HomeWork/react2/node_modules/tar/lib/get-write-flag.js

// Get the appropriate flag to use for creating files
// We use fmap on Windows platforms for files less than
// 512kb.  This is a fairly low limit, but avoids making
// things slower in some cases.  Since most of what this
// library is used for is extracting tarballs of many
// relatively small files in npm packages and the like,
// it can be a big boost on Windows platforms.
// Only supported in Node v12.9.0 and above.
const platform = process.env.__FAKE_PLATFORM__ || process.platform
const isWindows = platform === 'win32'
const fs = global.__FAKE_TESTING_FS__ || require('fs')

/* istanbul ignore next */
const { O_CREAT, O_TRUNC, O_WRONLY, UV_FS_O_FILEMAP = 0 } = fs.constants

const fMapEnabled = isWindows && !!UV_FS_O_FILEMAP
const fMapLimit = 512 * 1024
const fMapFlag = UV_FS_O_FILEMAP | O_TRUNC | O_CREAT | O_WRONLY
module.exports = !fMapEnabled ? () => 'w'
  : size => size < fMapLimit ? fMapFlag : 'w'