fs: implement copyFileSync in C++ - #21
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Move path validation, file URL conversion, NUL checks, mode validation, permission checks, and the copy into a dedicated C++ binding so fs.copyFileSync() no longer goes through getValidatedPath() in JavaScript. Signed-off-by: Yagiz Nizipli <yagiz-twitter@nizipli.com> Co-authored-by: Yagiz Nizipli <anonrig@users.noreply.github.com> Signed-off-by: Yagiz Nizipli <yagiz-twitter@nizipli.com>
Exercise the C++ copyFileSync validator with Buffer paths, file: URLs, and a non-file URL scheme. Signed-off-by: Yagiz Nizipli <yagiz-twitter@nizipli.com> Co-authored-by: Yagiz Nizipli <anonrig@users.noreply.github.com>
The C++ FileURLToPath helper aborted on file URLs with a hostname because the ERR_INVALID_FILE_URL_HOST format string was missing %s. copyFileSync now converts URLs in C++, so that path was user-visible. Also match JS fileURLToPath's ERR_INVALID_URL_SCHEME message and cover Uint8Array paths, encoded slashes, and file URL hosts. Co-authored-by: Yagiz Nizipli <anonrig@users.noreply.github.com>
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August 18, 2026 02:29
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What
Rewrite
fs.copyFileSync()so the entire implementation lives in C++.JavaScript now only does VFS dispatch. Everything else — path type checks (
string/Buffer/Uint8Array/URL), file URL conversion, embedded-NUL rejection, mode validation, permission-model checks, and the copy — runs in a dedicatedbinding.copyFileSync()function.The copy itself still uses
uv_fs_copyfile, so flags (COPYFILE_EXCL,COPYFILE_FICLONE,COPYFILE_FICLONE_FORCE), mode/timestamp preservation, same-file handling, and UV error shapes (syscall: 'copyfile',path/dest) stay identical.Also fixes a crash in the C++
FileURLToPathhelper:ERR_INVALID_FILE_URL_HOSTused a format string without%s, which aborted when converting a file URL with a hostname (now reachable fromcopyFileSync).Why
copyFileSyncwas paying for twogetValidatedPath()trips in JS on every call. Moving that work next to the existing C++ permission checks anduv_fs_copyfileremoves that overhead without changing behavior.Testing
All of the following passed against
./out/Release/node:test/parallel/test-fs-copyfile.js(Buffer,Uint8Array,file:URL, non-file URL, encoded slashes, file URL host)test/parallel/test-fs-copyfile-respect-permissions.jstest/parallel/test-fs-null-bytes.jstest/parallel/test-fs-error-messages.jstest/parallel/test-fs-whatwg-url.jstest/parallel/test-url-fileurltopath.jstest-vfs-fs-copyFileSync.js,test-vfs-copyfile-mode.js,test-vfs-mount-errors.js, real/memory providerstest-permission-fs-read.js,test-permission-fs-write.jscopyFileSynccallers:test-fs-lchown.js,test-fs-fsync.js,test-fs-open-flags.js,test-trace-events-fs-sync.js,test-require-symlink.jsCompared C++
copyFileSyncvs the old JSgetValidatedPath+binding.copyFilepath (n=1e4):Official
benchmark/fs/bench-copyFileSync.jsalso ran (type=valid/type=invalid,n=10000).