cbe_program/

lib.rs

//! The base library for all Cartallum CBE on-chain Rust programs.
//!
//! All Cartallum CBE Rust programs that run on-chain will link to this crate, which
//! acts as a standard library for Cartallum CBE programs. Cartallum CBE programs also link to
//! the [Rust standard library][std], though it is [modified][sstd] for the
//! Cartallum CBE runtime environment. While off-chain programs that interact with the
//! Cartallum CBE network _can_ link to this crate, they typically instead use the
//! [`cbe-sdk`] crate, which reexports all modules from `cbe-program`.
//!
//! [std]: https://doc.rust-lang.org/stable/std/
//! [sstd]: https://docs.cartallum.com/developing/on-chain-programs/developing-rust#restrictions
//! [`cbe-sdk`]: https://docs.cartallum.com/cbe-sdk/latest/cbe_sdk/
//!
//! This library defines
//!
//! - macros for declaring the [program entrypoint][pe],
//! - [core data types][cdt],
//! - [logging] macros,
//! - [serialization] methods,
//! - methods for [cross-program instruction execution][cpi],
//! - program IDs and instruction constructors for the system program and other
//!   [native programs][np],
//! - [sysvar] accessors.
//!
//! [pe]: #defining-a-cbe-program
//! [cdt]: #core-data-types
//! [logging]: crate::log
//! [serialization]: #serialization
//! [np]: #native-programs
//! [cpi]: #cross-program-instruction-execution
//! [sysvar]: crate::sysvar
//!
//! Idiomatic examples of `cbe-program` usage can be found in
//! [the Cartallum CBE Program Library][spl].
//!
//! [spl]: https://github.com/Cartallum/cbe-program-library
//!
//! # Defining a cbe program
//!
//! Cartallum CBE program crates have some unique properties compared to typical Rust
//! programs:
//!
//! - They are often compiled for both on-chain use and off-chain use. This is
//!   primarily because off-chain clients may need access to data types
//!   defined by the on-chain program.
//! - They do not define a `main` function, but instead define their entrypoint
//!   with the [`entrypoint!`] macro.
//! - They are compiled as the ["cdylib"] crate type for dynamic loading
//!   by the Cartallum CBE runtime.
//! - They run in a constrained VM environment, and while they do have access to
//!   the [Rust standard library][std], many features of the standard library,
//!   particularly related to OS services, will fail at runtime, will silently
//!   do nothing, or are not defined. See the [restrictions to the Rust standard
//!   library][sstd] in the Cartallum CBE documentation for more.
//!
//! [std]: https://doc.rust-lang.org/std/index.html
//! ["cdylib"]: https://doc.rust-lang.org/reference/linkage.html
//!
//! Because multiple crates that are linked together cannot all define
//! program entrypoints (see the [`entrypoint!`] documentation) a common
//! convention is to use a [Cargo feature] called `no-entrypoint` to allow
//! the program entrypoint to be disabled.
//!
//! [Cargo feature]: https://doc.rust-lang.org/cargo/reference/features.html
//!
//! The skeleton of a Cartallum CBE program typically looks like:
//!
//! ```
//! #[cfg(not(feature = "no-entrypoint"))]
//! pub mod entrypoint {
//!     use cbe_program::{
//!         account_info::AccountInfo,
//!         entrypoint,
//!         entrypoint::ProgramResult,
//!         pubkey::Pubkey,
//!     };
//!
//!     entrypoint!(process_instruction);
//!
//!     pub fn process_instruction(
//!         program_id: &Pubkey,
//!         accounts: &[AccountInfo],
//!         instruction_data: &[u8],
//!     ) -> ProgramResult {
//!         // Decode and dispatch instructions here.
//!         todo!()
//!     }
//! }
//!
//! // Additional code goes here.
//! ```
//!
//! With a `Cargo.toml` file that contains
//!
//! ```toml
//! [lib]
//! crate-type = ["cdylib", "rlib"]
//!
//! [features]
//! no-entrypoint = []
//! ```
//!
//! Note that a Cartallum CBE program must specify its crate-type as "cdylib", and
//! "cdylib" crates will automatically be discovered and built by the `cargo
