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/*
* libjingle
* Copyright 2004--2010, Google Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
* EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef TALK_BASE_LATEBINDINGSYMBOLTABLE_H_
#define TALK_BASE_LATEBINDINGSYMBOLTABLE_H_
#include <string.h>
#include "talk/base/common.h"
#include "talk/base/logging.h"
// This file provides macros for creating "symbol table" classes to simplify the
// dynamic loading of symbols from DLLs. Currently the implementation only
// supports Linux and pure C symbols.
// See talk/sound/pulseaudiosymboltable.(h|cc) for an example.
namespace talk_base {
#ifdef LINUX
typedef void *DllHandle;
const DllHandle kInvalidDllHandle = NULL;
#else
#error Not implemented
#endif
// These are helpers for use only by the class below.
DllHandle InternalLoadDll(const char dll_name[]);
void InternalUnloadDll(DllHandle handle);
bool InternalLoadSymbols(DllHandle handle,
int num_symbols,
const char *const symbol_names[],
void *symbols[]);
template <int SYMBOL_TABLE_SIZE,
const char kDllName[],
const char *const kSymbolNames[]>
class LateBindingSymbolTable {
public:
LateBindingSymbolTable()
: handle_(kInvalidDllHandle),
undefined_symbols_(false) {
memset(symbols_, 0, sizeof(symbols_));
}
~LateBindingSymbolTable() {
Unload();
}
static int NumSymbols() {
return SYMBOL_TABLE_SIZE;
}
// We do not use this, but we offer it for theoretical convenience.
static const char *GetSymbolName(int index) {
ASSERT(index < NumSymbols());
return kSymbolNames[index];
}
bool IsLoaded() const {
return handle_ != kInvalidDllHandle;
}
// Loads the DLL and the symbol table. Returns true iff the DLL and symbol
// table loaded successfully.
bool Load() {
if (IsLoaded()) {
return true;
}
if (undefined_symbols_) {
// We do not attempt to load again because repeated attempts are not
// likely to succeed and DLL loading is costly.
LOG(LS_ERROR) << "We know there are undefined symbols";
return false;
}
handle_ = InternalLoadDll(kDllName);
if (!IsLoaded()) {
return false;
}
if (!InternalLoadSymbols(handle_, NumSymbols(), kSymbolNames, symbols_)) {
undefined_symbols_ = true;
Unload();
return false;
}
return true;
}
void Unload() {
if (!IsLoaded()) {
return;
}
InternalUnloadDll(handle_);
handle_ = kInvalidDllHandle;
memset(symbols_, 0, sizeof(symbols_));
}
// Retrieves the given symbol. NOTE: Recommended to use LATESYM_GET below
// instead of this.
void *GetSymbol(int index) const {
ASSERT(IsLoaded());
ASSERT(index < NumSymbols());
return symbols_[index];
}
private:
DllHandle handle_;
bool undefined_symbols_;
void *symbols_[SYMBOL_TABLE_SIZE];
DISALLOW_COPY_AND_ASSIGN(LateBindingSymbolTable);
};
// This macro must be invoked in a header to declare a symbol table class.
#define LATE_BINDING_SYMBOL_TABLE_DECLARE_BEGIN(ClassName) \
enum {
// This macro must be invoked in the header declaration once for each symbol
// (recommended to use an X-Macro to avoid duplication).
// This macro defines an enum with names built from the symbols, which
// essentially creates a hash table in the compiler from symbol names to their
// indices in the symbol table class.
#define LATE_BINDING_SYMBOL_TABLE_DECLARE_ENTRY(ClassName, sym) \
ClassName##_SYMBOL_TABLE_INDEX_##sym,
// This macro completes the header declaration.
#define LATE_BINDING_SYMBOL_TABLE_DECLARE_END(ClassName) \
ClassName##_SYMBOL_TABLE_SIZE \
}; \
\
extern const char ClassName##_kDllName[]; \
extern const char *const \
ClassName##_kSymbolNames[ClassName##_SYMBOL_TABLE_SIZE]; \
\
typedef ::talk_base::LateBindingSymbolTable<ClassName##_SYMBOL_TABLE_SIZE, \
ClassName##_kDllName, \
ClassName##_kSymbolNames> \
ClassName;
// This macro must be invoked in a .cc file to define a previously-declared
// symbol table class.
#define LATE_BINDING_SYMBOL_TABLE_DEFINE_BEGIN(ClassName, dllName) \
const char ClassName##_kDllName[] = dllName; \
const char *const ClassName##_kSymbolNames[ClassName##_SYMBOL_TABLE_SIZE] = {
// This macro must be invoked in the .cc definition once for each symbol
// (recommended to use an X-Macro to avoid duplication).
// This would have to use the mangled name if we were to ever support C++
// symbols.
#define LATE_BINDING_SYMBOL_TABLE_DEFINE_ENTRY(ClassName, sym) \
#sym,
#define LATE_BINDING_SYMBOL_TABLE_DEFINE_END(ClassName) \
};
// Index of a given symbol in the given symbol table class.
#define LATESYM_INDEXOF(ClassName, sym) \
(ClassName##_SYMBOL_TABLE_INDEX_##sym)
// Returns a reference to the given late-binded symbol, with the correct type.
#define LATESYM_GET(ClassName, inst, sym) \
(*reinterpret_cast<typeof(&sym)>( \
(inst)->GetSymbol(LATESYM_INDEXOF(ClassName, sym))))
} // namespace talk_base
#endif // TALK_BASE_LATEBINDINGSYMBOLTABLE_H_