chore: Remove unused warning in api integration test

Resolve a warning of unused `output` variable.

Fixes: 0745019 docs(cli): Create commented config file

Signed-off-by: Paul Spooren <mail@aparcar.org>

Cargo.lock

@@ -403,9 +403,9 @@ dependencies = [
 
 [[package]]
 name = "clap_complete"
-version = "4.5.38"
+version = "4.5.40"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d9647a559c112175f17cf724dc72d3645680a883c58481332779192b0d8e7a01"
+checksum = "ac2e663e3e3bed2d32d065a8404024dad306e699a04263ec59919529f803aee9"
 dependencies = [
  "clap 4.5.23",
 ]

Cargo.toml

@@ -49,7 +49,7 @@ typenum = "1.17.0"
 log = { version = "0.4.22" }
 clap = { version = "4.5.23", features = ["derive"] }
 clap_mangen = "0.2.24"
-clap_complete = "4.5.38"
+clap_complete = "4.5.40"
 serde = { version = "1.0.216", features = ["derive"] }
 arbitrary = { version = "1.4.1", features = ["derive"] }
 anyhow = { version = "1.0.94", features = ["backtrace", "std"] }

ciphers/src/hash_domain.rs

@@ -13,7 +13,6 @@ pub use hash::KEY_LEN;
 /// # rosenpass_secret_memory::secret_policy_use_only_malloc_secrets();
 ///
 /// const PROTOCOL_IDENTIFIER: &str = "MY_PROTOCOL:IDENTIFIER";
-/// # fn do_doc_test() -> Result<(), Box<dyn std::error::Error>> {
 /// // create use once hash domain for the protocol identifier
 /// let mut hash_domain = HashDomain::zero();
 /// hash_domain = hash_domain.mix(PROTOCOL_IDENTIFIER.as_bytes())?;
@@ -31,10 +30,7 @@ pub use hash::KEY_LEN;
 /// let new_key_identifier = "my_new_key_identifier".as_bytes();
 /// let new_key = secret_hash_domain.mix(new_key_identifier)?.into_secret();
 ///
-/// # Ok(())
-/// # }
-/// # do_doc_test().unwrap();
-///
+/// # Ok::<(), anyhow::Error>(())
 ///```
 ///
 

constant-time/Cargo.toml

@@ -20,3 +20,6 @@ memsec = { workspace = true }
 
 [dev-dependencies]
 rand = "0.8.5"
+
+[lints.rust]
+unexpected_cfgs = { level = "allow", check-cfg = ['cfg(coverage)'] }

constant-time/src/compare.rs

@@ -2,14 +2,29 @@
 
 use core::ptr;
 
-/// Little endian memcmp version of quinier/memsec
-/// https://github.com/quininer/memsec/blob/bbc647967ff6d20d6dccf1c85f5d9037fcadd3b0/src/lib.rs#L30
+/// Little endian memcmp version of [quinier/memsec](https://github.com/quininer/memsec/blob/bbc647967ff6d20d6dccf1c85f5d9037fcadd3b0/src/lib.rs#L30)
 ///
 /// # Panic & Safety
 ///
 /// Both input arrays must be at least of the indicated length.
 ///
 /// See [std::ptr::read_volatile] on safety.
+///
+/// # Examples
+/// ```
+/// let a = [1, 2, 3, 4];
+/// let b = [1, 2, 3, 4];
+/// let c = [1, 2, 2, 5];
+/// let d = [1, 2, 2, 4];
+///
+/// unsafe {
+///     use rosenpass_constant_time::memcmp_le;
+///     assert_eq!(memcmp_le(a.as_ptr(), b.as_ptr(), 4), 0);
+///     assert!(memcmp_le(a.as_ptr(), c.as_ptr(), 4) < 0);
+///     assert!(memcmp_le(a.as_ptr(), d.as_ptr(), 4) > 0);
+///     assert_eq!(memcmp_le(a.as_ptr(), b.as_ptr(), 2), 0);
+/// }
+/// ```
 #[inline(never)]
 pub unsafe fn memcmp_le(b1: *const u8, b2: *const u8, len: usize) -> i32 {
     let mut res = 0;
@@ -77,3 +92,23 @@ pub fn compare(a: &[u8], b: &[u8]) -> i32 {
     assert!(a.len() == b.len());
     unsafe { memcmp_le(a.as_ptr(), b.as_ptr(), a.len()) }
 }
+
+#[cfg(test)]
+mod tests {
+    use crate::compare::memcmp_le;
+
+    #[test]
+    fn memcmp_le_test() {
+        let a = [1, 2, 3, 4];
+        let b = [1, 2, 3, 4];
+        let c = [1, 2, 2, 5];
+        let d = [1, 2, 2, 4];
+
+        unsafe {
+            assert_eq!(memcmp_le(a.as_ptr(), b.as_ptr(), 4), 0);
+            assert!(memcmp_le(a.as_ptr(), c.as_ptr(), 4) < 0);
+            assert!(memcmp_le(a.as_ptr(), d.as_ptr(), 4) > 0);
+            assert_eq!(memcmp_le(a.as_ptr(), b.as_ptr(), 2), 0);
+        }
+    }
+}

constant-time/src/increment.rs

@@ -6,8 +6,16 @@ use core::hint::black_box;
 /// and increment that integer.
 ///
 /// # Leaks
-/// TODO: mention here if this function leaks any information, see
-/// <https://github.com/rosenpass/rosenpass/issues/232>
+/// This function may leak timing information in the following ways:
+///
+/// - The function execution time is linearly proportional to the input length
+/// - The number of carry operations that occur may affect timing slightly
+/// - Memory access patterns are sequential and predictable
+///
+/// The carry operation timing variation is mitigated through the use of black_box,
+/// but the linear scaling with input size is inherent to the operation.
+/// These timing characteristics are generally considered acceptable for most
+/// cryptographic counter implementations.
 ///
 /// ## Tests
 /// For discussion on how to ensure the constant-time execution of this function, see

constant-time/src/lib.rs

@@ -7,6 +7,32 @@
 //! ## TODO
 //! Figure out methodology to ensure that code is actually constant time, see
 //! <https://github.com/rosenpass/rosenpass/issues/232>
+//!
+//! # Examples
+//!
+//! ```rust
+//! use rosenpass_constant_time::{memcmp, compare};
+//!
+//! let a = [1, 2, 3, 4];
+//! let b = [1, 2, 3, 4];
+//! let c = [1, 2, 3, 5];
+//!
+//! // Compare for equality
+//! assert!(memcmp(&a, &b));
+//! assert!(!memcmp(&a, &c));
+//!
+//! // Compare lexicographically
+//! assert_eq!(compare(&a, &c), -1); // a < c
+//! assert_eq!(compare(&c, &a), 1);  // c > a
+//! assert_eq!(compare(&a, &b), 0);  // a == b
+//! ```
+//!
+//! # Security Notes
+//!
+//! While these functions aim to be constant-time, they may leak timing information in some cases:
+//!
+//! - Length mismatches between inputs are immediately detectable
+//! - Execution time scales linearly with input size
 
 mod compare;
 mod increment;
@@ -14,6 +40,7 @@ mod memcmp;
 mod xor;
 
 pub use compare::compare;
+pub use compare::memcmp_le;
 pub use increment::increment;
 pub use memcmp::memcmp;
 pub use xor::xor;

constant-time/src/memcmp.rs

@@ -113,9 +113,10 @@ mod tests {
         // Pearson correlation
         let correlation = cv / (sd_x * sd_y);
         println!("correlation: {:.6?}", correlation);
+        #[cfg(not(coverage))]
         assert!(
             correlation.abs() < 0.01,
             "execution time correlates with result"
-        )
+        );
     }
 }

constant-time/src/xor.rs

@@ -5,12 +5,23 @@ use rosenpass_to::{with_destination, To};
 
 /// Xors the source into the destination
 ///
+/// Performs a constant-time XOR operation between two byte slices
+///
+/// Takes a source slice and XORs it with the destination slice in-place using the
+/// rosenpass_to trait for destination management.
+///
 /// # Panics
 /// If source and destination are of different sizes.
 ///
 /// # Leaks
-/// TODO: mention here if this function leaks any information, see
-/// <https://github.com/rosenpass/rosenpass/issues/232>
+/// This function may leak timing information in the following ways:
+///
+/// - The function execution time is linearly proportional to the input length
+/// - Length mismatches between source and destination are immediately detectable via panic
+/// - Memory access patterns follow a predictable sequential pattern
+///
+/// These leaks are generally considered acceptable in most cryptographic contexts
+/// as they don't reveal information about the actual content being XORed.
 ///
 /// ## Tests
 /// For discussion on how to ensure the constant-time execution of this function, see

rosenpass/Cargo.toml

@@ -91,3 +91,6 @@ experiment_api = [
 internal_signal_handling_for_coverage_reports = ["signal-hook"]
 internal_testing = []
 internal_bin_gen_ipc_msg_types = ["hex", "heck"]
+
+[lints.rust]
+unexpected_cfgs = { level = "allow", check-cfg = ['cfg(coverage)'] }

rosenpass/tests/api-integration-tests-api-setup.rs

@@ -39,7 +39,7 @@ impl Drop for KillChild {
         // system is a bit broken; there is probably a few functions that just restart on EINTR
         // so the signal is absorbed
         loop {
-            rustix::process::kill_process(pid, Term).discard_result();
+            kill_process(pid, Term).discard_result();
             if self.0.try_wait().unwrap().is_some() {
                 break;
             }

rosenpass/tests/integration_test.rs

@@ -160,6 +160,9 @@ fn check_example_config() {
         .output()
         .expect("EXAMPLE_CONFIG not valid");
 
+    let stderr = String::from_utf8_lossy(&output.stderr);
+    assert_eq!(stderr, "");
+
     fs::copy(
         tmp_dir.path().join("rp-public-key"),
         tmp_dir.path().join("rp-peer-public-key"),

rosenpass/tests/poll_example.rs

@@ -2,11 +2,9 @@
 use std::{
     borrow::{Borrow, BorrowMut},
     collections::VecDeque,
-    fmt::{Debug, Write},
-    ops::{DerefMut, RangeBounds},
+    ops::DerefMut,
 };
 
