UXFileIO

UXFileIO reads a whole file into a Data and writes one back:

Data* bytes = UXFileIO.read(path);          // null if it cannot be read
bool ok = UXFileIO.write(path, bytes);        // false if it did not happen

It is libc’s stdio underneath, which every native target has: macOS, Linux, Windows, iOS and Android inside their sandboxes, and GEM through its own libc. The standard library’s Files.xc exists only on the host architectures, so a document app built on it could not save on a device or on GEM. UXFileIO can.

Saving is atomic

write puts the bytes in path + .uxtmp first. It renames that over the original only when every byte is written and the file is closed.

A full disk, a missing folder or a failed write therefore leaves the previous document exactly as it was, instead of truncating it. The temporary file is removed on failure.

The web

A browser has no file system, so on a page UXKit keeps one: a store of files by path, held where the app runs. write puts the file in the store and hands it to the browser as a download, so saving a document downloads it. read reads from the store, which is where a file the user opens with UXOpenPanel is put. Nothing in the store outlives the page.

Under node, which runs the wasm32 tests, the same calls read and write real files.

The phones

On iOS and Android, UXSavePanel asks where a document goes before anything is written, and hands back a staging path in the app’s own space. A write to that path is written as above, then copied on to the chosen document. write returns true only if the copy arrives too.

Topics

read

static Data* read(u8* path)

The whole file, or null if it does not exist or cannot be read. An empty file reads as an empty Data, not as null.

write

static bool write(u8* path, Data* d)

Writes d to path, replacing it only if every byte made it to disk.