1 files changed, 91 insertions, 0 deletions
diff --git a/src/snapshot_creator.cc b/src/snapshot_creator.cc
new file mode 100644
index 000000000..b822abd6e
--- /dev/null
+++ b/src/snapshot_creator.cc
@@ -0,0 +1,91 @@
+// Copyright 2018 Ryan Dahl <ry@tinyclouds.org>
+// All rights reserved. MIT License.
+// Hint: --trace_serializer is a useful debugging flag.
+#include "deno_internal.h"
+#include "file_util.h"
+#include "include/deno.h"
+#include "v8/include/v8.h"
+#include "v8/src/base/logging.h"
+
+namespace deno {
+
+v8::StartupData SerializeInternalFields(v8::Local<v8::Object> holder, int index,
+                                        void* data) {
+  DCHECK_EQ(data, nullptr);
+  InternalFieldData* embedder_field = static_cast<InternalFieldData*>(
+      holder->GetAlignedPointerFromInternalField(index));
+  if (embedder_field == nullptr) return {nullptr, 0};
+  int size = sizeof(*embedder_field);
+  char* payload = new char[size];
+  // We simply use memcpy to serialize the content.
+  memcpy(payload, embedder_field, size);
+  return {payload, size};
+}
+
+v8::StartupData MakeSnapshot(const char* js_filename, const char* js_source) {
+  auto* creator = new v8::SnapshotCreator(external_references);
+  auto* isolate = creator->GetIsolate();
+  v8::Isolate::Scope isolate_scope(isolate);
+  {
+    v8::HandleScope handle_scope(isolate);
+    auto context = v8::Context::New(isolate);
+    InitializeContext(isolate, context, js_filename, js_source);
+    creator->SetDefaultContext(context, v8::SerializeInternalFieldsCallback(
+                                            SerializeInternalFields, nullptr));
+  }
+
+  // Note that using kKeep here will cause segfaults. This is demoed in the
+  // "SnapshotBug" test case.
+  auto snapshot_blob =
+      creator->CreateBlob(v8::SnapshotCreator::FunctionCodeHandling::kClear);
+
+  return snapshot_blob;
+}
+
+// Wrap the js_source in an IIFE to work around a bug in the V8 snapshot
+// serializer. Without it, CreateBlob() triggers the following assert:
+//   Debug check failed : outer_scope_info()->IsScopeInfo() || is_toplevel().
+//   ==== C stack trace ====
+//   v8::internal::SharedFunctionInfo::FlushCompiled
+//   v8::SnapshotCreator::CreateBlob
+//   deno::MakeSnapshot
+// Avoid misaligning the source map, and ensure that the sourceMappingUrl
+// comment remains at the last line.
+// Try removing this when this bug is fixed:
+// https://bugs.chromium.org/p/v8/issues/detail?id=7857
+std::string WrapSourceCode(const std::string& js_source) {
+  auto smu_offset = js_source.rfind("//# sourceMappingURL=");
+  std::string tail =
+      smu_offset == std::string::npos ? "" : js_source.substr(smu_offset);
+  auto wrapped_js_source =
+      "(function() {" + js_source.substr(0, smu_offset) + "\n})();\n" + tail;
+  // Double check that the source mapping url comment is at the last line.
+  auto last_line = wrapped_js_source.substr(wrapped_js_source.rfind('\n'));
+  CHECK(smu_offset == std::string::npos ||
+        last_line.find("sourceMappingURL") != std::string::npos);
+  return wrapped_js_source;
+}
+
+}  // namespace deno
+
+int main(int argc, char** argv) {
+  const char* js_fn = argv[1];
+  const char* snapshot_out_cc = argv[2];
+
+  v8::V8::SetFlagsFromCommandLine(&argc, argv, true);
+
+  CHECK_EQ(argc, 3);
+  CHECK_NE(js_fn, nullptr);
+  CHECK_NE(snapshot_out_cc, nullptr);
+
+  std::string js_source;
+  CHECK(deno::ReadFileToString(js_fn, &js_source));
+
+  auto wrapped_js_source = deno::WrapSourceCode(js_source);
+
+  deno_init();
+  auto snapshot_blob = deno::MakeSnapshot(js_fn, wrapped_js_source.c_str());
+  std::string snapshot_str(snapshot_blob.data, snapshot_blob.raw_size);
+
+  CHECK(deno::WriteDataAsCpp("snapshot", snapshot_out_cc, snapshot_str));
+}