Systems programming concepts and techniques Timothy Samuel McNamara MANNING Raw Pointer Box Rc Arc The cousins *mut T and *const T are the free radicals of the pointer world. Lightning fast, but wildly unsafe. Store anything in a box. Accepts almost any type for long-term storage. The workhorse of a new, safe programming era. The reference counted pointer, Rc is Rust's competent, yet miserly bookkeeper. It knows who has borrowed what and when. Arc is Rust’s ambassador. It can share values across threads, guaranteeing that these will not interfere with each other. • Store a value in central storage in a location called “the heap” • Shared access to values • Runtime cost • Shared access to values • Not threadsafe • Threadsafe • Speed • Unsafe • Can interact with the outside world • Runtime cost Cell RefCell Cow String An expert in metamorphosis, Cell confers the ability to mutate immutable values. Performs mutation on immutable references with RefCel. Its mind-bending powers come with some costs. Why write something down when you only need to read it? Perhaps you only want to make modifications. This is the role of Cow (copy on write). Acting as a guide on how to deal with the uncertainties of user input, String shows us how to build safe abstractions. • Interior mutability • Performance • Can be nested within Rc and Arc, which only accept immutable refs • Runtime cost • Avoids writes when only read access is used • Interior mutability • Lack of compiletime guarantees • Possible size increase • Grows dynamically as required • Can over allocate size • Guarantees correct encoding at runtime Arc RawVec Unique Shared Your program’s main storage system. Vec keeps your data orderly as values are created and destroyed. The bedrock of Vec and other dynamically sized types. Understands how to provide a home for your data as needed. Sole owner of a value, a unique pointer is guaranteed to possess full control. Sharing ownership is hard. Shared makes life a little bit easier. • Grows dynamically as required • Can over allocate size • Grows dynamically as required • Works with the memory allocator to find space • Not directly applicable from your code • Base for types • Not appropriate such as Strings, for application requiring exclusive code directly possession of values. • Shared ownership • Can align memory to T’s width, even when empty • Not appropriate for application code directly Rust in Action Rust in Action SYSTEMS PROGRAMMING CONCEPTS AND TECHNIQUES TIM MCNAMARA MANNING SHELTER ISLAND For online information and ordering of this and other Manning books, please visit The publisher offers discounts on this book when ordered in quantity. For more information, please contact Special Sales Department Manning Publications Co. 20 Baldwin Road PO Box 761 Shelter Island, NY 11964 Email: ©2021 by Manning Publications Co. . No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by means electronic, mechanical, photocopying, or otherwise, without prior written permission of the publisher. Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in the book, and Manning Publications was aware of a trademark claim, the designations have been Recognizing the importance of preserving what has been written, it is Manning’s policy to have the books we publish printed on acid-free paper, and we exert our best efforts to that end. Recognizing also our responsibility to conserve the resources of our planet, Manning books are printed on paper that is at least 15 percent recycled and processed without the use of elemental chlorine. Manning Publications Co. 20 Baldwin Road PO Box 761 Shelter Island, NY 11964 Development editor: Elesha Hyde Technical development editor: René van den Berg Review editor: Mihaela Batinic Production editor: Deirdre S. Hiam Copy editor: Frances Buran Proofreader: Melody Dolab Technical proofreader: Jerry Kuch Typesetter: Dennis Dalinnik Cover designer: Marija Tudor To everyone aspiring to write safer software. contents preface xv acknowledgments xvii about this book xix about the author xxii about the cover illustration xxiii Introducing Rust 1.1 1.2 1.3 Where is Rust used? 2 Advocating for Rust at work A taste of the language 4 Cheating your way to “Hello, world!” program 7 1.4 1.5 1.6 Your first Rust Downloading the book’s source code 8 What does Rust look and feel like? 8 What is Rust? 11 Goal of Rust: Safety 12 Goal of Rust: Productivity Goal of Rust: Control 18 1.7 Rust’s big features Performance Concurrency vii Memory efficiency CONTENTS viii 1.8 Downsides of Rust 20 Cyclic data structures 20 Compile times Size of the language 21 Hype 21 Strictness 1.9 TLS security case studies Heartbleed 1.10 Goto fail; Where does Rust fit best? Command-line utilities 23 Data processing 24 Extending applications 24 Resource-constrained environments 24 Server-side applications 25 Desktop applications 25 Desktop 25 Mobile 25 Web 26 Systems programming 26 1.11 1.12 PART 1 Rust’s hidden feature: Its community Rust phrase book 26 RUST LANGUAGE DISTINCTIVES ..........................29 Language foundations 2.1 Creating a running program 33 Compiling single files with rustc 33 with cargo 33 2.2 A glance at Rust’s syntax Compiling Rust projects Defining variables and calling functions 2.3 Numbers Integers and decimal (floating-point) numbers 36 Integers with base 2, base 8, and base 16 notation 37 Comparing numbers 38 Rational, complex numbers, and other numeric types 43 2.4 Flow control For: The central pillar of iteration 45 Continue: Skipping the rest of the current iteration 47 While: Looping until a condition changes its state 47 Loop: The basis for Rust’s looping constructs 48 Break: Aborting a loop 48 If, if else, and else: Conditional branching 49 Match: Type-aware pattern matching 51 2.5 2.6 2.7 Defining functions 52 Using references 53 Project: Rendering the Mandelbrot set 54