minicbor-lease adapter for encoding straight into a lease

Cargo.toml

@@ -92,7 +92,7 @@ leb128 = { version = "0.2.5", default-features = false }
 lpc55-pac = { version = "0.4", default-features = false }
 memchr = { version = "2.4", default-features = false }
 memoffset = { version = "0.6.5", default-features = false }
-minicbor = { version = "0.26.4", default-features = false }
+minicbor = { version = "2.1.1", default-features = false }
 multimap = { version = "0.8.3", default-features = false }
 nb = { version = "1", default-features = false }
 num = { version = "0.4", default-features = false }
@@ -163,6 +163,10 @@ tlvc-text = { git = "https://github.com/oxidecomputer/tlvc", default-features =
 transceiver-messages = { git = "https://github.com/oxidecomputer/transceiver-control/", default-features = false }
 vsc7448-pac = { git = "https://github.com/oxidecomputer/vsc7448", default-features = false }
 
+[patch.crates-io]
+# See https://gitlab.com/robigalia/ssmarshal/-/merge_requests/2
+ssmarshal = { git = "https://gitlab.com/de-vri-es/ssmarshal", rev = "10e90cbe389c8f07c52815857551a051946881ab" }
+
 [workspace.lints.rust]
 elided_lifetimes_in_paths = "warn"
 

lib/minicbor-lease/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "minicbor-lease"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+minicbor = { workspace = true }
+idol-runtime = { workspace = true }
+
+[lib]
+test = false
+doctest = false
+bench = false
+
+[lints]
+workspace = true

lib/minicbor-lease/src/lib.rs

@@ -0,0 +1,122 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+//! An adapter implementing [`minicbor::encode::write::Write`] for
+//! [`idol_runtime::Leased`] byte buffers.
+
+#![no_std]
+
+/// An adapter implementing [`minicbor::encode::write::Write`] for
+/// [`idol_runtime::Leased`] byte buffers.
+pub struct LeasedWriter<'lease, A>
+where
+    A: idol_runtime::AttributeWrite,
+{
+    lease: &'lease mut idol_runtime::Leased<A, [u8]>,
+    pos: usize,
+    ran_out_of_space: bool,
+}
+
+/// Errors returned by the [`minicbor::encode::write::Write`] implementation for
+/// [`LeasedWriter`].
+#[derive(Copy, Clone, PartialEq, Debug)]
+pub enum Error {
+    /// The other side of the lease has gone away.
+    WentAway,
+    /// Data could not be written as there was no room left in the lease.
+    EndOfLease,
+}
+
+impl core::fmt::Display for Error {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        f.write_str(match self {
+            Self::WentAway => "lease went away",
+            Self::EndOfLease => "end of lease",
+        })
+    }
+}
+
+impl<A> minicbor::encode::write::Write for LeasedWriter<'_, A>
+where
+    A: idol_runtime::AttributeWrite,
+{
+    type Error = Error;
+
+    fn write_all(&mut self, buf: &[u8]) -> Result<(), Self::Error> {
+        let Some(end) = self.pos.checked_add(buf.len()) else {
+            self.ran_out_of_space = true;
+            return Err(Error::EndOfLease);
+        };
+        if end >= self.lease.len() {
+            self.ran_out_of_space = true;
+            return Err(Error::EndOfLease);
+        }
+        self.lease
+            .write_range(self.pos..end, buf)
+            .map_err(|_| Error::WentAway)?;
+
+        self.pos += buf.len();
+
+        Ok(())
+    }
+}
+
+impl<'lease, A> LeasedWriter<'lease, A>
+where
+    A: idol_runtime::AttributeWrite,
+{
+    /// Returns a new `LeasedWriter` starting at byte 0 of the lease.
+    pub fn new(lease: &'lease mut idol_runtime::Leased<A, [u8]>) -> Self {
+        Self {
+            lease,
+            pos: 0,
+            ran_out_of_space: false,
+        }
+    }
+
+    /// Returns a new `LeasedWriter` starting at the specified byte position in
+    /// the lease.
+    ///
+    /// This is intended for cases where some data has already been written to
+    /// the lease.
+    pub fn starting_at(
+        position: usize,
+        lease: &'lease mut idol_runtime::Leased<A, [u8]>,
+    ) -> Self {
+        Self {
+            lease,
+            pos: position,
+            ran_out_of_space: false,
+        }
+    }
+
+    /// Returns the current byte position within the lease.
+    pub fn position(&self) -> usize {
+        self.pos
+    }
+
+    /// Borrows the underlying lease from the writer.
+    pub fn lease(&self) -> &idol_runtime::Leased<A, [u8]> {
+        self.lease
+    }
+
+    /// Returns the underlying lease, consuming the writer.
+    pub fn into_inner(self) -> &'lease mut idol_runtime::Leased<A, [u8]> {
+        self.lease
+    }
+
+    /// Returns `true` if the last `w
+    pub fn ran_out_of_space(&self) -> bool {
+        self.ran_out_of_space
+    }
+}
+
+impl From<Error> for idol_runtime::ClientError {
+    fn from(error: Error) -> Self {
+        match error {
+            Error::EndOfLease => idol_runtime::ClientError::BadLease,
+            Error::WentAway => idol_runtime::ClientError::WentAway,
+        }
+    }
+}

task/packrat/Cargo.toml

@@ -23,6 +23,7 @@ task-packrat-api = { path = "../packrat-api" }
 userlib = { path = "../../sys/userlib", features = ["panic-messages"] }
 snitch-core = { version = "0.1.0", path = "../../lib/snitch-core", optional = true, features = ["counters"] }
 minicbor = { workspace = true,  optional = true }
+minicbor-lease = { path = "../../lib/minicbor-lease", optional = true }
 
 [build-dependencies]
 anyhow.workspace = true
@@ -37,7 +38,7 @@ gimlet = ["drv-cpu-seq-api"]
 grapefruit = []
 boot-kmdb = []
 no-ipc-counters = ["idol/no-counters"]
-ereport = ["dep:drv-rng-api", "dep:snitch-core", "dep:minicbor", "dep:quote"]
+ereport = ["dep:drv-rng-api", "dep:snitch-core", "dep:minicbor", "dep:minicbor-lease", "dep:quote"]
 
 # This section is here to discourage RLS/rust-analyzer from doing test builds,
 # since test builds don't work for cross compilation.