src/snapshot/mksnapshot.cc - v8/v8.git - Git at Google

 // Copyright 2006-2008 the V8 project 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 <errno.h>
 #include <signal.h>
 #include <stdio.h>

 #include "include/libplatform/libplatform.h"
 #include "src/assembler.h"
 #include "src/base/platform/platform.h"
 #include "src/flags.h"
 #include "src/msan.h"
 #include "src/snapshot/natives.h"
 #include "src/snapshot/partial-serializer.h"
 #include "src/snapshot/snapshot.h"
 #include "src/snapshot/startup-serializer.h"

 namespace {
 class SnapshotWriter {
  public:
   SnapshotWriter()
       : snapshot_cpp_path_(nullptr), snapshot_blob_path_(nullptr) {}

 #ifdef V8_EMBEDDED_BUILTINS
   void SetEmbeddedFile(const char* embedded_cpp_file) {
     embedded_cpp_path_ = embedded_cpp_file;
   }

   void SetEmbeddedVariant(const char* embedded_variant) {
     embedded_variant_ = embedded_variant;
   }
 #endif

   void SetSnapshotFile(const char* snapshot_cpp_file) {
     snapshot_cpp_path_ = snapshot_cpp_file;
   }

   void SetStartupBlobFile(const char* snapshot_blob_file) {
     snapshot_blob_path_ = snapshot_blob_file;
   }

   void WriteSnapshot(v8::StartupData blob) const {
     // TODO(crbug/633159): if we crash before the files have been fully created,
     // we end up with a corrupted snapshot file. The build step would succeed,
     // but the build target is unusable. Ideally we would write out temporary
     // files and only move them to the final destination as last step.
     i::Vector<const i::byte> blob_vector(
         reinterpret_cast<const i::byte*>(blob.data), blob.raw_size);
     MaybeWriteSnapshotFile(blob_vector);
     MaybeWriteStartupBlob(blob_vector);
   }

 #ifdef V8_EMBEDDED_BUILTINS
   void WriteEmbedded(const i::EmbeddedData* blob) const {
     MaybeWriteEmbeddedFile(blob);
   }
 #endif

  private:
   void MaybeWriteStartupBlob(const i::Vector<const i::byte>& blob) const {
     if (!snapshot_blob_path_) return;

     FILE* fp = GetFileDescriptorOrDie(snapshot_blob_path_);
     size_t written = fwrite(blob.begin(), 1, blob.length(), fp);
     fclose(fp);
     if (written != static_cast<size_t>(blob.length())) {
       i::PrintF("Writing snapshot file failed.. Aborting.\n");
       remove(snapshot_blob_path_);
       exit(1);
     }
   }

   void MaybeWriteSnapshotFile(const i::Vector<const i::byte>& blob) const {
     if (!snapshot_cpp_path_) return;

     FILE* fp = GetFileDescriptorOrDie(snapshot_cpp_path_);

     WriteSnapshotFilePrefix(fp);
     WriteSnapshotFileData(fp, blob);
     WriteSnapshotFileSuffix(fp);

     fclose(fp);
   }

   static void WriteSnapshotFilePrefix(FILE* fp) {
     fprintf(fp, "// Autogenerated snapshot file. Do not edit.\n\n");
     fprintf(fp, "#include \"src/v8.h\"\n");
     fprintf(fp, "#include \"src/base/platform/platform.h\"\n\n");
     fprintf(fp, "#include \"src/snapshot/snapshot.h\"\n\n");
     fprintf(fp, "namespace v8 {\n");
     fprintf(fp, "namespace internal {\n\n");
   }

   static void WriteSnapshotFileSuffix(FILE* fp) {
     fprintf(fp, "const v8::StartupData* Snapshot::DefaultSnapshotBlob() {\n");
     fprintf(fp, "  return &blob;\n");
     fprintf(fp, "}\n\n");
     fprintf(fp, "}  // namespace internal\n");
     fprintf(fp, "}  // namespace v8\n");
   }

   static void WriteSnapshotFileData(FILE* fp,
                                     const i::Vector<const i::byte>& blob) {
     fprintf(fp, "static const byte blob_data[] = {\n");
     WriteBinaryContentsAsCArray(fp, blob);
     fprintf(fp, "};\n");
     fprintf(fp, "static const int blob_size = %d;\n", blob.length());
     fprintf(fp, "static const v8::StartupData blob =\n");
     fprintf(fp, "{ (const char*) blob_data, blob_size };\n");
   }

   static void WriteBinaryContentsAsCArray(
       FILE* fp, const i::Vector<const i::byte>& blob) {
     for (int i = 0; i < blob.length(); i++) {
       if ((i & 0x1F) == 0x1F) fprintf(fp, "\n");
       if (i > 0) fprintf(fp, ",");
       fprintf(fp, "%u", static_cast<unsigned char>(blob.at(i)));
     }
     fprintf(fp, "\n");
   }

