[Bindings] Create and use V8 context snapshots

gin/v8_initializer.cc

 // Copyright 2013 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 "gin/v8_initializer.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <memory>
 
 #include "base/debug/alias.h"
 #include "base/debug/crash_logging.h"
 #include "base/feature_list.h"
 #include "base/files/file.h"
 #include "base/files/file_path.h"
 #include "base/files/memory_mapped_file.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/metrics/histogram_macros.h"
+#include "base/path_service.h"
 #include "base/rand_util.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/sys_info.h"
 #include "base/threading/platform_thread.h"
 #include "base/time/time.h"
 
 #if defined(V8_USE_EXTERNAL_STARTUP_DATA)
 #if defined(OS_ANDROID)
 #include "base/android/apk_assets.h"
+#elif defined(OS_MACOSX)
+#include "base/mac/foundation_util.h"
 #endif
-#if defined(OS_MACOSX)
-#include "base/mac/foundation_util.h"
-#endif  // OS_MACOSX
-#include "base/path_service.h"
 #endif  // V8_USE_EXTERNAL_STARTUP_DATA
 
 namespace gin {
 
 namespace {
 
 // None of these globals are ever freed nor closed.
 base::MemoryMappedFile* g_mapped_natives = nullptr;
 base::MemoryMappedFile* g_mapped_snapshot = nullptr;
+base::MemoryMappedFile* g_mapped_blink_v8_snapshot = nullptr;
 
-#if defined(V8_USE_EXTERNAL_STARTUP_DATA)
+const char kBlinkV8SnapshotFileName[] = "blink_v8_snapshot.bin";
 
 // File handles intentionally never closed. Not using File here because its
 // Windows implementation guards against two instances owning the same
 // PlatformFile (which we allow since we know it is never freed).
-typedef std::map<const char*,
-                 std::pair<base::PlatformFile, base::MemoryMappedFile::Region>>
-    OpenedFileMap;
-static base::LazyInstance<OpenedFileMap>::Leaky g_opened_files =
+using OpenedFileMap =
+    std::map<const char*,
+             std::pair<base::PlatformFile, base::MemoryMappedFile::Region>>;
+base::LazyInstance<OpenedFileMap>::Leaky g_opened_files =
     LAZY_INSTANCE_INITIALIZER;
 
 OpenedFileMap::mapped_type& GetOpenedFile(const char* file) {
   OpenedFileMap& opened_files(g_opened_files.Get());
   if (opened_files.find(file) == opened_files.end()) {
     opened_files[file] = std::make_pair(base::kInvalidPlatformFile,
                                         base::MemoryMappedFile::Region());
   }
   return opened_files[file];
 }
 
+#if defined(V8_USE_EXTERNAL_STARTUP_DATA)
+
 const char kNativesFileName[] = "natives_blob.bin";
 
 #if defined(OS_ANDROID)
 const char kSnapshotFileName64[] = "snapshot_blob_64.bin";
 const char kSnapshotFileName32[] = "snapshot_blob_32.bin";
 
 #if defined(__LP64__)
 #define kSnapshotFileName kSnapshotFileName64
 #else
 #define kSnapshotFileName kSnapshotFileName32
 #endif
 
 #else  // defined(OS_ANDROID)
 const char kSnapshotFileName[] = "snapshot_blob.bin";
 #endif  // defined(OS_ANDROID)
 
+#endif  // defined(V8_USE_EXTERNAL_STATUP_DATA)
+
 void GetV8FilePath(const char* file_name, base::FilePath* path_out) {
 #if !defined(OS_MACOSX)
   base::FilePath data_path;
 #if defined(OS_ANDROID)
   // This is the path within the .apk.
   data_path = base::FilePath(FILE_PATH_LITERAL("assets"));
 #elif defined(OS_POSIX)
   PathService::Get(base::DIR_EXE, &data_path);
 #elif defined(OS_WIN)
   PathService::Get(base::DIR_MODULE, &data_path);
 #endif
   DCHECK(!data_path.empty());
 
