds the symbol \p symbolName with the
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/// value \p symbolValue. These symbols are searched before any
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/// libraries.
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/// @brief Add searchable symbol/value pair.
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static void AddSymbol(StringRef symbolName, void *symbolValue);
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};
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} // End sys namespace
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} // End llvm namespace
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#endif // LLVM_SYSTEM_DYNAMIC_LIBRARY_H
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