 #ifdef V8_EMBEDDED_BUILTINS
   void MaybeWriteEmbeddedFile(const i::EmbeddedData* blob) const {
     if (embedded_cpp_path_ == nullptr) return;

     FILE* fp = GetFileDescriptorOrDie(embedded_cpp_path_);

     WriteEmbeddedFilePrefix(fp);
     WriteEmbeddedFileData(fp, blob, embedded_variant_);
     WriteEmbeddedFileSuffix(fp, embedded_variant_);

     fclose(fp);
   }

   static void WriteEmbeddedFilePrefix(FILE* fp) {
     fprintf(fp, "// Autogenerated file. Do not edit.\n\n");
     fprintf(fp, "#include <cstdint>\n\n");
     fprintf(fp, "#include \"src/snapshot/macros.h\"\n\n");
     fprintf(fp, "namespace v8 {\n");
     fprintf(fp, "namespace internal {\n\n");
     fprintf(fp, "namespace {\n\n");
   }

   static void WriteEmbeddedFileSuffix(FILE* fp, const char* embedded_variant) {
     fprintf(fp, "}  // namespace\n\n");
     fprintf(fp,
             "const uint8_t* %sEmbeddedBlob() { return "
             "v8_%s_embedded_blob_; }\n",
             embedded_variant, embedded_variant);
     fprintf(fp,
             "uint32_t %sEmbeddedBlobSize() { return "
             "v8_embedded_blob_size_; }\n\n",
             embedded_variant);
     fprintf(fp, "}  // namespace internal\n");
     fprintf(fp, "}  // namespace v8\n");
   }

   static void WriteEmbeddedFileData(FILE* fp, const i::EmbeddedData* blob,
                                     const char* embedded_variant) {
     // Note: On some platforms (observed on mac64), inserting labels into the
     // .byte stream causes the compiler to reorder symbols, invalidating stored
     // offsets.
     // We either need to avoid doing so, or stop relying on our own offset table
     // and directly reference symbols instead. But there is another complication
     // there since the chrome build process on mac verifies the order of symbols
     // present in the binary.
     // For now, the straight-forward solution seems to be to just emit a pure
     // .byte stream.
     fprintf(fp, "V8_EMBEDDED_TEXT_HEADER(v8_%s_embedded_blob_)\n",
             embedded_variant);
     WriteBinaryContentsAsByteDirective(fp, blob->data(), blob->size());
     fprintf(fp, "extern \"C\" const uint8_t v8_%s_embedded_blob_[];\n",
             embedded_variant);
     fprintf(fp, "static const uint32_t v8_embedded_blob_size_ = %d;\n\n",
             blob->size());
   }

   static void WriteBinaryContentsAsByteDirective(FILE* fp, const uint8_t* data,
                                                  uint32_t size) {
     static const int kTextWidth = 80;
     int current_line_length = 0;
     int printed_chars;

     fprintf(fp, "__asm__(\n");
     for (uint32_t i = 0; i < size; i++) {
       if (current_line_length == 0) {
         printed_chars = fprintf(fp, "%s", "  \".byte ");
         DCHECK_LT(0, printed_chars);
         current_line_length += printed_chars;
       } else {
         printed_chars = fprintf(fp, ",");
         DCHECK_EQ(1, printed_chars);
         current_line_length += printed_chars;
       }

       printed_chars = fprintf(fp, "0x%02x", data[i]);
       DCHECK_LT(0, printed_chars);
       current_line_length += printed_chars;

       if (current_line_length + strlen(",0xFF\\n\"") > kTextWidth) {
         fprintf(fp, "\\n\"\n");
         current_line_length = 0;
       }
     }

     if (current_line_length != 0) fprintf(fp, "\\n\"\n");
     fprintf(fp, ");\n");
   }
 #endif

   static FILE* GetFileDescriptorOrDie(const char* filename) {
     FILE* fp = v8::base::OS::FOpen(filename, "wb");
     if (fp == nullptr) {
       i::PrintF("Unable to open file \"%s\" for writing.\n", filename);
       exit(1);
     }
     return fp;
   }

