Crate flatbuffers_build
source ·Expand description
This crate provides a set of functions to facilitate compiling flatbuffers to Rust from within
Rust. This is particularly helpful for use in build.rs
scripts. Please note that for
compatiblity this crate will only support a single version of the flatc
compiler. Please
check what version that is against whatever version is installed on your system.That said, due
to flatbuffers’ versioning policy, it could be ok to mix patch and even minor versions.
§Usage
If you’re not sure where to start, take a look at BuilderOptions
. Please also look at the
flatbuffers-example
folder in the repo for an example. However, we’ll explain the full functionality here.
As an example, imagine a crate with the following folder structure:
├── build.rs
├── Cargo.toml
├── schemas
│ ├── example.fbs
│ └── weapon.fbs
└── src
└── main.rs
In order to compile and use the code generated from both example.fbs
and weapon.fbs
, first
you need to add flatbuffers-build
to your build dependencies, as well as a matching version
of flatbuffers
:
# Cargo.toml
# [...]
[dependencies]
flatbuffers = "=23.5.26"
[build-dependencies]
flatbuffers-build = "=23.5.26"
# [...]
You can then have a very simple build.rs
as follows:
use flatbuffers_build::BuilderOptions;
BuilderOptions::new_with_files(["schemas/weapon.fbs", "schemas/example.fbs"])
.set_symlink_directory("src/gen_flatbuffers")
.compile()
.expect("flatbuffer compilation failed");
Note here that weapon.fbs
and example.fbs
are based on the schemas provided by
flatbuffers
as an example. The namespace is MyGame.Sample
and it contains multiple tables
and structs, including a Monster
table.
This will just compile the flatbuffers and drop them in ${OUT_DIR}/flatbuffers
and will
create a symlink under src/gen_flatbuffers
. You can then use them in lib.rs
like so:
#[allow(warnings)]
mod gen_flatbuffers;
use gen_flatbuffers::my_game::sample::Monster;
fn some_fn() {
// Make use of `Monster`
}
Note that since this will generate a symlink under src/gen_flatbuffers
, you need to add this
file to your gitignore as this symlink will dynamically change at runtime.
§On file ordering
Unfortunately due to a quirk in the flatc
compiler the order you provide the fbs
files does
matter. From some experimentation, the guidance is to always list files after their
dependencies. Otherwise, the resulting mod.rs
will be unusable. As an example, we have a
weapon.fbs
and example.fbs
. Since the latter has an include
directive for weapon.fbs
,
it should go after in the list. If you were to put example.fbs
before weapon.fbs
, you’d
end up only being able to import the contents of weapon.fbs
and with compilation errors if
you tried to use any other components.
Structs§
- Builder for options to the flatc compiler options. When consumed using
BuilderOptions::compile
, this generates rust code from the flatbuffer definition files provided. The basic usage for this struct looks something like this:
Enums§
- Primary error type returned when you compile your flatbuffer specifications to Rust.
Constants§
- Version of
flatc
supported by this library. Make sure this matches exactly with theflatc
binary you’re using and the version of theflatbuffers
rust library.
Type Aliases§
- Alias for a Result that uses
Error
as the default error type.