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Seal the features contexts
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lightning/src/ln/features.rs

+87-91
Original file line numberDiff line numberDiff line change
@@ -8,125 +8,143 @@ use std::marker::PhantomData;
88
use ln::msgs::DecodeError;
99
use util::ser::{Readable, Writeable, Writer};
1010

11-
/// The context in which a Feature object appears determines which bits of features the node
12-
/// supports will be set. We use this when creating our own Feature objects to select which bits to
13-
/// set and when passing around Feature objects to ensure the bits we're checking for are
14-
/// available.
15-
///
16-
/// This Context represents when the Feature appears in the init message, sent between peers and not
17-
/// rumored around the P2P network.
18-
pub struct FeatureContextInit {}
19-
/// The context in which a Feature object appears determines which bits of features the node
20-
/// supports will be set. We use this when creating our own Feature objects to select which bits to
21-
/// set and when passing around Feature objects to ensure the bits we're checking for are
22-
/// available.
23-
///
24-
/// This Context represents when the Feature appears in the node_announcement message, as it is
25-
/// rumored around the P2P network.
26-
pub struct FeatureContextNode {}
27-
/// The context in which a Feature object appears determines which bits of features the node
28-
/// supports will be set. We use this when creating our own Feature objects to select which bits to
29-
/// set and when passing around Feature objects to ensure the bits we're checking for are
30-
/// available.
31-
///
32-
/// This Context represents when the Feature appears in the ChannelAnnouncement message, as it is
33-
/// rumored around the P2P network.
34-
pub struct FeatureContextChannel {}
35-
/// The context in which a Feature object appears determines which bits of features the node
36-
/// supports will be set. We use this when creating our own Feature objects to select which bits to
37-
/// set and when passing around Feature objects to ensure the bits we're checking for are
38-
/// available.
39-
///
40-
/// This Context represents when the Feature appears in an invoice, used to determine the different
41-
/// options available for routing a payment.
42-
///
43-
/// Note that this is currently unused as invoices come to us via a different crate and are not
44-
/// native to rust-lightning directly.
45-
pub struct FeatureContextInvoice {}
11+
mod sealed { // You should just use the type aliases instead.
12+
pub struct InitContext {}
13+
pub struct NodeContext {}
14+
pub struct ChannelContext {}
4615

47-
/// An internal trait capturing the various future context types
48-
pub trait FeatureContext {}
49-
impl FeatureContext for FeatureContextInit {}
50-
impl FeatureContext for FeatureContextNode {}
51-
impl FeatureContext for FeatureContextChannel {}
52-
impl FeatureContext for FeatureContextInvoice {}
16+
/// An internal trait capturing the various feature context types
17+
pub trait Context {}
18+
impl Context for InitContext {}
19+
impl Context for NodeContext {}
20+
impl Context for ChannelContext {}
5321

54-
/// An internal trait capturing FeatureContextInit and FeatureContextNode
55-
pub trait FeatureContextInitNode : FeatureContext {}
56-
impl FeatureContextInitNode for FeatureContextInit {}
57-
impl FeatureContextInitNode for FeatureContextNode {}
22+
pub trait DataLossProtect: Context {}
23+
impl DataLossProtect for InitContext {}
24+
impl DataLossProtect for NodeContext {}
25+
26+
pub trait InitialRoutingSync: Context {}
27+
impl InitialRoutingSync for InitContext {}
28+
29+
pub trait UpfrontShutdownScript: Context {}
30+
impl UpfrontShutdownScript for InitContext {}
31+
impl UpfrontShutdownScript for NodeContext {}
32+
}
5833

5934
/// Tracks the set of features which a node implements, templated by the context in which it
6035
/// appears.
61-
pub struct Features<T: FeatureContext> {
36+
pub struct Features<T: sealed::Context> {
6237
/// Note that, for convinience, flags is LITTLE endian (despite being big-endian on the wire)
6338
flags: Vec<u8>,
6439
mark: PhantomData<T>,
6540
}
6641

