Add c/c++ call rust lib example

Author: pymongo

Cargo.toml

@@ -7,6 +7,7 @@ edition = "2018"
 [workspace]
 members = [
     "rust_call_cpp_static_lib",
+    "c_call_rust_lib"
 ]
 
 [dev-dependencies]

c_call_rust_lib/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "c_call_rust_lib"
+version = "0.1.0"
+authors = ["wuaoxiang <[email protected]>"]
+edition = "2018"
+
+[lib]
+name = "c_call_rust_lib"
+crate-type = ["staticlib", "cdylib"]
+
+[dependencies]

c_call_rust_lib/a.out

@@ -0,0 +1,12 @@
+void p();
+void hello(const char *str);
+
+/*
+static  link: gcc main.c ../target/debug/libc_call_rust_lib.a
+dynamic link: gcc main.c -Isrc -L ../target/debug/ -lc_call_rust_lib
+*/
+int main() {
+    p();
+    hello("rust");
+    return 0;
+}

c_call_rust_lib/main.c

@@ -0,0 +1,18 @@
+use std::os::raw::{c_char, c_int};
+use std::ffi::CStr;
+
+#[no_mangle]
+pub extern "C" fn p() {
+    println!("call println in rust code");
+}
+
+#[no_mangle]
+pub extern "C" fn hello(name: *const c_char) {
+    let c_str = unsafe {
+        CStr::from_ptr(name)
+    };
+    println!("hello {:?}", c_str);
+}
+
+#[no_mangle]
+pub extern "C" fn repeat_hi()

c_call_rust_lib/src/lib.rs

@@ -1,5 +1,5 @@
 const fn gcd(x: u32, y: u32) -> u32 {
-    let (mut a, mut b) = if x > y {(x, y)} else {(y, x)};
+    let (mut a, mut b) = if x > y { (x, y) } else { (y, x) };
     let mut temp = a % b;
     while temp != 0 {
         a = b;
@@ -13,11 +13,7 @@ const GCD: u32 = gcd(18, 12);
 
 const fn fib(n: u32) -> u32 {
     const fn helper(n: u32, a: u32, b: u32) -> u32 {
-        return if n <= 2 {
-            b
-        } else {
-            helper(n - 1, b, a + b)
-        }
+        return if n <= 2 { b } else { helper(n - 1, b, a + b) };
     }
     helper(n, 1, 1)
 }
@@ -28,4 +24,4 @@ const FIB_5: u32 = fib(5);
 fn main() {
     dbg!(GCD);
     dbg!(FIB_5);
-}
+}

examples/const_fn.rs

@@ -1,5 +1,4 @@
-#![feature(const_generics)]
-
+#![feature(const_generics, const_fn, const_in_array_repeat_expressions)]
 use std::mem::MaybeUninit;
 
 /**
@@ -8,7 +7,18 @@ use std::mem::MaybeUninit;
 */
 struct Array<T, const N: usize> {
     items: [MaybeUninit<T>; N],
-    length: usize
+    length: usize,
+}
+
+trait ArrayLen {
+    fn len(&self) -> usize;
+}
+
+impl<T, const N: usize> ArrayLen for Array<T, { N }> {
+    #[inline]
+    fn len(&self) -> usize {
+        self.length
+    }
 }
 
 /**
@@ -17,20 +27,21 @@ struct Array<T, const N: usize> {
 > Syntactically we may distinguish these expressions with braces
 两个常量表达式的typechecking是T-lang团队的主要问题，目前{N+1}和{1+N}两个常量泛型长度会不一样
 */
-impl<T, const N: usize> Array<T, {N}> {
-    fn new() -> Self {
-        // Self {
-        //     items: [MaybeUninit<T>; N],
-        //     length: N
-        // }
-        todo!("")
+impl<T: Copy, const N: usize> Array<T, { N }> {
+    const fn new() -> Self {
+        Self {
+            items: [MaybeUninit::uninit(); N],
+            length: 0,
+        }
+    }
+
+    #[inline]
+    const fn capacity(&self) -> usize {
+        N
     }
 }
 
 fn main() {
-    // fn foo() -> impl ToString {
-    //     "Hello, world!"
-    // }
-    // let _: &str = foo();
-    // let a: Array<bool, 1> = Array::new();
-}
+    let visited: Array<bool, 8> = Array::new();
+    dbg!(visited.len(), visited.capacity());
+}

examples/const_generic.rs

@@ -1,5 +1,14 @@
+#![feature(array_chunks)]
 use itertools::Itertools;
 
+#[test]
+fn generic_const_api_array_chunks() {
+    let data = [1, 2, 3, 4, 5, 6];
+    // 分割数组，每组计算完之后再求和
+    let sum = data.array_chunks().map(|&[a1, a2]| a1 * a2).sum::<i32>();
+    assert_eq!(sum, (1 * 2) + (3 * 4) + (5 * 6));
+}
+
 fn main() {
     let data = ["1", "22", "4444", "666666", "999999999"];
     let batch_size = 10;