gnu: Add rust-packed-struct.

* gnu/packages/crates-io.scm (rust-packed-struct): New variable.

gnu/packages/crates-io.scm

@@ -30762,3 +30762,44 @@ (define-public rust-zoneinfo-compiled-0.4
     (description
      "This package provides a library for parsing compiled zoneinfo files.")
     (license license:expat)))
+
+(define-public rust-packed-struct
+  (package
+    (name "rust-packed-struct")
+    (version "0.3.0")
+    (source
+      (origin
+        (method url-fetch)
+        (uri (crate-uri "packed_struct" version))
+        (file-name
+	  (string-append name "-" version ".tar.gz"))
+        (sha256
+	  (base32
+	    "10b2fmxchmcigwagnhi42frj74dl02wyv0xwmbr9839qfh7gijlh"))))
+    (build-system cargo-build-system)
+    (arguments
+      `(#:cargo-inputs
+        (("rust-serde" ,rust-serde-1)
+         ("rust-serde-derive" ,rust-serde-derive-1))))
+    (home-page "http://www.hashmismatch.net/libraries/packed-struct/")
+    (synopsis "Binary-level structure packing and unpacking generator")
+    (description "This package provides bit-level packing an unpacking
+of structs.  The library provides a meta-programming approach, using
+attributes to define fields and how they should be packed.  The resulting
+trait implementations provide safe packing, unpacking and runtime debugging
+formatters with per-field documentation generated for each structure.
+
+@itemize
+@item Plain Rust structures, decorated with attributes
+@item MSB or LSB integers of user-defined bit widths
+@item Primitive enum code generation helper
+@item MSB0 or LSB0 bit positioning
+@item Documents the field's packing table
+@item Runtime packing visualization
+@item Nested packed types
+@item Arrays of packed structures as fields
+@item Reserved fields, their bits are always 0 or 1
+@end itemize")
+    ;; User can choose either license.
+    (license (list license:expat license:asl2.0))))
+