snapshot_creator.cc

// Copyright 2018 Ryan Dahl <ry@tinyclouds.org>
// All rights reserved. MIT License.
#include <assert.h>
#include <stdio.h>
#include <string.h>
#include <fstream>
#include <iterator>
#include <vector>

#include "v8/include/v8.h"

#include "./deno.h"

class StartupDataCppWriter {
 public:
  StartupDataCppWriter(const char* name, const char* filename,
                       v8::StartupData sd)
      : name_(name),
        filename_(filename),
        sd_(sd),
        file_(filename_, std::ios::binary) {}

  void Write() {
    WritePrefix();
    WriteData();
    WriteSuffix();

    file_.close();
    if (file_.bad()) {
      printf("Unable to open file \"%s\" for writing.\n", filename_);
      exit(1);
    }
    printf("Wrote %s %d %s \n", name_, sd_.raw_size, filename_);
  }

 private:
  void WritePrefix() {
    file_ << "// Autogenerated snapshot file. Do not edit.\n\n";
    file_ << "#include \"v8/include/v8.h\"\n\n";
  }

  void WriteSuffix() {
    char buffer[500];
    snprintf(buffer, sizeof(buffer),
             "const v8::StartupData* StartupBlob_%s() {\n", name_);
    file_ << buffer;
    snprintf(buffer, sizeof(buffer), "  return &%s_blob;\n", name_);
    file_ << buffer;
    file_ << "}\n\n";
  }

  void WriteBinaryContentsAsCArray() {
    char buffer[5];
    for (int i = 0; i < sd_.raw_size; i++) {
      if ((i & 0x1F) == 0x1F) file_ << "\n";
      if (i > 0) file_ << ",";
      snprintf(buffer, sizeof(buffer), "%u",
               static_cast<unsigned char>(sd_.data[i]));
      file_ << buffer;
    }
    file_ << "\n";
  }

  void WriteData() {
    char buffer[500];
    snprintf(buffer, sizeof(buffer), "static const char %s_blob_data[] = {\n",
             name_);
    file_ << buffer;
    WriteBinaryContentsAsCArray();
    file_ << "};\n";
    snprintf(buffer, sizeof(buffer), "static const int %s_blob_size = %d;\n",
             name_, sd_.raw_size);
    file_ << buffer;
    snprintf(buffer, sizeof(buffer), "static const v8::StartupData %s_blob =\n",
             name_);
    file_ << buffer;
    snprintf(buffer, sizeof(buffer),
             "{ (const char*) %s_blob_data, %s_blob_size };\n", name_, name_);
    file_ << buffer;
  }

  const char* name_;
  const char* filename_;
  v8::StartupData sd_;
  std::ofstream file_;
};

// Caller must free returned value.
static v8::StartupData ReadFile(const char* fn) {
  std::ifstream input(fn, std::ios::binary);
  if (input.bad()) {
    printf("Error reading %s\n", fn);
    exit(1);
  }
  // Note the allocated buffer is intentionally not freed in this program.
  // It may show up as a memory leak some day, but other than that it's
  // harmless.
  auto* buffer = new std::vector<char>((std::istreambuf_iterator<char>(input)),
                                       (std::istreambuf_iterator<char>()));
  v8::StartupData sd;
  sd.data = buffer->data();
  sd.raw_size = static_cast<int>(buffer->size());
  if (input.bad()) {
    printf("Error reading %s\n", fn);
    exit(1);
  }
  return sd;
}

void WriteFile(const char* fn, v8::StartupData startup_data) {
  std::ofstream output(fn, std::ios::binary);
  output.write(startup_data.data, startup_data.raw_size);
  output.close();
  if (output.bad()) {
    printf("Error writing %s\n", fn);
    exit(1);
  }
}

int main(int argc, char** argv) {
  // The only documentation for this programs arguments is right here.
  const char* js_fn = argv[1];
  const char* natives_in_bin = argv[2];
  const char* snapshot_in_bin = argv[3];
  const char* natives_out_cc = argv[4];
  const char* snapshot_out_cc = argv[5];

  v8_init();

  auto js_data = ReadFile(js_fn);
  auto natives_blob = ReadFile(natives_in_bin);
  auto snapshot_in_blob = ReadFile(snapshot_in_bin);

  v8::V8::SetNativesDataBlob(&natives_blob);
  v8::V8::SetSnapshotDataBlob(&snapshot_in_blob);

  auto snapshot_blob = deno_make_snapshot(js_fn, js_data.data);

  StartupDataCppWriter nativesWriter("natives", natives_out_cc, natives_blob);
  nativesWriter.Write();

  StartupDataCppWriter snapshotWriter("snapshot", snapshot_out_cc,
                                      snapshot_blob);
  snapshotWriter.Write();
}