socket.io/is-buffer.js

module.exports = isBuf;

var withNativeBuffer = typeof global.Buffer === 'function' && typeof global.Buffer.isBuffer === 'function';
var withNativeArrayBuffer = typeof global.ArrayBuffer === 'function';

var isView = (function () {
  if (withNativeArrayBuffer && typeof global.ArrayBuffer.isView === 'function') {
    return global.ArrayBuffer.isView;
  } else {
    return function (obj) { return obj.buffer instanceof global.ArrayBuffer; };
  }
})();

/**
 * Returns true if obj is a buffer or an arraybuffer.
 *
 * @api private
 */

function isBuf(obj) {
  return (withNativeBuffer && global.Buffer.isBuffer(obj)) ||
          (withNativeArrayBuffer && (obj instanceof global.ArrayBuffer || isView(obj)));
}