src: support snapshot in single executable applications

Author: joyeecheung

src/env.h

@@ -525,10 +525,12 @@ struct SnapshotData {
   bool Check() const;
   static bool FromFile(SnapshotData* out, FILE* in);
   static bool FromBlob(SnapshotData* out, const std::vector<char>& in);
+  static bool FromBlob(SnapshotData* out, std::string_view in);
   static const SnapshotData* FromEmbedderWrapper(
       const EmbedderSnapshotData* data);
   EmbedderSnapshotData::Pointer AsEmbedderWrapper() const;
 
+  static bool IsSnapshotBlob(std::string_view data);
   ~SnapshotData();
 };
 

src/node.cc

@@ -295,6 +295,31 @@ MaybeLocal<Value> StartExecution(Environment* env, StartExecutionCallback cb) {
     }));
   }
 
+#ifndef DISABLE_SINGLE_EXECUTABLE_APPLICATION
+  if (sea::IsSingleExecutable()) {
+    const std::string_view sea_code = sea::FindSingleExecutableCode();
+    if (SnapshotData::IsSnapshotBlob(sea_code)) {
+      if (env->snapshot_deserialize_main().IsEmpty()) {
+        fprintf(
+            stderr,
+            "No deserialized main function found for the snapshot blob found"
+            " in single executable binary.\n");
+        return MaybeLocal<Value>();
+      } else {
+        return env->RunSnapshotDeserializeMain();
+      }
+    }
+
+    // TODO(addaleax): Find a way to reuse:
+    //
+    // LoadEnvironment(Environment*, const char*)
+    //
+    // instead and not add yet another main entry point here because this
+    // already duplicates existing code.
+    return StartExecution(env, "internal/main/single_executable_application");
+  }
+#endif
+
   // TODO(joyeecheung): move these conditions into JS land and let the
   // deserialize main function take precedence. For workers, we need to
   // move the pre-execution part into a different file that can be
@@ -312,18 +337,6 @@ MaybeLocal<Value> StartExecution(Environment* env, StartExecutionCallback cb) {
     first_argv = env->argv()[1];
   }
 
-#ifndef DISABLE_SINGLE_EXECUTABLE_APPLICATION
-  if (sea::IsSingleExecutable()) {
-    // TODO(addaleax): Find a way to reuse:
-    //
-    // LoadEnvironment(Environment*, const char*)
-    //
-    // instead and not add yet another main entry point here because this
-    // already duplicates existing code.
-    return StartExecution(env, "internal/main/single_executable_application");
-  }
-#endif
-
   if (first_argv == "inspect") {
     return StartExecution(env, "internal/main/inspect");
   }
@@ -1177,8 +1190,25 @@ ExitCode LoadSnapshotDataAndRun(const SnapshotData** snapshot_data_ptr,
   ExitCode exit_code = result->exit_code_enum();
   // nullptr indicates there's no snapshot data.
   DCHECK_NULL(*snapshot_data_ptr);
-  // --snapshot-blob indicates that we are reading a customized snapshot.
-  if (!per_process::cli_options->snapshot_blob.empty()) {
+
+  bool has_cli_snapshot_blob = !per_process::cli_options->snapshot_blob.empty();
+#ifndef DISABLE_SINGLE_EXECUTABLE_APPLICATION
+  if (sea::IsSingleExecutable()) {
+    const std::string_view sea_code = sea::FindSingleExecutableCode();
+    if (SnapshotData::IsSnapshotBlob(sea_code)) {
+      std::unique_ptr<SnapshotData> read_data =
+          std::make_unique<SnapshotData>();
+      if (SnapshotData::FromBlob(read_data.get(), sea_code)) {
+        *snapshot_data_ptr = read_data.release();
+      } else {
+        fprintf(stderr, "Invalid snapshot data in single executable binary\n");
+        return ExitCode::kGenericUserError;
+      }
+    }
+  } else if (has_cli_snapshot_blob) {
+#else
+  if (has_cli_snapshot_blob) {
+#endif
     std::string filename = per_process::cli_options->snapshot_blob;
     FILE* fp = fopen(filename.c_str(), "rb");
     if (fp == nullptr) {

