rust/bt-common/src/packet_encoding.rs

// Copyright 2023 Google LLC
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

use thiserror::Error;

/// A decodable type can be created from a byte buffer.
/// The type returned is separate (copied) from the buffer once decoded.
pub trait Decodable: ::core::marker::Sized {
    type Error;

    /// Decodes into a new object with the number of bytes that were decoded, or returns an error.
    fn decode(buf: &[u8]) -> ::core::result::Result<(Self, usize), Self::Error>;
}

/// An encodable type can write itself into a byte buffer.
pub trait Encodable: ::core::marker::Sized {
    type Error;

    /// Returns the number of bytes necessary to encode |self|.
    fn encoded_len(&self) -> ::core::primitive::usize;

    /// Writes the encoded version of |self| at the start of |buf|.
    /// |buf| must be at least |self.encoded_len()| length.
    fn encode(&self, buf: &mut [u8]) -> ::core::result::Result<(), Self::Error>;
}

#[derive(Error, Debug, PartialEq)]
pub enum Error {
    #[error("Parameter is not valid: {0}")]
    InvalidParameter(String),

    #[error("Out-of-range enum value")]
    OutOfRange,

    #[error("Encoding buffer is too small")]
    BufferTooSmall,

    #[error("Buffer being decoded is invalid length")]
    UnexpectedDataLength,
}