-use rand::distributions::uniform::SampleBorrow;
 use rosenpass_cipher_traits::Kem;
 use rosenpass_ciphers::kem::StaticKem;
 use rosenpass_util::result::OkExt;
@@ -28,48 +26,53 @@ fn test_successful_exchange_with_poll() -> anyhow::Result<()> {
     sim.poll_loop(150)?; // Poll 75 times
     let transcript = sim.transcript;
 
-    let completions: Vec<_> = transcript
+    let _completions: Vec<_> = transcript
         .iter()
         .filter(|elm| matches!(elm, (_, TranscriptEvent::CompletedExchange(_))))
         .collect();
 
+    #[cfg(not(coverage))]
     assert!(
-        !completions.is_empty(),
+        !_completions.is_empty(),
         "\
         Should have performed a successful key exchanged!\n\
           Transcript: {transcript:?}\n\
-          Completions: {completions:?}\
+          Completions: {_completions:?}\
         "
     );
+    #[cfg(not(coverage))]
     assert!(
-        completions[0].0 < 20.0,
+        _completions[0].0 < 20.0,
         "\
         First key exchange should happen in under twenty seconds!\n\
           Transcript: {transcript:?}\n\
-          Completions: {completions:?}\
+          Completions: {_completions:?}\
         "
     );
 
+    #[cfg(not(coverage))]
     assert!(
-        completions.len() >= 3,
+        _completions.len() >= 3,
         "\
         Should have at least two renegotiations!\n\
           Transcript: {transcript:?}\n\
-          Completions: {completions:?}\
+          Completions: {_completions:?}\
         "
     );
+    #[cfg(not(coverage))]
     assert!(
-        (110.0..175.0).contains(&completions[1].0),
+        (110.0..175.0).contains(&_completions[1].0),
         "\
         First renegotiation should happen in between two and three minutes!\n\
           Transcript: {transcript:?}\n\
-          Completions: {completions:?}\
+          Completions: {_completions:?}\
         "
     );
-    assert!((110.0..175.0).contains(&(completions[2].0 - completions[1].0)), "\
+    #[cfg(not(coverage))]
+    assert!((110.0..175.0).contains(&(_completions[2].0 - _completions[1].0)), "\
         First renegotiation should happen in between two and three minutes after the first renegotiation!\n\
           Transcript: {transcript:?}\n\
-          Completions: {completions:?}\
+          Completions: {_completions:?}\
         ");
 
     Ok(())
@@ -106,48 +109,53 @@ fn test_successful_exchange_under_packet_loss() -> anyhow::Result<()> {
     }
 
     let transcript = sim.transcript;
-    let completions: Vec<_> = transcript
+    let _completions: Vec<_> = transcript
         .iter()
         .filter(|elm| matches!(elm, (_, TranscriptEvent::CompletedExchange(_))))
         .collect();
 
+    #[cfg(not(coverage))]
     assert!(
-        !completions.is_empty(),
+        !_completions.is_empty(),
         "\
         Should have performed a successful key exchanged!\n\
           Transcript: {transcript:?}\n\
-          Completions: {completions:?}\
+          Completions: {_completions:?}\
         "
     );
+    #[cfg(not(coverage))]
     assert!(
-        completions[0].0 < 10.0,
+        _completions[0].0 < 10.0,
         "\
           First key exchange should happen in under twenty seconds!\n\
           Transcript: {transcript:?}\n\
-          Completions: {completions:?}\
+          Completions: {_completions:?}\
         "
     );
 
+    #[cfg(not(coverage))]
     assert!(
-        completions.len() >= 3,
+        _completions.len() >= 3,
         "\
         Should have at least two renegotiations!\n\
           Transcript: {transcript:?}\n\
-          Completions: {completions:?}\
+          Completions: {_completions:?}\
         "
     );
+    #[cfg(not(coverage))]
     assert!(
-        (110.0..175.0).contains(&completions[1].0),
+        (110.0..175.0).contains(&_completions[1].0),
         "\
         First renegotiation should happen in between two and three minutes!\n\
           Transcript: {transcript:?}\n\
-          Completions: {completions:?}\
+          Completions: {_completions:?}\
         "
     );
-    assert!((110.0..175.0).contains(&(completions[2].0 - completions[1].0)), "\
+    #[cfg(not(coverage))]
+    assert!((110.0..175.0).contains(&(_completions[2].0 - _completions[1].0)), "\
         First renegotiation should happen in between two and three minutes after the first renegotiation!\n\
           Transcript: {transcript:?}\n\
-          Completions: {completions:?}\
+          Completions: {_completions:?}\
         ");
 
     Ok(())

to/README.md

@@ -17,13 +17,14 @@ use rosenpass_to::{to, with_destination, To};
 use std::ops::BitXorAssign;
 
 // Destination functions return some value that implements the To trait.
-// Unfortunately dealing with lifetimes is a bit more finicky than it would#
+// Unfortunately dealing with lifetimes is a bit more finicky than it would
 // be without destination parameters
 fn xor_slice<'a, T>(src: &'a [T]) -> impl To<[T], ()> + 'a
 where
     T: BitXorAssign + Clone,
 {
     // Custom implementations of the to trait can be created, but the easiest
+    // way to create them is to use the provided helper functions like with_destination.
     with_destination(move |dst: &mut [T]| {
         assert!(src.len() == dst.len());
         for (d, s) in dst.iter_mut().zip(src.iter()) {

to/src/ops.rs

@@ -1,4 +1,5 @@
-//! Functions with destination copying data between slices and arrays.
+//! Functions that make it easy to copy data between arrays and slices using functions with
+//! destinations. See the specific functions for examples and more explanations.
 
 use crate::{with_destination, To};
 
@@ -8,6 +9,17 @@ use crate::{with_destination, To};
 /// # Panics
 ///
 /// This function will panic if the two slices have different lengths.
+///
+/// # Example
+/// ```
+/// use rosenpass_to::To;
+/// # use crate::rosenpass_to::ops::copy_slice;
+/// let to_function = copy_slice(&[0; 16]);
+/// let mut dst = [255; 16];
+/// to_function.to(&mut dst);
+/// // After the operation `dst` will hold the same data as the original slice.
+/// assert!(dst.iter().all(|b| *b == 0));
+/// ```
 pub fn copy_slice<T>(origin: &[T]) -> impl To<[T], ()> + '_
 where
     T: Copy,
@@ -23,6 +35,19 @@ where
 /// # Panics
 ///
 /// This function will panic if destination is shorter than origin.
+///
+/// # Example
+/// ```
+/// use rosenpass_to::To;
+/// # use crate::rosenpass_to::ops::copy_slice_least_src;
+/// let to_function = copy_slice_least_src(&[0; 16]);
+/// let mut dst = [255; 32];
+/// to_function.to(&mut dst);
+/// // After the operation the first half of `dst` will hold the same data as the original slice.
+/// assert!(dst[0..16].iter().all(|b| *b == 0));
+/// // The second half will have remained the same
+/// assert!(dst[16..32].iter().all(|b| *b == 255));
+/// ```
 pub fn copy_slice_least_src<T>(origin: &[T]) -> impl To<[T], ()> + '_
 where
     T: Copy,
@@ -34,6 +59,18 @@ where
 /// destination.
 ///
 /// Copies as much data as is present in the shorter slice.
+/// # Example
+/// ```
+/// use rosenpass_to::To;
+/// # use crate::rosenpass_to::ops::copy_slice_least;
+/// let to_function = copy_slice_least(&[0; 16]);
+/// let mut dst = [255; 32];
+/// to_function.to(&mut dst);
+/// // After the operation the first half of `dst` will hold the same data as the original slice.
+/// assert!(dst[0..16].iter().all(|b| *b == 0));
+/// // The second half will have remained the same.
+/// assert!(dst[16..32].iter().all(|b| *b == 255));
+/// ```
 pub fn copy_slice_least<T>(origin: &[T]) -> impl To<[T], ()> + '_
 where
     T: Copy,
@@ -47,6 +84,24 @@ where
 /// Function with destination that attempts to copy data from origin into the destination.
 ///
 /// Will return None if the slices are of different lengths.
+/// # Example
+/// ```
+/// use rosenpass_to::To;
+/// # use crate::rosenpass_to::ops::try_copy_slice;
+/// let to_function = try_copy_slice(&[0; 16]);
+/// let mut dst = [255; 32];
+/// let result = to_function.to(&mut dst);
+/// // This will return None because the slices do not have the same length.
+/// assert!(result.is_none());
+///
+/// let to_function = try_copy_slice(&[0; 16]);
+/// let mut dst = [255; 16];
+/// let result = to_function.to(&mut dst);
+/// // This time it works:
+/// assert!(result.is_some());
+/// // After the operation `dst` will hold the same data as the original slice.
+/// assert!(dst.iter().all(|b| *b == 0));
+/// ```
 pub fn try_copy_slice<T>(origin: &[T]) -> impl To<[T], Option<()>> + '_
 where
     T: Copy,
@@ -62,6 +117,26 @@ where
 /// Destination may be longer than origin.
 ///
 /// Will return None if the destination is shorter than origin.
+/// # Example
+/// ```rust
+/// use rosenpass_to::To;
+/// # use crate::rosenpass_to::ops::try_copy_slice_least_src;
+/// let to_function = try_copy_slice_least_src(&[0; 16]);
+/// let mut dst = [255; 15];
+/// let result = to_function.to(&mut dst);
+/// // This will return None because the destination is to short.
+/// assert!(result.is_none());
+///
+/// let to_function = try_copy_slice_least_src(&[0; 16]);
+/// let mut dst = [255; 32];
+/// let result = to_function.to(&mut dst);
+/// // This time it works:
+/// assert!(result.is_some());
+/// // After the operation, the first half of `dst` will hold the same data as the original slice.
+/// assert!(dst[0..16].iter().all(|b| *b == 0));
+/// // The second half will have remained the same.
+/// assert!(dst[16..32].iter().all(|b| *b == 255));
+/// ```
 pub fn try_copy_slice_least_src<T>(origin: &[T]) -> impl To<[T], Option<()>> + '_
 where
     T: Copy,
@@ -72,6 +147,18 @@ where
 }
 
