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ironrdp-error

A lightweight, no_std-compatible generic error type used throughout the IronRDP project.

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Overview

The ironrdp-error crate provides a flexible Error<Kind> type that combines a static context string with a user-defined error kind enum. It supports optional error chaining through source errors and works in no_std environments with or without allocation. Source: crates/ironrdp-error/

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Features

  • Generic Error Kind: Parameterized by user-defined error kind enums
  • Static Context: Zero-allocation context strings using &'static str
  • Source Chaining: Optional error source tracking (requires alloc feature)
  • no_std Support: Works in embedded and bare-metal environments
  • Conversion Support: Convert between different error kinds

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Feature Flags

FeatureDefaultDescription
stdYesEnable standard library support and std::error::Error trait
allocEnabled by stdEnable allocations for error sources (requires alloc crate)

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API Reference

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Error<Kind>

Generic error type combining context and kind.

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Construction

use ironrdp_error::Error;

// Create new error with context and kind
let error = Error::new("connection", MyErrorKind::Timeout);

// Add source error for chaining
let error = Error::new("connection", MyErrorKind::Timeout)
    .with_source(std::io::Error::from(std::io::ErrorKind::TimedOut));

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Methods

// Get the error kind
fn kind(&self) -> &Kind

// Update the context (useful when propagating)
fn set_context(&mut self, context: &'static str)

// Convert to different error kind
fn into_other_kind<OtherKind>(self) -> Error<OtherKind>
where
    Kind: Into<OtherKind>

// Get detailed error report (includes source chain)
fn report(&self) -> ErrorReport<'_, Kind>

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ErrorReport

Wrapper for formatted error output including full source chain. 
// Display full error chain
println!("{}", error.report());
// Output: [connection] timeout, caused by: connection timed out
The ErrorReport type implements Display and formats the error with all causes in the chain.

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Error Source Trait

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Source Trait

Abstraction over error sources that works in both std and no_std environments. 
// With std feature
pub trait Source: core::error::Error + Sync + Send + 'static {}

// Without std feature
pub trait Source: fmt::Display + fmt::Debug + Send + Sync + 'static {}
All types implementing the appropriate bounds automatically implement Source.

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Usage Examples

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Basic Error Handling

use ironrdp_error::Error;

#[derive(Debug)]
enum ConnectorErrorKind {
    Negotiation,
    Authentication,
    Network,
}

impl std::fmt::Display for ConnectorErrorKind {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::Negotiation => write!(f, "protocol negotiation failed"),
            Self::Authentication => write!(f, "authentication failed"),
            Self::Network => write!(f, "network error"),
        }
    }
}

type ConnectorError = Error<ConnectorErrorKind>;

fn establish_connection() -> Result<(), ConnectorError> {
    // Error with static context
    return Err(Error::new("establish_connection", ConnectorErrorKind::Negotiation));
}

match establish_connection() {
    Ok(()) => println!("Connected"),
    Err(e) => {
        println!("Error: {}", e);
        // Output: [establish_connection] protocol negotiation failed
        println!("Kind: {:?}", e.kind());
        // Output: Kind: Negotiation
    }
}

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Error Chaining

use ironrdp_error::Error;

#[derive(Debug, thiserror::Error)]
enum PduErrorKind {
    #[error("encoding failed")]
    Encode,
    #[error("decoding failed")]
    Decode,
}

type PduError = Error<PduErrorKind>;

fn decode_packet(data: &[u8]) -> Result<(), PduError> {
    // Parse operation that might fail
    let result = bincode::deserialize::<Packet>(data)
        .map_err(|e| Error::new("decode_packet", PduErrorKind::Decode)
                          .with_source(e))?;
    Ok(())
}

match decode_packet(&[]) {
    Err(e) => {
        // Full error report with source chain
        eprintln!("Decode failed: {}", e.report());
        // Output: [decode_packet] decoding failed, caused by: unexpected end of file
    }
    Ok(()) => {}
}

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Converting Error Kinds

use ironrdp_error::Error;

