src/lib.rs

// Copyright 2023 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! Helper definitions used used by the generated Rust backend.

use bytes::Bytes;
use thiserror::Error;

/// Type of parsing errors.
#[derive(Debug, Error, PartialEq, Eq)]
pub enum Error {
    #[error("Packet parsing failed")]
    InvalidPacketError,
    #[error("{field} was {value:x}, which is not known")]
    ConstraintOutOfBounds { field: String, value: u64 },
    #[error("Got {actual:x}, expected {expected:x}")]
    InvalidFixedValue { expected: u64, actual: u64 },
    #[error("when parsing {obj} needed length of {wanted} but got {got}")]
    InvalidLengthError { obj: String, wanted: usize, got: usize },
    #[error("array size ({array} bytes) is not a multiple of the element size ({element} bytes)")]
    InvalidArraySize { array: usize, element: usize },
    #[error("Due to size restrictions a struct could not be parsed.")]
    ImpossibleStructError,
    #[error("when parsing field {obj}.{field}, {value} is not a valid {type_} value")]
    InvalidEnumValueError { obj: String, field: String, value: u64, type_: String },
    #[error("expected child {expected}, got {actual}")]
    InvalidChildError { expected: &'static str, actual: String },
}

/// Trait implemented for all toplevel packet declarations.
pub trait Packet {
    fn to_bytes(self) -> Bytes;
    fn to_vec(self) -> Vec<u8>;
}

/// Private prevents users from creating arbitrary scalar values
/// in situations where the value needs to be validated.
/// Users can freely deref the value, but only the backend
/// may create it.
#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord)]
pub struct Private<T>(T);

impl<T> std::ops::Deref for Private<T> {
    type Target = T;
    fn deref(&self) -> &Self::Target {
        &self.0
    }
}