FileSystemSyncAccessHandle.md

FileSystemSyncAccessHandle

Namespace: SpawnDev.SpawnJS.JSObjects
Inherits: SpawnJSObject
Source: JSObjects/FileSystemSyncAccessHandle.cs
MDN Reference: FileSystemSyncAccessHandle on MDN

https://developer.mozilla.org/en-US/docs/Web/API/FileSystemSyncAccessHandle

Methods

Method	Return Type	Description
Close()	void	The close() method of the FileSystemSyncAccessHandle interface closes an open synchronous file handle, disabling any further operations on it and releasing the exclusive lock previously put on the file associated with the file handle.
Flush()	void	The flush() method of the FileSystemSyncAccessHandle interface persists any changes made to the file associated with the handle via the write() method to disk. Bear in mind that you only need to call this method if you need the changes committed to disk at a specific time, otherwise you can leave the underlying operating system to handle this when it sees fit, which should be OK in most cases.
GetSize()	long	The getSize() method of the FileSystemSyncAccessHandle interface returns the size of the file associated with the handle in bytes.
Read(ArrayBuffer buffer, FileSystemSyncReadWriteOptions? options)	long	The read() method of the FileSystemSyncAccessHandle interface reads the content of the file associated with the handle into a specified buffer, optionally at a given offset.
Read(TypedArray buffer, FileSystemSyncReadWriteOptions? options)	long	The read() method of the FileSystemSyncAccessHandle interface reads the content of the file associated with the handle into a specified buffer, optionally at a given offset.
Read(DataView buffer, FileSystemSyncReadWriteOptions? options)	long	The read() method of the FileSystemSyncAccessHandle interface reads the content of the file associated with the handle into a specified buffer, optionally at a given offset.
Read(byte[] buffer, FileSystemSyncReadWriteOptions? options)	long	The read() method of the FileSystemSyncAccessHandle interface reads the content of the file associated with the handle into a specified buffer, optionally at a given offset.
Truncate(long newSize)	void	The truncate() method of the FileSystemSyncAccessHandle interface resizes the file associated with the handle to a specified number of bytes.
Write(ArrayBuffer buffer, FileSystemSyncReadWriteOptions? options)	long	The write() method of the FileSystemSyncAccessHandle interface writes the content of a specified buffer to the file associated with the handle, optionally at a given offset. Files within the origin private file system are not visible to end-users, therefore are not subject to the same security checks as methods running on files within the user-visible file system. As a result, writes performed using FileSystemSyncAccessHandle.write() are much more performant. This makes them suitable for significant, large-scale file updates such as SQLite database modifications.
Write(TypedArray buffer, FileSystemSyncReadWriteOptions? options)	long	The write() method of the FileSystemSyncAccessHandle interface writes the content of a specified buffer to the file associated with the handle, optionally at a given offset. Files within the origin private file system are not visible to end-users, therefore are not subject to the same security checks as methods running on files within the user-visible file system. As a result, writes performed using FileSystemSyncAccessHandle.write() are much more performant. This makes them suitable for significant, large-scale file updates such as SQLite database modifications.
Write(DataView buffer, FileSystemSyncReadWriteOptions? options)	long	The write() method of the FileSystemSyncAccessHandle interface writes the content of a specified buffer to the file associated with the handle, optionally at a given offset. Files within the origin private file system are not visible to end-users, therefore are not subject to the same security checks as methods running on files within the user-visible file system. As a result, writes performed using FileSystemSyncAccessHandle.write() are much more performant. This makes them suitable for significant, large-scale file updates such as SQLite database modifications.
Write(byte[] buffer, FileSystemSyncReadWriteOptions? options)	long	The write() method of the FileSystemSyncAccessHandle interface writes the content of a specified buffer to the file associated with the handle, optionally at a given offset. Files within the origin private file system are not visible to end-users, therefore are not subject to the same security checks as methods running on files within the user-visible file system. As a result, writes performed using FileSystemSyncAccessHandle.write() are much more performant. This makes them suitable for significant, large-scale file updates such as SQLite database modifications.

Examples

SpawnDev.SpawnJS Mapping Note: The JavaScript examples below show the standard Web API usage. In SpawnDev.SpawnJS, the same API is available with C# conventions:

• Properties and methods use PascalCase (e.g., readyState becomes ReadyState)
• Events use ActionEvent with +=/-= (e.g., addEventListener("click", fn) becomes OnClick += handler)
• Async methods return Task<T> instead of Promise<T>
• Objects should be disposed with using statements
• Access via JS.Get<FileSystemSyncAccessHandle>(...) or constructor new FileSystemSyncAccessHandle(...)

onmessage = async (e) => {
  // Retrieve message sent to work from main script
  const message = e.data;

  // Get handle to draft file
  const root = await navigator.storage.getDirectory();
  const draftHandle = await root.getFileHandle("draft.txt", { create: true });
  // Get sync access handle
  const accessHandle = await draftHandle.createSyncAccessHandle();

  // Get size of the file.
  const fileSize = accessHandle.getSize();
  // Read file content to a buffer.
  const buffer = new DataView(new ArrayBuffer(fileSize));
  const readBuffer = accessHandle.read(buffer, { at: 0 });

  // Write the message to the end of the file.
  const encoder = new TextEncoder();
  const encodedMessage = encoder.encode(message);
  const writeBuffer = accessHandle.write(encodedMessage, { at: readBuffer });

  // Persist changes to disk.
  accessHandle.flush();

  // Always close FileSystemSyncAccessHandle if done.
  accessHandle.close();
};

See full example on MDN