67-
impl<T: FeatureContext> Clone for Features<T> {
42+
impl<T: sealed::Context> Clone for Features<T> {
6843
fn clone(&self) -> Self {
6944
Self {
7045
flags: self.flags.clone(),
7146
mark: PhantomData,
7247
}
7348
}
7449
}
75-
impl<T: FeatureContext> PartialEq for Features<T> {
50+
impl<T: sealed::Context> PartialEq for Features<T> {
7651
fn eq(&self, o: &Self) -> bool {
7752
self.flags.eq(&o.flags)
7853
}
7954
}
80-
impl<T: FeatureContext> fmt::Debug for Features<T> {
55+
impl<T: sealed::Context> fmt::Debug for Features<T> {
8156
fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
8257
self.flags.fmt(fmt)
8358
}
8459
}
8560

8661
/// A feature message as it appears in an init message
87-
pub type InitFeatures = Features<FeatureContextInit>;
62+
pub type InitFeatures = Features<sealed::InitContext>;
8863
/// A feature message as it appears in a node_announcement message
89-
pub type NodeFeatures = Features<FeatureContextNode>;
64+
pub type NodeFeatures = Features<sealed::NodeContext>;
9065
/// A feature message as it appears in a channel_announcement message
91-
pub type ChannelFeatures = Features<FeatureContextChannel>;
66+
pub type ChannelFeatures = Features<sealed::ChannelContext>;
9267

93-
impl<T: FeatureContextInitNode> Features<T> {
68+
impl InitFeatures {
9469
/// Create a Features with the features we support
9570
#[cfg(not(feature = "fuzztarget"))]
96-
pub(crate) fn our_features() -> Features<T> {
97-
Features {
71+
pub(crate) fn our_features() -> InitFeatures {
72+
InitFeatures {
9873
flags: vec![2 | 1 << 5],
9974
mark: PhantomData,
10075
}
10176
}
10277
#[cfg(feature = "fuzztarget")]
103-
pub fn our_features() -> Features<T> {
104-
Features {
78+
pub fn our_features() -> InitFeatures {
79+
InitFeatures {
10580
flags: vec![2 | 1 << 5],
10681
mark: PhantomData,
10782
}
10883
}
84+
85+
/// Writes all features present up to, and including, 13.
86+
pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
87+
let len = cmp::min(2, self.flags.len());
88+
w.size_hint(len + 2);
89+
(len as u16).write(w)?;
90+
for i in (0..len).rev() {
91+
if i == 0 {
92+
self.flags[i].write(w)?;
93+
} else {
94+
// On byte 1, check (1 << 14) - 1 up all bits-up-to-but-not-including-bit-14.
95+
(self.flags[i] & ((1 << (14 - 8)) - 1)).write(w)?;
96+
}
97+
}
98+
Ok(())
99+
}
100+
101+
/// or's another InitFeatures into this one.
102+
pub(crate) fn or(&mut self, o: &InitFeatures) {
103+
let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
104+
self.flags.resize(total_feature_len, 0u8);
105+
for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
106+
*byte |= *o_byte;
107+
}
108+
}
109109
}
110110

111-
impl Features<FeatureContextChannel> {
111+
impl ChannelFeatures {
112112
/// Create a Features with the features we support
113113
#[cfg(not(feature = "fuzztarget"))]
114-
pub(crate) fn our_features() -> Features<FeatureContextChannel> {
115-
Features {
114+
pub(crate) fn our_features() -> ChannelFeatures {
115+
ChannelFeatures {
116116
flags: Vec::new(),
117117
mark: PhantomData,
118118
}
119119
}
120120
#[cfg(feature = "fuzztarget")]
121-
pub fn our_features() -> Features<FeatureContextChannel> {
122-
Features {
121+
pub fn our_features() -> ChannelFeatures {
122+
ChannelFeatures {
123123
flags: Vec::new(),
124124
mark: PhantomData,
125125
}
126126
}
127127
}
128128

