bindings.js

/**
 * Module dependencies.
 */

var fs = require('fs'),
  path = require('path'),
  fileURLToPath = require('file-uri-to-path'),
  join = path.join,
  dirname = path.dirname,
  exists =
    (fs.accessSync &&
      function(path) {
        try {
          fs.accessSync(path);
        } catch (e) {
          return false;
        }
        return true;
      }) ||
    fs.existsSync ||
    path.existsSync,
  defaults = {
    arrow: process.env.NODE_BINDINGS_ARROW || ' → ',
    compiled: process.env.NODE_BINDINGS_COMPILED_DIR || 'compiled',
    platform: process.platform,
    arch: process.arch,
    nodePreGyp:
      'node-v' +
      process.versions.modules +
      '-' +
      process.platform +
      '-' +
      process.arch,
    version: process.versions.node,
    bindings: 'bindings.node',
    try: [
      // node-gyp's linked version in the "build" dir
      ['module_root', 'build', 'bindings'],
      // node-waf and gyp_addon (a.k.a node-gyp)
      ['module_root', 'build', 'Debug', 'bindings'],
      ['module_root', 'build', 'Release', 'bindings'],
      // Debug files, for development (legacy behavior, remove for node v0.9)
      ['module_root', 'out', 'Debug', 'bindings'],
      ['module_root', 'Debug', 'bindings'],
      // Release files, but manually compiled (legacy behavior, remove for node v0.9)
      ['module_root', 'out', 'Release', 'bindings'],
      ['module_root', 'Release', 'bindings'],
      // Legacy from node-waf, node <= 0.4.x
      ['module_root', 'build', 'default', 'bindings'],
      // Production "Release" buildtype binary (meh...)
      ['module_root', 'compiled', 'version', 'platform', 'arch', 'bindings'],
      // node-qbs builds
      ['module_root', 'addon-build', 'release', 'install-root', 'bindings'],
      ['module_root', 'addon-build', 'debug', 'install-root', 'bindings'],
      ['module_root', 'addon-build', 'default', 'install-root', 'bindings'],
      // node-pre-gyp path ./lib/binding/{node_abi}-{platform}-{arch}
      ['module_root', 'lib', 'binding', 'nodePreGyp', 'bindings']
    ]
  };

/**
 * The main `bindings()` function loads the compiled bindings for a given module.
 * It uses V8's Error API to determine the parent filename that this function is
 * being invoked from, which is then used to find the root directory.
 */

function bindings(opts) {
  // Argument surgery
  if (typeof opts == 'string') {
    opts = { bindings: opts };
  } else if (!opts) {
    opts = {};
  }

  // maps `defaults` onto `opts` object
  Object.keys(defaults).map(function(i) {
    if (!(i in opts)) opts[i] = defaults[i];
  });

  // Get the module root
  if (!opts.module_root) {
    const fileName = exports.getFileName();
    let module_root = exports.getRoot(fileName);

    // Filename is undefined when eval() was used to execute code with bindings in it. We don't have a valid
    // module-root in that case and need to use a heuristic to hopefully find the correct directory.
    if (!fileName) {
      // Derive module_root from ".node"-filename
      const possible_package_name = opts.bindings.replace('.node', '');
      let best_score = -1;
      let best_match = "";
      for (const file of fs.readdirSync(join(module_root, 'node_modules'))) {
          const current_score = compare(file, possible_package_name);
          if (current_score > best_score) {
              best_score = current_score;
              best_match = file;
          }
      }

      module_root = join(module_root, 'node_modules', best_match);
    }

    opts.module_root = module_root;
  }

  // Ensure the given bindings name ends with .node
  if (path.extname(opts.bindings) != '.node') {
    opts.bindings += '.node';
  }

  // https://github.com/webpack/webpack/issues/4175#issuecomment-342931035
  var requireFunc =
    typeof __webpack_require__ === 'function'
      ? __non_webpack_require__
      : require;

  var tries = [],
    i = 0,
    l = opts.try.length,
    n,
    b,
    err;

  for (; i < l; i++) {
    n = join.apply(
      null,
      opts.try[i].map(function(p) {
        return opts[p] || p;
      })
    );
    tries.push(n);
    try {
      b = opts.path ? requireFunc.resolve(n) : requireFunc(n);
      if (!opts.path) {
        b.path = n;
      }
      return b;
    } catch (e) {
      if (e.code !== 'MODULE_NOT_FOUND' &&
          e.code !== 'QUALIFIED_PATH_RESOLUTION_FAILED' &&
          !/not find/i.test(e.message)) {
        throw e;
      }
    }
  }

  err = new Error(
    'Could not locate the bindings file. Tried:\n' +
      tries
        .map(function(a) {
          return opts.arrow + a;
        })
        .join('\n')
  );
  err.tries = tries;
  throw err;
}
module.exports = exports = bindings;

/**
 * Returns a similarity score for two strings.
 * See: https://stackoverflow.com/questions/10473745/compare-strings-javascript-return-of-likely
 */
function compare(strA, strB){
    for(var result = 0, i = strA.length; i--;){
        if(typeof strB[i] == 'undefined' || strA[i] == strB[i]);
        else if(strA[i].toLowerCase() == strB[i].toLowerCase())
            result++;
        else
            result += 4;
    }
    return 1 - (result + 4*Math.abs(strA.length - strB.length))/(2*(strA.length+strB.length));
}

/**
 * Gets the filename of the JavaScript file that invokes this function.
 * Used to help find the root directory of a module.
 * Optionally accepts an filename argument to skip when searching for the invoking filename
 */

exports.getFileName = function getFileName(calling_file) {
  var origPST = Error.prepareStackTrace,
    origSTL = Error.stackTraceLimit,
    dummy = {},
    fileName;

  Error.stackTraceLimit = 10;

  Error.prepareStackTrace = function(e, st) {
    for (var i = 0, l = st.length; i < l; i++) {
      fileName = st[i].getFileName();
      if (fileName !== __filename) {
        if (calling_file) {
          if (fileName !== calling_file) {
            return;
          }
        } else {
          return;
        }
      }
    }
  };

  // run the 'prepareStackTrace' function above
  Error.captureStackTrace(dummy);
  dummy.stack;

  // cleanup
  Error.prepareStackTrace = origPST;
  Error.stackTraceLimit = origSTL;

  if (!fileName) {
      return "";
  }

  // handle filename that starts with "file://"
  var fileSchema = 'file://';
  if (fileName.indexOf(fileSchema) === 0) {
    fileName = fileURLToPath(fileName);
  }

  return fileName;
};

/**
 * Gets the root directory of a module, given an arbitrary filename
 * somewhere in the module tree. The "root directory" is the directory
 * containing the `package.json` file.
 *
 *   In:  /home/nate/node-native-module/lib/index.js
 *   Out: /home/nate/node-native-module
 */

exports.getRoot = function getRoot(file) {
  var dir = dirname(file),
    prev;
  while (true) {
    if (dir === '.') {
      // Avoids an infinite loop in rare cases, like the REPL
      dir = process.cwd();
    }
    if (
      exists(join(dir, 'package.json')) ||
      exists(join(dir, 'node_modules'))
    ) {
      // Found the 'package.json' file or 'node_modules' dir; we're done
      return dir;
    }
    if (prev === dir) {
      // Got to the top
      throw new Error(
        'Could not find module root given file: "' +
          file +
          '". Do you have a `package.json` file? '
      );
    }
    // Try the parent dir next
    prev = dir;
    dir = join(dir, '..');
  }
};