 /// Function with destination that copies all data between two array references.
+///
+/// # Example
+/// ```rust
+/// use rosenpass_to::ops::copy_array;
+/// use rosenpass_to::To;
+/// let my_arr: [u8; 32] = [0; 32];
+/// let to_function = copy_array(&my_arr);
+/// let mut dst = [255; 32];
+/// to_function.to(&mut dst);
+/// // After the operation `dst` will hold the same data as the original slice.
+/// assert!(dst.iter().all(|b| *b == 0));
+/// ```
 pub fn copy_array<T, const N: usize>(origin: &[T; N]) -> impl To<[T; N], ()> + '_
 where
     T: Copy,

to/src/to/beside.rs

@@ -1,6 +1,11 @@
+//! This module provides the [Beside] struct. In the context of functions with targets,
+//! [Beside] structures the destination value and the return value unmistakably and offers useful
+//! helper functions to work with them.
+
 use crate::CondenseBeside;
 
-/// Named tuple holding the return value and the output from a function with destinations.
+/// Named tuple holding the return value and the destination from a function with destinations.
+/// See the respective functions for usage examples.
 #[derive(Debug, PartialEq, Eq, Default, PartialOrd, Ord, Copy, Clone)]
 pub struct Beside<Val, Ret>(pub Val, pub Ret);
 
@@ -59,7 +64,7 @@ impl<Val, Ret> Beside<Val, Ret> {
         &mut self.1
     }
 
-    /// Perform beside condensation. See [CondenseBeside]
+    /// Perform beside condensation. See [CondenseBeside] for more details.
     ///
     /// # Example
     /// ```
@@ -90,3 +95,25 @@ impl<Val, Ret> From<Beside<Val, Ret>> for (Val, Ret) {
         (val, ret)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use crate::Beside;
+
+    #[test]
+    fn from_tuple() {
+        let tuple = (21u8, 42u16);
+        let beside: Beside<u8, u16> = Beside::from(tuple);
+        assert_eq!(beside.dest(), &21u8);
+        assert_eq!(beside.ret(), &42u16);
+    }
+
+    #[test]
+    fn from_beside() {
+        let beside: Beside<u8, u16> = Beside(21u8, 42u16);
+        type U8u16 = (u8, u16);
+        let tuple = U8u16::from(beside);
+        assert_eq!(tuple.0, 21u8);
+        assert_eq!(tuple.1, 42u16);
+    }
+}

to/src/to/condense.rs

@@ -1,4 +1,11 @@
-/// Beside condensation.
+//! This module provides condensation for values that stand side by side,
+//! which is often useful when working with destination parameters. See [CondenseBeside]
+//! for more details.
+
+/// Condenses two values that stand beside each other into one value.
+/// For example, a blanked implementation for [Result<(), Error>](Result) is provided. If
+/// `condense(val)` is called on such an object, a [Result<Val, Error>](Result) will
+/// be returned, if `val` is of type `Val`.
 ///
 /// This trait can be used to enable the use of [to_this(|| ...)](crate::To::to_this),
 /// [to_value()](crate::To::to_value), and [collect::<...>()](crate::To::collect) with custom
@@ -6,6 +13,19 @@
 ///
 /// The function [Beside::condense()](crate::Beside::condense) is a shorthand for using the
 /// condense trait.
+///
+/// # Example
+/// As an example implementation, we take a look at the blanket implementation for [Option]
+/// ```ignore
+/// impl<Val> CondenseBeside<Val> for Option<()> {
+///     type Condensed = Option<Val>;
+///
+///     /// Replaces the empty tuple inside this [Option] with `ret`.
+///     fn condense(self, ret: Val) -> Option<Val> {
+///         self.map(|()| ret)
+///     }
+/// }
+/// ```
 pub trait CondenseBeside<Val> {
     /// The type that results from condensation.
     type Condensed;
@@ -17,6 +37,7 @@ pub trait CondenseBeside<Val> {
 impl<Val> CondenseBeside<Val> for () {
     type Condensed = Val;
 
+    /// Replaces this empty tuple with `ret`.
     fn condense(self, ret: Val) -> Val {
         ret
     }
@@ -25,6 +46,7 @@ impl<Val> CondenseBeside<Val> for () {
 impl<Val, Error> CondenseBeside<Val> for Result<(), Error> {
     type Condensed = Result<Val, Error>;
 
+    /// Replaces the empty tuple inside this [Result] with `ret`.
     fn condense(self, ret: Val) -> Result<Val, Error> {
         self.map(|()| ret)
     }
@@ -33,6 +55,7 @@ impl<Val, Error> CondenseBeside<Val> for Result<(), Error> {
 impl<Val> CondenseBeside<Val> for Option<()> {
     type Condensed = Option<Val>;
 
+    /// Replaces the empty tuple inside this [Option] with `ret`.
     fn condense(self, ret: Val) -> Option<Val> {
         self.map(|()| ret)
     }

to/src/to/dst_coercion.rs

@@ -1,5 +1,28 @@
-/// Helper performing explicit unsized coercion.
-/// Used by the [to](crate::to()) function.
+//! This module provides explicit type coercion from [Sized] types to [?Sized][core::marker::Sized]
+//! types. See [DstCoercion] for more details.
+
+/// Helper Trait for performing explicit coercion from [Sized] types to
+/// [?Sized][core::marker::Sized] types. It's used by the [to](crate::to()) function.
+///
+/// We provide blanket implementations for any [Sized] type and for any array of [Sized] types.
+///
+/// # Example
+/// It can be used as follows:
+/// ```
+/// # use rosenpass_to::DstCoercion;
+/// // Consider a sized type like this example:
+/// struct SizedStruct {
+///     x: u32
+/// }
+/// // Then we can coerce it to be unsized:
+/// let mut sized = SizedStruct { x: 42 };
+/// assert_eq!(42, sized.coerce_dest().x);
+///
+/// // Analogously, we can coerce arrays to slices:
+/// let mut sized_array = [1, 2, 3, 4, 5, 6, 7, 8, 9];
+/// let un_sized: &[i32] = sized_array.coerce_dest();
+/// assert_eq!(un_sized, un_sized);
+/// ```
 pub trait DstCoercion<Dst: ?Sized> {
     /// Performs an explicit coercion to the destination type.
     fn coerce_dest(&mut self) -> &mut Dst;

to/src/to/mod.rs

@@ -6,11 +6,16 @@
 //! - `Dst: ?Sized`; (e.g. [u8]) – The target to write to
 //! - `Out: Sized = &mut Dst`; (e.g. &mut [u8]) – A reference to the target to write to
 //! - `Coercable: ?Sized + DstCoercion<Dst>`; (e.g. `[u8]`, `[u8; 16]`) – Some value that
-//!   destination coercion can be applied to. Usually either `Dst` itself (e.g. `[u8]` or some sized variant of
+//!   destination coercion can be applied to. Usually either `Dst` itself (e.g. `[u8]` or
+//!   some sized variant of
 //!   `Dst` (e.g. `[u8; 64]`).
-//! - `Ret: Sized`; (anything) – must be `CondenseBeside<_>` if condensing is to be applied. The ordinary return value of a function with an output
-//! - `Val: Sized + BorrowMut<Dst>`; (e.g. [u8; 16]) – Some owned storage that can be borrowed as `Dst`
-//! - `Condensed: Sized = CondenseBeside<Val>::Condensed`; (e.g. [u8; 16], Result<[u8; 16]>) – The combiation of Val and Ret after condensing was applied (`Beside<Val, Ret>::condense()`/`Ret::condense(v)` for all `v : Val`).
+//! - `Ret: Sized`; (anything) – must be `CondenseBeside<_>` if condensing is to be applied. The
+//!    ordinary return value of a function with an output
+//! - `Val: Sized + BorrowMut<Dst>`; (e.g. [u8; 16]) – Some owned storage that can be borrowed as
+//!   `Dst`
+//! - `Condensed: Sized = CondenseBeside<Val>::Condensed`; (e.g. [u8; 16], Result<[u8; 16]>)
+//! – The combiation of Val and Ret after condensing was applied
+//!   (`Beside<Val, Ret>::condense()`/`Ret::condense(v)` for all `v : Val`).
 
 pub mod beside;
 pub mod condense;

to/src/to/to_function.rs

@@ -1,9 +1,23 @@
+//! This module provides the [To::to] function which allows to use functions with destination in
+//! a manner akin to that of a variable assignment. See [To::to] for more details.
+
 use crate::{DstCoercion, To};
 
 /// Alias for [To::to] moving the destination to the left.
 ///
 /// This provides similar haptics to the let assignment syntax is rust, which also keeps
 /// the variable to assign to on the left and the generating function on the right.
+///
+/// # Example
+/// ```rust
+/// // Using the to function to have data flowing from the right to the left,
+/// // performing something akin to a variable assignment.
+/// use rosenpass_to::ops::copy_slice_least;
+/// # use rosenpass_to::to;
+/// let mut dst = b"           ".to_vec();
+/// to(&mut dst[..], copy_slice_least(b"Hello World"));
+/// assert_eq!(&dst[..], b"Hello World");
+/// ```
 pub fn to<Coercable, Src, Dst, Ret>(dst: &mut Coercable, src: Src) -> Ret
 where
     Coercable: ?Sized + DstCoercion<Dst>,

to/src/to/to_trait.rs

@@ -1,12 +1,46 @@
+//! Module that contains the [To] crate which is the container used to
+//! implement the core functionality of this crate.
+
 use crate::{Beside, CondenseBeside};
 use std::borrow::BorrowMut;
 
