tools: refactor snapshot builder

This patch:

- Moves the snapshot building code to src/ so that we can reuse it
  later when generating custom snapshots from an entry point accepted
  by the node binary.
- Create a SnapshotData struct that incorporates all the data useful
  for a snapshot blob, including both the V8 data and the Node.js
  data.

PR-URL: https://github.com/nodejs/node/pull/38902
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>

4 files changed, 2 insertions, 189 deletions

diff --git a/tools/snapshot/README.md b/tools/snapshot/README.md
index 34dc574d56c..fb22c03ed50 100644
--- a/tools/snapshot/README.md
+++ b/tools/snapshot/README.md
@@ -23,7 +23,7 @@ into the Node.js executable, `libnode` is first built with these unresolved
 symbols:
 
 - `node::NodeMainInstance::GetEmbeddedSnapshotBlob`
-- `node::NodeMainInstance::GetIsolateDataIndexes`
+- `node::NodeMainInstance::GetIsolateDataIndices`
 
 Then the `node_mksnapshot` executable is built with C++ files in this
 directory, as well as `src/node_snapshot_stub.cc` which defines the unresolved
diff --git a/tools/snapshot/node_mksnapshot.cc b/tools/snapshot/node_mksnapshot.cc
index c5bfcd8fc5c..e591f64a2a0 100644
--- a/tools/snapshot/node_mksnapshot.cc
+++ b/tools/snapshot/node_mksnapshot.cc
@@ -7,7 +7,7 @@
 
 #include "libplatform/libplatform.h"
 #include "node_internals.h"
-#include "snapshot_builder.h"
+#include "node_snapshotable.h"
 #include "util-inl.h"
 #include "v8.h"
 
