Remove the futures flag

protocol/Cargo.toml

@@ -11,14 +11,11 @@ rust-version = "1.63.0"
 
 [features]
 default = ["std"]
-# High-level wrappers using futures traits.
-futures = ["std", "dep:futures"]
 # High-level wrappers using tokio traits - may affect MSRV requirements.
 tokio = ["std", "dep:tokio"]
 std = ["bitcoin/std", "bitcoin_hashes/std", "chacha20-poly1305/std", "rand/std", "rand/std_rng"]
 
 [dependencies]
-futures = { version = "0.3.30", default-features = false, optional = true, features = ["std"] }
 # The tokio feature may increase the MSRV beyond 1.63.0
 # depending on which version of tokio is selected by the caller.
 tokio = { version = "1", default-features = false, optional = true, features = ["io-util"] }

protocol/README.md

@@ -4,15 +4,14 @@ A BIP324 library to establish and communicate over an encrypted channel.
 
 The library is designed with a bare `no_std` and "Sans I/O" interface to keep it as agnostic as possible to application runtimes, but higher level interfaces are exposed for ease of use.
 
-The `futures` feature includes the high-level `AsyncProcotol` type which helps create and manage an encrypted channel. 
+The `tokio` feature includes the high-level `AsyncProcotol` type which helps create and manage an encrypted channel. 
 
 The lower-level `CipherSession` and `Handshake` types can be directly used by applications which require more control. The handshake performs the one-and-a-half round trip dance between the peers in order to generate secret materials and verify a channel. A successful handshake results in a cipher session which performs the encrypt and decrypt operations for the lifetime of the channel.
 
 ## Feature Flags
 
 * `std` -- Standard library dependencies for I/O, memory allocation, and random number generators.
-* `futures` -- High level wrappers for asynchronous read and write runtimes using agnostic futures-rs traits.
-* `tokio` -- Same wrappers as `futures`, but using the popular tokio runtime's specific traits instead of futures-rs.
+* `tokio` -- High level I/O wrappers for asynchronous tokio runtime.
 
 ## Minimum Supported Rust Version (MSRV)
 

protocol/src/io.rs

@@ -4,35 +4,31 @@
 //! connections over Read/Write transports.
 
 use core::fmt;
-
-#[cfg(feature = "std")]
+#[cfg(feature = "tokio")]
 use std::vec;
-#[cfg(feature = "std")]
 use std::vec::Vec;
 
-use bitcoin::Network;
+use crate::{Error, PacketType};
 
-// Default to the futures-rs traits, but can overwrite with more specific
-// tokio implementations for easier caller integration.
-#[cfg(all(feature = "futures", not(feature = "tokio")))]
-use futures::{AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt};
 #[cfg(feature = "tokio")]
-use tokio::io::{AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt};
+use bitcoin::Network;
 
+#[cfg(feature = "tokio")]
 use crate::{
     handshake::{self, GarbageResult, VersionResult},
-    Error, Handshake, InboundCipher, OutboundCipher, PacketType, Role, NUM_ELLIGATOR_SWIFT_BYTES,
+    Handshake, InboundCipher, OutboundCipher, Role, NUM_ELLIGATOR_SWIFT_BYTES,
     NUM_GARBAGE_TERMINTOR_BYTES,
 };
 
+#[cfg(feature = "tokio")]
+use tokio::io::{AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt};
+
 /// A decrypted BIP324 payload with its packet type.
-#[cfg(feature = "std")]
 pub struct Payload {
     contents: Vec<u8>,
     packet_type: PacketType,
 }
 
-#[cfg(feature = "std")]
 impl Payload {
     /// Create a new payload.
     pub fn new(contents: Vec<u8>, packet_type: PacketType) -> Self {
@@ -54,7 +50,6 @@ impl Payload {
 }
 
 /// High level error type for the protocol interface.
-#[cfg(feature = "std")]
 #[derive(Debug)]
 pub enum ProtocolError {
     /// Wrap all IO errors with suggestion for next step on failure.
@@ -64,7 +59,6 @@ pub enum ProtocolError {
 }
 
 /// Suggest to caller next step on protocol failure.
-#[cfg(feature = "std")]
 #[derive(Debug)]
 pub enum ProtocolFailureSuggestion {
     /// Caller could attempt to retry the connection with protocol V1 if desired.
@@ -73,7 +67,6 @@ pub enum ProtocolFailureSuggestion {
     Abort,
 }
 
-#[cfg(feature = "std")]
 impl From<std::io::Error> for ProtocolError {
     fn from(error: std::io::Error) -> Self {
         // Detect IO errors which possibly mean the remote doesn't understand
@@ -94,19 +87,18 @@ impl From<std::io::Error> for ProtocolError {
     }
 }
 
-#[cfg(feature = "std")]
 impl From<Error> for ProtocolError {
     fn from(error: Error) -> Self {
         ProtocolError::Internal(error)
     }
 }
 
-#[cfg(feature = "std")]
 impl ProtocolError {
     /// Create an EOF error that suggests retrying with V1 protocol.
     ///
     /// This is used when the remote peer closes the connection during handshake,
     /// which often indicates they don't support the V2 protocol.
+    #[cfg(feature = "tokio")]
     fn eof() -> Self {
         ProtocolError::Io(
             std::io::Error::new(
@@ -118,7 +110,6 @@ impl ProtocolError {
     }
 }
 