 /// The To trait is the core of the to crate; most functions with destinations will either return
-/// an object that is an instance of this trait or they will return `-> impl To<Destination,
-/// Return_value`.
+/// an object that is an instance of this trait, or they will return `-> impl To<Destination,
+/// Return_value>`.
 ///
 /// A quick way to implement a function with destination is to use the
-/// [with_destination(|param: &mut Type| ...)] higher order function.
+/// [with_destination(|param: &mut Type| ...)](crate::with_destination) higher order function.
+///
+/// # Example
+/// Below, we provide a very simple example for how the Trait can be implemented. More examples for
+/// how this Trait is best implemented can be found in the overall [crate documentation](crate).
+/// ```
+/// use rosenpass_to::To;
+///
+/// // This is a simple wrapper around a String that can be written into a byte array using to.
+/// struct StringToBytes {
+///    inner: String
+/// }
+///
+/// impl To<[u8], Result<(), String>> for StringToBytes {
+///     fn to(self, out: &mut [u8]) -> Result<(), String> {
+///         let bytes = self.inner.as_bytes();
+///         if bytes.len() > out.len() {
+///             return Err("out is to short".to_string());
+///         }
+///         for i in 0..bytes.len() {
+///             (*out)[i] = bytes[i];
+///         }
+///         Ok(())
+///     }
+/// }
+///
+/// let string_to_bytes = StringToBytes { inner: "my message".to_string() };
+/// let mut buffer: [u8; 10] = [0; 10];
+/// let result = string_to_bytes.to(&mut buffer);
+/// assert_eq!(buffer, [109, 121, 32, 109, 101, 115, 115, 97, 103, 101]);
+/// assert!(result.is_ok());
+/// ```
 pub trait To<Dst: ?Sized, Ret>: Sized {
     /// Writes self to the destination `out` and returns a value of type `Ret`.
     ///
@@ -19,6 +53,36 @@ pub trait To<Dst: ?Sized, Ret>: Sized {
     /// calls [crate::to()] to evaluate the function and finally
     /// returns a [Beside] instance containing the generated destination value and the return
     /// value.
+    ///
+    /// # Example
+    /// Below, we rewrite the example for the overall [To]-Trait and simplify it by using
+    /// [self.to_this_beside]. We refer to the overall [crate documentation](crate)
+    /// for more examples and general explanations.
+    /// ```
+    /// # use rosenpass_to::To;
+    /// use rosenpass_to::Beside;
+    /// # struct StringToBytes {
+    /// #   inner: String
+    /// # }
+    ///
+    /// # impl To<[u8], Result<(), String>> for StringToBytes {
+    /// #    fn to(self, out: &mut [u8]) -> Result<(), String> {
+    /// #        let bytes = self.inner.as_bytes();
+    /// #        if bytes.len() > out.len() {
+    /// #            return Err("out is to short".to_string());
+    /// #        }
+    /// #        for i in 0..bytes.len() {
+    /// #            (*out)[i] = bytes[i];
+    /// #        }
+    /// #        Ok(())
+    /// #    }
+    /// # }
+    /// // StringToBytes is taken from the overall Trait example.
+    /// let string_to_bytes = StringToBytes { inner: "my message".to_string() };
+    /// let Beside(dst, result) = string_to_bytes.to_this_beside(|| [0; 10]);
+    /// assert_eq!(dst, [109, 121, 32, 109, 101, 115, 115, 97, 103, 101]);
+    /// assert!(result.is_ok());
+    /// ```
     fn to_this_beside<Val, Fun>(self, fun: Fun) -> Beside<Val, Ret>
     where
         Val: BorrowMut<Dst>,
@@ -31,10 +95,21 @@ pub trait To<Dst: ?Sized, Ret>: Sized {
 
     /// Generate a destination on the fly using default.
     ///
-    /// Uses [Default] to create a value,
-    /// calls [crate::to()] to evaluate the function and finally
+    /// Uses [Default] to create a value, calls [crate::to()] to evaluate the function and finally
     /// returns a [Beside] instance containing the generated destination value and the return
     /// value.
+    ///
+    /// # Example
+    /// Below, we provide a simple example for the usage of [to_value_beside](To::to_value_beside).
+    /// We refer to the overall [crate documentation](crate) for more examples and general
+    /// explanations.
+    /// ```
+    /// use rosenpass_to::Beside;
+    /// use rosenpass_to::To;
+    /// use rosenpass_to::ops::*;
+    /// let Beside(dst, ret) = copy_array(&[42u8; 16]).to_value_beside();
+    /// assert_eq!(dst, [42u8; 16]);
+    /// ```
     fn to_value_beside(self) -> Beside<Dst, Ret>
     where
         Dst: Sized + Default,
@@ -53,6 +128,19 @@ pub trait To<Dst: ?Sized, Ret>: Sized {
     /// when the Destination is unsized.
     ///
     /// This could be the case when the destination is an `[u8]` for instance.
+    ///
+    /// # Example
+    /// Below, we provide a simple example for the usage of [collect_beside](To::collect_beside).
+    /// We refer to the overall [crate documentation](crate) for more examples and general
+    /// explanations.
+    /// ```
+    /// use rosenpass_to::Beside;
+    /// use rosenpass_to::To;
+    /// use rosenpass_to::ops::*;
+    ///
+    /// let Beside(dst, ret) = copy_slice(&[42u8; 16]).collect_beside::<[u8; 16]>();
+    /// assert_eq!(dst, [42u8; 16]);
+    /// ```
     fn collect_beside<Val>(self) -> Beside<Val, Ret>
     where
         Val: Default + BorrowMut<Dst>,
@@ -64,6 +152,36 @@ pub trait To<Dst: ?Sized, Ret>: Sized {
     /// return value into one.
     ///
     /// This is like using [Self::to_this_beside] followed by calling [Beside::condense].
+    /// # Example
+    /// Below, we rewrite the example for the overall [To]-Trait and simplify it by using
+    /// [Self::to_this]. We refer to the overall [crate documentation](crate)
+    /// for more examples and general explanations.
+    /// ```
+    /// # use rosenpass_to::To;
+    /// use rosenpass_to::Beside;
+    /// # struct StringToBytes {
+    /// #   inner: String
+    /// # }
+    ///
+    /// # impl To<[u8], Result<(), String>> for StringToBytes {
+    /// #    fn to(self, out: &mut [u8]) -> Result<(), String> {
+    /// #        let bytes = self.inner.as_bytes();
+    /// #        if bytes.len() > out.len() {
+    /// #            return Err("out is to short".to_string());
+    /// #        }
+    /// #        for i in 0..bytes.len() {
+    /// #            (*out)[i] = bytes[i];
+    /// #        }
+    /// #        Ok(())
+    /// #    }
+    /// # }
+    /// // StringToBytes is taken from the overall Trait example.
+    /// let string_to_bytes = StringToBytes { inner: "my message".to_string() };
+    /// let result = string_to_bytes.to_this_beside(|| [0; 10]).condense();
+    /// assert!(result.is_ok());
+    /// assert_eq!(result.unwrap(), [109, 121, 32, 109, 101, 115, 115, 97, 103, 101]);
+    ///
+    /// ```
     fn to_this<Val, Fun>(self, fun: Fun) -> <Ret as CondenseBeside<Val>>::Condensed
     where
         Ret: CondenseBeside<Val>,
@@ -77,6 +195,18 @@ pub trait To<Dst: ?Sized, Ret>: Sized {
     /// return value into one.
     ///
     /// This is like using [Self::to_value_beside] followed by calling [Beside::condense].
+    ///
+    /// # Example
+    /// Below, we provide a simple example for the usage of [to_value](To::to_value).
+    /// We refer to the overall [crate documentation](crate) for more examples and general
+    /// explanations.
+    /// ```
+    /// use rosenpass_to::Beside;
+    /// use rosenpass_to::To;
+    /// use rosenpass_to::ops::*;
+    /// let dst = copy_array(&[42u8; 16]).to_value_beside().condense();
+    /// assert_eq!(dst, [42u8; 16]);
+    /// ```
     fn to_value(self) -> <Ret as CondenseBeside<Dst>>::Condensed
     where
         Dst: Sized + Default,
@@ -89,6 +219,19 @@ pub trait To<Dst: ?Sized, Ret>: Sized {
     /// return value into one.
     ///
     /// This is like using [Self::collect_beside] followed by calling [Beside::condense].
+    ///
+    /// # Example
+    /// Below, we provide a simple example for the usage of [collect](To::collect).
+    /// We refer to the overall [crate documentation](crate) for more examples and general
+    /// explanations.
+    /// ```
+    /// use rosenpass_to::Beside;
+    /// use rosenpass_to::To;
+    /// use rosenpass_to::ops::*;
+    ///
+    /// let dst = copy_slice(&[42u8; 16]).collect_beside::<[u8; 16]>().condense();
+    /// assert_eq!(dst, [42u8; 16]);
+    /// ```
     fn collect<Val>(self) -> <Ret as CondenseBeside<Val>>::Condensed
     where
         Val: Default + BorrowMut<Dst>,

to/src/to/with_destination.rs

@@ -1,15 +1,19 @@
+//! The module provides the [with_destination] function, which makes it easy to create
+//! a [To] from a lambda function. See [with_destination] and the [crate documentation](crate)
+//! for more details and examples.
+
 use crate::To;
 use std::marker::PhantomData;
 
-/// A struct that wraps a closure and implements the `To` trait
+/// A struct that wraps a closure and implements the `To` trait.
 ///
 /// This allows passing closures that operate on a destination type `Dst`
-/// and return `Ret`.
+/// and return `Ret`. It is only internally used to implement [with_destination].
 ///
 /// # Type Parameters
-/// * `Dst` - The destination type the closure operates on
-/// * `Ret` - The return type of the closure
-/// * `Fun` - The closure type that implements `FnOnce(&mut Dst) -> Ret`
+/// * `Dst` - The destination type the closure operates on.
+/// * `Ret` - The return type of the closure.
+/// * `Fun` - The closure type that implements `FnOnce(&mut Dst) -> Ret`.
 struct ToClosure<Dst, Ret, Fun>
 where
     Dst: ?Sized,
@@ -17,11 +21,11 @@ where
 {
     /// The function to call.
     fun: Fun,
-    /// Phantom data to hold the destination type
+    /// Phantom data to hold the destination type.
     _val: PhantomData<Box<Dst>>,
 }
 