129-
impl<T: FeatureContext> Features<T> {
129+
impl NodeFeatures {
130+
/// Create a Features with the features we support
131+
#[cfg(not(feature = "fuzztarget"))]
132+
pub(crate) fn our_features() -> NodeFeatures {
133+
NodeFeatures {
134+
flags: vec![2 | 1 << 5],
135+
mark: PhantomData,
136+
}
137+
}
138+
#[cfg(feature = "fuzztarget")]
139+
pub fn our_features() -> NodeFeatures {
140+
NodeFeatures {
141+
flags: vec![2 | 1 << 5],
142+
mark: PhantomData,
143+
}
144+
}
145+
}
146+
147+
impl<T: sealed::Context> Features<T> {
130148
/// Create a blank Features with no fetures set
131149
pub fn empty() -> Features<T> {
132150
Features {
@@ -186,11 +204,13 @@ impl<T: FeatureContext> Features<T> {
186204
}
187205
}
188206

189-
impl<T: FeatureContextInitNode> Features<T> {
207+
impl<T: sealed::DataLossProtect> Features<T> {
190208
pub(crate) fn supports_data_loss_protect(&self) -> bool {
191209
self.flags.len() > 0 && (self.flags[0] & 3) != 0
192210
}
211+
}
193212

213+
impl<T: sealed::UpfrontShutdownScript> Features<T> {
194214
pub(crate) fn supports_upfront_shutdown_script(&self) -> bool {
195215
self.flags.len() > 0 && (self.flags[0] & (3 << 4)) != 0
196216
}
@@ -200,7 +220,7 @@ impl<T: FeatureContextInitNode> Features<T> {
200220
}
201221
}
202222

203-
impl Features<FeatureContextInit> {
223+
impl<T: sealed::InitialRoutingSync> Features<T> {
204224
pub(crate) fn initial_routing_sync(&self) -> bool {
205225
self.flags.len() > 0 && (self.flags[0] & (1 << 3)) != 0
206226
}
@@ -211,33 +231,9 @@ impl Features<FeatureContextInit> {
211231
self.flags[0] |= 1 << 3;
212232
}
213233
}
214-
215-
/// Writes all features present up to, and including, 13.
216-
pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
217-
let len = cmp::min(2, self.flags.len());
218-
w.size_hint(len + 2);
219-
(len as u16).write(w)?;
220-
for i in (0..len).rev() {
221-
if i == 0 {
222-
self.flags[i].write(w)?;
223-
} else {
224-
(self.flags[i] & ((1 << (14 - 8)) - 1)).write(w)?;
225-
}
226-
}
227-
Ok(())
228-
}
229-
230-
/// or's another InitFeatures into this one.
231-
pub(crate) fn or(&mut self, o: &InitFeatures) {
232-
let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
233-
self.flags.resize(total_feature_len, 0u8);
234-
for (feature, o_feature) in self.flags.iter_mut().zip(o.flags.iter()) {
235-
*feature |= *o_feature;
236-
}
237-
}
238234
}
239235

240-
impl<T: FeatureContext> Writeable for Features<T> {
236+
impl<T: sealed::Context> Writeable for Features<T> {
241237
fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
242238
w.size_hint(self.flags.len() + 2);
243239
(self.flags.len() as u16).write(w)?;
@@ -248,7 +244,7 @@ impl<T: FeatureContext> Writeable for Features<T> {
248244
}
249245
}
250246

251-
impl<R: ::std::io::Read, T: FeatureContext> Readable<R> for Features<T> {
247+
impl<R: ::std::io::Read, T: sealed::Context> Readable<R> for Features<T> {
252248
fn read(r: &mut R) -> Result<Self, DecodeError> {
253249
let mut flags: Vec<u8> = Readable::read(r)?;
254250
flags.reverse(); // Swap to little-endian

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