Browser use case

Convert a file directly to disk

The File System Access API lets Chromium-based browsers persist each output chunk as it arrives. Diakrio awaits every write, so a slower disk applies backpressure to the converter instead of growing an output queue.

Direct-to-disk CSV → NDJSON

The runnable harness uses the same local streaming path and discards output after a small preview, so you can measure it without opening a save dialog.

10,000 generated CSV records

import { ConvertBuddy, getSuggestedFilename } from '@diakrio/converter/browser';

const [fileHandle] = await window.showOpenFilePicker();
const input = await fileHandle.getFile();
const output = await window.showSaveFilePicker({
  suggestedName: getSuggestedFilename(input.name, 'ndjson')
});
const writable = await output.createWritable();

try {
  const controller = new ConvertBuddy({ profile: true }).stream(input, {
    inputFormat: 'csv',
    outputFormat: 'ndjson',
    onBytes: (chunk) => writable.write(chunk)
  });
  const stats = await controller.done;
  await writable.close();
  console.table(stats);
} catch (error) {
  await writable.abort(error);
  throw error;
}

Measured on this device

Browser · WASM· preview discarded· idle

End-to-end

0.0 MB/s

Records/sec

Records

Duration

0 ms

Engine peak buffer

0 B

Runtime heap

Unavailable

Input

0 B

Output

0 B

Engine buffer is exact. Runtime heap is shown only when the runtime exposes a measurement API. Engine-only throughput: 0.0 MB/s.

Fallback behavior

showSaveFilePicker is not available in every browser. Feature-detect it and either use a bounded in-memory Blob for modest files or ask the user to switch to a supported browser. Diakrio cannot make an in-memory destination constant-memory.

if ('showSaveFilePicker' in window) {
  // stream to FileSystemWritableFileStream
} else if (file.size <= 256 * 1024 * 1024) {
  // collect output chunks, then download a Blob
} else {
  // explain that direct file saving is required
}

What the memory number means

maxBufferSize is the exact peak partial-record buffer reported by the engine.
Browser heap is an approximate runtime-wide value and is shown only when the browser exposes it.
OS file caches, WASM pages, and browser internals may not be represented in JavaScript heap.

import { ConvertBuddy, getSuggestedFilename } from '@diakrio/converter/browser'; const [fileHandle] = await window.showOpenFilePicker(); const input = await fileHandle.getFile(); const output = await window.showSaveFilePicker({ suggestedName: getSuggestedFilename(input.name, 'ndjson') }); const writable = await output.createWritable(); try { const controller = new ConvertBuddy({ profile: true }).stream(input, { inputFormat: 'csv', outputFormat: 'ndjson', onBytes: (chunk) => writable.write(chunk) }); const stats = await controller.done; await writable.close(); console.table(stats); } catch (error) { await writable.abort(error); throw error; }

Fallback behavior

if ('showSaveFilePicker' in window) { // stream to FileSystemWritableFileStream } else if (file.size <= 256 * 1024 * 1024) { // collect output chunks, then download a Blob } else { // explain that direct file saving is required }