@bun-win32/cldapi

Zero-dependency, zero-overhead Win32 Cloud Filter API (cldapi.dll) bindings for Bun on Windows.

Overview

@bun-win32/cldapi exposes the cldapi.dll exports using Bun's FFI. It provides a single class, Cldapi, which lazily binds native symbols on first use. You can optionally preload a subset or all symbols up-front via Preload().

cldapi.dll is the Cloud Files API (header cfapi.h) — the platform behind OneDrive Files On-Demand. It lets a sync provider register a sync root, project placeholder files (files that appear with full size and metadata in Explorer but occupy no disk until hydrated), hydrate/dehydrate on demand, and inspect the placeholder/sync-root state of any file.

The bindings are strongly typed for a smooth DX in TypeScript.

Features

• Bun-first ergonomics on Windows 10/11.
• Direct FFI to cldapi.dll (sync roots, placeholders, hydration, transfer keys, platform info).
• In-source docs in structs/Cldapi.ts with links to Microsoft Docs.
• Lazy binding on first call; optional eager preload (Cldapi.Preload()).
• No wrapper overhead; calls map 1:1 to native APIs.
• Strongly-typed Win32 aliases (see types/Cldapi.ts).

Requirements

• Bun runtime
• Windows 10 version 1709 or later

Installation

bun add @bun-win32/cldapi

Quick Start

import Cldapi from '@bun-win32/cldapi';

// CF_PLATFORM_INFO { DWORD BuildNumber; DWORD RevisionNumber; DWORD IntegrationNumber; }
const info = Buffer.alloc(12);
const hr = Cldapi.CfGetPlatformInfo(info.ptr!);

if (hr === 0) {
  console.log('Build      :', info.readUInt32LE(0));
  console.log('Revision   :', info.readUInt32LE(4));
  console.log('Integration: 0x' + info.readUInt32LE(8).toString(16));
}

// Decode the placeholder state of any file straight from its attributes/reparse tag
const FILE_ATTRIBUTE_DIRECTORY = 0x10;
const state = Cldapi.CfGetPlaceholderStateFromAttributeTag(FILE_ATTRIBUTE_DIRECTORY, 0);
console.log('Placeholder state:', state);

[!NOTE] AI agents: see AI.md for the package binding contract and source-navigation guidance. It explains how to use the package without scanning the entire implementation.

Examples

Run the included examples:

bun run example/cloud-mirage.ts
bun run example/placeholder-diagnostic.ts

• cloud-mirage — registers a real sync root in a temp directory and projects a catalog of multi-gigabyte placeholder "files" that occupy zero bytes on disk, then animates the reveal and decodes every placeholder's state. Pure FFI; no provider process.
• placeholder-diagnostic — a full Cloud Files report: platform version + integration capability gates, sync-root detection for any directory (OneDrive included), and per-file placeholder/pin/in-sync/on-disk-vs-logical analysis.

Notes

• Either rely on lazy binding or call Cldapi.Preload().
• HRESULT returns are number; S_OK is 0. Negative-looking values are error HRESULTs — mask with >>> 0 to print as hex.
• CF_CONNECTION_KEY, CF_TRANSFER_KEY, and CF_REQUEST_KEY are opaque 8-byte keys modeled as bigint (passed/returned by value); their P* pointer forms are Pointer out-params.
• Windows only. Bun runtime required.
• SAL types & naming: nullability is in the type — Optional<T> (formally optional, SAL _*opt_) and Nullable<T> (plain [in]/[out] the docs say can be NULL), the null sentinel derived from T (null for pointers LP*/P*, 0n for handles/by-value addresses); direction is in the parameter name — _out (_Out_), _in_out (_Inout_), _In_ bare. See AI.md and the repo AGENTS.md.