Initial commit

.gitignore

+/target

Cargo.lock

+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "log-0"
+version = "0.1.0"

Cargo.toml

+[package]
+name = "log-0"
+version = "0.1.0"
+authors = ["Per Lindgren <per.lindgren@ltu.se>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

src/main.rs

+use std::any::{Any, TypeId};
+use std::convert::TryInto;
+use std::fmt::Debug;
+use std::mem::size_of;
+use std::mem::transmute;
+
+// log data and and move write pointer forward
+fn log<T: Sized + Any>(s: &T, v: &mut [u8], p: &mut usize) {
+    let type_id = TypeId::of::<T>();
+    let size = size_of::<T>();
+
+    // store type_id
+    let bytes: [u8; 8] = unsafe { transmute(type_id) };
+    v[*p..*p + 8].copy_from_slice(&bytes);
+    *p += 8;
+
+    // store data
+    let view = s as *const _ as *const u8;
+    let slice = unsafe { std::slice::from_raw_parts(view, size) };
+    v[*p..*p + size].copy_from_slice(slice);
+    *p += size;
+}
+
+// helper to expand data and move read pointer forward
+fn exp2<T>(v: &[u8], p: &mut usize)
+where
+    T: Debug,
+{
+    let size = size_of::<T>();
+    let data: &T = unsafe { transmute(&v[*p] as *const _ as *const T) };
+    println!("{:?}", data);
+    *p += size;
+}
+
+// expand data and move read pointer forward
+fn exp(v: &[u8], p: &mut usize) {
+    let bytes: &[u8; 8] = v[*p..*p + 8].try_into().unwrap();
+    let type_id: &u64 = unsafe { transmute(bytes) };
+    let type_id: &TypeId = unsafe { transmute(type_id) };
+    *p += 8;
+
+    if *type_id == TypeId::of::<T1>() {
+        exp2::<T1>(v, p);
+    } else if *type_id == TypeId::of::<T2>() {
+        exp2::<T2>(v, p);
+    } else {
+        unreachable!();
+    }
+}
+
+#[derive(Debug)]
+#[repr(C)]
+struct T1 {
+    x: i32,
+    y: i32,
+}
+
+#[derive(Debug)]
+#[repr(C)]
+struct T2 {
+    y: i64,
+}
+
+fn main() {
+    let mut v = [0u8; 256];
+    let mut w = 0;
+
+    // example log two variables
+    let t1 = T1 { x: 72, y: 52 };
+    let t2 = T2 { y: 112 };
+    println!("{:?}", t1);
+    println!("{:?}", t2);
+    log(&t1, &mut v, &mut w);
+    log(&t2, &mut v, &mut w);
+
+    // example expand the logged data
+    let mut r = 0;
+    exp(&v, &mut r);
+    exp(&v, &mut r);
+}