 #ifdef V8_EMBEDDED_BUILTINS
   const char* embedded_cpp_path_ = nullptr;
   const char* embedded_variant_ = "Default";
 #endif
   const char* snapshot_cpp_path_;
   const char* snapshot_blob_path_;
 };

 char* GetExtraCode(char* filename, const char* description) {
   if (filename == nullptr || strlen(filename) == 0) return nullptr;
   ::printf("Loading script for %s: %s\n", description, filename);
   FILE* file = v8::base::OS::FOpen(filename, "rb");
   if (file == nullptr) {
     fprintf(stderr, "Failed to open '%s': errno %d\n", filename, errno);
     exit(1);
   }
   fseek(file, 0, SEEK_END);
   size_t size = ftell(file);
   rewind(file);
   char* chars = new char[size + 1];
   chars[size] = '\0';
   for (size_t i = 0; i < size;) {
     size_t read = fread(&chars[i], 1, size - i, file);
     if (ferror(file)) {
       fprintf(stderr, "Failed to read '%s': errno %d\n", filename, errno);
       exit(1);
     }
     i += read;
   }
   fclose(file);
   return chars;
 }

 bool RunExtraCode(v8::Isolate* isolate, v8::Local<v8::Context> context,
                   const char* utf8_source, const char* name) {
   v8::base::ElapsedTimer timer;
   timer.Start();
   v8::Context::Scope context_scope(context);
   v8::TryCatch try_catch(isolate);
   v8::Local<v8::String> source_string;
   if (!v8::String::NewFromUtf8(isolate, utf8_source, v8::NewStringType::kNormal)
            .ToLocal(&source_string)) {
     return false;
   }
   v8::Local<v8::String> resource_name =
       v8::String::NewFromUtf8(isolate, name, v8::NewStringType::kNormal)
           .ToLocalChecked();
   v8::ScriptOrigin origin(resource_name);
   v8::ScriptCompiler::Source source(source_string, origin);
   v8::Local<v8::Script> script;
   if (!v8::ScriptCompiler::Compile(context, &source).ToLocal(&script))
     return false;
   if (script->Run(context).IsEmpty()) return false;
   if (i::FLAG_profile_deserialization) {
     i::PrintF("Executing custom snapshot script %s took %0.3f ms\n", name,
               timer.Elapsed().InMillisecondsF());
   }
   timer.Stop();
   CHECK(!try_catch.HasCaught());
   return true;
 }

 v8::StartupData CreateSnapshotDataBlob(v8::SnapshotCreator* snapshot_creator,
                                        const char* script_source = NULL) {
   // Create a new isolate and a new context from scratch, optionally run
   // a script to embed, and serialize to create a snapshot blob.
   v8::StartupData result = {nullptr, 0};
   v8::base::ElapsedTimer timer;
   timer.Start();
   {
     v8::Isolate* isolate = snapshot_creator->GetIsolate();
     {
       v8::HandleScope scope(isolate);
       v8::Local<v8::Context> context = v8::Context::New(isolate);
       if (script_source != nullptr &&
           !RunExtraCode(isolate, context, script_source, "<embedded>")) {
         return result;
       }
       snapshot_creator->SetDefaultContext(context);
     }
     result = snapshot_creator->CreateBlob(
         v8::SnapshotCreator::FunctionCodeHandling::kClear);
   }

   if (i::FLAG_profile_deserialization) {
     i::PrintF("Creating snapshot took %0.3f ms\n",
               timer.Elapsed().InMillisecondsF());
   }
   timer.Stop();
   return result;
 }

