Zero copy

ZeroCopyBuffer<Vec<u8>> (and its friends like ZeroCopyBuffer<Vec<i8>>) sends the data from Rust to Dart without making copies¹. Thus, you save the time of copying data, which can be large if your data is big (such as a high-resolution image).

Make it the default

If you don't want to wrap Vec<u8> and its friends with ZeroCopyBuffer over and over again to avoid copying memory, you can alternatively provide a cargo feature called zero-copy. With this feature enabled, Vec<u8> and its friends will be zero-copied by default.

# Cargo.toml
[dependencies]
flutter_rust_bridge = { version = "...", features = ["zero-copy"] }

Example

pub fn draw_tree(tree: Vec<TreeNode>) -> ZeroCopyBuffer<Vec<u8>> { ... }

Becomes:

Future<Uint8List> drawTree({required List<TreeNode> tree});

The generated Dart code looks exactly the same as the case without ZeroCopyBuffer. However, the internal implementation changes and now there is no memory copy at all!

If you are curious about what those Vec<u8> and its friends actually are, take a look at this.