tor_bytes/

lib.rs

#![cfg_attr(docsrs, feature(doc_cfg))]
#![doc = include_str!("../README.md")]
// @@ begin lint list maintained by maint/add_warning @@
#![allow(renamed_and_removed_lints)] // @@REMOVE_WHEN(ci_arti_stable)
#![allow(unknown_lints)] // @@REMOVE_WHEN(ci_arti_nightly)
#![warn(missing_docs)]
#![warn(noop_method_call)]
#![warn(unreachable_pub)]
#![warn(clippy::all)]
#![deny(clippy::await_holding_lock)]
#![deny(clippy::cargo_common_metadata)]
#![deny(clippy::cast_lossless)]
#![deny(clippy::checked_conversions)]
#![warn(clippy::cognitive_complexity)]
#![deny(clippy::debug_assert_with_mut_call)]
#![deny(clippy::exhaustive_enums)]
#![deny(clippy::exhaustive_structs)]
#![deny(clippy::expl_impl_clone_on_copy)]
#![deny(clippy::fallible_impl_from)]
#![deny(clippy::implicit_clone)]
#![deny(clippy::large_stack_arrays)]
#![warn(clippy::manual_ok_or)]
#![deny(clippy::missing_docs_in_private_items)]
#![warn(clippy::needless_borrow)]
#![warn(clippy::needless_pass_by_value)]
#![warn(clippy::option_option)]
#![deny(clippy::print_stderr)]
#![deny(clippy::print_stdout)]
#![warn(clippy::rc_buffer)]
#![deny(clippy::ref_option_ref)]
#![warn(clippy::semicolon_if_nothing_returned)]
#![warn(clippy::trait_duplication_in_bounds)]
#![deny(clippy::unchecked_time_subtraction)]
#![deny(clippy::unnecessary_wraps)]
#![warn(clippy::unseparated_literal_suffix)]
#![deny(clippy::unwrap_used)]
#![deny(clippy::mod_module_files)]
#![allow(clippy::let_unit_value)] // This can reasonably be done for explicitness
#![allow(clippy::uninlined_format_args)]
#![allow(clippy::significant_drop_in_scrutinee)] // arti/-/merge_requests/588/#note_2812945
#![allow(clippy::result_large_err)] // temporary workaround for arti#587
#![allow(clippy::needless_raw_string_hashes)] // complained-about code is fine, often best
#![allow(clippy::needless_lifetimes)] // See arti#1765
#![allow(mismatched_lifetime_syntaxes)] // temporary workaround for arti#2060
#![deny(clippy::unused_async)]
//! <!-- @@ end lint list maintained by maint/add_warning @@ -->

mod err;
mod impls;
mod reader;
mod secretbuf;
mod writer;

pub use err::{EncodeError, Error};
pub use reader::{Cursor, Reader};
pub use secretbuf::SecretBuf;
pub use writer::Writer;

/// Result type returned by this crate for [`Reader`]-related methods.
pub type Result<T> = std::result::Result<T, Error>;
/// Result type returned by this crate for [`Writer`]-related methods.
pub type EncodeResult<T> = std::result::Result<T, EncodeError>;

/// Trait for an object that can be encoded onto a Writer by reference.
///
/// Implement this trait in order to make an object writeable.
///
/// Most code won't need to call this directly, but will instead use
/// it implicitly via the Writer::write() method.
///
/// # Example
///
/// ```
/// use tor_bytes::{Writeable, Writer, EncodeResult};
/// #[derive(Debug, Eq, PartialEq)]
/// struct Message {
///   flags: u32,
///   cmd: u8
/// }
///
/// impl Writeable for Message {
///     fn write_onto<B:Writer+?Sized>(&self, b: &mut B) -> EncodeResult<()> {
///         // We'll say that a "Message" is encoded as flags, then command.
///         b.write_u32(self.flags);
///         b.write_u8(self.cmd);
///         Ok(())
///     }
/// }
///
/// let msg = Message { flags: 0x43, cmd: 0x07 };
/// let mut writer: Vec<u8> = Vec::new();
/// writer.write(&msg);
/// assert_eq!(writer, &[0x00, 0x00, 0x00, 0x43, 0x07 ]);
/// ```
pub trait Writeable {
    /// Encode this object into the writer `b`.
    fn write_onto<B: Writer + ?Sized>(&self, b: &mut B) -> EncodeResult<()>;
}

