The Tor Browser: comparison ipc/chromium/src/base/thread_local_storage

--1:000000000000
+:5d0bd4abcd13
+// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+#include "base/thread_local_storage.h"
+#include <windows.h>
+#include "base/logging.h"
+// In order to make TLS destructors work, we need to keep function
+// pointers to the destructor for each TLS that we allocate.
+// We make this work by allocating a single OS-level TLS, which
+// contains an array of slots for the application to use.  In
+// parallel, we also allocate an array of destructors, which we
+// keep track of and call when threads terminate.
+// tls_key_ is the one native TLS that we use.  It stores our
+// table.
+long ThreadLocalStorage::tls_key_ = TLS_OUT_OF_INDEXES;
+// tls_max_ is the high-water-mark of allocated thread local storage.
+// We intentionally skip 0 so that it is not confused with an
+// unallocated TLS slot.
+long ThreadLocalStorage::tls_max_ = 1;
+// An array of destructor function pointers for the slots.  If
+// a slot has a destructor, it will be stored in its corresponding
+// entry in this array.
+ThreadLocalStorage::TLSDestructorFunc
+ThreadLocalStorage::tls_destructors_[kThreadLocalStorageSize];
+void** ThreadLocalStorage::Initialize() {
+if (tls_key_ == TLS_OUT_OF_INDEXES) {
+long value = TlsAlloc();
+DCHECK(value != TLS_OUT_OF_INDEXES);
+// Atomically test-and-set the tls_key.  If the key is TLS_OUT_OF_INDEXES,
+// go ahead and set it.  Otherwise, do nothing, as another
+// thread already did our dirty work.
+if (InterlockedCompareExchange(&tls_key_, value, TLS_OUT_OF_INDEXES) !=
+TLS_OUT_OF_INDEXES) {
+// We've been shortcut. Another thread replaced tls_key_ first so we need
+// to destroy our index and use the one the other thread got first.
+TlsFree(value);
+}
+}
+DCHECK(TlsGetValue(tls_key_) == NULL);
+// Create an array to store our data.
+void** tls_data = new void*[kThreadLocalStorageSize];
+memset(tls_data, 0, sizeof(void*[kThreadLocalStorageSize]));
+TlsSetValue(tls_key_, tls_data);
+return tls_data;
+}
+ThreadLocalStorage::Slot::Slot(TLSDestructorFunc destructor)
+: initialized_(false) {
+Initialize(destructor);
+}
+bool ThreadLocalStorage::Slot::Initialize(TLSDestructorFunc destructor) {
+if (tls_key_ == TLS_OUT_OF_INDEXES || !TlsGetValue(tls_key_))
+ThreadLocalStorage::Initialize();
+// Grab a new slot.
+slot_ = InterlockedIncrement(&tls_max_) - 1;
+if (slot_ >= kThreadLocalStorageSize) {
+NOTREACHED();
+return false;
+}
+// Setup our destructor.
+tls_destructors_[slot_] = destructor;
+initialized_ = true;
+return true;
+}
+void ThreadLocalStorage::Slot::Free() {
+// At this time, we don't reclaim old indices for TLS slots.
+// So all we need to do is wipe the destructor.
+tls_destructors_[slot_] = NULL;
+initialized_ = false;
+}
+void* ThreadLocalStorage::Slot::Get() const {
+void** tls_data = static_cast<void**>(TlsGetValue(tls_key_));
+if (!tls_data)
+tls_data = ThreadLocalStorage::Initialize();
+DCHECK(slot_ >= 0 && slot_ < kThreadLocalStorageSize);
+return tls_data[slot_];
+}
+void ThreadLocalStorage::Slot::Set(void* value) {
+void** tls_data = static_cast<void**>(TlsGetValue(tls_key_));
+if (!tls_data)
+tls_data = ThreadLocalStorage::Initialize();
+DCHECK(slot_ >= 0 && slot_ < kThreadLocalStorageSize);
+tls_data[slot_] = value;
+}
+void ThreadLocalStorage::ThreadExit() {
+if (tls_key_ == TLS_OUT_OF_INDEXES)
+return;
+void** tls_data = static_cast<void**>(TlsGetValue(tls_key_));
+// Maybe we have never initialized TLS for this thread.
+if (!tls_data)
+return;
+for (int slot = 0; slot < tls_max_; slot++) {
+if (tls_destructors_[slot] != NULL) {
+void* value = tls_data[slot];
+tls_destructors_[slot](value);
+}
+}
+delete[] tls_data;
+// In case there are other "onexit" handlers...
+TlsSetValue(tls_key_, NULL);
+}
+// Thread Termination Callbacks.
+// Windows doesn't support a per-thread destructor with its
+// TLS primitives.  So, we build it manually by inserting a
+// function to be called on each thread's exit.
+// This magic is from http://www.codeproject.com/threads/tls.asp
+// and it works for VC++ 7.0 and later.
+#ifdef _WIN64
+// This makes the linker create the TLS directory if it's not already
+// there.  (e.g. if __declspec(thread) is not used).
+#pragma comment(linker, "/INCLUDE:_tls_used")
+#else  // _WIN64
+// This makes the linker create the TLS directory if it's not already
+// there.  (e.g. if __declspec(thread) is not used).
+#pragma comment(linker, "/INCLUDE:__tls_used")
+#endif  // _WIN64
+// Static callback function to call with each thread termination.
+void NTAPI OnThreadExit(PVOID module, DWORD reason, PVOID reserved)
+{
+// On XP SP0 & SP1, the DLL_PROCESS_ATTACH is never seen. It is sent on SP2+
+// and on W2K and W2K3. So don't assume it is sent.
+if (DLL_THREAD_DETACH == reason || DLL_PROCESS_DETACH == reason)
+ThreadLocalStorage::ThreadExit();
+}
+// .CRT$XLA to .CRT$XLZ is an array of PIMAGE_TLS_CALLBACK pointers that are
+// called automatically by the OS loader code (not the CRT) when the module is
+// loaded and on thread creation. They are NOT called if the module has been
+// loaded by a LoadLibrary() call. It must have implicitly been loaded at
+// process startup.
+// By implicitly loaded, I mean that it is directly referenced by the main EXE
+// or by one of its dependent DLLs. Delay-loaded DLL doesn't count as being
+// implicitly loaded.
+//
+// See VC\crt\src\tlssup.c for reference.
+#ifdef _WIN64
+// .CRT section is merged with .rdata on x64 so it must be constant data.
+#pragma const_seg(".CRT$XLB")
+// When defining a const variable, it must have external linkage to be sure the
+// linker doesn't discard it. If this value is discarded, the OnThreadExit
+// function will never be called.
+extern const PIMAGE_TLS_CALLBACK p_thread_callback;
+const PIMAGE_TLS_CALLBACK p_thread_callback = OnThreadExit;
+// Reset the default section.
+#pragma const_seg()
+#else  // _WIN64
+#pragma data_seg(".CRT$XLB")
+PIMAGE_TLS_CALLBACK p_thread_callback = OnThreadExit;
+// Reset the default section.
+#pragma data_seg()
+#endif  // _WIN64

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comparison: ipc/chromium/src/base/thread_local_storage_win.cc

ipc/chromium/src/base/thread_local_storage_win.cc