### Install cargo-afl

Source: https://github.com/tokio-rs/prost/blob/master/FUZZING.md

Install the necessary cargo-afl tool before running fuzz tests.

```bash
cargo install -f afl
```

--------------------------------

### Install build tools on MacOS

Source: https://github.com/tokio-rs/prost/blob/master/prost/README.md

Install automake and libtool on MacOS to resolve build errors related to missing autoreconf.

```ignore
brew install automake
brew install libtool
```

--------------------------------

### Example .proto File Definition

Source: https://github.com/tokio-rs/prost/blob/master/README.md

Defines a Person message with nested PhoneNumber and PhoneType, and an AddressBook message. This serves as the input for Prost code generation.

```protobuf
syntax = "proto3";
package tutorial;

message Person {
  string name = 1;
  int32 id = 2;  // Unique ID number for this person.
  string email = 3;

  enum PhoneType {
    MOBILE = 0;
    HOME = 1;
    WORK = 2;
  }

  message PhoneNumber {
    string number = 1;
    PhoneType type = 2;
  }

  repeated PhoneNumber phones = 4;
}

// Our address book file is just one of these.
message AddressBook {
  repeated Person people = 1;
}

```

--------------------------------

### Converting i32 to Rust Enum using TryFrom

Source: https://github.com/tokio-rs/prost/blob/master/prost/README.md

Example of converting an i32 to a Rust enum using `TryFrom`.

```rust
let phone_type = 2i32;

match PhoneType::try_from(phone_type) {
    Ok(PhoneType::Mobile) => ...,
    Ok(PhoneType::Home) => ...,
    Ok(PhoneType::Work) => ...,
    Err(_) => ...,
}
```

--------------------------------

### Protobuf Enum Definition

Source: https://github.com/tokio-rs/prost/blob/master/prost/README.md

Example of a protobuf enum definition.

```protobuf
enum PhoneType {
  MOBILE = 0;
  HOME = 1;
  WORK = 2;
}
```

--------------------------------

### Protobuf Oneof Definition

Source: https://github.com/tokio-rs/prost/blob/master/prost/README.md

Example of a protobuf message with a oneof field.

```protobuf
message Foo {
  oneof widget {
    int32 quux = 1;
    string bar = 2;
  }
}
```

--------------------------------

### Tag Inference for Existing Rust Types

Source: https://github.com/tokio-rs/prost/blob/master/prost/README.md

Demonstrates how Prost infers tags for existing Rust structs. Fields are tagged sequentially starting from 1, with options to skip tags using the `tag` attribute.

```rust
use prost;
use prost::{Enumeration, Message};

#[derive(Clone, PartialEq, Message)]
struct Person {
    #[prost(string, tag = "1")]
    pub id: String, // tag=1
    // NOTE: Old "name" field has been removed
    // pub name: String, // tag=2 (Removed)
    #[prost(string, tag = "6")]
    pub given_name: String, // tag=6
    #[prost(string)]
    pub family_name: String, // tag=7
    #[prost(string)]
    pub formatted_name: String, // tag=8
    #[prost(uint32, tag = "3")]
    pub age: u32, // tag=3
    #[prost(uint32)]
    pub height: u32, // tag=4
    #[prost(enumeration = "Gender")]
    pub gender: i32, // tag=5
    // NOTE: Skip to less commonly occurring fields
    #[prost(string, tag = "16")]
    pub name_prefix: String, // tag=16  (eg. mr/mrs/ms)
    #[prost(string)]
    pub name_suffix: String, // tag=17  (eg. jr/esq)
    #[prost(string)]
    pub maiden_name: String, // tag=18
}

#[derive(Clone, Copy, Debug, PartialEq, Eq, Enumeration)]
pub enum Gender {
    Unknown = 0,
    Female = 1,
    Male = 2,
}
```

--------------------------------

### Protobuf Package to Rust Module Mapping

Source: https://github.com/tokio-rs/prost/blob/master/README.md

Prost translates the Protobuf 'package' specifier into a Rust module structure. For example, 'package foo.bar;' results in Rust types within the 'foo::bar' module.

```protobuf
package foo.bar;
```

