From a8ec4664e4dec00f9e31b71a1c206f56da6225c6 Mon Sep 17 00:00:00 2001
From: Julien Palard <julien@palard.fr>
Date: Wed, 15 Nov 2023 17:11:39 +0100
Subject: [PATCH] Initial commit.

---
 .gitignore   |  3 +++
 Cargo.lock   |  7 +++++++
 Cargo.toml   | 11 +++++++++++
 README.md    | 19 +++++++++++++++++++
 python_add.c | 39 +++++++++++++++++++++++++++++++++++++++
 setup.py     |  7 +++++++
 src/lib.rs   |  5 +++++
 7 files changed, 91 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Cargo.lock
 create mode 100644 Cargo.toml
 create mode 100644 README.md
 create mode 100644 python_add.c
 create mode 100644 setup.py
 create mode 100644 src/lib.rs

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..0cd5f4e
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+/target
+/Cargo.lock
+build/
diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..421fa90
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "rust_add_lib"
+version = "0.1.0"
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..2691e2b
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "rust_add_lib"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+
+[lib]
+crate-type = ["cdylib"]
\ No newline at end of file
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..700a62b
--- /dev/null
+++ b/README.md
@@ -0,0 +1,19 @@
+# Calling a rust function from Python
+
+- `cargo build` builds a `./target/debug/librust_add_lib.so` with a `rust_add` function in it.
+- `LDFLAGS='-L target/debug/' python setup.py build` builds a Python module using `rust_add_lib`.
+
+Then the module can be imported and used from Python:
+
+```bash
+$ LD_LIBRARY_PATH=target/debug PYTHONPATH='./build/lib.linux-x86_64-cpython-311/' python
+Python 3.11.6 (main, Oct  8 2023, 05:06:43) [GCC 13.2.0] on linux
+Type "help", "copyright", "credits" or "license" for more information.
+>>> import add
+>>> add.add(.1, .2)
+[src/lib.rs:3] left = 0.1
+[src/lib.rs:3] right = 0.2
+[src/lib.rs:4] left + right = 0.30000000000000004
+0.30000000000000004
+>>>
+```
diff --git a/python_add.c b/python_add.c
new file mode 100644
index 0000000..96aa837
--- /dev/null
+++ b/python_add.c
@@ -0,0 +1,39 @@
+#define PY_SSIZE_T_CLEAN
+#include <Python.h>
+
+double rust_add(double, double); // from rust, from librust_lib.so
+
+
+static PyObject *python_add(PyObject *self, PyObject *args)
+{
+    double float_left;
+    double float_right;
+    double result;
+
+    if (!PyArg_ParseTuple(args, "dd", &float_left, &float_right))
+        return NULL;
+
+    result = rust_add(float_left, float_right);
+
+    return PyFloat_FromDouble(result);
+}
+
+static PyMethodDef AddMethods[] = {
+    {"add",  python_add, METH_VARARGS,
+     "Just add from rust."},
+    {NULL, NULL, 0, NULL}        /* Sentinel */
+};
+
+static struct PyModuleDef addmodule = {
+    PyModuleDef_HEAD_INIT,
+    "add",   /* name of module */
+    NULL   , /* module documentation, may be NULL */
+    -1,      /* size of per-interpreter state of the module,
+                or -1 if the module keeps state in global variables. */
+    AddMethods
+};
+
+PyMODINIT_FUNC PyInit_add(void)
+{
+    return PyModule_Create(&addmodule);
+}
diff --git a/setup.py b/setup.py
new file mode 100644
index 0000000..429f90d
--- /dev/null
+++ b/setup.py
@@ -0,0 +1,7 @@
+from distutils.core import setup
+from distutils.extension import Extension
+
+setup(name='add',
+      version='1.0',
+      ext_modules=[Extension('add', ['python_add.c'], libraries=['rust_add_lib'])],
+      )
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..f31908a
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,5 @@
+#[no_mangle]
+pub extern "C" fn rust_add(left: f64, right: f64) -> f64 {
+    dbg!(left, right);
+    dbg!(left + right)
+}