//! build-bpf` command. Cartallum CBE programs also often have crate-type "rlib" so
//! they can be linked to other Rust crates.
//!
//! # On-chain vs. off-chain compilation targets
//!
//! Cartallum CBE programs run on the [rbpf] VM, which implements a variant of the
//! [eBPF] instruction set. Because this crate can be compiled for both on-chain
//! and off-chain execution, the environments of which are significantly
//! different, it extensively uses [conditional compilation][cc] to tailor its
//! implementation to the environment. The `cfg` predicate used for identifying
//! compilation for on-chain programs is `target_os = "cbe"`, as in this
//! example from the `cbe-program` codebase that logs a message via a
//! syscall when run on-chain, and via a library call when offchain:
//!
//! [rbpf]: https://github.com/Cartallum/rbpf
//! [eBPF]: https://ebpf.io/
//! [cc]: https://doc.rust-lang.org/reference/conditional-compilation.html
//!
//! ```
//! pub fn cbe_log(message: &str) {
//!     #[cfg(target_os = "cbe")]
//!     unsafe {
//!         cbe_log_(message.as_ptr(), message.len() as u64);
//!     }
//!
//!     #[cfg(not(target_os = "cbe"))]
//!     program_stubs::cbe_log(message);
//! }
//! # mod program_stubs {
//! #     pub(crate) fn cbe_log(message: &str) { }
//! # }
//! ```
//!
//! This `cfg` pattern is suitable as well for user code that needs to work both
//! on-chain and off-chain.
//!
//! `cbe-program` and `cbe-sdk` were previously a single crate. Because of
//! this history, and because of the dual-usage of `cbe-program` for two
//! different environments, it contains some features that are not available to
//! on-chain programs at compile-time. It also contains some on-chain features
//! that will fail in off-chain scenarios at runtime. This distinction is not
//! well-reflected in the documentation.
//!
//! For a more complete description of Cartallum CBE's implementation of eBPF and its
//! limitations, see the main Cartallum CBE documentation for [on-chain programs][ocp].
//!
//! [ocp]: https://docs.cartallum.com/developing/on-chain-programs/overview
//!
//! # Core data types
//!
//! - [`Pubkey`] — The address of a [Cartallum CBE account][acc]. Some account
//!   addresses are [ed25519] public keys, with corresponding secret keys that
//!   are managed off-chain. Often, though, account addresses do not have
//!   corresponding secret keys — as with [_program derived
//!   addresses_][pdas] — or the secret key is not relevant to the
//!   operation of a program, and may have even been disposed of. As running
//!   Cartallum CBE programs can not safely create or manage secret keys, the full
//!   [`Keypair`] is not defined in `cbe-program` but in `cbe-sdk`.
//! - [`Hash`] — A cryptographic hash. Used to uniquely identify blocks,
//!   and also for general purpose hashing.
//! - [`AccountInfo`] — A description of a single Cartallum CBE account. All accounts
//!   that might be accessed by a program invocation are provided to the program
//!   entrypoint as `AccountInfo`.
//! - [`Instruction`] — A directive telling the runtime to execute a program,
//!   passing it a set of accounts and program-specific data.
//! - [`ProgramError`] and [`ProgramResult`] — The error type that all programs
//!   must return, reported to the runtime as a `u64`.
//! - [`CBC`] — The Cartallum CBE native token type, with conversions to and from
//!   [_scoobies_], the smallest fractional unit of CBC, in the [`native_token`]
//!   module.
//!
//! [acc]: https://docs.cartallum.com/developing/programming-model/accounts
//! [`Pubkey`]: pubkey::Pubkey
//! [`Hash`]: hash::Hash
//! [`Instruction`]: instruction::Instruction
//! [`AccountInfo`]: account_info::AccountInfo
//! [`ProgramError`]: program_error::ProgramError
//! [`ProgramResult`]: entrypoint::ProgramResult
//! [ed25519]: https://ed25519.cr.yp.to/
//! [`Keypair`]: https://docs.cartallum.com/cbe-sdk/latest/cbe_sdk/signer/keypair/struct.Keypair.html
//! [SHA-256]: https://en.wikipedia.org/wiki/SHA-2
//! [`CBC`]: native_token::CBC