-/// Implementation of the `To` trait for ToClosure
+/// Implementation of the `To` trait for ToClosure.
 ///
 /// This enables calling the wrapped closure with a destination reference.
 impl<Dst, Ret, Fun> To<Dst, Ret> for ToClosure<Dst, Ret, Fun>
@@ -33,6 +37,7 @@ where
     ///
     /// # Arguments
     /// * `out` - Mutable reference to the destination
+    /// See the tutorial in [readme.md] for examples and more explanations.
     fn to(self, out: &mut Dst) -> Ret {
         (self.fun)(out)
     }
@@ -48,7 +53,24 @@ where
 /// * `Ret` - The return type of the closure
 /// * `Fun` - The closure type that implements `FnOnce(&mut Dst) -> Ret`
 ///
-/// See the tutorial in [readme.me]..
+/// See the tutorial in the [crate documentation](crate) for more examples and more explanations.
+/// # Example
+/// ```
+/// # use rosenpass_to::with_destination;
+/// use crate::rosenpass_to::To;
+/// let my_origin_data: [u8; 16]= [2; 16];
+/// let times_two = with_destination( move |dst: &mut [u8; 16]| {
+///     for (dst, org) in dst.iter_mut().zip(my_origin_data.iter()) {
+///         *dst = dst.clone() * org;
+///     }
+/// });
+/// let mut dst: [u8; 16] = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15];
+/// times_two.to(&mut dst);
+/// for i in 0..16 {
+///     assert_eq!(dst[i], (2 * i) as u8);
+/// }
+///
+/// ```
 pub fn with_destination<Dst, Ret, Fun>(fun: Fun) -> impl To<Dst, Ret>
 where
     Dst: ?Sized,

util/src/build.rs

@@ -78,8 +78,8 @@ pub trait Build<T>: Sized {
 
 /// A type that can be incrementally built from a type that can [Build] it
 ///
-/// This is similar to an option, where [Self::Void] is [std::Option::None],
-/// [Self::Product] is [std::Option::Some], except that there is a third
+/// This is similar to an option, where [Self::Void] is [std::option::Option::None],
+/// [Self::Product] is [std::option::Option::Some], except that there is a third
 /// intermediate state [Self::Builder] that represents a Some/Product value
 /// in the process of being made.
 ///
@@ -508,9 +508,9 @@ where
         matches!(self, Self::Void)
     }
 
-    /// Returns `true` if the construction site is [`InProgress`].
+    /// Returns `true` if the construction site is in the [`Builder`] phase.
     ///
-    /// [`InProgress`]: ConstructionSite::InProgress
+    /// [`Builder`]: ConstructionSite::Builder
     ///
     /// # Examples
     ///
@@ -541,9 +541,10 @@ where
         matches!(self, Self::Builder(..))
     }
 
-    /// Returns `true` if the construction site is [`Done`].
+    /// Returns `true` if the construction site is in the [`Product`] phase and
+    /// is therefore done.
     ///
-    /// [`Done`]: ConstructionSite::Done
+    /// [`Product`]: ConstructionSite::Product
     ///
     /// # Examples
     ///

util/src/controlflow.rs

@@ -1,4 +1,4 @@
-/// A collection of control flow utility macros
+//! A collection of control flow utility macros
 
 #[macro_export]
 /// A simple for loop to repeat a $body a number of times
@@ -33,7 +33,7 @@ macro_rules! repeat {
 ///     0
 /// }
 /// assert_eq!(test_fn(), 0);
-
+///
 /// fn test_fn2() -> i32 {
 ///     return_unless!(false, 1);
 ///     0
@@ -65,7 +65,7 @@ macro_rules! return_unless {
 ///     0
 /// }
 /// assert_eq!(test_fn(), 1);
-
+///
 /// fn test_fn2() -> i32 {
 ///     return_if!(false, 1);
 ///     0
@@ -98,7 +98,7 @@ macro_rules! return_if {
 ///     sum += 1;
 /// }
 /// assert_eq!(sum, 5);
-
+///
 /// let mut sum = 0;
 /// 'one: for _ in 0..10 {
 ///     for j in 0..20 {
@@ -134,7 +134,7 @@ macro_rules! break_if {
 ///     sum += 1;
 /// }
 /// assert_eq!(sum, 9);
-
+///
 /// let mut sum = 0;
 /// 'one: for i in 0..10 {
 ///     continue_if!(i == 5, 'one);

util/src/fd.rs

@@ -89,6 +89,30 @@ pub fn claim_fd_inplace(fd: RawFd) -> rustix::io::Result<OwnedFd> {
 ///
 /// Will panic if the given file descriptor is negative of or larger than
 /// the file descriptor numbers permitted by the operating system.
+///
+/// # Example
+/// ```
+/// # use std::fs::File;
+/// # use std::io::Read;
+/// # use std::os::unix::io::{AsRawFd, FromRawFd};
+/// # use std::os::fd::IntoRawFd;
+/// # use rustix::fd::AsFd;
+/// # use rosenpass_util::fd::mask_fd;
+///
+/// // Open a temporary file
+/// let fd = tempfile::tempfile().unwrap().into_raw_fd();
+/// assert!(fd >= 0);
+///
+/// // Mask the file descriptor
+/// mask_fd(fd).unwrap();
+///
+/// // Verify the file descriptor now points to `/dev/null`
+/// // Reading from `/dev/null` always returns 0 bytes
+/// let mut replaced_file = unsafe { File::from_raw_fd(fd) };
+/// let mut buffer = [0u8; 4];
+/// let bytes_read = replaced_file.read(&mut buffer).unwrap();
+/// assert_eq!(bytes_read, 0);
+/// ```
 pub fn mask_fd(fd: RawFd) -> rustix::io::Result<()> {
     // Safety: because the OwnedFd resulting from OwnedFd::from_raw_fd is wrapped in a Forgetting,
     // it never gets dropped, meaning that fd is never closed and thus outlives the OwnedFd
@@ -286,14 +310,14 @@ where
     }
 }
 
-/// Distinguish different socket address familys; e.g. IP and unix sockets
+/// Distinguish different socket address families; e.g. IP and unix sockets
 #[cfg(target_os = "linux")]
 pub trait GetSocketDomain {
     /// Error type returned by operations in this trait
     type Error;
     /// Retrieve the socket domain (address family)
     fn socket_domain(&self) -> Result<rustix::net::AddressFamily, Self::Error>;
-    /// Alias for [socket_domain]
+    /// Alias for [Self::socket_domain]
     fn socket_address_family(&self) -> Result<rustix::net::AddressFamily, Self::Error> {
         self.socket_domain()
     }
@@ -320,9 +344,67 @@ where
 pub trait GetUnixSocketType {
     /// Error type returned by operations in this trait
     type Error;
-    /// Check if the socket is a unix stream socket
+
+    /// Checks whether the socket is a Unix stream socket.
+    ///
+    /// # Returns
+    /// - `Ok(true)` if the socket is a Unix stream socket.
+    /// - `Ok(false)` if the socket is not a Unix stream socket.
+    /// - `Err(Self::Error)` if there is an error while performing the check.
+    ///
+    /// # Examples
+    /// ```
+    /// # use std::fs::File;
+    /// # use std::os::fd::{AsFd, BorrowedFd};
+    /// # use std::os::unix::net::UnixListener;
+    /// # use tempfile::NamedTempFile;
+    /// # use rosenpass_util::fd::GetUnixSocketType;
+    /// let f = {
+    ///     // Generate a temp file and take its path
+    ///     // Remove the temp file
+    ///     // Create a unix socket on the temp path that is not unused
+    ///     let temp_file = NamedTempFile::new().unwrap();
+    ///     let socket_path = temp_file.path().to_owned();
+    ///     std::fs::remove_file(&socket_path).unwrap();
+    ///     UnixListener::bind(socket_path).unwrap()
+    /// };
+    /// assert!(matches!(f.as_fd().is_unix_stream_socket(), Ok(true)));
+    /// ```
     fn is_unix_stream_socket(&self) -> Result<bool, Self::Error>;
     /// Returns Ok(()) only if the underlying socket is a unix stream socket
+    /// # Examples
+    /// ```
+    /// # use std::fs::File;
+    /// # use std::os::fd::{AsFd, BorrowedFd};
+    /// # use std::os::unix::net::{UnixDatagram, UnixListener};
+    /// # use tempfile::NamedTempFile;
+    /// # use rosenpass_util::fd::GetUnixSocketType;
+    /// let f = {
+    ///     // Generate a temp file and take its path
+    ///     // Remove the temp file
+    ///     // Create a unix socket on the temp path that is not unused
+    ///     let temp_file = NamedTempFile::new().unwrap();
+    ///     let socket_path = temp_file.path().to_owned();
+    ///     std::fs::remove_file(&socket_path).unwrap();
+    ///     UnixListener::bind(socket_path).unwrap()
+    /// };
+    /// assert!(matches!(f.as_fd().demand_unix_stream_socket(), Ok(())));
+    /// // Error if the FD is a file
+    /// let temp_file = NamedTempFile::new().unwrap();
+    /// assert_eq!(temp_file.as_fd().demand_unix_stream_socket().err().unwrap().to_string(),
+    ///  "Socket operation on non-socket (os error 88)"
+    /// );
+    /// // Error if the FD is a Unix stream with a wrong mode (e.g. Datagram)
+    /// let f = {
+    ///     let temp_file = NamedTempFile::new().unwrap();
+    ///     let socket_path = temp_file.path().to_owned();
+    ///     std::fs::remove_file(&socket_path).unwrap();
+    ///     UnixDatagram::bind(socket_path).unwrap()
+    /// };
+    /// assert_eq!(f.as_fd().demand_unix_stream_socket().err().unwrap().to_string(),
+    ///  "Expected unix socket in stream mode, but mode is SocketType(2)"
+    /// );
+    /// ```
     fn demand_unix_stream_socket(&self) -> anyhow::Result<()>;
 }
 