--------------------------------

### Generated Rust Code for Person and AddressBook

Source: https://github.com/tokio-rs/prost/blob/master/README.md

The Rust code generated by Prost from the example .proto file. It includes structs for Person, PhoneNumber, and AddressBook, along with the PhoneType enum.

```rust
#[derive(Clone, PartialEq, ::prost::Message)]
pub struct Person {
    #[prost(string, tag="1")]
    pub name: ::prost::alloc::string::String,
    /// Unique ID number for this person.
    #[prost(int32, tag="2")]
    pub id: i32,
    #[prost(string, tag="3")]
    pub email: ::prost::alloc::string::String,
    #[prost(message, repeated, tag="4")]
    pub phones: ::prost::alloc::vec::Vec<person::PhoneNumber>,
}
/// Nested message and enum types in `Person`.
pub mod person {
    #[derive(Clone, PartialEq, ::prost::Message)]
    pub struct PhoneNumber {
        #[prost(string, tag="1")]
        pub number: ::prost::alloc::string::String,
        #[prost(enumeration="PhoneType", tag="2")]
        pub r#type: i32,
    }
    #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord, ::prost::Enumeration)]
    #[repr(i32)]
    pub enum PhoneType {
        Mobile = 0,
        Home = 1,
        Work = 2,
    }
}
/// Our address book file is just one of these.
#[derive(Clone, PartialEq, ::prost::Message)]
pub struct AddressBook {
    #[prost(message, repeated, tag="1")]
    pub people: ::prost::alloc::vec::Vec<Person>,
}

```

--------------------------------

### Develop with Nix Flakes

Source: https://github.com/tokio-rs/prost/blob/master/prost/README.md

Enter a development shell with all project dependencies configured using Nix flakes.

```bash
nix develop
```

--------------------------------

### Build and run afl fuzz target

Source: https://github.com/tokio-rs/prost/blob/master/FUZZING.md

Navigate to the target directory, build the binary, and initiate the fuzzing process.

```bash
cd fuzz/afl/<target>/
cargo afl build --bin fuzz-target
cargo afl fuzz -i in -o out target/debug/fuzz-target
```

--------------------------------

### Develop with Minimum Rust Version using Nix

Source: https://github.com/tokio-rs/prost/blob/master/prost/README.md

Enter a development shell using the minimum supported Rust version as required by policy, ensuring compatibility testing.

```bash
nix develop .#rust_minimum_version
```

--------------------------------

### Generate proto3 binary test corpus

Source: https://github.com/tokio-rs/prost/blob/master/fuzz/afl/proto3/README.md

Uses the prost library to encode a TestAllTypesProto3 message into a binary file. Ensure the protobuf test messages are available in your project dependencies.

```rust
use prost::Message;
use protobuf::test_messages::proto3::TestAllTypesProto3;

fn main() {
    let msg = TestAllTypesProto3 {
        optional_int32: 42,
        optional_fixed64: 9983748923,
        optional_bool: true,
        recursive_message: Some(
            Box::new(TestAllTypesProto3 {
                repeated_int32: vec![1, 2, 99, 50, -5],
                ..Default::default()
            })
        ),
        repeated_sfixed32: vec![1, -1, 1, -1],
        repeated_float: vec![-1.0, 10.10, 1.337, std::f32::NAN],
        ..Default::default()
    };
    let mut buf = vec![];
    msg.encode(&mut buf).unwrap();
    std::fs::write("proto3-default.bin", buf).unwrap();
}
```

--------------------------------

### Prost no_std Configuration

Source: https://github.com/tokio-rs/prost/blob/master/prost/README.md

Configure Prost for no_std environments by disabling default features and using BTreeMaps for map fields.

```ignore
[dependencies]
prost = { version = "0.14.3", default-features = false, features = ["derive"] }
# Only necessary if using Protobuf well-known types:
prost-types = { version = "0.14.3", default-features = false }
```

```rust
let mut config = prost_build::Config::new();
config.btree_map(&["."]);
```

--------------------------------

### Reproduce a crash

Source: https://github.com/tokio-rs/prost/blob/master/FUZZING.md

Use the reproduction binary to analyze specific crash files generated by the fuzzer.

```bash
cd fuzz/afl/<target>/
cargo build --bin reproduce
cargo run --bin reproduce -- out/crashes/<crashfile>
```

--------------------------------

### Add Prost and Prost-Types to Cargo.toml

Source: https://github.com/tokio-rs/prost/blob/master/prost/README.md

Include prost and prost-types in your project's dependencies. Prost-types is only needed if you plan to use Protobuf's well-known types.

```toml
[dependencies]
prost = "0.14"
# Only necessary if using Protobuf well-known types:
prost-types = "0.14"
```

