generate_code_cache.js

'use strict';

// Flags: --expose-internals

// This file generates the code cache for builtin modules and
// writes them into static char arrays of a C++ file that can be
// compiled into the binary using the `--code-cache-path` option
// of `configure`.

const {
  getCodeCache,
  cachableBuiltins
} = require('internal/bootstrap/cache');

const fs = require('fs');

const resultPath = process.argv[2];
if (!resultPath) {
  console.error(`Usage: ${process.argv[0]} ${process.argv[1]}` +
                'path/to/node_code_cache.cc');
  process.exit(1);
}

/**
 * Format a number of a size in bytes into human-readable strings
 * @param {number} num
 * @return {string}
 */
function formatSize(num) {
  if (num < 1024) {
    return `${(num).toFixed(2)}B`;
  } else if (num < 1024 ** 2) {
    return `${(num / 1024).toFixed(2)}KB`;
  } else if (num < 1024 ** 3) {
    return `${(num / (1024 ** 2)).toFixed(2)}MB`;
  } else {
    return `${(num / (1024 ** 3)).toFixed(2)}GB`;
  }
}

/**
 * Generates the source code of definitions of the char arrays
 * that contains the code cache and the source code of the
 * initializers of the code cache.
 *
 * @param {string} key ID of the builtin module
 * @param {Buffer} cache Code cache of the builtin module
 * @return { definition: string, initializer: string }
 */
function getInitalizer(key, cache) {
  const defName = key.replace(/\//g, '_').replace(/-/g, '_');
  const definition = `static uint8_t ${defName}_raw[] = {\n` +
                     `${cache.join(',')}\n};`;
  const initializer = `
  v8::Local<v8::ArrayBuffer> ${defName}_ab =
    v8::ArrayBuffer::New(isolate, ${defName}_raw, ${cache.length});
  v8::Local<v8::Uint8Array> ${defName}_array =
    v8::Uint8Array::New(${defName}_ab, 0, ${cache.length});
  target->Set(context,
              FIXED_ONE_BYTE_STRING(isolate, "${key}"),
              ${defName}_array).FromJust();
  `;
  return {
    definition, initializer
  };
}

const cacheDefinitions = [];
const cacheInitializers = [];
let totalCacheSize = 0;


for (const key of cachableBuiltins) {
  const cachedData = getCodeCache(key);
  if (!cachedData.length) {
    console.error(`Failed to generate code cache for '${key}'`);
    process.exit(1);
  }

  const length = cachedData.length;
  totalCacheSize += length;
  const { definition, initializer } = getInitalizer(key, cachedData);
  cacheDefinitions.push(definition);
  cacheInitializers.push(initializer);
  console.log(`Generated cache for '${key}', size = ${formatSize(length)}` +
              `, total = ${formatSize(totalCacheSize)}`);
}

const result = `#include "node.h"
#include "node_code_cache.h"
#include "v8.h"
#include "env.h"
#include "env-inl.h"

// This file is generated by tools/generate_code_cache.js
// and is used when configure is run with \`--code-cache-path\`

namespace node {

${cacheDefinitions.join('\n\n')}

// The target here will be returned as \`internalBinding('code_cache')\`
void DefineCodeCache(Environment* env, v8::Local<v8::Object> target) {
  v8::Isolate* isolate = env->isolate();
  v8::Local<v8::Context> context = env->context();
  ${cacheInitializers.join('\n')}
}

}  // namespace node
`;

fs.writeFileSync(resultPath, result);
console.log(`Generated code cache C++ file to ${resultPath}`);