-#[cfg(feature = "std")]
 impl std::error::Error for ProtocolError {
     fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
         match self {
@@ -128,7 +119,6 @@ impl std::error::Error for ProtocolError {
     }
 }
 
-#[cfg(feature = "std")]
 impl fmt::Display for ProtocolError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
@@ -149,13 +139,13 @@ impl fmt::Display for ProtocolError {
 }
 
 /// A protocol session with handshake and send/receive packet management.
-#[cfg(any(feature = "futures", feature = "tokio"))]
+#[cfg(feature = "tokio")]
 pub struct AsyncProtocol {
     reader: AsyncProtocolReader,
     writer: AsyncProtocolWriter,
 }
 
-#[cfg(any(feature = "futures", feature = "tokio"))]
+#[cfg(feature = "tokio")]
 impl AsyncProtocol {
     /// New protocol session which completes the initial handshake and returns a handler.
     ///
@@ -297,7 +287,9 @@ impl AsyncProtocol {
 }
 
 /// State machine of an asynchronous packet read.
-#[cfg(any(feature = "futures", feature = "tokio"))]
+///
+/// This maintains state between await points to ensure cancellation safety.
+#[cfg(feature = "tokio")]
 #[derive(Debug)]
 enum DecryptState {
     ReadingLength {
@@ -310,7 +302,7 @@ enum DecryptState {
     },
 }
 
-#[cfg(any(feature = "futures", feature = "tokio"))]
+#[cfg(feature = "tokio")]
 impl DecryptState {
     /// Transition state to reading the length bytes.
     fn init_reading_length() -> Self {
@@ -330,13 +322,13 @@ impl DecryptState {
 }
 
 /// Manages an async buffer to automatically decrypt contents of received packets.
-#[cfg(any(feature = "futures", feature = "tokio"))]
+#[cfg(feature = "tokio")]
 pub struct AsyncProtocolReader {
     inbound_cipher: InboundCipher,
     state: DecryptState,
 }
 
-#[cfg(any(feature = "futures", feature = "tokio"))]
+#[cfg(feature = "tokio")]
 impl AsyncProtocolReader {
     /// Decrypt contents of received packet from buffer.
     ///
@@ -397,12 +389,12 @@ impl AsyncProtocolReader {
 }
 
 /// Manages an async buffer to automatically encrypt and send contents in packets.
-#[cfg(any(feature = "futures", feature = "tokio"))]
+#[cfg(feature = "tokio")]
 pub struct AsyncProtocolWriter {
     outbound_cipher: OutboundCipher,
 }
 
-#[cfg(any(feature = "futures", feature = "tokio"))]
+#[cfg(feature = "tokio")]
 impl AsyncProtocolWriter {
     /// Encrypt contents and write packet buffer.
     ///

protocol/src/lib.rs

@@ -23,7 +23,7 @@ extern crate std;
 
 mod fschacha20poly1305;
 mod handshake;
-#[cfg(any(feature = "futures", feature = "tokio"))]
+#[cfg(feature = "std")]
 pub mod io;
 #[cfg(feature = "std")]
 pub mod serde;
@@ -43,14 +43,7 @@ pub use handshake::{
     GarbageResult, Handshake, Initialized, ReceivedGarbage, ReceivedKey, SentKey, SentVersion,
     VersionResult,
 };
-// Re-exports from io module (async I/O types for backwards compatibility)
-#[cfg(any(feature = "futures", feature = "tokio"))]
-pub use io::{
-    AsyncProtocol, AsyncProtocolReader, AsyncProtocolWriter, Payload, ProtocolError,
-    ProtocolFailureSuggestion,
-};
 
-// Internal imports
 use fschacha20poly1305::{FSChaCha20, FSChaCha20Poly1305};
 
 /// Value for header byte with the decoy flag flipped to true.

proxy/src/bin/proxy.rs

@@ -6,8 +6,9 @@
 use std::str::FromStr;
 
 use bip324::{
+    io::{AsyncProtocol, ProtocolFailureSuggestion},
     serde::{deserialize, serialize},
-    AsyncProtocol, PacketType, ProtocolFailureSuggestion, Role,
+    PacketType, Role,
 };
 use bip324_proxy::{V1ProtocolReader, V1ProtocolWriter};
 use bitcoin::Network;
@@ -87,7 +88,9 @@ async fn v2_proxy(
     .await
     {
         Ok(p) => p,
-        Err(bip324::ProtocolError::Io(_, ProtocolFailureSuggestion::RetryV1)) if v1_fallback => {
+        Err(bip324::io::ProtocolError::Io(_, ProtocolFailureSuggestion::RetryV1))
+            if v1_fallback =>
+        {
             info!("V2 protocol failed, falling back to V1...");
             return v1_proxy(client, network).await;
         }

proxy/src/lib.rs

@@ -34,7 +34,7 @@ pub enum Error {
     WrongCommand,
     Serde,
     Io(std::io::Error),
-    Protocol(bip324::ProtocolError),
+    Protocol(bip324::io::ProtocolError),
 }
 
 impl fmt::Display for Error {
@@ -61,8 +61,8 @@ impl std::error::Error for Error {
     }
 }
 
-impl From<bip324::ProtocolError> for Error {
-    fn from(e: bip324::ProtocolError) -> Self {
+impl From<bip324::io::ProtocolError> for Error {
+    fn from(e: bip324::io::ProtocolError) -> Self {
         Error::Protocol(e)
     }
 }