Effective Rust(31)　Chapter6

Last updated at 2024-08-23Posted at 2024-08-19

Effective Rust
https://learning.oreilly.com/library/view/effective-rust/9781098151393/

Errata for Effective Rust
https://www.oreilly.com/catalog/errata.csp?isbn=0636920903642

Effective Rustは小説ではない。
逆順で読んでもよいかもってなった。

content

Preface

Chapter 1, “Types” Suggestions that revolve around Rust’s core type system

Chapter 2, “Traits” Suggestions for working with Rust’s traits

Chapter 3, “Concepts” Core ideas that form the design of Rust

Chapter 4, “Dependencies” Advice for working with Rust’s package ecosystem

Chapter 5, “Tooling” Suggestions for improving your codebase by going beyond just the Rust compiler

Chapter 6, “Beyond Standard Rust” Suggestions for when you have to work beyond Rust’s standard, safe environment

Afterword

Async Rust by Maxwell Flitton and Caroline Morton (O’Reilly, 2024)
The bare-metal Rust section of the Comprehensive Rust online course
Rust discussion forums such as the Rust language forum or Reddit’s r/rust
rewrite it in Rust (RiiR)
Jon Gjengset’s Rust for Rustaceans (No Starch, 2022)

Chapter 6, “Beyond Standard Rust”

The Rust toolchain includes support for a much wider variety of environments than just pure Rust application code, running in userspace:
It supports cross-compilation, where the system running the toolchain (the host) is not the same as the system that the compiled code will run on (the target), which makes it easy to target embedded systems.
It supports linking with code compiled from languages other than Rust, via built-in FFI capabilities.

FFI (foreign function interface)

Item 33: Consider making library code no_std compatible

//! My `no_std` compatible crate.
#![no_std]

// Requires `alloc`.
extern crate alloc;
Pulling in the alloc crate enables many familiar friends, now addressed by their true names:

alloc::boxed::Box<T>
alloc::rc::Rc<T>
alloc::sync::Arc<T>
alloc::vec::Vec<T>
alloc::string::String
alloc::format!
alloc::collections::BTreeMap<K, V>
alloc::collections::BTreeSet<T>

#![cfg_attr(not(feature = "std"), no_std)]
or alloc, if it turns on use of alloc-derived functionality:

#[cfg(feature = "alloc")]
extern crate alloc;

let mut v = Vec::new();
v.push(1); // might allocate
v.push(2); // might allocate
v.push(3); // might allocate
v.push(4); // might allocate

fn try_build_a_vec() -> Result<Vec<u8>, String> {
    let mut v = Vec::new();

    // Perform a careful calculation to figure out how much space is needed,
    // here simplified to...
    let required_size = 4;

    v.try_reserve(required_size)
        .map_err(|_e| format!("Failed to allocate {} items!", required_size))?;

    // We now know that it's safe to do:
    v.push(1);
    v.push(2);
    v.push(3);
    v.push(4);

    Ok(v)
}

Invoking C Functions from Rust

lib.c

/* File lib.c */
#include "lib.h"

/* C function definition. */
int add(int x, int y) {
  return x + y;
}

lib.h

/* File lib.h */
#ifndef LIB_H
#define LIB_H

/* C function declaration. */
int add(int x, int y);

#endif  /* LIB_H */

use std::os::raw::c_int;
extern "C" {
    pub fn add(x: c_int, y: c_int) -> c_int;
}

Linking logistics

#[link(name = "cffi")] // An external library like `libcffi.a` is needed
extern "C" {
    // ...
}

#[link(name = "cffi")] // An external library like `libcffi.a` is needed
extern "C" {
    // ...
}

build.rs

// File build.rs
fn main() {
    // ...

    // Retrieve the location of `Cargo.toml`.
    let dir = std::env::var("CARGO_MANIFEST_DIR").unwrap();
    // Look for native libraries one directory higher up.
    println!(
        "cargo:rustc-link-search=native={}",
        std::path::Path::new(&dir).join("..").display()
    );
}

// C++ code
namespace ns1 {
int32_t add(int32_t a, int32_t b) { return a+b; }
int64_t add(int64_t a, int64_t b) { return a+b; }
}
namespace ns2 {
int32_t add(int32_t a, int32_t b) { return a+b; }
}

