[−][src]Crate jlrs
The main goal behind jlrs
is to provide a simple and safe interface to the Julia C API.
Currently this crate is only tested on Linux and Windows in combination with Julia 1.4.2, if
you try to use it on another OS or with an earlier version of Julia it will likely fail to
generate the bindings or crash when these bindings are used.
Features
An incomplete list of features that are currently supported by jlrs
:
- Access arbitrary Julia modules and their contents.
- Call arbitrary Julia functions.
- Include and use your own Julia code.
- Create values that Julia can use, and convert them back to Rust, from Rust.
- Access the type information and fields of values and check their properties.
- Support for mapping isbits tuples and structs to Rust structs.
- Create and use n-dimensional arrays.
Generating the bindings
This crate depends on jl-sys
which contains the raw bindings to the Julia C API, these are
generated by bindgen
. You can find the requirements for using bindgen
in
their User Guide.
Linux
The recommended way to install Julia is to download the binaries from the official website,
which is distributed in an archive containing a directory called julia-x.y.z
. This directory
contains several other directories, including a bin
directory containing the julia
executable.
In order to ensure the julia.h
header file can be found, either /usr/include/julia/julia.h
must exist, or you have to set the JULIA_DIR
environment variable to /path/to/julia-x.y.z
.
The environment variable can be used to override the default. Similarly, in order to load
libjulia.so
you must add /path/to/julia-x.y.z/lib
to the LD_LIBRARY_PATH
environment
variable.
Windows
The recommended way to install Julia is to download the installer from the official website,
which will install Julia in a folder called Julia-x.y.z
. This folder contains several other
folders, including a bin
folder containing the julia.exe
executable. You must set the
JULIA_DIR
environment variable to the Julia-x.y.z
folder and add Julia-x.y.z\bin
to the
PATH
environment variable. For example, if Julia is installed at D:\Julia-x.y.z
,
JULIA_DIR
must be set to D:\Julia-x.y.z
and D:\Julia-x.y.z\bin
must be added to PATH
.
Additionally, MinGW must be installed through Cygwin. To install this and all potentially
required dependencies, follow steps 1-4 of
the instructions for compiling Julia on Windows using Cygwin and MinGW.
You must set the CYGWIN_DIR
environment variable to the installation folder of Cygwin; this
folder contains some icons, Cygwin.bat
and folders with names like usr
and bin
. For
example, if Cygwin is installed at D:\cygwin64
, CYGWIN_DIR
must be set to D:\cygwin64
.
Julia is compatible with the GNU toolchain on Windows. If you use rustup, you can set the
toolchain for a project that depends on jl-sys
by calling the command
rustup override set stable-gnu
in the project root folder.
Using this crate
The first thing you should do is use
the prelude
-module with an asterisk, this will
bring all the structs and traits you're likely to need into scope. Before you can use Julia it
must first be initialized. You do this by calling Julia::init
. Note that this method can
only be called once, if you drop Julia
you won't be able to create a new one and have to
restart the entire program. If you want to use a custom system image, you must call
Julia::init_with_image
instead of Julia::init
.
You can call Julia::include
to include your own Julia code and either Julia::frame
or
Julia::dynamic_frame
to interact with Julia. If you want to have improved support for
backtraces jlrs.jl
must be included. You can find this file in the root of this crate's github
repository. This is necessary because this functionality depends on some Julia code defined in
that file.
The other two methods, Julia::frame
and Julia::dynamic_frame
, take a closure that
provides you with a Global
, and either a StaticFrame
or DynamicFrame
respectively.
Global
is a token that lets you access Julia modules their contents, and other global
values, while the frames are used to deal with local Julia data.
Local data must be handled properly: Julia is a programming language with a garbage collector
that is unaware of any references to data outside of Julia. In order to make it aware of this
usage a stack must be maintained. You choose this stack's size when calling Julia::init
.
