5 files changed, 160 insertions, 0 deletions
diff --git a/src/rust/cargo/README.md b/src/rust/cargo/README.md
new file mode 100644
index 0000000..5ac8e27
--- /dev/null
+++ b/src/rust/cargo/README.md
@@ -0,0 +1,45 @@
+# Importing cargo dependencies
+
+The [rules for rust](https://github.com/just-buildsystem/rules-rust) also
+bring a tool to import dependencies from cargo. Here we give an overview of
+its usage, using the subidrectory `circle` as a dependency.
+
+## Files written by hand
+
+Cargo dependencies are described as dependencies of a crate. So all the
+files you would normally write by hand when writing a crate have to be
+manually added. As we define a binary, those are
+  - `Cargo.toml`, and
+  - `src/main.rs`.
+
+## Using `just-import-cargo`
+
+As other import tools, `just-import-cargo` expects a repository specification
+on standard input and returns one on standard output. It needs to know
+ - the root of the pyhsical repository, and
+ - the location of the crate directory, relative to the root of the physical
+   repository.
+ - the name of the already imported `rules-rust` repository.
+
+While the tool in general can also import `rules-rust` itself, we need to import
+the rules manually first, as we have to provide our own target root for the
+defaults. Future versions of the rules might bring a defaults target suitable
+for our use case, but so far this is not the case.
+
+The name of the imported main repository is the crate name (without version),
+as specified in the `Cargo.toml` file. Some care should be taken that is does
+not conflict with already existing repositories; repositories from the
+`etc/repos.templace.json` can have a binding to that still to be imported
+repository, as usual.
+
+As opposed to other import tools, however, `just-import-cargo` also creates
+files in the pysical repository. Those are the following.
+ - In the crate the file `Cargo.lock` generated by the call to cargo, as
+   well as a target file,
+ - The file `etc/defaults/rust/TARGETS` relative to in the top-level of the
+   physical repository (with a content independent of the respective crate).
+   This file is the reason that our `rules-rust/nix` use `nix.TARGETS` as
+   target-file name.
+ - In the directory `etc/deps-rust` target files for all the imported crates.
+   As their name encode crate name and version, calling `just-import-cargo`
+   for several crates should not cause a conflict here.
diff --git a/src/rust/cargo/circle/Cargo.lock b/src/rust/cargo/circle/Cargo.lock
new file mode 100644
index 0000000..9b1bff2
--- /dev/null
+++ b/src/rust/cargo/circle/Cargo.lock
@@ -0,0 +1,75 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "cfg-if"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
+
+[[package]]
+name = "circle_sampling"
+version = "0.1.0"
+dependencies = [
+ "rand",
+]
+
+[[package]]
+name = "getrandom"
+version = "0.2.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c4567c8db10ae91089c99af84c68c38da3ec2f087c3f82960bcdbf3656b6f4d7"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "wasi",
+]
+
+[[package]]
+name = "libc"
+version = "0.2.155"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "97b3888a4aecf77e811145cadf6eef5901f4782c53886191b2f693f24761847c"
+
+[[package]]
+name = "ppv-lite86"
+version = "0.2.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5b40af805b3121feab8a3c29f04d8ad262fa8e0561883e7653e024ae4479e6de"
+
+[[package]]
+name = "rand"
+version = "0.8.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "34af8d1a0e25924bc5b7c43c079c942339d8f0a8b57c39049bef581b46327404"
+dependencies = [
+ "libc",
+ "rand_chacha",
+ "rand_core",
+]
+
+[[package]]
+name = "rand_chacha"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e6c10a63a0fa32252be49d21e7709d4d4baf8d231c2dbce1eaa8141b9b127d88"
+dependencies = [
+ "ppv-lite86",
+ "rand_core",
+]
+
+[[package]]
+name = "rand_core"
+version = "0.6.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ec0be4795e2f6a28069bec0b5ff3e2ac9bafc99e6a9a7dc3547996c5c816922c"
+dependencies = [
+ "getrandom",
+]
+
+[[package]]
+name = "wasi"
+version = "0.11.0+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9c8d87e72b64a3b4db28d11ce29237c246188f4f51057d65a7eab63b7987e423"
diff --git a/src/rust/cargo/circle/Cargo.toml b/src/rust/cargo/circle/Cargo.toml
new file mode 100644
index 0000000..563be5e
--- /dev/null
+++ b/src/rust/cargo/circle/Cargo.toml
@@ -0,0 +1,7 @@
+[package]
+name = "circle_sampling"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+rand = "0.8.5"
diff --git a/src/rust/cargo/circle/TARGETS b/src/rust/cargo/circle/TARGETS
new file mode 100644
index 0000000..9085e22
--- /dev/null
+++ b/src/rust/cargo/circle/TARGETS
@@ -0,0 +1,15 @@
+{ "circle_sampling":
+  { "type": ["@", "rules", "rust", "binary"]
+  , "name": ["circle_sampling"]
+  , "crate_root": ["src/main.rs"]
+  , "srcs": ["src/main.rs"]
+  , "edition": ["2021"]
+  , "arguments_config":
+    ["ARCH", "HOST_ARCH", "TARGET_ARCH", "ENV", "TOOLCHAIN_CONFIG"]
+  , "deps": [["@", "rand", "", "rand"]]
+  , "cargo_features": []
+  , "stage": ["circle_sampling-0.1.0"]
+  , "version": ["0", "1", "0"]
+  , "pkg_name": ["circle_sampling"]
+  }
+}
diff --git a/src/rust/cargo/circle/src/main.rs b/src/rust/cargo/circle/src/main.rs
new file mode 100644
index 0000000..329542f
--- /dev/null
+++ b/src/rust/cargo/circle/src/main.rs
@@ -0,0 +1,18 @@
+use rand::Rng;
+
+fn main() {
+    let mut x :i16;
+    let mut y :i16;
+    let mut rng = rand::thread_rng();
+
+    loop {
+       x = rng.gen_range(-100..=100);
+       y = rng.gen_range(-100..=100);
+
+       if x*x + y*y < 100*100 {
+           break;
+       }
+    }
+
+    println!("{x} {y}")
+}