   *path_out = data_path.AppendASCII(file_name);
 #else   // !defined(OS_MACOSX)
   base::ScopedCFTypeRef<CFStringRef> natives_file_name(
       base::SysUTF8ToCFStringRef(file_name));
   *path_out = base::mac::PathForFrameworkBundleResource(natives_file_name);
 #endif  // !defined(OS_MACOSX)
-  DCHECK(!path_out->empty());
 }
 
-static bool MapV8File(base::PlatformFile platform_file,
-                      base::MemoryMappedFile::Region region,
-                      base::MemoryMappedFile** mmapped_file_out) {
+bool MapV8File(base::PlatformFile platform_file,
+               base::MemoryMappedFile::Region region,
+               base::MemoryMappedFile** mmapped_file_out) {
   DCHECK(*mmapped_file_out == NULL);
   std::unique_ptr<base::MemoryMappedFile> mmapped_file(
       new base::MemoryMappedFile());
   if (mmapped_file->Initialize(base::File(platform_file), region)) {
     *mmapped_file_out = mmapped_file.release();
     return true;
   }
   return false;
 }
 
@@ skipping 57 matching lines @@
     }
   }
 #endif  // defined(OS_ANDROID)
 
   UMA_HISTOGRAM_ENUMERATION("V8.Initializer.OpenV8File.Result",
                             result,
                             OpenV8FileResult::MAX_VALUE);
   return file.TakePlatformFile();
 }
 
-static const OpenedFileMap::mapped_type OpenFileIfNecessary(
-    const char* file_name) {
+const OpenedFileMap::mapped_type OpenFileIfNecessary(const char* file_name) {
   OpenedFileMap::mapped_type& opened = GetOpenedFile(file_name);
   if (opened.first == base::kInvalidPlatformFile) {
     opened.first = OpenV8File(file_name, &opened.second);
   }
   return opened;
 }
 
-#endif  // V8_USE_EXTERNAL_STARTUP_DATA
-
 bool GenerateEntropy(unsigned char* buffer, size_t amount) {
   base::RandBytes(buffer, amount);
   return true;
 }
 
-}  // namespace
-
-#if defined(V8_USE_EXTERNAL_STARTUP_DATA)
-
-namespace {
-
 enum LoadV8FileResult {
   V8_LOAD_SUCCESS = 0,
   V8_LOAD_FAILED_OPEN,
   V8_LOAD_FAILED_MAP,
   V8_LOAD_FAILED_VERIFY,  // Deprecated.
   V8_LOAD_MAX_VALUE
 };
 
-static LoadV8FileResult MapOpenedFile(
-    const OpenedFileMap::mapped_type& file_region,
-    base::MemoryMappedFile** mmapped_file_out) {
+LoadV8FileResult MapOpenedFile(const OpenedFileMap::mapped_type& file_region,
+                               base::MemoryMappedFile** mmapped_file_out) {
   if (file_region.first == base::kInvalidPlatformFile)
     return V8_LOAD_FAILED_OPEN;
   if (!MapV8File(file_region.first, file_region.second, mmapped_file_out))
     return V8_LOAD_FAILED_MAP;
   return V8_LOAD_SUCCESS;
 }
 
 }  // namespace
 
+#if defined(V8_USE_EXTERNAL_STARTUP_DATA)
+
 // static
 void V8Initializer::LoadV8Snapshot() {
   if (g_mapped_snapshot)
     return;
 
   OpenFileIfNecessary(kSnapshotFileName);
   LoadV8FileResult result = MapOpenedFile(GetOpenedFile(kSnapshotFileName),
                                           &g_mapped_snapshot);
   // V8 can't start up without the source of the natives, but it can
   // start up (slower) without the snapshot.
@@ skipping 128 matching lines @@
     static const char flag[] = "--experimental_extras";
     v8::V8::SetFlagsFromString(flag, sizeof(flag) - 1);
   }
 