//! [_scoobies_]: https://docs.cartallum.com/introduction#what-are-cbcs
//!
//! # Serialization
//!
//! Within the Cartallum CBE runtime, programs, and network, at least three different
//! serialization formats are used, and `cbe-program` provides access to
//! those needed by programs.
//!
//! In user-written Cartallum CBE program code, serialization is primarily used for
//! accessing [`AccountInfo`] data and [`Instruction`] data, both of which are
//! program-specific binary data. Every program is free to decide their own
//! serialization format, but data received from other sources —
//! [sysvars][sysvar] for example — must be deserialized using the methods
//! indicated by the documentation for that data or data type.
//!
//! [`AccountInfo`]: account_info::AccountInfo
//! [`Instruction`]: instruction::Instruction
//!
//! The three serialization formats in use in Cartallum CBE are:
//!
//! - __[Borsh]__, a compact and well-specified format developed by the [NEAR]
//!   project, suitable for use in protocol definitions and for archival storage.
//!   It has a [Rust implementation][brust] and a [JavaScript implementation][bjs]
//!   and is recommended for all purposes.
//!
//!   Users need to import the [`borsh`] crate themselves — it is not
//!   re-exported by `cbe-program`, though this crate provides several useful
//!   utilities in its [`borsh` module][borshmod] that are not available in the
//!   `borsh` library.
//!
//!   The [`Instruction::new_with_borsh`] function creates an `Instruction` by
//!   serializing a value with borsh.
//!
//!   [Borsh]: https://borsh.io/
//!   [NEAR]: https://near.org/
//!   [brust]: https://docs.cartallum.com/borsh
//!   [bjs]: https://github.com/near/borsh-js
//!   [`borsh`]: https://docs.cartallum.com/borsh
//!   [borshmod]: crate::borsh
//!   [`Instruction::new_with_borsh`]: instruction::Instruction::new_with_borsh
//!
//! - __[Bincode]__, a compact serialization format that implements the [Serde]
//!   Rust APIs. As it does not have a specification nor a JavaScript
//!   implementation, and uses more CPU than borsh, it is not recommend for new
//!   code.
//!
//!   Many system program and native program instructions are serialized with
//!   bincode, and it is used for other purposes in the runtime. In these cases
//!   Rust programmers are generally not directly exposed to the encoding format
//!   as it is hidden behind APIs.
//!
//!   The [`Instruction::new_with_bincode`] function creates an `Instruction` by
//!   serializing a value with bincode.
//!
//!   [Bincode]: https://docs.cartallum.com/bincode
//!   [Serde]: https://serde.rs/
//!   [`Instruction::new_with_bincode`]: instruction::Instruction::new_with_bincode
//!
//! - __[`Pack`]__, a Cartallum CBE-specific serialization API that is used by many
//!   older programs in the [Cartallum CBE Program Library][spl] to define their
//!   account format. It is difficult to implement and does not define a
//!   language-independent serialization format. It is not generally recommended
//!   for new code.
//!
//!   [`Pack`]: program_pack::Pack
//!
//! Developers should carefully consider the CPU cost of serialization, balanced
//! against the need for correctness and ease of use: off-the-shelf
//! serialization formats tend to be more expensive than carefully hand-written
//! application-specific formats; but application-specific formats are more
//! difficult to ensure the correctness of, and to provide multi-language
//! implementations for. It is not uncommon for programs to pack and unpack
//! their data with hand-written code.
//!
//! # Cross-program instruction execution
//!
//! Cartallum CBE programs may call other programs, termed [_cross-program
//! invocation_][cpi] (CPI), with the [`invoke`] and [`invoke_signed`]
//! functions. When calling another program the caller must provide the
//! [`Instruction`] to be invoked, as well as the [`AccountInfo`] for every
//! account required by the instruction. Because the only way for a program to
//! acquire `AccountInfo` values is by receiving them from the runtime at the