 v8::StartupData WarmUpSnapshotDataBlob(v8::SnapshotCreator* snapshot_creator,
                                        const char* warmup_source) {
   CHECK_NOT_NULL(warmup_source);
   // Use following steps to create a warmed up snapshot blob from a cold one:
   //  - Create a new isolate from the cold snapshot.
   //  - Create a new context to run the warmup script. This will trigger
   //    compilation of executed functions.
   //  - Create a new context. This context will be unpolluted.
   //  - Serialize the isolate and the second context into a new snapshot blob.
   v8::StartupData result = {nullptr, 0};
   v8::base::ElapsedTimer timer;
   timer.Start();
   {
     v8::Isolate* isolate = snapshot_creator->GetIsolate();
     {
       v8::HandleScope scope(isolate);
       v8::Local<v8::Context> context = v8::Context::New(isolate);
       if (!RunExtraCode(isolate, context, warmup_source, "<warm-up>")) {
         return result;
       }
     }
     {
       v8::HandleScope handle_scope(isolate);
       isolate->ContextDisposedNotification(false);
       v8::Local<v8::Context> context = v8::Context::New(isolate);
       snapshot_creator->SetDefaultContext(context);
     }
     result = snapshot_creator->CreateBlob(
         v8::SnapshotCreator::FunctionCodeHandling::kKeep);
   }

   if (i::FLAG_profile_deserialization) {
     i::PrintF("Warming up snapshot took %0.3f ms\n",
               timer.Elapsed().InMillisecondsF());
   }
   timer.Stop();
   return result;
 }

 #ifdef V8_EMBEDDED_BUILTINS
 void WriteEmbeddedFile(v8::SnapshotCreator* creator, SnapshotWriter* writer) {
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(creator->GetIsolate());
   isolate->PrepareEmbeddedBlobForSerialization();
   i::EmbeddedData embedded_blob = i::EmbeddedData::FromBlob();
   writer->WriteEmbedded(&embedded_blob);
 }
 #endif  // V8_EMBEDDED_BUILTINS
 }  // namespace

 int main(int argc, char** argv) {
   v8::base::EnsureConsoleOutput();

   // Make mksnapshot runs predictable to create reproducible snapshots.
   i::FLAG_predictable = true;

   // Print the usage if an error occurs when parsing the command line
   // flags or if the help flag is set.
   int result = i::FlagList::SetFlagsFromCommandLine(&argc, argv, true);
   if (result > 0 || (argc > 3) || i::FLAG_help) {
     ::printf("Usage: %s --startup_src=... --startup_blob=... [extras]\n",
              argv[0]);
     i::FlagList::PrintHelp();
     return !i::FLAG_help;
   }

   i::CpuFeatures::Probe(true);
   v8::V8::InitializeICUDefaultLocation(argv[0]);
   std::unique_ptr<v8::Platform> platform = v8::platform::NewDefaultPlatform();
   v8::V8::InitializePlatform(platform.get());
   v8::V8::Initialize();

   {
     SnapshotWriter writer;
     if (i::FLAG_startup_src) writer.SetSnapshotFile(i::FLAG_startup_src);
     if (i::FLAG_startup_blob) writer.SetStartupBlobFile(i::FLAG_startup_blob);
 #ifdef V8_EMBEDDED_BUILTINS
     if (i::FLAG_embedded_src) writer.SetEmbeddedFile(i::FLAG_embedded_src);
     if (i::FLAG_embedded_variant)
       writer.SetEmbeddedVariant(i::FLAG_embedded_variant);
 #endif

     std::unique_ptr<char> embed_script(
         GetExtraCode(argc >= 2 ? argv[1] : nullptr, "embedding"));
     std::unique_ptr<char> warmup_script(
         GetExtraCode(argc >= 3 ? argv[2] : nullptr, "warm up"));

     v8::StartupData blob;
     {
       v8::SnapshotCreator snapshot_creator;
 #ifdef V8_EMBEDDED_BUILTINS
       // This process is a bit tricky since we might go on to make a second
       // snapshot if a warmup script is passed. In that case, create the first
       // snapshot without off-heap trampolines and only move code off-heap for
       // the warmed-up snapshot.
       if (!warmup_script) WriteEmbeddedFile(&snapshot_creator, &writer);
 #endif
       blob = CreateSnapshotDataBlob(&snapshot_creator, embed_script.get());
     }

     if (warmup_script) {
       CHECK(blob.raw_size > 0 && blob.data != nullptr);
       v8::StartupData cold = blob;
       v8::SnapshotCreator snapshot_creator(nullptr, &cold);
 #ifdef V8_EMBEDDED_BUILTINS
       WriteEmbeddedFile(&snapshot_creator, &writer);
 #endif
       blob = WarmUpSnapshotDataBlob(&snapshot_creator, warmup_script.get());
       delete[] cold.data;
     }

     CHECK(blob.data);
     writer.WriteSnapshot(blob);
     delete[] blob.data;
   }

   v8::V8::Dispose();
   v8::V8::ShutdownPlatform();
   return 0;
 }
	// Copyright 2006-2008 the V8 project 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 <errno.h>
	#include <signal.h>
	#include <stdio.h>

