extract-base-iterator/dist/esm/waitForAccess.js

Base iterator for extract iterators like tar-iterator and zip-iterator

import fs from 'graceful-fs';
// Backward compatible: waitForAccess(path, callback) or waitForAccess(path, noFollow, callback)
export default function waitForAccess(fullPath, noFollow, callback) {
    callback = typeof noFollow === 'function' ? noFollow : callback;
    noFollow = typeof noFollow === 'function' ? false : noFollow;
    // Exponential backoff: 5, 10, 20, 40, 80, 160, 320, 640, 1280, 2560ms
    // Total max wait: ~5 seconds
    function waitSymlink(attempts, cb) {
        fs.lstat(fullPath, (err)=>{
            if (err) {
                if (err.code === 'ENOENT' && attempts < 10) {
                    const delay = Math.min(5 * 2 ** attempts, 2560);
                    return setTimeout(()=>waitSymlink(attempts + 1, cb), delay);
                }
                return cb(err);
            }
            cb();
        });
    }
    function waitOpen(attempts, cb) {
        fs.open(fullPath, 'r', (err, fd)=>{
            if (err) {
                if (err.code === 'ENOENT' && attempts < 10) {
                    const delay = Math.min(5 * 2 ** attempts, 2560);
                    return setTimeout(()=>waitOpen(attempts + 1, cb), delay);
                }
                return cb(err);
            }
            fs.close(fd, ()=>cb());
        });
    }
    // Windows: NTFS metadata may not be committed yet, verify accessibility
    // Node 0.10: the write stream's finish/close events may fire before the file is fully flushed to disk
    // For symlinks (noFollow=true), use lstat to check the link itself exists
    // For files/dirs/hardlinks, use open to verify the file is accessible
    noFollow ? waitSymlink(0, callback) : waitOpen(0, callback);
}