//! [program entrypoint][entrypoint!], any account required by the callee
//! program must transitively be required by the caller program, and provided by
//! _its_ caller.
//!
//! [`invoke`]: program::invoke
//! [`invoke_signed`]: program::invoke_signed
//! [cpi]: https://docs.cartallum.com/developing/programming-model/calling-between-programs
//!
//! A simple example of transferring scoobies via CPI:
//!
//! ```
//! use cbe_program::{
//!     account_info::{next_account_info, AccountInfo},
//!     entrypoint,
//!     entrypoint::ProgramResult,
//!     program::invoke,
//!     pubkey::Pubkey,
//!     system_instruction,
//!     system_program,
//! };
//!
//! entrypoint!(process_instruction);
//!
//! fn process_instruction(
//!     program_id: &Pubkey,
//!     accounts: &[AccountInfo],
//!     instruction_data: &[u8],
//! ) -> ProgramResult {
//!     let account_info_iter = &mut accounts.iter();
//!
//!     let payer = next_account_info(account_info_iter)?;
//!     let recipient = next_account_info(account_info_iter)?;
//!     // The system program is a required account to invoke a system
//!     // instruction, even though we don't use it directly.
//!     let system_account = next_account_info(account_info_iter)?;
//!
//!     assert!(payer.is_writable);
//!     assert!(payer.is_signer);
//!     assert!(recipient.is_writable);
//!     assert!(system_program::check_id(system_account.key));
//!
//!     let scoobies = 1000000;
//!
//!     invoke(
//!         &system_instruction::transfer(payer.key, recipient.key, scoobies),
//!         &[payer.clone(), recipient.clone(), system_account.clone()],
//!     )
//! }
//! ```
//!
//! Cartallum CBE also includes a mechanism to let programs control and sign for
//! accounts without needing to protect a corresponding secret key, called
//! [_program derived addresses_][pdas]. PDAs are derived with the
//! [`Pubkey::find_program_address`] function. With a PDA, a program can call
//! `invoke_signed` to call another program while virtually "signing" for the
//! PDA.
//!
//! [pdas]: https://docs.cartallum.com/developing/programming-model/calling-between-programs#program-derived-addresses
//! [`Pubkey::find_program_address`]: pubkey::Pubkey::find_program_address
//!
//! A simple example of creating an account for a PDA:
//!
//! ```
//! use cbe_program::{
//!     account_info::{next_account_info, AccountInfo},
//!     entrypoint,
//!     entrypoint::ProgramResult,
//!     program::invoke_signed,
//!     pubkey::Pubkey,
//!     system_instruction,
//!     system_program,
//! };
//!
//! entrypoint!(process_instruction);
//!
//! fn process_instruction(
//!     program_id: &Pubkey,
//!     accounts: &[AccountInfo],
//!     instruction_data: &[u8],
//! ) -> ProgramResult {
//!     let account_info_iter = &mut accounts.iter();
//!     let payer = next_account_info(account_info_iter)?;
//!     let vault_pda = next_account_info(account_info_iter)?;
//!     let system_program = next_account_info(account_info_iter)?;
//!
//!     assert!(payer.is_writable);
//!     assert!(payer.is_signer);
//!     assert!(vault_pda.is_writable);
//!     assert_eq!(vault_pda.owner, &system_program::ID);
//!     assert!(system_program::check_id(system_program.key));
//!
//!     let vault_bump_seed = instruction_data[0];
//!     let vault_seeds = &[b"vault", payer.key.as_ref(), &[vault_bump_seed]];
//!     let expected_vault_pda = Pubkey::create_program_address(vault_seeds, program_id)?;
//!
//!     assert_eq!(vault_pda.key, &expected_vault_pda);
//!
//!     let scoobies = 10000000;
//!     let vault_size = 16;
//!
//!     invoke_signed(
//!         &system_instruction::create_account(
//!             &payer.key,
//!             &vault_pda.key,
//!             scoobies,
//!             vault_size,
//!             &program_id,
//!         ),
//!         &[
//!             payer.clone(),
//!             vault_pda.clone(),
//!         ],
//!         &[
//!             &[
//!                 b"vault",
//!                 payer.key.as_ref(),
