feat: add rust link a

__ffi/rust_link_a/.cargo/config.toml

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+[build]
+rustflags = ["-C", "link-args=-L. -lhello"]

__ffi/rust_link_a/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "rust_link_a"
+version = "0.1.0"

__ffi/rust_link_a/Cargo.toml

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+[package]
+name = "rust_link_a"
+version = "0.1.0"
+authors = ["Hatter Jiang <jht5945@gmail.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

__ffi/rust_link_a/README.md

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+
+```toml
+[build]
+rustflags = ["-C", "link-args=-Llib -l*LIBNAME* -std=c++11 -stdlib=libc++ -lc++ -lz"]
+```

__ffi/rust_link_a/hello.c

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+#include <stdio.h>
+#include "hello.h"
+
+void print_line(const char* str) {
+  for (int i = 0; str[i] != 0; i++) {
+    char c = str[i];
+    printf("PUT:%d - %c\n", c, c);
+  }
+  // str++;
+  printf("puts:%s\n", str);
+}

__ffi/rust_link_a/hello.h

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+
+void print_line(const char* str);

__ffi/rust_link_a/justfile

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+_:
+  @just --list
+
+# generage .rs
+create-rs:
+  bindgen hello.h -o src/hello.rs
+
+# create .a file
+create-ar:
+  gcc -c -o hello.o hello.c
+  ar -cr libhello.a hello.o
+
+# re-run
+re-run:
+  rm hello.o || true
+  rm libhello.a || true
+  rm -rf target/ || true
+  @just create-ar
+  @just create-rs
+  cargo r
+

__ffi/rust_link_a/src/hello.rs

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+/* automatically generated by rust-bindgen 0.56.0 */
+
+extern "C" {
+    pub fn print_line(str_: *const ::std::os::raw::c_char);
+}

__ffi/rust_link_a/src/main.rs

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+mod hello;
+
+use std::ffi::CString;
+use hello::print_line;
+
+fn main() {
+    let str = "Hello world!";
+    let c_str = CString::new(str).unwrap();
+
+    unsafe {
+        print_line(c_str.as_ptr());
+    }
+}