/// Trait for an object that can be encoded and consumed by a Writer.
///
/// Implement this trait in order to make an object that can be
/// written more efficiently by absorbing it into the writer.
///
/// Most code won't need to call this directly, but will instead use
/// it implicitly via the Writer::write_and_consume() method.
pub trait WriteableOnce: Sized {
    /// Encode this object into the writer `b`, and consume it.
    fn write_into<B: Writer + ?Sized>(self, b: &mut B) -> EncodeResult<()>;
}

impl<W: Writeable + Sized> WriteableOnce for W {
    fn write_into<B: Writer + ?Sized>(self, b: &mut B) -> EncodeResult<()> {
        self.write_onto(b)
    }
}

impl<W: Writeable + ?Sized> Writeable for &W {
    fn write_onto<B: Writer + ?Sized>(&self, b: &mut B) -> EncodeResult<()> {
        (*self).write_onto(b)
    }
}

// ----------------------------------------------------------------------

/// Trait for an object that can be extracted from a Reader.
///
/// Implement this trait in order to make an object that can (maybe)
/// be decoded from a reader.
//
/// Most code won't need to call this directly, but will instead use
/// it implicitly via the Reader::extract() method.
///
/// # Correctness (determinism), and error handling
///
/// The `take_from` method should produce consistent and deterministic results.
///
/// If `take_from` returns `Ok`, consuming some data,
/// a future call with a reader which has that consumed data as a prefix,
/// must consume the same data and succeed with an equivalent value.
///
/// If `take_from` returns `Err`, it is allowed to have consumed
/// none, any, or all, of the `Reader`.
///
/// If `take_from` returns `Error::Incomplete`:
/// then calling `take_from` again on a similar `Reader`
/// (ie, where the old reader is a prefix of the new, or vice versa)
/// must do one of the following:
///  * Succeed, consuming at least as many bytes as
///    were available in the previous reader plus `deficit`.
///  * Return `Error::Incomplete` with a consistent value of `deficit`.
///
/// If `take_from` fails another way with some reader, it must fail the same way
/// with all other readers which have that reader as a prefix.
///
/// (Here, "prefix" and "length" relate only to the remaining bytes in the `Reader`,
/// irrespective of the length or value of any bytes which were previously consumed.)
///
/// (tor-socksproto relies on these properties.)
///
/// Specific implementations may provide stronger guarantees.
///
/// # Example
///
/// ```
/// use tor_bytes::{Readable,Reader,Result};
/// #[derive(Debug, Eq, PartialEq)]
/// struct Message {
///   flags: u32,
///   cmd: u8
/// }
///
/// impl Readable for Message {
///     fn take_from(r: &mut Reader<'_>) -> Result<Self> {
///         // A "Message" is encoded as flags, then command.
///         let flags = r.take_u32()?;
///         let cmd = r.take_u8()?;
///         Ok(Message{ flags, cmd })
///     }
/// }
///
/// let encoded = [0x00, 0x00, 0x00, 0x43, 0x07 ];
/// let mut reader = Reader::from_slice(&encoded);
/// let m: Message = reader.extract()?;
/// assert_eq!(m, Message { flags: 0x43, cmd: 0x07 });
/// reader.should_be_exhausted()?; // make sure there are no bytes left over
/// # Result::Ok(())
/// ```
pub trait Readable: Sized {
    /// Try to extract an object of this type from a Reader.
    ///
    /// Implementations should generally try to be efficient: this is
    /// not the right place to check signatures or perform expensive
    /// operations.  If you have an object that must not be used until
    /// it is finally validated, consider making this function return
    /// a wrapped type that can be unwrapped later on once it gets
    /// checked.
    fn take_from(b: &mut Reader<'_>) -> Result<Self>;
}

// ----------------------------------------------------------------------

#[cfg(test)]
mod test {
    // @@ begin test lint list maintained by maint/add_warning @@
    #![allow(clippy::bool_assert_comparison)]
    #![allow(clippy::clone_on_copy)]
    #![allow(clippy::dbg_macro)]
    #![allow(clippy::mixed_attributes_style)]
    #![allow(clippy::print_stderr)]
    #![allow(clippy::print_stdout)]
    #![allow(clippy::single_char_pattern)]
    #![allow(clippy::unwrap_used)]
    #![allow(clippy::unchecked_time_subtraction)]
    #![allow(clippy::useless_vec)]
    #![allow(clippy::needless_pass_by_value)]
    //! <!-- @@ end test lint list maintained by maint/add_warning @@ -->
    use super::*;

    #[test]
    fn writer() {
        let mut v: Vec<u8> = Vec::new();
        v.write_u8(0x57);
        v.write_u16(0x6520);
        v.write_u32(0x68617665);
        v.write_u64(0x2061206d61636869);
        v.write_all(b"ne in a plexiglass dome");
        v.write_zeros(3);
        assert_eq!(&v[..], &b"We have a machine in a plexiglass dome\0\0\0"[..]);
    }
}