//!                 &[vault_bump_seed],
//!             ],
//!         ]
//!     )?;
//!     Ok(())
//! }
//! ```
//!
//! # Native programs
//!
//! Some Cartallum CBE programs are [_native programs_][np2], running native machine
//! code that is distributed with the runtime, with well-known program IDs.
//!
//! [np2]: https://docs.cartallum.com/developing/runtime-facilities/programs
//!
//! Some native programs can be [invoked][cpi] by other programs, but some can
//! only be executed as "top-level" instructions included by off-chain clients
//! in a [`Transaction`].
//!
//! [`Transaction`]: https://docs.cartallum.com/cbe-sdk/latest/cbe_sdk/transaction/struct.Transaction.html
//!
//! This crate defines the program IDs for most native programs. Even though
//! some native programs cannot be invoked by other programs, a Cartallum CBE program
//! may need access to their program IDs. For example, a program may need to
//! verify that an ed25519 signature verification instruction was included in
//! the same transaction as its own instruction. For many native programs, this
//! crate also defines enums that represent the instructions they process, and
//! constructors for building the instructions.
//!
//! Locations of program IDs and instruction constructors are noted in the list
//! below, as well as whether they are invokable by other programs.
//!
//! While some native programs have been active since the genesis block, others
//! are activated dynamically after a specific [slot], and some are not yet
//! active. This documentation does not distinguish which native programs are
//! active on any particular network. The `cbe feature status` CLI command
//! can help in determining active features.
//!
//! [slot]: https://docs.cartallum.com/terminology#slot
//!
//! Native programs important to Cartallum CBE program authors include:
//!
//! - __System Program__: Creates new accounts, allocates account data, assigns
//!   accounts to owning programs, transfers scoobies from System Program owned
//!   accounts and pays transaction fees.
//!   - ID: [`cbe_program::system_program`]
//!   - Instruction: [`cbe_program::system_instruction`]
//!   - Invokable by programs? yes
//!
//! - __Compute Budget Program__: Requests additional CPU or memory resources
//!   for a transaction. This program does nothing when called from another
//!   program.
//!   - ID: [`cbe_sdk::compute_budget`](https://docs.cartallum.com/cbe-sdk/latest/cbe_sdk/compute_budget/index.html)
//!   - Instruction: [`cbe_sdk::compute_budget`](https://docs.cartallum.com/cbe-sdk/latest/cbe_sdk/compute_budget/index.html)
//!   - Invokable by programs? no
//!
//! - __ed25519 Program__: Verifies an ed25519 signature.
//!   - ID: [`cbe_program::ed25519_program`]
//!   - Instruction: [`cbe_sdk::ed25519_instruction`](https://docs.cartallum.com/cbe-sdk/latest/cbe_sdk/ed25519_instruction/index.html)
//!   - Invokable by programs? no
//!
//! - __secp256k1 Program__: Verifies secp256k1 public key recovery operations.
//!   - ID: [`cbe_program::secp256k1_program`]
//!   - Instruction: [`cbe_sdk::secp256k1_instruction`](https://docs.cartallum.com/cbe-sdk/latest/cbe_sdk/secp256k1_instruction/index.html)
//!   - Invokable by programs? no
//!
//! - __BPF Loader__: Deploys, and executes immutable programs on the chain.
//!   - ID: [`cbe_program::bpf_loader`]
//!   - Instruction: [`cbe_program::loader_instruction`]
//!   - Invokable by programs? yes
//!
//! - __Upgradable BPF Loader__: Deploys, upgrades, and executes upgradable
//!   programs on the chain.
//!   - ID: [`cbe_program::bpf_loader_upgradeable`]
//!   - Instruction: [`cbe_program::loader_upgradeable_instruction`]
//!   - Invokable by programs? yes
//!
//! - __Deprecated BPF Loader__: Deploys, and executes immutable programs on the
//!   chain.
//!   - ID: [`cbe_program::bpf_loader_deprecated`]
//!   - Instruction: [`cbe_program::loader_instruction`]
//!   - Invokable by programs? yes
//!
//! [lut]: https://docs.cartallum.com/proposals/versioned-transactions