	#include "include/libplatform/libplatform.h"
	#include "src/assembler.h"
	#include "src/base/platform/platform.h"
	#include "src/flags.h"
	#include "src/msan.h"
	#include "src/snapshot/natives.h"
	#include "src/snapshot/partial-serializer.h"
	#include "src/snapshot/snapshot.h"
	#include "src/snapshot/startup-serializer.h"

	namespace {
	class SnapshotWriter {
	public:
	SnapshotWriter()
	: snapshot_cpp_path_(nullptr), snapshot_blob_path_(nullptr) {}

	#ifdef V8_EMBEDDED_BUILTINS
	void SetEmbeddedFile(const char* embedded_cpp_file) {
	embedded_cpp_path_ = embedded_cpp_file;
	}

	void SetEmbeddedVariant(const char* embedded_variant) {
	embedded_variant_ = embedded_variant;
	}
	#endif

	void SetSnapshotFile(const char* snapshot_cpp_file) {
	snapshot_cpp_path_ = snapshot_cpp_file;
	}

	void SetStartupBlobFile(const char* snapshot_blob_file) {
	snapshot_blob_path_ = snapshot_blob_file;
	}

	void WriteSnapshot(v8::StartupData blob) const {
	// TODO(crbug/633159): if we crash before the files have been fully created,
	// we end up with a corrupted snapshot file. The build step would succeed,
	// but the build target is unusable. Ideally we would write out temporary
	// files and only move them to the final destination as last step.
	i::Vector<const i::byte> blob_vector(
	reinterpret_cast<const i::byte*>(blob.data), blob.raw_size);
	MaybeWriteSnapshotFile(blob_vector);
	MaybeWriteStartupBlob(blob_vector);
	}

	#ifdef V8_EMBEDDED_BUILTINS
	void WriteEmbedded(const i::EmbeddedData* blob) const {
	MaybeWriteEmbeddedFile(blob);
	}
	#endif

	private:
	void MaybeWriteStartupBlob(const i::Vector<const i::byte>& blob) const {
	if (!snapshot_blob_path_) return;

	FILE* fp = GetFileDescriptorOrDie(snapshot_blob_path_);
	size_t written = fwrite(blob.begin(), 1, blob.length(), fp);
	fclose(fp);
	if (written != static_cast<size_t>(blob.length())) {
	i::PrintF("Writing snapshot file failed.. Aborting.\n");
	remove(snapshot_blob_path_);
	exit(1);
	}
	}

	void MaybeWriteSnapshotFile(const i::Vector<const i::byte>& blob) const {
	if (!snapshot_cpp_path_) return;

	FILE* fp = GetFileDescriptorOrDie(snapshot_cpp_path_);

	WriteSnapshotFilePrefix(fp);
	WriteSnapshotFileData(fp, blob);
	WriteSnapshotFileSuffix(fp);

	fclose(fp);
	}

	static void WriteSnapshotFilePrefix(FILE* fp) {
	fprintf(fp, "// Autogenerated snapshot file. Do not edit.\n\n");
	fprintf(fp, "#include \"src/v8.h\"\n");
	fprintf(fp, "#include \"src/base/platform/platform.h\"\n\n");
	fprintf(fp, "#include \"src/snapshot/snapshot.h\"\n\n");
	fprintf(fp, "namespace v8 {\n");
	fprintf(fp, "namespace internal {\n\n");
	}

	static void WriteSnapshotFileSuffix(FILE* fp) {
	fprintf(fp, "const v8::StartupData* Snapshot::DefaultSnapshotBlob() {\n");
	fprintf(fp, " return &blob;\n");
	fprintf(fp, "}\n\n");
	fprintf(fp, "} // namespace internal\n");
	fprintf(fp, "} // namespace v8\n");
	}

	static void WriteSnapshotFileData(FILE* fp,
	const i::Vector<const i::byte>& blob) {
	fprintf(fp, "static const byte blob_data[] = {\n");
	WriteBinaryContentsAsCArray(fp, blob);
	fprintf(fp, "};\n");
	fprintf(fp, "static const int blob_size = %d;\n", blob.length());
	fprintf(fp, "static const v8::StartupData blob =\n");
	fprintf(fp, "{ (const char*) blob_data, blob_size };\n");
	}

	static void WriteBinaryContentsAsCArray(
	FILE* fp, const i::Vector<const i::byte>& blob) {
	for (int i = 0; i < blob.length(); i++) {
	if ((i & 0x1F) == 0x1F) fprintf(fp, "\n");
	if (i > 0) fprintf(fp, ",");
	fprintf(fp, "%u", static_cast<unsigned char>(blob.at(i)));
	}
	fprintf(fp, "\n");
	}

