mid-net 1.0.0

Network adapter for the `middleware` protocol implementation
Documentation 
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use std::io;

use crate::proto::PacketType;

pub trait FancyUtilExt {
    fn unitize_io(self) -> io::Result<()>;
}

impl<T> FancyUtilExt for io::Result<T> {
    fn unitize_io(self) -> io::Result<()> {
        self.map(|_| ())
    }
}

#[rustfmt::skip]
pub mod flags {
    pub const SHORT: u8        = 1 << 0;
    pub const SHORT_CLIENT: u8 = 1 << 1;
    pub const COMPRESSED: u8   = 1 << 2;

    /// Checks whether packet is short or not (size of length = 1 or 2).
    /// 
    /// Example:
    /// ```
    /// use mid_net::utils::{flags, encode_type};
    /// 
    /// assert!(
    ///     flags::is_short(encode_type(13, flags::COMPRESSED | flags::SHORT))
    /// );
    /// ```
    pub const fn is_short(f: u8) -> bool {
        (f & SHORT) != 0
    }

    /// Checks whether client id field is short or not
    /// (size of client id = 1 or 2).
    /// 
    /// Example:
    /// ```
    /// use mid_net::utils::{flags, encode_type};
    /// 
    /// assert!(
    ///     flags::is_short_client(encode_type(31, flags::SHORT_CLIENT))
    /// );
    /// ```
    pub const fn is_short_client(f: u8) -> bool {
        (f & SHORT_CLIENT) != 0
    }

    /// Checks whether packet payload is compressed or not.
    /// 
    /// Example:
    /// ```
    /// use mid_net::utils::{flags, encode_type};
    /// 
    /// assert!(
    ///     flags::is_compressed(encode_type(12, flags::COMPRESSED))
    /// );
    /// ```
    pub const fn is_compressed(f: u8) -> bool {
        (f & COMPRESSED) != 0
    }
}

pub const fn encode_fwd_header(
    client_id: u16,
    length: u16,
    compressed: bool,
) -> ([u8; 5], usize) {
    let mut flags: u8 = 0;
    let mut offset: usize = 1;
    let mut buf = [0; 5];

    offset += if client_id <= 0xff {
        flags |= flags::SHORT_CLIENT;
        buf[offset] = client_id as u8;

        1
    } else {
        buf[offset] = (client_id & 0xff) as u8;
        buf[offset + 1] = (client_id >> 8) as u8;

        2
    };
    offset += if length <= 0xff {
        flags |= flags::SHORT;
        buf[offset] = length as u8;

        1
    } else {
        buf[offset] = (length & 0xff) as u8;
        buf[offset + 1] = (length >> 8) as u8;

        2
    };

    if compressed {
        flags |= flags::COMPRESSED;
    }

    buf[0] = encode_type(PacketType::Forward as u8, flags);
    (buf, offset)
}

/// Decodes packed type. Returns `packet type` and `flags`.
///
/// Example:
/// ```
/// use mid_net::utils::{
///     decode_type,
///     encode_type,
/// };
///
/// assert_eq!(decode_type(encode_type(10, 0b111)), (10, 0b111));
/// ```
pub const fn decode_type(pkt_type: u8) -> (u8, u8) {
    (pkt_type >> 3, pkt_type & 0b111)
}

/// Encodes packet type to contain both type & flags.
///
/// Example:
/// ```
/// use mid_net::utils::encode_type;
///
/// assert_eq!(encode_type(0, 0b111), 0b111);
/// assert_eq!(encode_type(1, 0b111), (1 << 3) | 0b111);
/// ```
pub const fn encode_type(pkt_type: u8, pkt_flags: u8) -> u8 {
    debug_assert!(pkt_flags <= 0b111);
    debug_assert!(pkt_type <= 0x1f);

    (pkt_type << 3) | pkt_flags
}

/// Same as [`encode_type`], but pkt_flags = 0
///
/// Example:
/// ```
/// use mid_net::utils::{
///     encode_type,
///     ident_type,
/// };
///
/// assert_eq!(ident_type(10), encode_type(10, 0));
/// assert_eq!(ident_type(4), encode_type(4, 0));
/// assert_eq!(ident_type(0), encode_type(0, 0));
/// ```
pub const fn ident_type(pkt_type: u8) -> u8 {
    encode_type(pkt_type, 0)
}