The elements of this stack are called stack frames; they contain a pointer to the previous
frame, the number of protected values, and that number of pointers to values. The two frame
types offered by jlrs
take care of all the technical details, a DynamicFrame
will grow
to the required size while a StaticFrame
has a definite number of slots. These frames can
be nested (ie stacked) arbitrarily.
In order to call a Julia function, you'll need two things: a function to call, and arguments
to call it with. You can acquire the function through the module that defines it with
Module::function
; Module::base
and Module::core
provide access to Julia's Base
and Core
module respectively, while everything you include through Julia::include
is
made available relative to the Main
module which you can access by calling Module::main
.
Julia data is represented by a Value
. Basic data types like numbers, booleans, and strings
can be created through Value::new
and several methods exist to create an n-dimensional
array. Each value will be protected by a frame, and the two share a lifetime in order to
enforce that a value can only be used as long as its protecting frame hasn't been dropped.
Julia functions, their arguments and their results are all Value
s too. All Value
s can be
called as functions, whether this will succeed depends on the value actually being a function.
You can copy data from Julia to Rust by calling Value::cast
.
As a simple example, let's create two values and add them:
let mut julia = unsafe { Julia::init(16).unwrap() }; julia.dynamic_frame(|global, frame| { // Create the two arguments let i = Value::new(frame, 2u64)?; let j = Value::new(frame, 1u32)?; // We can find the addition-function in the base module let func = Module::base(global).function("+")?; // Call the function and unbox the result let output = func.call2(frame, i, j)?.unwrap(); output.cast::<u64>() }).unwrap();
You can also do this with a static frame:
let mut julia = unsafe { Julia::init(16).unwrap() }; // Three slots; two for the inputs and one for the output. julia.frame(3, |global, frame| { // Create the two arguments, each value requires one slot let i = Value::new(frame, 2u64)?; let j = Value::new(frame, 1u32)?; // We can find the addition-function in the base module let func = Module::base(global).function("+")?; // Call the function and unbox the result. let output = func.call2(frame, i, j)?.unwrap(); output.cast::<u64>() }).unwrap();
This is only a small example, other things can be done with Value
as well: their fields
can be accessed if the Value
is some tuple or struct. They can contain more complex data;
if a function returns an array or a module it will still be returned as a Value
. There
complex types are compatible with Value::cast
. Additionally, you can create Output
s in
a frame in order to protect a value from with a specific frame; this value will share that
frame's lifetime.
Custom types
Two traits can be used to make your own structs work in combination with Value::new
and
Value::cast
, JuliaTuple
and JuliaStruct
. The first can be used in combination with
tuple structs in Rust, it will map to a tuple in Julia whose field types match the field types
in Rust. The second can be used in combination with structs with named fields in Rust and must
be explicitly mapped to a struct in Julia.
Lifetimes
While reading the documentation for this crate, you will see that a lot of lifetimes are used. Most of these lifetimes have a specific meaning:
-
'base
is the lifetime of a frame created throughJulia::frame
orJulia::dynamic_frame
. This lifetime prevents you from using global Julia data outside of a frame. -
'frame
is the lifetime of an arbitrary frame; in the base frame it will be the same as'base
. This lifetime prevents you from using Julia data after the frame that protects it from garbage collection goes out of scope. -
'data
or'borrow
is the lifetime of data that is borrowed. This lifetime prevents you from mutably aliasing data and trying to use it after the borrowed data is dropped. -
'output
is the lifetime of the frame that created the output. This lifetime ensures that when Julia data is protected by an older frame this data can be used until that frame goes out of scope.
Limitations
Calling Julia is entirely single-threaded. You won't be able to use Julia
from another
thread than the thread that has been used to initialize Julia, and while Julia is doing stuff
you won't be able to interact with it.
Modules
error | Everything related to errors. |
frame | Frames ensure Julia's garbage collector is properly managed. |
global | Access token for global Julia data. |
prelude | Reexports structs and traits you're likely to need. |
traits | All traits used by this crate. |
value | Julia values and functions. |
Structs
Julia | This struct can be created only once during the lifetime of your program. You must create it
with |