	#ifdef V8_EMBEDDED_BUILTINS
	void MaybeWriteEmbeddedFile(const i::EmbeddedData* blob) const {
	if (embedded_cpp_path_ == nullptr) return;

	FILE* fp = GetFileDescriptorOrDie(embedded_cpp_path_);

	WriteEmbeddedFilePrefix(fp);
	WriteEmbeddedFileData(fp, blob, embedded_variant_);
	WriteEmbeddedFileSuffix(fp, embedded_variant_);

	fclose(fp);
	}

	static void WriteEmbeddedFilePrefix(FILE* fp) {
	fprintf(fp, "// Autogenerated file. Do not edit.\n\n");
	fprintf(fp, "#include <cstdint>\n\n");
	fprintf(fp, "#include \"src/snapshot/macros.h\"\n\n");
	fprintf(fp, "namespace v8 {\n");
	fprintf(fp, "namespace internal {\n\n");
	fprintf(fp, "namespace {\n\n");
	}

	static void WriteEmbeddedFileSuffix(FILE* fp, const char* embedded_variant) {
	fprintf(fp, "} // namespace\n\n");
	fprintf(fp,
	"const uint8_t* %sEmbeddedBlob() { return "
	"v8_%s_embedded_blob_; }\n",
	embedded_variant, embedded_variant);
	fprintf(fp,
	"uint32_t %sEmbeddedBlobSize() { return "
	"v8_embedded_blob_size_; }\n\n",
	embedded_variant);
	fprintf(fp, "} // namespace internal\n");
	fprintf(fp, "} // namespace v8\n");
	}

	static void WriteEmbeddedFileData(FILE* fp, const i::EmbeddedData* blob,
	const char* embedded_variant) {
	// Note: On some platforms (observed on mac64), inserting labels into the
	// .byte stream causes the compiler to reorder symbols, invalidating stored
	// offsets.
	// We either need to avoid doing so, or stop relying on our own offset table
	// and directly reference symbols instead. But there is another complication
	// there since the chrome build process on mac verifies the order of symbols
	// present in the binary.
	// For now, the straight-forward solution seems to be to just emit a pure
	// .byte stream.
	fprintf(fp, "V8_EMBEDDED_TEXT_HEADER(v8_%s_embedded_blob_)\n",
	embedded_variant);
	WriteBinaryContentsAsByteDirective(fp, blob->data(), blob->size());
	fprintf(fp, "extern \"C\" const uint8_t v8_%s_embedded_blob_[];\n",
	embedded_variant);
	fprintf(fp, "static const uint32_t v8_embedded_blob_size_ = %d;\n\n",
	blob->size());
	}

	static void WriteBinaryContentsAsByteDirective(FILE* fp, const uint8_t* data,
	uint32_t size) {
	static const int kTextWidth = 80;
	int current_line_length = 0;
	int printed_chars;

	fprintf(fp, "__asm__(\n");
	for (uint32_t i = 0; i < size; i++) {
	if (current_line_length == 0) {
	printed_chars = fprintf(fp, "%s", " \".byte ");
	DCHECK_LT(0, printed_chars);
	current_line_length += printed_chars;
	} else {
	printed_chars = fprintf(fp, ",");
	DCHECK_EQ(1, printed_chars);
	current_line_length += printed_chars;
	}

	printed_chars = fprintf(fp, "0x%02x", data[i]);
	DCHECK_LT(0, printed_chars);
	current_line_length += printed_chars;

	if (current_line_length + strlen(",0xFF\\n\"") > kTextWidth) {
	fprintf(fp, "\\n\"\n");
	current_line_length = 0;
	}
	}

	if (current_line_length != 0) fprintf(fp, "\\n\"\n");
	fprintf(fp, ");\n");
	}
	#endif

	static FILE* GetFileDescriptorOrDie(const char* filename) {
	FILE* fp = v8::base::OS::FOpen(filename, "wb");
	if (fp == nullptr) {
	i::PrintF("Unable to open file \"%s\" for writing.\n", filename);
	exit(1);
	}
	return fp;
	}

