feat: add ffi c_layout

__ffi/c_layout/src/main_3.rs

@@ -0,0 +1,43 @@
+use std::mem;
+use std::io::{Read, Write, Result};
+use std::path::Path;
+use std::fs::File;
+
+#[derive(Debug)]
+#[repr(C)]
+struct Header {
+    name: [u8; 4],
+    size: u32,
+    reserved: u64,
+}
+
+fn parse<P: AsRef<Path>>(path: P) -> Result<()> {
+    let mut file = File::open(path)?;
+
+    let header: Header = {
+        let mut h = [0u8; mem::size_of::<Header>()];
+        file.read_exact(&mut h[..])?;
+        unsafe { mem::transmute(h) }
+    };
+
+    println!("{:#?}", header);
+    Ok(())
+}
+fn write<P: AsRef<Path>>(path: P, h: Header) -> Result<()> {
+    let mut file = File::create(path)?;
+    let bytes: [u8; mem::size_of::<Header>()] = unsafe { mem::transmute(h) };
+    file.write_all(&bytes)?;
+
+    Ok(())
+}
+
+pub fn run_main() {
+    let h = Header {
+        name: [1,2,3,4],
+        size: 0xabcdef,
+        reserved: 0x0123456789abcdef,
+    };
+
+    write("/tmp/test.dat", h).unwrap();
+    parse("/tmp/test.dat").unwrap();
+}