Crate gstd

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Expand description

Standard library for use in Gear programs.

This library should be used as a standard library when writing Gear programs. Compared to gcore crate, this library provides higher-level primitives that allow you to develop more complex dApps. Choose this library if you are ready to spend more gas but receive refined code.

gstd crate provides many advanced tools for a developer, such as asynchronous programming primitives, arbitrary types encoding/decoding, providing convenient instruments for creating programs from programs, etc.

§Minimum supported Rust version

This crate requires Rust >= 1.81 due to the implementation of the panic handler in the stable version.

§Crate features

§Default features:

  • panic-message

§Panic handler profiles

We currently use the following format for panic messages from Rust code: panicked with '{message}'[ at '{location}']. Also Panic occurred: will be added to the beginning of the panic message by our core-backend.

So the final panic message looks like this: Panic occurred: panicked with '{message}'[ at '{location}'].

You can configure which panic handler profile you need by specifying one of the following functions:

  • panic-handler — When enabled, a minimal panic handler is provided by this crate. Instead of a panic message, <unknown> is displayed.
  • panic-message (enabled by default) — When enabled, a panic handler will also display a panic message.
  • panic-location — When enabled, a panic handler will also display a panic message and location. This function is not recommended for use in production environment because it displays the code path.

For example, if you don’t use the panic-location feature, the compiler will remove all locations such as /home/username/dapp/src/lib.rs:1:2 from the binary. The size of program will be reduced and /home/username/... information will not be included in the binary.

§Nightly features

The final binary gets additional optimizations when using the nightly compiler.

  • nightly — Enables all features below. These features depend on unstable Rust API and require nightly toolchain.
  • oom-handler — When enabled, an OOM error handler is provided. Relies on alloc_error_handler.

§Additional features

  • ethexe — Disables unsupported syscalls and their calls for executing on ethexe.
  • debug — Enables debug logging; this heavily impacts gas cost and is therefore disabled by default.

§Examples

Decode input payload using a custom type:

#![no_std]

use gstd::{msg, prelude::*};

#[derive(Decode, Encode, TypeInfo)]
#[codec(crate = gstd::codec)]
#[scale_info(crate = gstd::scale_info)]
struct Payload {
    question: String,
    answer: u8,
}

#[no_mangle]
extern "C" fn handle() {
    let payload: Payload = msg::load().expect("Unable to decode payload");
    if payload.question == "life-universe-everything" {
        msg::reply(payload.answer, 0).expect("Unable to reply");
    }
}

Asynchronous program example.

It sends empty messages to three addresses and waits for at least two replies (“approvals”) during initialization. When invoked, it handles only PING messages and sends empty messages to the three addresses, and waits for just one approval. If approval is obtained, the program replies with PONG.

# const _: &'static str = stringify! {
#![no_std]
# };
use futures::future;
use gstd::{msg, prelude::*, ActorId};

static mut APPROVERS: [ActorId; 3] = [ActorId::zero(); 3];

#[derive(Debug, Decode, TypeInfo)]
#[codec(crate = gstd::codec)]
#[scale_info(crate = gstd::scale_info)]
pub struct Input {
    pub approvers: [ActorId; 3],
}

#[gstd::async_init]
async fn init() {
    let payload: Input = msg::load().expect("Failed to decode input");
    unsafe { APPROVERS = payload.approvers };

    let mut requests: Vec<_> = unsafe { APPROVERS }
        .iter()
        .map(|addr| msg::send_bytes_for_reply(*addr, b"", 0, 0))
        .collect::<Result<_, _>>()
        .unwrap();

    let mut threshold = 0;
    while !requests.is_empty() {
        let (.., remaining) = future::select_all(requests).await;
        threshold += 1;
        if threshold >= 2 {
            break;
        }
        requests = remaining;
    }
}

#[gstd::async_main]
async fn main() {
    let message = msg::load_bytes().expect("Failed to load payload bytes");
    if message != b"PING" {
        return;
    }

    let requests: Vec<_> = unsafe { APPROVERS }
        .iter()
        .map(|addr| msg::send_bytes_for_reply(*addr, b"", 0, 0))
        .collect::<Result<_, _>>()
        .unwrap();

    _ = future::select_all(requests).await;
    msg::reply(b"PONG", 0).expect("Unable to reply");
}
# fn main() {}

Re-exports§

Modules§

  • critical
    Critical hook that guarantees code section execution.
  • errors
    Type definitions and helpers for error handling.
  • exec
    Utility functions related to the current execution context or program execution flow.
  • ext
    Extensions for additional features.
  • msg
    Messaging API for Gear programs.
  • prelude
    The gstd default prelude. Re-imports default std modules and traits. std can be safely replaced to gstd in the Rust programs.
  • prog
    Functions and helpers for creating programs from programs.
  • sync
    Data access synchronization objects.
  • util
    Utility functions.

Macros§

  • actor_id
    Macro to declare ActorId from hexadecimal and ss58 format.
  • bail
    Unwrap Result<T, E> to T if it is Ok(T) or panic with the provided message if the result is Err(E).
  • dbg
    Prints and returns the value of a given expression for quick and dirty debugging.
  • debug
    Add a debug message to the log.
  • heap_debug
    Add a debug message to the log.

Structs§

Constants§

  • SYSTEM_RESERVE
    Constant declaring default Config::system_reserve() in case of not “ethexe” feature.

Traits§

Functions§

Type Aliases§

Attribute Macros§

  • async_init
    Mark async function to be the program initialization method.
  • async_main
    Mark the main async function to be the program entry point.