	#ifdef V8_EMBEDDED_BUILTINS
	const char* embedded_cpp_path_ = nullptr;
	const char* embedded_variant_ = "Default";
	#endif
	const char* snapshot_cpp_path_;
	const char* snapshot_blob_path_;
	};

	char* GetExtraCode(char* filename, const char* description) {
	if (filename == nullptr \|\| strlen(filename) == 0) return nullptr;
	::printf("Loading script for %s: %s\n", description, filename);
	FILE* file = v8::base::OS::FOpen(filename, "rb");
	if (file == nullptr) {
	fprintf(stderr, "Failed to open '%s': errno %d\n", filename, errno);
	exit(1);
	}
	fseek(file, 0, SEEK_END);
	size_t size = ftell(file);
	rewind(file);
	char* chars = new char[size + 1];
	chars[size] = '\0';
	for (size_t i = 0; i < size;) {
	size_t read = fread(&chars[i], 1, size - i, file);
	if (ferror(file)) {
	fprintf(stderr, "Failed to read '%s': errno %d\n", filename, errno);
	exit(1);
	}
	i += read;
	}
	fclose(file);
	return chars;
	}

	bool RunExtraCode(v8::Isolate* isolate, v8::Local<v8::Context> context,
	const char* utf8_source, const char* name) {
	v8::base::ElapsedTimer timer;
	timer.Start();
	v8::Context::Scope context_scope(context);
	v8::TryCatch try_catch(isolate);
	v8::Local<v8::String> source_string;
	if (!v8::String::NewFromUtf8(isolate, utf8_source, v8::NewStringType::kNormal)
	.ToLocal(&source_string)) {
	return false;
	}
	v8::Local<v8::String> resource_name =
	v8::String::NewFromUtf8(isolate, name, v8::NewStringType::kNormal)
	.ToLocalChecked();
	v8::ScriptOrigin origin(resource_name);
	v8::ScriptCompiler::Source source(source_string, origin);
	v8::Local<v8::Script> script;
	if (!v8::ScriptCompiler::Compile(context, &source).ToLocal(&script))
	return false;
	if (script->Run(context).IsEmpty()) return false;
	if (i::FLAG_profile_deserialization) {
	i::PrintF("Executing custom snapshot script %s took %0.3f ms\n", name,
	timer.Elapsed().InMillisecondsF());
	}
	timer.Stop();
	CHECK(!try_catch.HasCaught());
	return true;
	}

	v8::StartupData CreateSnapshotDataBlob(v8::SnapshotCreator* snapshot_creator,
	const char* script_source = NULL) {
	// Create a new isolate and a new context from scratch, optionally run
	// a script to embed, and serialize to create a snapshot blob.
	v8::StartupData result = {nullptr, 0};
	v8::base::ElapsedTimer timer;
	timer.Start();
	{
	v8::Isolate* isolate = snapshot_creator->GetIsolate();
	{
	v8::HandleScope scope(isolate);
	v8::Local<v8::Context> context = v8::Context::New(isolate);
	if (script_source != nullptr &&
	!RunExtraCode(isolate, context, script_source, "<embedded>")) {
	return result;
	}
	snapshot_creator->SetDefaultContext(context);
	}
	result = snapshot_creator->CreateBlob(
	v8::SnapshotCreator::FunctionCodeHandling::kClear);
	}

	if (i::FLAG_profile_deserialization) {
	i::PrintF("Creating snapshot took %0.3f ms\n",
	timer.Elapsed().InMillisecondsF());
	}
	timer.Stop();
	return result;
	}

	v8::StartupData WarmUpSnapshotDataBlob(v8::SnapshotCreator* snapshot_creator,
	const char* warmup_source) {
	CHECK_NOT_NULL(warmup_source);
	// Use following steps to create a warmed up snapshot blob from a cold one:
	// - Create a new isolate from the cold snapshot.
	// - Create a new context to run the warmup script. This will trigger
	// compilation of executed functions.
	// - Create a new context. This context will be unpolluted.
	// - Serialize the isolate and the second context into a new snapshot blob.
	v8::StartupData result = {nullptr, 0};
	v8::base::ElapsedTimer timer;
	timer.Start();
	{
	v8::Isolate* isolate = snapshot_creator->GetIsolate();
	{
	v8::HandleScope scope(isolate);
	v8::Local<v8::Context> context = v8::Context::New(isolate);
	if (!RunExtraCode(isolate, context, warmup_source, "<warm-up>")) {
	return result;
	}
	}
	{
	v8::HandleScope handle_scope(isolate);
	isolate->ContextDisposedNotification(false);
	v8::Local<v8::Context> context = v8::Context::New(isolate);
	snapshot_creator->SetDefaultContext(context);
	}
	result = snapshot_creator->CreateBlob(
	v8::SnapshotCreator::FunctionCodeHandling::kKeep);
	}