@@ -352,16 +434,65 @@ where
 #[cfg(target_os = "linux")]
 /// Distinguish between different network socket protocols (e.g. tcp, udp)
 pub trait GetSocketProtocol {
-    /// Retrieve the socket protocol
+    /// Retrieves the socket's protocol.
+    ///
+    /// # Returns
+    /// - `Ok(Some(Protocol))`: The protocol of the socket if available.
+    /// - `Ok(None)`: If the protocol information is unavailable.
+    /// - `Err(rustix::io::Errno)`: If an error occurs while retrieving the protocol.
+    ///
+    /// # Examples
+    /// ```
+    /// # use std::net::UdpSocket;
+    /// # use std::os::fd::{AsFd, AsRawFd};
+    /// # use rosenpass_util::fd::GetSocketProtocol;
+    /// let socket = UdpSocket::bind("127.0.0.1:0")?;
+    /// assert_eq!(socket.as_fd().socket_protocol().unwrap().unwrap(), rustix::net::ipproto::UDP);
+    /// # Ok::<(), std::io::Error>(())
+    /// ```
     fn socket_protocol(&self) -> Result<Option<rustix::net::Protocol>, rustix::io::Errno>;
     /// Check if the socket is a udp socket
+    ///
+    /// # Examples
+    /// ```
+    /// # use std::net::UdpSocket;
+    /// # use std::net::TcpListener;
+    /// # use std::os::fd::{AsFd, AsRawFd};
+    /// # use rosenpass_util::fd::GetSocketProtocol;
+    /// let socket = UdpSocket::bind("127.0.0.1:0")?;
+    /// assert!(socket.as_fd().is_udp_socket().unwrap());
+    ///
+    /// let socket = TcpListener::bind("127.0.0.1:0")?;
+    /// assert!(!socket.as_fd().is_udp_socket().unwrap());
+    /// # Ok::<(), std::io::Error>(())
+    /// ```
     fn is_udp_socket(&self) -> Result<bool, rustix::io::Errno> {
         self.socket_protocol()?
             .map(|p| p == rustix::net::ipproto::UDP)
             .unwrap_or(false)
             .ok()
     }
-    /// Return Ok(()) only if the socket is a udp socket
+
+    /// Ensures that the socket is a UDP socket, returning an error otherwise.
+    ///
+    /// # Returns
+    /// - `Ok(())` if the socket is a UDP socket.
+    /// - `Err(anyhow::Error)` if the socket is not a UDP socket or if an error occurs retrieving the socket protocol.
+    ///
+    /// # Examples
+    /// ```
+    /// # use std::net::UdpSocket;
+    /// # use std::net::TcpListener;
+    /// # use std::os::fd::{AsFd, AsRawFd};
+    /// # use rosenpass_util::fd::GetSocketProtocol;
+    /// let socket = UdpSocket::bind("127.0.0.1:0")?;
+    /// assert!(matches!(socket.as_fd().demand_udp_socket(), Ok(())));
+    ///
+    /// let socket = TcpListener::bind("127.0.0.1:0")?;
+    /// assert_eq!(socket.as_fd().demand_udp_socket().unwrap_err().to_string(),
+    ///     "Not a udp socket, instead socket protocol is: Protocol(6)");
+    /// # Ok::<(), std::io::Error>(())
+    /// ```
     fn demand_udp_socket(&self) -> anyhow::Result<()> {
         match self.socket_protocol() {
             Ok(Some(rustix::net::ipproto::UDP)) => Ok(()),

util/src/io.rs

@@ -244,7 +244,6 @@
 use std::{borrow::Borrow, io};
 
 use anyhow::ensure;
-use zerocopy::AsBytes;
 
 /// Generic trait for accessing [std::io::Error::kind]
 ///

util/src/lib.rs

@@ -22,7 +22,7 @@ pub mod io;
 pub mod length_prefix_encoding;
 /// Memory manipulation and allocation utilities.
 pub mod mem;
-/// MIO integration utilities.
+/// [MIO (Metal I/O)](https://docs.rs/crate/mio/) integration utilities.
 pub mod mio;
 /// Extended Option type functionality.
 pub mod option;

util/src/mem.rs

@@ -1,10 +1,33 @@
+//!
+//! This module provides functions for copying data, concatenating byte arrays,
+//! and various traits and types that help manage values, including preventing
+//! drops, discarding results, and swapping values.
+
 use std::borrow::{Borrow, BorrowMut};
 use std::cmp::min;
 use std::mem::{forget, swap};
 use std::ops::{Deref, DerefMut};
 
-/// Concatenate two byte arrays
 // TODO: Zeroize result?
+/// Concatenate multiple byte slices into a fixed-size byte array.
+///
+/// # Panics
+///
+/// Panics if the concatenated length does not match the declared length.
+///
+/// # Examples
+///
+/// ```rust
+/// use rosenpass_util::cat;
+/// let arr = cat!(6; b"abc", b"def");
+/// assert_eq!(&arr, b"abcdef");
+///
+/// let err = std::panic::catch_unwind(|| cat!(5; b"abc", b"def"));
+/// assert!(matches!(err, Err(_)));
+///
+/// let err = std::panic::catch_unwind(|| cat!(7; b"abc", b"def"));
+/// assert!(matches!(err, Err(_)));
+/// ```
 #[macro_export]
 macro_rules! cat {
     ($len:expr; $($toks:expr),+) => {{
@@ -22,12 +45,37 @@ macro_rules! cat {
 }
 
 // TODO: consistent inout ordering
-/// Copy all bytes from `src` to `dst`. The lengths must match.
+/// Copy bytes from `src` to `dst`, requiring equal lengths.
+///
+/// # Panics
+///
+/// Panics if lengths differ.
+///
+/// # Examples
+///
+/// ```rust
+/// use rosenpass_util::mem::cpy;
+/// let src = [1, 2, 3];
+/// let mut dst = [0; 3];
+/// cpy(&src, &mut dst);
+/// assert_eq!(dst, [1, 2, 3]);
+/// ```
 pub fn cpy<T: BorrowMut<[u8]> + ?Sized, F: Borrow<[u8]> + ?Sized>(src: &F, dst: &mut T) {
     dst.borrow_mut().copy_from_slice(src.borrow());
 }
 
-/// Copy from `src` to `dst`. If `src` and `dst` are not of equal length, copy as many bytes as possible.
+/// Copy from `src` to `dst`. If `src` and `dst` are not of equal length,
+/// copy as many bytes as possible.
+///
+/// # Examples
+///
+/// ```rust
+/// use rosenpass_util::mem::cpy_min;
+/// let src = [1, 2, 3, 4];
+/// let mut dst = [0; 2];
+/// cpy_min(&src, &mut dst);
+/// assert_eq!(dst, [1, 2]);
+/// ```
 pub fn cpy_min<T: BorrowMut<[u8]> + ?Sized, F: Borrow<[u8]> + ?Sized>(src: &F, dst: &mut T) {
     let src = src.borrow();
     let dst = dst.borrow_mut();
@@ -35,20 +83,30 @@ pub fn cpy_min<T: BorrowMut<[u8]> + ?Sized, F: Borrow<[u8]> + ?Sized>(src: &F, d
     dst[..len].copy_from_slice(&src[..len]);
 }
 
-/// Wrapper type to inhibit calling [std::mem::Drop] when the underlying variable is freed
+/// Wrapper type to inhibit calling [std::mem::Drop] when the underlying
+/// variable is freed
+///
+/// # Examples
+///
+/// ```rust
+/// use rosenpass_util::mem::Forgetting;
+/// let f = Forgetting::new(String::from("hello"));
+/// assert_eq!(&*f, "hello");
+/// let val = f.extract();
+/// assert_eq!(val, "hello");
+/// ```
 #[derive(PartialEq, Eq, PartialOrd, Ord, Debug, Clone, Default)]
 pub struct Forgetting<T> {
     value: Option<T>,
 }
 
 impl<T> Forgetting<T> {
-    /// Creates a new `Forgetting<T>` instance containing the given value.
+    /// Create a new `Forgetting` wrapping `value`.
     pub fn new(value: T) -> Self {
-        let value = Some(value);
-        Self { value }
+        Self { value: Some(value) }
     }
 
-    /// Extracts and returns the contained value, consuming self.
+    /// Consume and return the inner value.
     pub fn extract(mut self) -> T {
         let mut value = None;
         swap(&mut value, &mut self.value);
@@ -97,6 +155,13 @@ impl<T> Drop for Forgetting<T> {
 }
 
 /// A trait that provides a method to discard a value without explicitly handling its results.
+///
+/// # Examples
+///
+/// ```rust
+/// # use rosenpass_util::mem::DiscardResultExt;
+/// let result: () = (|| { return 42 })().discard_result(); // Just discard
+/// ```
 pub trait DiscardResultExt {
     /// Consumes and discards a value without doing anything with it.
     fn discard_result(self);
@@ -107,8 +172,16 @@ impl<T> DiscardResultExt for T {
 }
 
 /// Trait that provides a method to explicitly forget values.
+///
+/// # Examples
+///
+/// ```rust
+/// # use rosenpass_util::mem::ForgetExt;
+/// let s = String::from("no drop");
+/// s.forget(); // destructor not run
+/// ```
 pub trait ForgetExt {
-    /// Consumes and forgets a value, preventing its destructor from running.
+    /// Forget the value.
     fn forget(self);
 }
 
@@ -119,10 +192,23 @@ impl<T> ForgetExt for T {
 }
 
 /// Extension trait that provides methods for swapping values.
+///
+/// # Examples
+///
+/// ```rust
+/// use rosenpass_util::mem::SwapWithExt;
+/// let mut x = 10;
+/// let mut y = x.swap_with(20);
+/// assert_eq!(x, 20);
+/// assert_eq!(y, 10);
+/// y.swap_with_mut(&mut x);
+/// assert_eq!(x, 10);
+/// assert_eq!(y, 20);
+/// ```
 pub trait SwapWithExt {
-    /// Takes ownership of `other` and swaps its value with `self`, returning the original value.
+    /// Swap values and return the old value of `self`.
     fn swap_with(&mut self, other: Self) -> Self;
-    /// Swaps the values between `self` and `other` in place.
+    /// Swap values in place with another mutable reference.
     fn swap_with_mut(&mut self, other: &mut Self);
 }
 
@@ -138,8 +224,18 @@ impl<T> SwapWithExt for T {
 }
 
 /// Extension trait that provides methods for swapping values with default values.
+///
+/// # Examples
+///
+/// ```rust
+/// # use rosenpass_util::mem::SwapWithDefaultExt;
+/// let mut s = String::from("abc");
+/// let old = s.swap_with_default();
+/// assert_eq!(old, "abc");
+/// assert_eq!(s, "");
+/// ```
 pub trait SwapWithDefaultExt {
-    /// Takes the current value and replaces it with the default value, returning the original.
+    /// Swap with `Self::default()`.
     fn swap_with_default(&mut self) -> Self;
 }
 
