io / file-io
src/io/fileIO.ts is a pure-DOM toolkit for browser-side file IO. No React, no store — easy to mock in unit tests via document.createElement stubs.
Exported symbols
ts
export function pickFile(accept: string): Promise<File | null>;
export function readFileAsBytes(file: Blob): Promise<Uint8Array>;
export function readFileAsText(file: Blob): Promise<string>;
export function downloadBlob(blob: Blob, filename: string): void;Source:
src/io/fileIO.ts:1-66.
pickFile(accept)
Open a hidden <input type="file"> and resolve to the selected File or null (cancellation). accept is a comma-separated list of extensions and MIME types, e.g. '.bin,.txt,application/octet-stream'.
Notes:
- Reads
input.files[0]from the'change'event. - Uses the native
'cancel'event for cancellation. We deliberately avoid focus-based heuristics; on macOS the window can re-focus before the file is committed, racing with'change'and producing false cancellations. - Removes the hidden input from the DOM after settling.
- A
settledflag prevents latecancelfrom overriding a realchange.
ts
const file = await pickFile('.bin,.txt,.pb.txt');
if (file) {
const bytes = await readFileAsBytes(file);
}readFileAsBytes(file)
ts
const buf = await file.arrayBuffer();
return new Uint8Array(buf);readFileAsText(file)
ts
return file.text(); // UTF-8 decodedownloadBlob(blob, filename)
Synthesise an <a href="${objectURL}" download="${filename}"> and click it. The object URL is revoked after a 1 s timeout so the download has time to start:
ts
const blob = new Blob([bytes.buffer], { type: 'application/octet-stream' });
downloadBlob(blob, 'apollo-base-map.bin');Constraints
- Browser-only (including Tauri webview). Electron main-process dialogs come from
electron/preload. - Single-file selection only. The current Apollo import path expects one file, so
input.multiple = false. pickFilenever rejects; cancellation falls through tonull.
See also
- io/map-io — primary consumer.
- Import / Parse Base Map
- Export / Base Map
Contributors
kent