diff --git a/tools/snapshot/snapshot_builder.cc b/tools/snapshot/snapshot_builder.cc
deleted file mode 100644
index cf76f38ece8..00000000000
--- a/tools/snapshot/snapshot_builder.cc
+++ /dev/null
@@ -1,172 +0,0 @@
-#include "snapshot_builder.h"
-#include <iostream>
-#include <sstream>
-#include "debug_utils-inl.h"
-#include "env-inl.h"
-#include "node_errors.h"
-#include "node_external_reference.h"
-#include "node_internals.h"
-#include "node_main_instance.h"
-#include "node_snapshotable.h"
-#include "node_v8_platform-inl.h"
-
-namespace node {
-
-using v8::Context;
-using v8::HandleScope;
-using v8::Isolate;
-using v8::Local;
-using v8::SnapshotCreator;
-using v8::StartupData;
-using v8::TryCatch;
-using v8::Value;
-
-template <typename T>
-void WriteVector(std::stringstream* ss, const T* vec, size_t size) {
-  for (size_t i = 0; i < size; i++) {
-    *ss << std::to_string(vec[i]) << (i == size - 1 ? '\n' : ',');
-  }
-}
-
-std::string FormatBlob(StartupData* blob,
-                       const std::vector<size_t>& isolate_data_indexes,
-                       const EnvSerializeInfo& env_info) {
-  std::stringstream ss;
-
-  ss << R"(#include <cstddef>
-#include "env.h"
-#include "node_main_instance.h"
-#include "v8.h"
-
-// This file is generated by tools/snapshot. Do not edit.
-
-namespace node {
-
-static const char blob_data[] = {
-)";
-  WriteVector(&ss, blob->data, blob->raw_size);
-  ss << R"(};
-
-static const int blob_size = )"
-     << blob->raw_size << R"(;
-static v8::StartupData blob = { blob_data, blob_size };
-)";
-
-  ss << R"(v8::StartupData* NodeMainInstance::GetEmbeddedSnapshotBlob() {
-  return &blob;
-}
-
-static const std::vector<size_t> isolate_data_indexes {
-)";
-  WriteVector(&ss, isolate_data_indexes.data(), isolate_data_indexes.size());
-  ss << R"(};
-
-const std::vector<size_t>* NodeMainInstance::GetIsolateDataIndexes() {
-  return &isolate_data_indexes;
-}
-
-static const EnvSerializeInfo env_info )"
-     << env_info << R"(;
-
-const EnvSerializeInfo* NodeMainInstance::GetEnvSerializeInfo() {
-  return &env_info;
-}
-
-}  // namespace node
-)";
-
-  return ss.str();
-}
-
-std::string SnapshotBuilder::Generate(
-    const std::vector<std::string> args,
-    const std::vector<std::string> exec_args) {
-  Isolate* isolate = Isolate::Allocate();
-  isolate->SetCaptureStackTraceForUncaughtExceptions(
-    true,
-    10,
-    v8::StackTrace::StackTraceOptions::kDetailed);
-  per_process::v8_platform.Platform()->RegisterIsolate(isolate,
-                                                       uv_default_loop());
-  std::unique_ptr<NodeMainInstance> main_instance;
-  std::string result;
-
-  {
-    std::vector<size_t> isolate_data_indexes;
-    EnvSerializeInfo env_info;
-
-    const std::vector<intptr_t>& external_references =
-        NodeMainInstance::CollectExternalReferences();
-    SnapshotCreator creator(isolate, external_references.data());
-    Environment* env;
-    {
-      main_instance =
-          NodeMainInstance::Create(isolate,
-                                   uv_default_loop(),
-                                   per_process::v8_platform.Platform(),
-                                   args,
-                                   exec_args);
-
-      HandleScope scope(isolate);
-      creator.SetDefaultContext(Context::New(isolate));
-      isolate_data_indexes = main_instance->isolate_data()->Serialize(&creator);
-
-      // Run the per-context scripts
-      Local<Context> context;
-      {
-        TryCatch bootstrapCatch(isolate);
-        context = NewContext(isolate);
-        if (bootstrapCatch.HasCaught()) {
-          PrintCaughtException(isolate, context, bootstrapCatch);
-          abort();
-        }
-      }
-      Context::Scope context_scope(context);
-
-      // Create the environment
-      env = new Environment(main_instance->isolate_data(),
-                            context,
-                            args,
-                            exec_args,
-                            nullptr,
-                            node::EnvironmentFlags::kDefaultFlags,
-                            {});
-      // Run scripts in lib/internal/bootstrap/
-      {
-        TryCatch bootstrapCatch(isolate);
-        v8::MaybeLocal<Value> result = env->RunBootstrapping();
-        if (bootstrapCatch.HasCaught()) {
-          PrintCaughtException(isolate, context, bootstrapCatch);
-        }
-        result.ToLocalChecked();
-      }
-
-      if (per_process::enabled_debug_list.enabled(DebugCategory::MKSNAPSHOT)) {
-        env->PrintAllBaseObjects();
-        printf("Environment = %p\n", env);
-      }
-
-      // Serialize the native states
-      env_info = env->Serialize(&creator);
-      // Serialize the context
-      size_t index = creator.AddContext(
-          context, {SerializeNodeContextInternalFields, env});
-      CHECK_EQ(index, NodeMainInstance::kNodeContextIndex);
-    }
-
-    // Must be out of HandleScope
-    StartupData blob =
-        creator.CreateBlob(SnapshotCreator::FunctionCodeHandling::kClear);
-    CHECK(blob.CanBeRehashed());
-    // Must be done while the snapshot creator isolate is entered i.e. the
-    // creator is still alive.
-    FreeEnvironment(env);
-    main_instance->Dispose();
-    result = FormatBlob(&blob, isolate_data_indexes, env_info);
-    delete[] blob.data;
-  }
-
-  per_process::v8_platform.Platform()->UnregisterIsolate(isolate);
-  return result;
-}
-}  // namespace node
diff --git a/tools/snapshot/snapshot_builder.h b/tools/snapshot/snapshot_builder.h
deleted file mode 100644
index 2e587d078b9..00000000000
--- a/tools/snapshot/snapshot_builder.h
+++ /dev/null
@@ -1,15 +0,0 @@
-#ifndef TOOLS_SNAPSHOT_SNAPSHOT_BUILDER_H_
-#define TOOLS_SNAPSHOT_SNAPSHOT_BUILDER_H_
-
-#include <string>
-#include <vector>
-
-namespace node {
-class SnapshotBuilder {
- public:
-  static std::string Generate(const std::vector<std::string> args,
-                              const std::vector<std::string> exec_args);
-};
-}  // namespace node
-
-#endif  // TOOLS_SNAPSHOT_SNAPSHOT_BUILDER_H_