src/node_sea.cc

@@ -31,28 +31,11 @@ using v8::Value;
 
 namespace {
 
-const std::string_view FindSingleExecutableCode() {
-  static const std::string_view sea_code = []() -> std::string_view {
-    size_t size;
-#ifdef __APPLE__
-    postject_options options;
-    postject_options_init(&options);
-    options.macho_segment_name = "NODE_JS";
-    const char* code = static_cast<const char*>(
-        postject_find_resource("NODE_JS_CODE", &size, &options));
-#else
-    const char* code = static_cast<const char*>(
-        postject_find_resource("NODE_JS_CODE", &size, nullptr));
-#endif
-    return {code, size};
-  }();
-  return sea_code;
-}
-
 void GetSingleExecutableCode(const FunctionCallbackInfo<Value>& args) {
   node::Environment* env = node::Environment::GetCurrent(args);
 
-  static const std::string_view sea_code = FindSingleExecutableCode();
+  static const std::string_view sea_code =
+      node::sea::FindSingleExecutableCode();
 
   if (sea_code.empty()) {
     return;
@@ -83,6 +66,24 @@ void GetSingleExecutableCode(const FunctionCallbackInfo<Value>& args) {
 namespace node {
 namespace sea {
 
+const std::string_view FindSingleExecutableCode() {
+  static const std::string_view sea_code = []() -> std::string_view {
+    size_t size;
+#ifdef __APPLE__
+    postject_options options;
+    postject_options_init(&options);
+    options.macho_segment_name = "NODE_JS";
+    const char* code = static_cast<const char*>(
+        postject_find_resource("NODE_JS_CODE", &size, &options));
+#else
+    const char* code = static_cast<const char*>(
+        postject_find_resource("NODE_JS_CODE", &size, nullptr));
+#endif
+    return {code, size};
+  }();
+  return sea_code;
+}
+
 bool IsSingleExecutable() {
   return postject_has_resource();
 }

src/node_sea.h

@@ -5,14 +5,15 @@
 
 #if !defined(DISABLE_SINGLE_EXECUTABLE_APPLICATION)
 
+#include <string_view>
 #include <tuple>
 
 namespace node {
 namespace sea {
 
 bool IsSingleExecutable();
 std::tuple<int, char**> FixupArgsForSEA(int argc, char** argv);
-
+const std::string_view FindSingleExecutableCode();
 }  // namespace sea
 }  // namespace node
 

src/node_snapshotable.cc

@@ -187,7 +187,7 @@ class SnapshotSerializerDeserializer {
 
 class SnapshotDeserializer : public SnapshotSerializerDeserializer {
  public:
-  explicit SnapshotDeserializer(const std::vector<char>& s)
+  explicit SnapshotDeserializer(const std::string_view s)
       : SnapshotSerializerDeserializer(), sink(s) {}
   ~SnapshotDeserializer() {}
 
@@ -246,7 +246,7 @@ class SnapshotDeserializer : public SnapshotSerializerDeserializer {
   }
 
   size_t read_total = 0;
-  const std::vector<char>& sink;
+  const std::string_view sink;
 
  private:
   // Helper for reading an array of numeric types.
@@ -883,6 +883,10 @@ bool SnapshotData::FromFile(SnapshotData* out, FILE* in) {
 }
 
 bool SnapshotData::FromBlob(SnapshotData* out, const std::vector<char>& in) {
+  return FromBlob(out, std::string_view(in.data(), in.size()));
+}
+
+bool SnapshotData::FromBlob(SnapshotData* out, const std::string_view in) {
   SnapshotDeserializer r(in);
   r.Debug("SnapshotData::FromBlob()\n");
 
@@ -909,6 +913,11 @@ bool SnapshotData::FromBlob(SnapshotData* out, const std::vector<char>& in) {
   return true;
 }
 
+bool SnapshotData::IsSnapshotBlob(const std::string_view data) {
+  const uint32_t* ptr = reinterpret_cast<const uint32_t*>(data.data());
+  return (ptr[0] == kMagic);
+}
+
 bool SnapshotData::Check() const {
   if (metadata.node_version != per_process::metadata.versions.node) {
     fprintf(stderr,