/* C data structure definition. */
/* Changes here must be reflected in lib.rs. */
typedef struct {
    uint8_t byte;
    uint32_t integer;
} FfiStruct;
// Equivalent Rust data structure.
// Changes here must be reflected in lib.h / lib.c.
#[repr(C)]
pub struct FfiStruct {
    pub byte: u8,
    pub integer: u32,
}

extern "C" {
    // C function that does some operation on the contents
    // of an `FfiStruct`.
    pub fn use_struct(v: *const FfiStruct) -> u32;
}
let v = FfiStruct {
    byte: 1,
    integer: 42,
};
let x = unsafe { use_struct(&v as *const FfiStruct) };

/* C functions. */

/* Allocate an `FfiStruct` */
FfiStruct* new_struct(uint32_t v);
/* Free a previously allocated `FfiStruct` */
void free_struct(FfiStruct* s);
// with corresponding Rust FFI declarations:

extern "C" {
    // C code to allocate an `FfiStruct`.
    pub fn new_struct(v: u32) -> *mut FfiStruct;
    // C code to free a previously allocated `FfiStruct`.
    pub fn free_struct(s: *mut FfiStruct);
}

/// Wrapper structure that owns memory allocated by the C library.
struct FfiWrapper {
    // Invariant: inner is non-NULL.
    inner: *mut FfiStruct,
}
and the Drop implementation returns that memory to the C library to avoid the potential for leaks:

/// Manual implementation of [`Drop`], which ensures that memory allocated
/// by the C library is freed by it.
impl Drop for FfiWrapper {
    fn drop(&mut self) {
        // Safety: `inner` is non-NULL, and besides `free_struct()` copes
        // with NULL pointers.
        unsafe { free_struct(self.inner) }
    }
}

type Error = String;

impl FfiWrapper {
    pub fn new(val: u32) -> Result<Self, Error> {
        let p: *mut FfiStruct = unsafe { new_struct(val) };
        // Raw pointers are not guaranteed to be non-NULL.
        if p.is_null() {
            Err("Failed to get inner struct!".into())
        } else {
            Ok(Self { inner: p })
        }
    }
}

ビルドエラーなどの記述があるのが嬉しい。

自分ではまだビルドできていない。

<この項は書きかけです。順次追記します。>
This article is not completed. I will add some words in order.

自己記事一覧

Qiitaで逆リンクを表示しなくなったような気がする。時々、スマフォで表示するとあらわっることがあり、完全に削除したのではなさそう。

４月以降、せっせとリンクリストを作り、統計を取って確率を説明しようとしている。
2025年２月末を目標にしている。

物理記事　上位100
https://qiita.com/kaizen_nagoya/items/66e90fe31fbe3facc6ff

量子(0) 計算機, 量子力学
https://qiita.com/kaizen_nagoya/items/1cd954cb0eed92879fd4

数学関連記事１００
https://qiita.com/kaizen_nagoya/items/d8dadb49a6397e854c6d

統計(0)一覧
https://qiita.com/kaizen_nagoya/items/80d3b221807e53e88aba

図(0) state, sequence and timing. UML and お絵描き
https://qiita.com/kaizen_nagoya/items/60440a882146aeee9e8f

品質一覧
https://qiita.com/kaizen_nagoya/items/2b99b8e9db6d94b2e971

言語・文学記事　１００
https://qiita.com/kaizen_nagoya/items/42d58d5ef7fb53c407d6

医工連携関連記事一覧
https://qiita.com/kaizen_nagoya/items/6ab51c12ba51bc260a82

自動車　記事　１００
https://qiita.com/kaizen_nagoya/items/f7f0b9ab36569ad409c5

通信記事１００
https://qiita.com/kaizen_nagoya/items/1d67de5e1cd207b05ef7

日本語（０）一欄
https://qiita.com/kaizen_nagoya/items/7498dcfa3a9ba7fd1e68

英語(0) 一覧
https://qiita.com/kaizen_nagoya/items/680e3f5cbf9430486c7d

転職(0)一覧
https://qiita.com/kaizen_nagoya/items/f77520d378d33451d6fe

仮説（0）一覧（目標100現在40）
https://qiita.com/kaizen_nagoya/items/f000506fe1837b3590df

音楽　一覧(0)
https://qiita.com/kaizen_nagoya/items/b6e5f42bbfe3bbe40f5d

「@kazuo_reve 新人の方によく展開している有益な情報」確認一覧
https://qiita.com/kaizen_nagoya/items/b9380888d1e5a042646b

Qiita(0)Qiita関連記事一覧（自分）
https://qiita.com/kaizen_nagoya/items/58db5fbf036b28e9dfa6

鉄道（０）鉄道のシステム考察はてっちゃんがてつだってくれる
https://qiita.com/kaizen_nagoya/items/26bda595f341a27901a0

安全（0）安全工学シンポジウムに向けて: 21
https://qiita.com/kaizen_nagoya/items/c5d78f3def8195cb2409