 #if defined(V8_USE_EXTERNAL_STARTUP_DATA)
   v8::StartupData natives;
   natives.data = reinterpret_cast<const char*>(g_mapped_natives->data());
   natives.raw_size = static_cast<int>(g_mapped_natives->length());
   v8::V8::SetNativesDataBlob(&natives);
 
-  if (g_mapped_snapshot != NULL) {
+  if (g_mapped_snapshot) {
     v8::StartupData snapshot;
     snapshot.data = reinterpret_cast<const char*>(g_mapped_snapshot->data());
     snapshot.raw_size = static_cast<int>(g_mapped_snapshot->length());
     v8::V8::SetSnapshotDataBlob(&snapshot);
   }
 #endif  // V8_USE_EXTERNAL_STARTUP_DATA
 
   v8::V8::SetEntropySource(&GenerateEntropy);
   v8::V8::Initialize();
 
@@ skipping 15 matching lines @@
   if (g_mapped_snapshot) {
     *snapshot_data_out =
         reinterpret_cast<const char*>(g_mapped_snapshot->data());
     *snapshot_size_out = static_cast<int>(g_mapped_snapshot->length());
   } else {
     *snapshot_data_out = NULL;
     *snapshot_size_out = 0;
   }
 }
 
+// static
+void V8Initializer::LoadBlinkV8Snapshot() {
+  if (g_mapped_blink_v8_snapshot)
+    return;
+#if defined(CHROME_MULTIPLE_DLL_BROWSER)

[Yuki, 2017/06/20 14:20:10]

Does this mean that, if we're building with is_component_build=true, the
snapshot will be disabled?  If so, it's not good because most of people are
developing with the component builds, and it will be hard to catch issues.

[peria, 2017/06/21 07:19:15]

This #if disables snasphot feature for non-component build on Windows.
I'll look for a workaround.

+  return;
+#endif
+
+  OpenFileIfNecessary(kBlinkV8SnapshotFileName);
+  LoadV8FileResult result = MapOpenedFile(
+      GetOpenedFile(kBlinkV8SnapshotFileName), &g_mapped_blink_v8_snapshot);
+
+  // The second condition is a workaround for unittests without resource
+  // bandles.
+  // TODO(peria): Remove the second condition in DCHECK()
+  DCHECK(g_mapped_blink_v8_snapshot || result == V8_LOAD_FAILED_OPEN);
+}
+
+// static
+void V8Initializer::LoadBlinkV8SnapshotFromFD(base::PlatformFile snapshot_pf,
+                                              int64_t snapshot_offset,
+                                              int64_t snapshot_size) {
+  if (g_mapped_blink_v8_snapshot)
+    return;
+  CHECK_NE(base::kInvalidPlatformFile, snapshot_pf);
+
+  base::MemoryMappedFile::Region snapshot_region =
+      base::MemoryMappedFile::Region::kWholeFile;
+  if (snapshot_size != 0 || snapshot_offset != 0) {
+    snapshot_region.offset = snapshot_offset;
+    snapshot_region.size = snapshot_size;
+  }
+
+  if (MapV8File(snapshot_pf, snapshot_region, &g_mapped_blink_v8_snapshot)) {
+    g_opened_files.Get()[kBlinkV8SnapshotFileName] =
+        std::make_pair(snapshot_pf, snapshot_region);
+  }
+}
+
+// static
+void V8Initializer::GetBlinkV8SnapshotData(const char** snapshot_data_out,
+                                           int* snapshot_size_out) {
+  if (g_mapped_blink_v8_snapshot) {
+    *snapshot_data_out =
+        reinterpret_cast<const char*>(g_mapped_blink_v8_snapshot->data());
+    *snapshot_size_out = static_cast<int>(g_mapped_blink_v8_snapshot->length());
+  } else {
+    *snapshot_data_out = nullptr;
+    *snapshot_size_out = 0;
+  }
+}
+
 }  // namespace gin