@@ -150,6 +246,26 @@ impl<T: Default> SwapWithDefaultExt for T {
 }
 
 /// Extension trait that provides a method to explicitly move values.
+///
+/// # Examples
+///
+/// ```rust
+/// # use std::rc::Rc;
+/// use rosenpass_util::mem::MoveExt;
+/// let val = 42;
+/// let another_val = val.move_here();
+/// assert_eq!(another_val, 42);
+/// // val is now inaccessible
+///
+/// let value = Rc::new(42);
+/// let clone = Rc::clone(&value);
+///
+/// assert_eq!(Rc::strong_count(&value), 2);
+///
+/// clone.move_here(); // this will drop the second reference
+///
+/// assert_eq!(Rc::strong_count(&value), 1);
+/// ```
 pub trait MoveExt {
     /// Deliberately move the value
     ///
@@ -163,3 +279,29 @@ impl<T: Sized> MoveExt for T {
         self
     }
 }
+
+#[cfg(test)]
+mod test_forgetting {
+    use crate::mem::Forgetting;
+    use std::sync::atomic::AtomicBool;
+    use std::sync::atomic::Ordering::SeqCst;
+    use std::sync::Arc;
+
+    #[test]
+    fn test_forgetting() {
+        let drop_was_called = Arc::new(AtomicBool::new(false));
+        struct SetFlagOnDrop(Arc<AtomicBool>);
+        impl Drop for SetFlagOnDrop {
+            fn drop(&mut self) {
+                self.0.store(true, SeqCst);
+            }
+        }
+        drop(SetFlagOnDrop(drop_was_called.clone()));
+        assert!(drop_was_called.load(SeqCst));
+        // reset flag and use Forgetting
+        drop_was_called.store(false, SeqCst);
+        let forgetting = Forgetting::new(SetFlagOnDrop(drop_was_called.clone()));
+        drop(forgetting);
+        assert_eq!(drop_was_called.load(SeqCst), false);
+    }
+}

util/src/mio/mio.rs

@@ -6,7 +6,7 @@ use crate::{
     result::OkExt,
 };
 
-/// Module containing I/O interest flags for Unix operations
+/// Module containing I/O interest flags for Unix operations (see also: [mio::Interest])
 pub mod interest {
     use mio::Interest;
 
@@ -20,9 +20,48 @@ pub mod interest {
     pub const RW: Interest = R.add(W);
 }
 
-/// Extension trait providing additional functionality for Unix listener
+/// Extension trait providing additional functionality for a Unix listener
+///
+/// # Example
+///
+/// ```rust
+/// use mio::net::{UnixListener, UnixStream};
+/// use rosenpass_util::mio::{UnixListenerExt, UnixStreamExt};
+///
+/// use std::os::unix::io::{AsRawFd, IntoRawFd, RawFd};
+/// use std::path::Path;
+///
+/// // This would be the UDS created by an external source
+/// let socket_path = "/tmp/rp_mio_uds_test_socket";
+/// if Path::new(socket_path).exists() {
+///     std::fs::remove_file(socket_path).expect("Failed to remove existing socket");
+/// }
+///
+/// // An extended MIO listener can then be created by claiming the existing socket
+/// // Note that the original descriptor is not reused, but copied before claiming it here
+/// let listener = UnixListener::bind(socket_path).unwrap();
+/// let listener_fd: RawFd = listener.as_raw_fd();
+/// let ext_listener = <UnixListener as UnixListenerExt>
+///     ::claim_fd(listener_fd).expect("Failed to claim_fd for ext_listener socket");
+///
+/// // Similarly, "client" connections can be established by claiming existing sockets
+/// // Note that in this case, the file descriptor will be reused (safety implications!)
+/// let stream = UnixStream::connect(socket_path).unwrap();
+/// let stream_fd = stream.into_raw_fd();
+/// let ext_stream = <UnixStream as UnixStreamExt>
+///     ::claim_fd_inplace(stream_fd).expect("Failed to claim_fd_inplace for ext_stream socket");
+///
+/// // Handle accepted connections...
+/// ext_listener.accept().expect("Failed to accept incoming connection");
+///
+/// // Send or receive messages ...
+///
+/// // Cleanup, shutdown etc. goes here ...
+/// std::fs::remove_file(socket_path).unwrap();
+/// ```
 pub trait UnixListenerExt: Sized {
     /// Creates a new Unix listener by claiming ownership of a raw file descriptor
+    /// (see [fd::claim_fd](crate::fd::claim_fd))
     fn claim_fd(fd: RawFd) -> anyhow::Result<Self>;
 }
 
@@ -36,15 +75,17 @@ impl UnixListenerExt for UnixListener {
     }
 }
 
-/// Extension trait providing additional functionality for Unix streams
+/// Extension trait providing additional functionality for a Unix stream
 pub trait UnixStreamExt: Sized {
     /// Creates a new Unix stream from an owned file descriptor
     fn from_fd(fd: OwnedFd) -> anyhow::Result<Self>;
 
     /// Claims ownership of a raw file descriptor and creates a new Unix stream
+    /// (see [fd::claim_fd](crate::fd::claim_fd))
     fn claim_fd(fd: RawFd) -> anyhow::Result<Self>;
 
     /// Claims ownership of a raw file descriptor in place and creates a new Unix stream
+    ///  (see [fd::claim_fd_inplace](crate::fd::claim_fd_inplace))
     fn claim_fd_inplace(fd: RawFd) -> anyhow::Result<Self>;
 }
 

util/src/mio/uds_recv_fd.rs

@@ -12,6 +12,58 @@ use crate::fd::{claim_fd_inplace, IntoStdioErr};
 /// A wrapper around a socket that combines reading from the socket with tracking
 /// received file descriptors. Limits the maximum number of file descriptors that
 /// can be received in a single read operation via the `MAX_FDS` parameter.
+///
+/// # Example
+///
+/// ```rust
+/// use std::collections::VecDeque;
+/// use std::io::Cursor;
+/// use std::io::Read;
+/// use std::os::fd::AsRawFd;
+/// use std::os::fd::OwnedFd;
+///
+/// use mio::net::UnixStream;
+/// use rosenpass_util::mio::ReadWithFileDescriptors;
+/// use rosenpass_util::io::TryIoResultKindHintExt;
+///
+/// const MAX_REQUEST_FDS : usize = 2; // Limit to 2 descriptors per read operation
+/// let mut read_fd_buffer = VecDeque::<OwnedFd>::new(); // File descriptor queue
+///
+/// // In this case, the unused writable end of the connection can be ignored
+/// let (io_stream, _) = UnixStream::pair().expect("failed to create socket pair");
+///
+/// // Wait until the output stream is writable...
+///
+/// // Wrap the socket to start tracking received file descriptors
+/// let mut fd_passing_sock = ReadWithFileDescriptors::<MAX_REQUEST_FDS, UnixStream, _, _>::new(
+///	&io_stream,
+///	&mut read_fd_buffer,
+/// );
+////
+/// // Simulated reads; the actual operations will depend on the protocol (implementation details)
+/// let mut recv_buffer = Vec::<u8>::new();
+/// let bytes_read = fd_passing_sock.read(&mut recv_buffer[..]).expect("error reading from socket");
+/// assert_eq!(bytes_read, 0);
+/// assert_eq!(&recv_buffer[..bytes_read], []);
+///
+/// // Alternatively, it's possible to use the try_io_err_kind_hint utility provided by this crate
+/// match fd_passing_sock.read(&mut recv_buffer).try_io_err_kind_hint() {
+///     Err(_) => {
+///         // Handle errors here ...
+///     }
+///     Ok(result) => {
+///         // Process messages here ...
+///         assert_eq!(0, result); // Nothing to read in this example
+///     }
+/// };
+///
+/// // The wrapped components can still be accessed
+/// assert_eq!(fd_passing_sock.socket().as_raw_fd(), io_stream.as_raw_fd());
+/// let (socket, fd_queue) = fd_passing_sock.into_parts();
+/// assert_eq!(socket.as_raw_fd(), io_stream.as_raw_fd());
+///
+/// // Shutdown, cleanup, etc. goes here ...
+/// ```
 pub struct ReadWithFileDescriptors<const MAX_FDS: usize, Sock, BorrowSock, BorrowFds>
 where
     Sock: FdPassingExt,

util/src/result.rs

@@ -1,6 +1,24 @@
 use std::convert::Infallible;
 
 /// Try block basically…returns a result and allows the use of the question mark operator inside
+///
+/// # Examples
+/// ```rust
+/// # use anyhow::Result;
+/// # use rosenpass_util::attempt;
+/// let result: Result<i32> = attempt!({
+///     let x = 42;
+///     Ok(x)
+/// });
+///
+/// assert_eq!(result.unwrap(), 42);
+///
+/// let error_result: Result<()> = attempt!({
+///     Err(anyhow::anyhow!("some error"))
+/// });
+///
+/// assert!(error_result.is_err());
+/// ```
 #[macro_export]
 macro_rules! attempt {
     ($block:expr) => {
@@ -9,6 +27,19 @@ macro_rules! attempt {
 }
 
 /// Trait for the ok operation, which provides a way to convert a value into a Result
+/// # Examples
+/// ```rust
+/// # use rosenpass_util::result::OkExt;
+/// let value: i32 = 42;
+/// let result: Result<i32, &str> = value.ok();
+///
+/// assert_eq!(result, Ok(42));
+///
+/// let value = "hello";
+/// let result: Result<&str, &str> = value.ok();
+///
+/// assert_eq!(result, Ok("hello"));
+/// ```
 pub trait OkExt<E>: Sized {
     /// Wraps a value in a Result::Ok variant
     fn ok(self) -> Result<Self, E>;
@@ -26,6 +57,11 @@ impl<T, E> OkExt<E> for T {
 /// the function will not panic.
 ///
 /// Implementations must not panic.
+/// # Examples
+/// ```
+/// # use rosenpass_util::result::GuaranteedValue;
+/// let x:u32 = 10u8.try_into().guaranteed();
+/// ```
 pub trait GuaranteedValue {
     /// The value type that will be returned by guaranteed()
     type Value;

util/src/typenum.rs

@@ -3,7 +3,23 @@ use typenum::int::{NInt, PInt, Z0};
 use typenum::marker_traits as markers;
 use typenum::uint::{UInt, UTerm};
 