#![allow(incomplete_features)]
#![cfg_attr(RUSTC_WITH_SPECIALIZATION, feature(specialization))]
#![cfg_attr(RUSTC_NEEDS_PROC_MACRO_HYGIENE, feature(proc_macro_hygiene))]

// Allows macro expansion of `use ::cbe_program::*` to work within this crate
extern crate self as cbe_program;

pub mod account_info;
pub mod address_lookup_table_account;
pub mod alt_bn128;
pub(crate) mod atomic_u64;
pub mod blake3;
pub mod borsh;
pub mod bpf_loader;
pub mod bpf_loader_deprecated;
pub mod bpf_loader_upgradeable;
pub mod clock;
pub mod debug_account_data;
pub mod decode_error;
pub mod ed25519_program;
pub mod entrypoint;
pub mod entrypoint_deprecated;
pub mod epoch_schedule;
pub mod feature;
pub mod fee_calculator;
pub mod hash;
pub mod incinerator;
pub mod instruction;
pub mod keccak;
pub mod scoobies;
pub mod loader_instruction;
pub mod loader_upgradeable_instruction;
pub mod log;
pub mod message;
pub mod native_token;
pub mod nonce;
pub mod program;
pub mod program_error;
pub mod program_memory;
pub mod program_option;
pub mod program_pack;
pub mod program_stubs;
pub mod program_utils;
pub mod pubkey;
pub mod rent;
pub mod sanitize;
pub mod secp256k1_program;
pub mod secp256k1_recover;
pub mod serde_varint;
pub mod serialize_utils;
pub mod short_vec;
pub mod slot_hashes;
pub mod slot_history;
pub mod stake;
pub mod stake_history;
pub mod syscalls;
pub mod system_instruction;
pub mod system_program;
pub mod sysvar;
pub mod vote;
pub mod wasm;

#[cfg(target_os = "cbe")]
pub use cbe_sdk_macro::wasm_bindgen_stub as wasm_bindgen;
/// Re-export of [wasm-bindgen].
///
/// [wasm-bindgen]: https://rustwasm.github.io/docs/wasm-bindgen/
#[cfg(not(target_os = "cbe"))]
pub use wasm_bindgen::prelude::wasm_bindgen;

/// The [config native program][np].
///
/// [np]: https://docs.cartallum.com/developing/runtime-facilities/programs#config-program
pub mod config {
    pub mod program {
        crate::declare_id!("Config1111111111111111111111111111111111111");
    }
}

/// A vector of Cartallum CBE SDK IDs.
pub mod sdk_ids {
    use {
        crate::{
            bpf_loader, bpf_loader_deprecated, bpf_loader_upgradeable, config, ed25519_program,
            feature, incinerator, secp256k1_program, cbe_program::pubkey::Pubkey, stake,
            system_program, sysvar, vote,
        },
        lazy_static::lazy_static,
    };

    lazy_static! {
        pub static ref SDK_IDS: Vec<Pubkey> = {
            let mut sdk_ids = vec![
                ed25519_program::id(),
                secp256k1_program::id(),
                system_program::id(),
                sysvar::id(),
                bpf_loader::id(),
                bpf_loader_upgradeable::id(),
                incinerator::id(),
                config::program::id(),
                vote::program::id(),
                feature::id(),
                bpf_loader_deprecated::id(),
                stake::config::id(),
            ];
            sdk_ids.extend(sysvar::ALL_IDS.iter());
            sdk_ids
        };
    }
}

/// Same as [`declare_id`] except that it reports that this ID has been deprecated.
pub use cbe_sdk_macro::program_declare_deprecated_id as declare_deprecated_id;
/// Convenience macro to declare a static public key and functions to interact with it.
///
/// Input: a single literal base58 string representation of a program's ID.
///
/// # Example
///
/// ```
/// # // wrapper is used so that the macro invocation occurs in the item position
/// # // rather than in the statement position which isn't allowed.
/// use std::str::FromStr;
/// use cbe_program::{declare_id, pubkey::Pubkey};
///
/// # mod item_wrapper {
/// #   use cbe_program::declare_id;
/// declare_id!("My11111111111111111111111111111111111111111");
/// # }
/// # use item_wrapper::id;
///
/// let my_id = Pubkey::from_str("My11111111111111111111111111111111111111111").unwrap();
/// assert_eq!(id(), my_id);
/// ```
pub use cbe_sdk_macro::program_declare_id as declare_id;
/// Convenience macro to define a static public key.
///
/// Input: a single literal base58 string representation of a Pubkey.
///
/// # Example
///
/// ```
/// use std::str::FromStr;
/// use cbe_program::{pubkey, pubkey::Pubkey};
///
/// static ID: Pubkey = pubkey!("My11111111111111111111111111111111111111111");
///
/// let my_id = Pubkey::from_str("My11111111111111111111111111111111111111111").unwrap();
/// assert_eq!(ID, my_id);
/// ```
pub use cbe_sdk_macro::program_pubkey as pubkey;

#[macro_use]
extern crate serde_derive;

#[macro_use]
extern crate cbe_frozen_abi_macro;