	if (i::FLAG_profile_deserialization) {
	i::PrintF("Warming up snapshot took %0.3f ms\n",
	timer.Elapsed().InMillisecondsF());
	}
	timer.Stop();
	return result;
	}

	#ifdef V8_EMBEDDED_BUILTINS
	void WriteEmbeddedFile(v8::SnapshotCreator* creator, SnapshotWriter* writer) {
	i::Isolate* isolate = reinterpret_cast<i::Isolate*>(creator->GetIsolate());
	isolate->PrepareEmbeddedBlobForSerialization();
	i::EmbeddedData embedded_blob = i::EmbeddedData::FromBlob();
	writer->WriteEmbedded(&embedded_blob);
	}
	#endif // V8_EMBEDDED_BUILTINS
	} // namespace

	int main(int argc, char** argv) {
	v8::base::EnsureConsoleOutput();

	// Make mksnapshot runs predictable to create reproducible snapshots.
	i::FLAG_predictable = true;

	// Print the usage if an error occurs when parsing the command line
	// flags or if the help flag is set.
	int result = i::FlagList::SetFlagsFromCommandLine(&argc, argv, true);
	if (result > 0 \|\| (argc > 3) \|\| i::FLAG_help) {
	::printf("Usage: %s --startup_src=... --startup_blob=... [extras]\n",
	argv[0]);
	i::FlagList::PrintHelp();
	return !i::FLAG_help;
	}

	i::CpuFeatures::Probe(true);
	v8::V8::InitializeICUDefaultLocation(argv[0]);
	std::unique_ptr<v8::Platform> platform = v8::platform::NewDefaultPlatform();
	v8::V8::InitializePlatform(platform.get());
	v8::V8::Initialize();

	{
	SnapshotWriter writer;
	if (i::FLAG_startup_src) writer.SetSnapshotFile(i::FLAG_startup_src);
	if (i::FLAG_startup_blob) writer.SetStartupBlobFile(i::FLAG_startup_blob);
	#ifdef V8_EMBEDDED_BUILTINS
	if (i::FLAG_embedded_src) writer.SetEmbeddedFile(i::FLAG_embedded_src);
	if (i::FLAG_embedded_variant)
	writer.SetEmbeddedVariant(i::FLAG_embedded_variant);
	#endif

	std::unique_ptr<char> embed_script(
	GetExtraCode(argc >= 2 ? argv[1] : nullptr, "embedding"));
	std::unique_ptr<char> warmup_script(
	GetExtraCode(argc >= 3 ? argv[2] : nullptr, "warm up"));

	v8::StartupData blob;
	{
	v8::SnapshotCreator snapshot_creator;
	#ifdef V8_EMBEDDED_BUILTINS
	// This process is a bit tricky since we might go on to make a second
	// snapshot if a warmup script is passed. In that case, create the first
	// snapshot without off-heap trampolines and only move code off-heap for
	// the warmed-up snapshot.
	if (!warmup_script) WriteEmbeddedFile(&snapshot_creator, &writer);
	#endif
	blob = CreateSnapshotDataBlob(&snapshot_creator, embed_script.get());
	}

	if (warmup_script) {
	CHECK(blob.raw_size > 0 && blob.data != nullptr);
	v8::StartupData cold = blob;
	v8::SnapshotCreator snapshot_creator(nullptr, &cold);
	#ifdef V8_EMBEDDED_BUILTINS
	WriteEmbeddedFile(&snapshot_creator, &writer);
	#endif
	blob = WarmUpSnapshotDataBlob(&snapshot_creator, warmup_script.get());
	delete[] cold.data;
	}

	CHECK(blob.data);
	writer.WriteSnapshot(blob);
	delete[] blob.data;
	}

	v8::V8::Dispose();
	v8::V8::ShutdownPlatform();
	return 0;
	}