rust/utils: Add Hexslice

Add a thin wrapper around [u8] to be able to represent an u8-slice as a
hex-string for Display and Serialize.

Acked-by: Qi Feng Huo <huoqif@cn.ibm.com>
Reviewed-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>

rust/utils/Cargo.toml

@@ -9,3 +9,4 @@ clap = { version ="4.1", features = ["derive", "wrap_help"] }
 libc = "0.2.49"
 log = { version = "0.4.6", features = ["std", "release_max_level_debug"] }
 pv = { path = "../pv" }
+serde = { version = "1.0.139"}

rust/utils/src/hexslice.rs

@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: MIT
+//
+// Copyright IBM Corp. 2024
+use serde::Serialize;
+
+/// Displays/Serializes an u8-slice into a Hex-string
+///
+/// Thin wrapper around an u8-slice.
+#[derive(Debug)]
+pub struct HexSlice<'a>(&'a [u8]);
+
+impl<'a> HexSlice<'a> {
+    /// Creates a [`HexSlice`] from the given value.
+    pub fn from<T>(s: &'a T) -> Self
+    where
+        T: ?Sized + AsRef<[u8]> + 'a,
+    {
+        s.into()
+    }
+}
+
+impl<'a, T> From<&'a T> for HexSlice<'a>
+where
+    T: ?Sized + AsRef<[u8]> + 'a,
+{
+    fn from(value: &'a T) -> Self {
+        Self(value.as_ref())
+    }
+}
+impl<'a> Serialize for HexSlice<'a> {
+    fn serialize<S>(&self, serializer: S) -> std::result::Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        serializer.serialize_str(&format!("{self:#}"))
+    }
+}
+
+impl std::fmt::Display for HexSlice<'_> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        if f.alternate() {
+            write!(f, "0x")?;
+        }
+        for byte in self.0 {
+            write!(f, "{:0>2x}", byte)?;
+        }
+        Ok(())
+    }
+}
+
+impl AsRef<[u8]> for HexSlice<'_> {
+    fn as_ref(&self) -> &[u8] {
+        self.0
+    }
+}

rust/utils/src/lib.rs

@@ -4,6 +4,7 @@
 //!
 //! Copyright IBM Corp. 2023, 2024
 mod cli;
+mod hexslice;
 mod log;
 mod tmpfile;
 
@@ -11,6 +12,7 @@ pub use crate::cli::CertificateOptions;
 pub use crate::cli::{get_reader_from_cli_file_arg, get_writer_from_cli_file_arg};
 pub use crate::cli::{print_cli_error, print_error};
 pub use crate::cli::{STDIN, STDOUT};
+pub use crate::hexslice::HexSlice;
 pub use crate::log::PvLogger;
 pub use crate::tmpfile::TemporaryDirectory;