/// Convenience macro for doing integer division where the operation's safety
/// can be checked at compile-time.
///
/// Since `unchecked_div_by_const!()` is supposed to fail at compile-time, abuse
/// doctests to cover failure modes
///
/// # Examples
///
/// Literal denominator div-by-zero fails:
///
/// ```compile_fail
/// # use cbe_program::unchecked_div_by_const;
/// # fn main() {
/// let _ = unchecked_div_by_const!(10, 0);
/// # }
/// ```
///
/// Const denominator div-by-zero fails:
///
/// ```compile_fail
/// # use cbe_program::unchecked_div_by_const;
/// # fn main() {
/// const D: u64 = 0;
/// let _ = unchecked_div_by_const!(10, D);
/// # }
/// ```
///
/// Non-const denominator fails:
///
/// ```compile_fail
/// # use cbe_program::unchecked_div_by_const;
/// # fn main() {
/// let d = 0;
/// let _ = unchecked_div_by_const!(10, d);
/// # }
/// ```
///
/// Literal denominator div-by-zero fails:
///
/// ```compile_fail
/// # use cbe_program::unchecked_div_by_const;
/// # fn main() {
/// const N: u64 = 10;
/// let _ = unchecked_div_by_const!(N, 0);
/// # }
/// ```
///
/// Const denominator div-by-zero fails:
///
/// ```compile_fail
/// # use cbe_program::unchecked_div_by_const;
/// # fn main() {
/// const N: u64 = 10;
/// const D: u64 = 0;
/// let _ = unchecked_div_by_const!(N, D);
/// # }
/// ```
///
/// Non-const denominator fails:
///
/// ```compile_fail
/// # use cbe_program::unchecked_div_by_const;
/// # fn main() {
/// # const N: u64 = 10;
/// let d = 0;
/// let _ = unchecked_div_by_const!(N, d);
/// # }
/// ```
///
/// Literal denominator div-by-zero fails:
///
/// ```compile_fail
/// # use cbe_program::unchecked_div_by_const;
/// # fn main() {
/// let n = 10;
/// let _ = unchecked_div_by_const!(n, 0);
/// # }
/// ```
///
/// Const denominator div-by-zero fails:
///
/// ```compile_fail
/// # use cbe_program::unchecked_div_by_const;
/// # fn main() {
/// let n = 10;
/// const D: u64 = 0;
/// let _ = unchecked_div_by_const!(n, D);
/// # }
/// ```
///
/// Non-const denominator fails:
///
/// ```compile_fail
/// # use cbe_program::unchecked_div_by_const;
/// # fn main() {
/// let n = 10;
/// let d = 0;
/// let _ = unchecked_div_by_const!(n, d);
/// # }
/// ```
#[macro_export]
macro_rules! unchecked_div_by_const {
    ($num:expr, $den:expr) => {{
        // Ensure the denominator is compile-time constant
        let _ = [(); ($den - $den) as usize];
        // Compile-time constant integer div-by-zero passes for some reason
        // when invoked from a compilation unit other than that where this
        // macro is defined. Do an explicit zero-check for now. Sorry about the
        // ugly error messages!
        // https://users.rust-lang.org/t/unexpected-behavior-of-compile-time-integer-div-by-zero-check-in-declarative-macro/56718
        let _ = [(); ($den as usize) - 1];
        #[allow(clippy::integer_arithmetic)]
        let quotient = $num / $den;
        quotient
    }};
}

// This module is purposefully listed after all other exports: because of an
// interaction within rustdoc between the reexports inside this module of
// `cbe_program`'s top-level modules, and `cbe_sdk`'s glob re-export of
// `cbe_program`'s top-level modules, if this module is not lexically last
// rustdoc fails to generate documentation for the re-exports within
// `cbe_sdk`.
#[cfg(not(target_os = "cbe"))]
pub mod example_mocks;

#[cfg(test)]
mod tests {
    use super::unchecked_div_by_const;

    #[test]
    fn test_unchecked_div_by_const() {
        const D: u64 = 2;
        const N: u64 = 10;
        let n = 10;
        assert_eq!(unchecked_div_by_const!(10, 2), 5);
        assert_eq!(unchecked_div_by_const!(N, 2), 5);
        assert_eq!(unchecked_div_by_const!(n, 2), 5);
        assert_eq!(unchecked_div_by_const!(10, D), 5);
        assert_eq!(unchecked_div_by_const!(N, D), 5);
        assert_eq!(unchecked_div_by_const!(n, D), 5);
    }
}