WasmVfs class final wasm

A VFS implementation based on the file system access API without shared workers.

The file system access API provides synchronous access to opened files. These need to be opened first however, and that process is asynchronous. SQLite, being a C library, expects synchronous access to the file system. WasmVfs is a workaround for this problem that relies on a pair of workers that together make asynchronous APIs synchronous.

1. One worker is responsible for hosting the database. This worker installs a WasmVfs on the registered SQLite instance. The worker uses WasmVfs.createOptions to obtain an options object containing shared array buffers for efficient communication.
2. Another worker is hosting the file system. This is asynchronous, but by using Atomics APIs and the shared array buffers, the database worker can access the file system synchronously.

The second worker is implemented by VfsWorker. Note that WasmVfs is only available in browsing contexts where shared array buffers and atomics are available. For an automatic feature detection and logic to pick a suitable implementation based on browser features, consider using a package like sqlite3_web (or sqlite_async for cross-platform support).

Inheritance

• Object
• VirtualFileSystem
• BaseVirtualFileSystem
• WasmVfs

Constructors

WasmVfs({Random? random, required WorkerOptions workerOptions, String chroot = '/', String vfsName = 'dart-sqlite3-vfs'})

Properties

chroot → String

final

hashCode → int

The hash code for this object.

no setter, inherited

name → String

The name of this virtual file system.

final, inherited

pathContext → Context

final

random → Random

final, inherited

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

serializer → MessageSerializer

final

synchronizer → RequestResponseSynchronizer

final

Methods

close() → void

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

toString() → String

A string representation of this object.

inherited

xAccess(String path, int flags) → int

Check whether a file can be accessed.

override

xCurrentTime() → DateTime

Returns the current time.

inherited

xDelete(String path, int syncDir) → void

Delete a file.

override

xFullPathName(String path) → String

Resolves a path name supplied by the user into a path that can be used by the other methods of this VFS.

override

xOpen(Sqlite3Filename path, int flags) → XOpenResult

Opens a file, returning supported flags and a file instance.

override

xRandomness(Uint8List target) → void

Fill the target with random bytes.

inherited

xSleep(Duration duration) → void

Sleeps for the passed duration.

override

Operators

operator ==(Object other) → bool

The equality operator.

inherited

Static Properties

supportsAtomicsAndSharedMemory → bool

no setter

Static Methods

createOptions({String root = 'pkg_sqlite3_db/'}) → WorkerOptions

Creates WorkerOptions that can be sent to an VfsWorker instance which is responsible for hosting the file system on the other end.