#[derive(Debug)]
enum SpecificError {
    Timeout,
    InvalidData,
}

#[derive(Debug)]
enum GeneralError {
    Specific(SpecificError),
    Unknown,
}

impl From<SpecificError> for GeneralError {
    fn from(e: SpecificError) -> Self {
        GeneralError::Specific(e)
    }
}

fn handle_specific() -> Result<(), Error<SpecificError>> {
    Err(Error::new("operation", SpecificError::Timeout))
}

fn handle_general() -> Result<(), Error<GeneralError>> {
    // Convert error kind while preserving context and source
    handle_specific()
        .map_err(|e| e.into_other_kind())?;
    Ok(())
}

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no_std Usage

#![no_std]

extern crate alloc;

use ironrdp_error::Error;
use alloc::string::String;

#[derive(Debug)]
enum EmbeddedError {
    BufferFull,
    InvalidState,
}

impl core::fmt::Display for EmbeddedError {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        match self {
            Self::BufferFull => write!(f, "buffer is full"),
            Self::InvalidState => write!(f, "invalid state"),
        }
    }
}

type Result<T> = core::result::Result<T, Error<EmbeddedError>>;

fn process_packet() -> Result<()> {
    Err(Error::new("process_packet", EmbeddedError::BufferFull))
}

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Integration with IronRDP

Throughout IronRDP, crates define their own error kind enums and use ironrdp_error::Error as the error type:

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IronRDP Connector Errors

// From ironrdp-connector
pub enum ConnectorErrorKind {
    Encode(/* ... */),
    Decode(/* ... */),
    Credssp(/* ... */),
    AccessDenied,
    // ...
}

pub type ConnectorError = ironrdp_error::Error<ConnectorErrorKind>;

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IronRDP Session Errors

// From ironrdp-session
pub enum SessionErrorKind {
    Pdu(/* ... */),
    Encode(/* ... */),
    Decode(/* ... */),
    // ...
}

pub type SessionError = ironrdp_error::Error<SessionErrorKind>;

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IronRDP PDU Errors

// From ironrdp-pdu
pub enum PduErrorKind {
    Unsupported { /* ... */ },
    InvalidMessage { /* ... */ },
    // ...
}

pub type PduError = ironrdp_error::Error<PduErrorKind>;

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Context Best Practices

Context strings should:
  • Be lowercase snake_case or function names
  • Describe the operation that failed
  • Be static strings (zero allocation)
  • Be concise (used as a prefix)
Good examples:
  • "connect"
  • "send_request"
  • "decode_packet"
  • "establish_channel"
Avoid:
  • Complete sentences
  • Duplicating error kind information
  • Dynamic strings

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Display Format

The error displays as [context] kind: 
let error = Error::new("parse_header", ParseError::InvalidMagic);
println!("{}", error);
// Output: [parse_header] invalid magic number

println!("{}", error.report());
// Output: [parse_header] invalid magic number, caused by: expected 0x52445000, found 0x00000000

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Conversion to std::io::Error

When the std feature is enabled, Error<Kind> can be converted to std::io::Error: 
use std::io;
use ironrdp_error::Error;

fn read_data() -> io::Result<Vec<u8>> {
    let result: Result<Vec<u8>, Error<MyErrorKind>> = perform_read();
    result.map_err(Into::into) // Converts to io::Error
}

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Dependencies

  • core: Rust core library (always available)
  • alloc: Allocation support (optional, for error sources in no_std)
All IronRDP crates use ironrdp-error for error handling:
  • ironrdp-core: Core encoding/decoding errors
  • ironrdp-pdu: PDU parsing errors
  • ironrdp-connector: Connection establishment errors
  • ironrdp-session: Session management errors
  • ironrdp-svc: Static virtual channel errors
  • ironrdp-dvc: Dynamic virtual channel errors

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Design Rationale

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Why Generic Error Kind?

Rather than a single global error enum, Error<Kind> allows each crate to define its own error taxonomy while sharing the error infrastructure (context, sources, reporting).

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Why Static Context?

Static context strings have zero runtime cost and don’t require allocations, making them suitable for performance-critical and no_std code paths.

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Why Optional Sources?

Error sources require allocation but provide valuable debugging information. Making them optional via feature flags allows usage in constrained environments while supporting rich error reports where possible.

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