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Now let's suppose we want to generate bindings for a non-system library. We
will be the same crate setup as the previous tutorial. First let's create a new
directory `hello` with two files inside it. A `c` source file `hello.c`
containing
```c
int hello() {
return 42;
}
```
and a `c` header file `hello.h` containing
```c
int hello();
```
given that the library has not been compiled yet, we need to modify the
`build.rs` build script to compile the `hello.c` source file into a static
libary:
```rust,ignore
extern crate bindgen;
use std::env;
use std::path::PathBuf;
use bindgen::CargoCallbacks;
fn main() {
// This is the directory where the `c` library is located.
let libdir_path = PathBuf::from("hello")
// Canonicalize the path as `rustc-link-search` requires an absolute
// path.
.canonicalize()
.expect("cannot canonicalize path");
// This is the path to the `c` headers file.
let headers_path = libdir_path.join("hello.h");
let headers_path_str = headers_path.to_str().expect("Path is not a valid string");
// This is the path to the intermediate object file for our library.
let obj_path = libdir_path.join("hello.o");
// This is the path to the static library file.
let lib_path = libdir_path.join("libhello.a");
// Tell cargo to look for shared libraries in the specified directory
println!("cargo:rustc-link-search={}", libdir_path.to_str().unwrap());
// Tell cargo to tell rustc to link our `hello` library. Cargo will
// automatically know it must look for a `libhello.a` file.
println!("cargo:rustc-link-lib=hello");
// Tell cargo to invalidate the built crate whenever the header changes.
println!("cargo:rerun-if-changed={}", headers_path_str);
// Run `clang` to compile the `hello.c` file into a `hello.o` object file.
// Unwrap if it is not possible to spawn the process.
if !std::process::Command::new("clang")
.arg("-c")
.arg("-o")
.arg(&obj_path)
.arg(libdir_path.join("hello.c"))
.output()
.expect("could not spawn `clang`")
.status
.success()
{
// Panic if the command was not successful.
panic!("could not compile object file");
}
// Run `ar` to generate the `libhello.a` file from the `hello.o` file.
// Unwrap if it is not possible to spawn the process.
if !std::process::Command::new("ar")
.arg("rcs")
.arg(lib_path)
.arg(obj_path)
.output()
.expect("could not spawn `ar`")
.status
.success()
{
// Panic if the command was not successful.
panic!("could not emit library file");
}
// The bindgen::Builder is the main entry point
// to bindgen, and lets you build up options for
// the resulting bindings.
let bindings = bindgen::Builder::default()
// The input header we would like to generate
// bindings for.
.header(headers_path_str)
// Tell cargo to invalidate the built crate whenever any of the
// included header files changed.
.parse_callbacks(Box::new(CargoCallbacks))
// Finish the builder and generate the bindings.
.generate()
// Unwrap the Result and panic on failure.
.expect("Unable to generate bindings");
// Write the bindings to the $OUT_DIR/bindings.rs file.
let out_path = PathBuf::from(env::var("OUT_DIR").unwrap()).join("bindings.rs");
bindings
.write_to_file(out_path)
.expect("Couldn't write bindings!");
}
```
|