--------------------------------

### Generated Rust Code from Protobuf

Source: https://github.com/tokio-rs/prost/blob/master/prost/README.md

This Rust code is generated from a .proto file using Prost. It defines structs and enums corresponding to the Protobuf message definitions.

```rust
#[derive(Clone, PartialEq, ::prost::Message)]
pub struct Person {
    #[prost(string, tag="1")]
    pub name: ::prost::alloc::string::String,
    /// Unique ID number for this person.
    #[prost(int32, tag="2")]
    pub id: i32,
    #[prost(string, tag="3")]
    pub email: ::prost::alloc::string::String,
    #[prost(message, repeated, tag="4")]
    pub phones: ::prost::alloc::vec::Vec<person::PhoneNumber>,
}
/// Nested message and enum types in `Person`.
pub mod person {
    #[derive(Clone, PartialEq, ::prost::Message)]
    pub struct PhoneNumber {
        #[prost(string, tag="1")]
        pub number: ::prost::alloc::string::String,
        #[prost(enumeration="PhoneType", tag="2")]
        pub r#type: i32,
    }
    #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord, ::prost::Enumeration)]
    #[repr(i32)]
    pub enum PhoneType {
        Mobile = 0,
        Home = 1,
        Work = 2,
    }
}
/// Our address book file is just one of these.
#[derive(Clone, PartialEq, ::prost::Message)]
pub struct AddressBook {
    #[prost(message, repeated, tag="1")]
    pub people: ::prost::alloc::vec::Vec<Person>,
}
```

--------------------------------

### Protobuf Message to Rust Struct Generation

Source: https://github.com/tokio-rs/prost/blob/master/README.md

A simple Protobuf message declaration is converted into a corresponding Rust struct. Prost applies derive attributes like Clone, Debug, PartialEq, and Message.

```protobuf
// Sample message.
message Foo {
}
```

--------------------------------

### Converting Rust Enum to i32

Source: https://github.com/tokio-rs/prost/blob/master/prost/README.md

How to convert a Rust enum value to an i32.

```rust
PhoneType::Mobile as i32
```

--------------------------------

### Protobuf Message with Enum Field

Source: https://github.com/tokio-rs/prost/blob/master/prost/README.md

A protobuf message containing an enum field.

```protobuf
message PhoneNumber {
  string number = 1;
  PhoneType type = 2;
}
```

--------------------------------

### Generated Rust Enum

Source: https://github.com/tokio-rs/prost/blob/master/prost/README.md

The corresponding Rust enum generated from a protobuf enum.

```rust
pub enum PhoneType {
    Mobile = 0,
    Home = 1,
    Work = 2,
}
```

--------------------------------

### Generated Rust Struct for Oneof

Source: https://github.com/tokio-rs/prost/blob/master/prost/README.md

The Rust struct and module generated from a protobuf message with a oneof field.

```rust
pub struct Foo {
    pub widget: Option<foo::Widget>,
}
pub mod foo {
    pub enum Widget {
        Quux(i32),
        Bar(String),
    }
}
```

--------------------------------

### Generated Rust Struct for Protobuf Message

Source: https://github.com/tokio-rs/prost/blob/master/README.md

This Rust struct is generated by Prost from a Protobuf message definition. It includes derive attributes and a public struct field.

```rust
/// Sample message.
#[derive(Clone, Debug, PartialEq, Message)]
pub struct Foo {
}
```

--------------------------------

### Generated Rust Struct with Enum Accessors

Source: https://github.com/tokio-rs/prost/blob/master/prost/README.md

The Rust struct generated from a protobuf message with an enum field, including accessor methods.

```rust
pub struct PhoneNumber {
    pub number: String,
    pub r#type: i32, // the `r#` is needed because `type` is a Rust keyword
}

impl PhoneNumber {
    pub fn r#type(&self) -> PhoneType { ... }
    pub fn set_type(&mut self, value: PhoneType) { ... }
}
```

--------------------------------

### Generated Enum Associated Functions

Source: https://github.com/tokio-rs/prost/blob/master/prost/README.md

Associated functions added to Rust enums by the `prost::Enumeration` derive macro.

```rust
impl PhoneType {
    pub const fn is_valid(value: i32) -> bool { ... }
    #[deprecated]
    pub fn from_i32(value: i32) -> Option<PhoneType> { ... }
}
```

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