f9/sdk/dart/package-fuchsia_vfs_vfs/PseudoFile/PseudoFile.readOnly.md

# PseudoFile.readOnly constructor




    *[<Null safety>](https://dart.dev/null-safety)*



PseudoFile.readOnly([ReadFn](../../package-fuchsia_vfs_vfs/ReadFn.md)? _readFn)


<p>Creates a new read-only <a href="../../package-fuchsia_vfs_vfs/PseudoFile-class.md">PseudoFile</a> backed by the specified read handler.</p>
<p>The handler is called every time a read operation is performed on the file.  It is only allowed
to read at offset 0, and all of the content returned by the handler is returned by the read
operation.  Subsequent reads act the same - there is no seek position, nor ability to read
content in chunks.</p>



## Implementation

```dart
PseudoFile.readOnly(this._readFn)
    : _capacity = 0,
      assert(_readFn != null);
```