一覧の一覧( The directory of directories of mine.) Qiita(100)
https://qiita.com/kaizen_nagoya/items/7eb0e006543886138f39

Ethernet 記事一覧　Ethernet(0)
https://qiita.com/kaizen_nagoya/items/88d35e99f74aefc98794

Wireshark 一覧 wireshark(0)、Ethernet(48)
https://qiita.com/kaizen_nagoya/items/fbed841f61875c4731d0

線網（Wi-Fi）空中線(antenna)(0) 記事一覧(118/300目標)
https://qiita.com/kaizen_nagoya/items/5e5464ac2b24bd4cd001

OSEK OS設計の基礎　OSEK(100)
https://qiita.com/kaizen_nagoya/items/7528a22a14242d2d58a3

Error一覧 error(0)
https://qiita.com/kaizen_nagoya/items/48b6cbc8d68eae2c42b8

++ Support(0)　
https://qiita.com/kaizen_nagoya/items/8720d26f762369a80514

Coding(0) Rules, C, Secure, MISRA and so on
https://qiita.com/kaizen_nagoya/items/400725644a8a0e90fbb0

coding (101) 一覧を作成し始めた。omake:最近のQiitaで表示しない5つの事象
https://qiita.com/kaizen_nagoya/items/20667f09f19598aedb68

プログラマによる、プログラマのための、統計(0)と確率のプログラミングとその後
https://qiita.com/kaizen_nagoya/items/6e9897eb641268766909

なぜdockerで機械学習するか書籍・ソース一覧作成中 (目標100)
https://qiita.com/kaizen_nagoya/items/ddd12477544bf5ba85e2

言語処理100本ノックをdockerで。python覚えるのに最適。:10+12
https://qiita.com/kaizen_nagoya/items/7e7eb7c543e0c18438c4

プログラムちょい替え（0）一覧:4件
https://qiita.com/kaizen_nagoya/items/296d87ef4bfd516bc394

Python(0)記事をまとめたい。
https://qiita.com/kaizen_nagoya/items/088c57d70ab6904ebb53

官公庁・学校・公的団体（NPOを含む）システムの課題、官（０）
https://qiita.com/kaizen_nagoya/items/04ee6eaf7ec13d3af4c3

「はじめての」シリーズ　ベクタージャパン　
https://qiita.com/kaizen_nagoya/items/2e41634f6e21a3cf74eb

AUTOSAR(0)Qiita記事一覧, OSEK(75)
https://qiita.com/kaizen_nagoya/items/89c07961b59a8754c869

プログラマが知っていると良い「公序良俗」
https://qiita.com/kaizen_nagoya/items/9fe7c0dfac2fbd77a945

LaTeX(0) 一覧　
https://qiita.com/kaizen_nagoya/items/e3f7dafacab58c499792

自動制御、制御工学一覧（０）
https://qiita.com/kaizen_nagoya/items/7767a4e19a6ae1479e6b

Rust(0) 一覧　
https://qiita.com/kaizen_nagoya/items/5e8bb080ba6ca0281927

100以上いいねをいただいた記事16選
https://qiita.com/kaizen_nagoya/items/f8d958d9084ffbd15d2a

小川清最終講義、最終講義（再）計画, Ethernet(100) 英語(100) 安全(100)
https://qiita.com/kaizen_nagoya/items/e2df642e3951e35e6a53

＜この記事は個人の過去の経験に基づく個人の感想です。現在所属する組織、業務とは関係がありません。＞
This article is an individual impression based on my individual experience. It has nothing to do with the organization or business to which I currently belong.

文書履歴(document history)

ver. 0.01 初稿　20240808

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Effective Rust(31)　Chapter6

content

Afterword

Chapter 6, “Beyond Standard Rust”

FFI (foreign function interface)

Item 33: Consider making library code no_std compatible

Invoking C Functions from Rust

Linking logistics

関連資料

Engineering Festa 2024前に必読記事一覧

自己記事一覧

文書履歴(document history)

最後までおよみいただきありがとうございました。

Thank you very much for reading to the last sentence.

Effective Rust(31) Chapter6

content

Afterword

Chapter 6, “Beyond Standard Rust”

FFI (foreign function interface)

Item 33: Consider making library code no_std compatible

Invoking C Functions from Rust

Linking logistics

関連資料

Engineering Festa 2024前に必読記事一覧

自己記事一覧

文書履歴(document history)

最後までおよみいただきありがとうございました。

Thank you very much for reading to the last sentence.

Effective Rust(31)　Chapter6