-/// Convenience macro to convert type numbers to constant integers
+/// Convenience macro to convert [`typenum`] type numbers to constant integers.
+///
+/// This macro takes a [`typenum`] type-level integer (like `U5`, `P3`, or `N7`)
+/// and converts it into its equivalent constant integer value at compile time.
+/// By default, it converts to a suitable unsigned integer type, but you can
+/// specify a target type explicitly using `typenum2const!(Type as i32)`,
+/// for example.
+///
+/// # Examples
+///
+/// ```rust
+/// # use typenum::consts::U10;
+/// # use rosenpass_util::typenum2const;
+///
+/// const TEN: u32 = typenum2const!(U10 as u32);
+/// assert_eq!(TEN, 10);
+/// ```
 #[macro_export]
 macro_rules! typenum2const {
     ($val:ty) => {
@@ -14,35 +30,80 @@ macro_rules! typenum2const {
     };
 }
 
-/// Trait implemented by constant integers to facilitate conversion to constant integers
+/// A trait implemented by type-level integers to facilitate their conversion
+/// into constant values.
+///
+/// Types from the [`typenum`] crate (like `U5`, `P3`, or `N7`) can implement
+/// `IntoConst` to produce a compile-time constant integer of the specified
+/// type. This trait is part of the underlying mechanism used by the
+/// [`crate::typenum2const`] macro.
+///
+/// # Examples
+///
+/// ```rust
+/// use rosenpass_util::typenum2const;
+/// use typenum::consts::U42;
+/// use rosenpass_util::typenum::IntoConst;
+///
+/// // Directly using IntoConst:
+/// const VALUE: u64 = <U42 as IntoConst<u64>>::VALUE;
+/// assert_eq!(VALUE, 42);
+///
+/// // Or via the macro:
+/// const VALUE_MACRO: u64 = typenum2const!(U42 as u64);
+/// assert_eq!(VALUE_MACRO, 42);
+/// ```
 pub trait IntoConst<T> {
-    /// The constant value after conversion
+    /// The constant value after conversion.
     const VALUE: T;
 }
 
 #[allow(dead_code)]
+/// Internal struct for applying a negative sign to an unsigned type-level integer during conversion.
+///
+/// This is part of the implementation detail for signed conversions. It uses
+/// [`AssociatedUnsigned`] to determine the underlying unsigned type and negates its value.
 struct ConstApplyNegSign<T: AssociatedUnsigned, Param: IntoConst<<T as AssociatedUnsigned>::Type>>(
     *const T,
     *const Param,
 );
 
 #[allow(dead_code)]
+/// Internal struct for applying a positive sign to an unsigned type-level integer during conversion.
+///
+/// This is used as part of converting a positive signed type-level integer to its runtime integer
+/// value, ensuring that the correct unsigned representation is known via [`AssociatedUnsigned`].
 struct ConstApplyPosSign<T: AssociatedUnsigned, Param: IntoConst<<T as AssociatedUnsigned>::Type>>(
     *const T,
     *const Param,
 );
 
 #[allow(dead_code)]
-struct ConstLshift<T, Param: IntoConst<T>, const SHIFT: i32>(*const T, *const Param); // impl IntoConst<T>
+/// Internal struct representing a left-shift operation on a type-level integer.
+///
+/// Used as part of compile-time computations. `SHIFT` determines how many bits the value will be
+/// shifted to the left.
+struct ConstLshift<T, Param: IntoConst<T>, const SHIFT: i32>(*const T, *const Param);
 
 #[allow(dead_code)]
-struct ConstAdd<T, Lhs: IntoConst<T>, Rhs: IntoConst<T>>(*const T, *const Lhs, *const Rhs); // impl IntoConst<T>
+/// Internal struct representing an addition operation between two type-level integers.
+///
+/// `ConstAdd` is another building block for compile-time arithmetic on type-level integers before
+/// their conversion to runtime constants.
+struct ConstAdd<T, Lhs: IntoConst<T>, Rhs: IntoConst<T>>(*const T, *const Lhs, *const Rhs);
 
-/// Assigns an unsigned type to a signed type
+/// Associates an unsigned type with a signed type, enabling conversions between signed and unsigned
+/// representations of compile-time integers.
+///
+/// This trait is used internally to facilitate the conversion of signed [`typenum`] integers by
+/// referencing their underlying unsigned representation.
 trait AssociatedUnsigned {
+    /// The associated unsigned type.
     type Type;
 }
 
+/// Internal macro implementing the [`IntoConst`] trait for a given mapping from a type-level integer
+/// to a concrete integer type.
 macro_rules! impl_into_const {
     ( $from:ty as $to:ty := $impl:expr) => {
         impl IntoConst<$to> for $from {
@@ -51,6 +112,10 @@ macro_rules! impl_into_const {
     };
 }
 
+/// Internal macro implementing common `IntoConst` logic for various numeric types.
+///
+/// It sets up `Z0`, `B0`, `B1`, `UTerm`, and also provides default implementations for
+/// `ConstLshift` and `ConstAdd`.
 macro_rules! impl_numeric_into_const_common {
     ($type:ty) => {
         impl_into_const! { Z0 as $type := 0 }
@@ -73,6 +138,10 @@ macro_rules! impl_numeric_into_const_common {
     };
 }
 
+/// Internal macro implementing `IntoConst` for unsigned integer types.
+///
+/// It sets up conversions for multiple unsigned integer target types and
+/// provides the positive sign application implementation.
 macro_rules! impl_numeric_into_const_unsigned {
     ($($to_list:ty),*) =>  {
         $( impl_numeric_into_const_unsigned! { @impl $to_list } )*
@@ -91,6 +160,9 @@ macro_rules! impl_numeric_into_const_unsigned {
     };
 }
 
+/// Internal macro implementing `IntoConst` for signed integer types.
+///
+/// It uses their associated unsigned types to handle positive and negative conversions correctly.
 macro_rules! impl_numeric_into_const_signed {
     ($($to_list:ty : $unsigned_list:ty),*) =>  {
         $( impl_numeric_into_const_signed! { @impl $to_list : $unsigned_list} )*
@@ -110,8 +182,7 @@ macro_rules! impl_numeric_into_const_signed {
         impl<Param: IntoConst<$unsigned>> IntoConst<$type> for ConstApplyNegSign<$type, Param> {
             const VALUE : $type =
                 if Param::VALUE == (1 as $unsigned).rotate_right(1) {
-                    // Handle the negative value without an associated positive value (e.g. -128
-                    // for i8)
+                    // Handling negative values at boundaries, such as i8::MIN
                     <$type>::MIN
                 } else {
                     -(Param::VALUE as $type)
@@ -122,10 +193,10 @@ macro_rules! impl_numeric_into_const_signed {
 
 impl_into_const! { B0 as bool := false }
 impl_into_const! { B1 as bool := true }
+
 impl_numeric_into_const_unsigned! { usize, u8, u16, u32, u64, u128 }
 impl_numeric_into_const_signed! { isize : usize, i8 : u8, i16 : u16, i32 : u32, i64 : u64, i128 : u128 }
 
-// Unsigned type numbers to const integers
 impl<Ret, Rest, Bit> IntoConst<Ret> for UInt<Rest, Bit>
 where
     Rest: IntoConst<Ret>,
@@ -133,26 +204,28 @@ where
     ConstLshift<Ret, Rest, 1>: IntoConst<Ret>,
     ConstAdd<Ret, ConstLshift<Ret, Rest, 1>, Bit>: IntoConst<Ret>,
 {
+    /// Converts an unsigned [`UInt`] typenum into its corresponding constant integer by
+    /// decomposing it into shifts and additions on its subparts.
     const VALUE: Ret = <ConstAdd<Ret, ConstLshift<Ret, Rest, 1>, Bit> as IntoConst<Ret>>::VALUE;
 }
 
-// Signed type numbers with positive sign to const integers
 impl<Ret, Unsigned> IntoConst<Ret> for PInt<Unsigned>
 where
     Ret: AssociatedUnsigned,
     Unsigned: markers::Unsigned + markers::NonZero + IntoConst<<Ret as AssociatedUnsigned>::Type>,
     ConstApplyPosSign<Ret, Unsigned>: IntoConst<Ret>,
 {
+    /// Converts a positive signed [`PInt`] typenum into its corresponding constant integer.
     const VALUE: Ret = <ConstApplyPosSign<Ret, Unsigned> as IntoConst<Ret>>::VALUE;
 }
 
-// Signed type numbers with negative sign to const integers
 impl<Ret, Unsigned> IntoConst<Ret> for NInt<Unsigned>
 where
     Ret: AssociatedUnsigned,
     Unsigned: markers::Unsigned + markers::NonZero + IntoConst<<Ret as AssociatedUnsigned>::Type>,
     ConstApplyNegSign<Ret, Unsigned>: IntoConst<Ret>,
 {
+    /// Converts a negative signed [`NInt`] typenum into its corresponding constant integer.
     const VALUE: Ret = <ConstApplyNegSign<Ret, Unsigned> as IntoConst<Ret>>::VALUE;
 }
 

util/src/zeroize/mod.rs

@@ -1,2 +1,23 @@
+//!
+//! This module provides an extension trait,
+//! [`ZeroizedExt`](crate::zeroize::ZeroizedExt), for all types implementing the
+//! `zeroize::Zeroize` trait.
+//! It introduces the [`zeroized`](crate::zeroize::ZeroizedExt::zeroized)
+//! method, which zeroizes a value in place and returns it, making it convenient
+//! for chaining operations and ensuring sensitive data is securely erased.
+//!
+//! # Examples
+//!
+//! ```rust
+//! use zeroize::Zeroize;
+//! use rosenpass_util::zeroize::ZeroizedExt;
+//!
+//! let mut value = String::from("hello");
+//! value.zeroize(); // Zeroizes in place
+//! assert_eq!(value, "");
+//!
+//! assert_eq!(String::from("hello").zeroized(), "");
+//! ```
+
 mod zeroized_ext;
 pub use zeroized_ext::*;