cbor: support deriving en/decoder for arrays/maps from structs

Author: karalabe

Cargo.lock

@@ -18,7 +18,7 @@ rustdoc-args = ["--cfg", "docsrs"]
 default = []
 argon2 = ["dep:argon2"]
 async = ["dep:futures"]
-cbor = ["dep:thiserror"]
+cbor = ["dep:thiserror", "dep:darkbio-crypto-cbor-derive"]
 cose = ["cbor", "xhpke"]
 eddsa = ["pem", "dep:ed25519-dalek", "dep:sha2", "dep:signature"]
 hkdf = ["dep:hkdf", "dep:sha2"]
@@ -32,6 +32,7 @@ xdsa = ["pem", "eddsa", "mldsa", "x509", "dep:x509-parser"]
 xhpke = ["pem", "xdsa", "dep:generic-array", "dep:hpke", "dep:rand", "dep:rand_chacha", "dep:x-wing"]
 
 [dependencies]
+darkbio-crypto-cbor-derive = { version = "0.11.0", path = "src/cbor/derive", optional = true }
 age-core = { version = "0.11.0", optional = true }
 argon2 = { version = "0.5.3", optional = true }
 base64 = { version = "0.22.1", optional = true }

Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "darkbio-crypto-cbor-derive"
+version = "0.11.0"
+authors = ["Péter Szilágyi <peter@dark.bio>"]
+description = "CBOR derive macros for darkbio-crypto"
+repository = "https://github.com/dark-bio/crypto-rs"
+license = "BSD-3-Clause"
+edition = "2024"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+proc-macro2 = "1.0"
+quote = "1.0"
+syn = { version = "2.0", features = ["full", "extra-traits"] }

src/cbor/derive/Cargo.toml

@@ -0,0 +1,41 @@
+// crypto-rs: cryptography primitives and wrappers
+// Copyright 2025 Dark Bio AG. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//! CBOR encoding helpers for compile-time key sorting.
+
+/// Encodes an integer key to its CBOR byte representation for sorting.
+/// Positive integers use major type 0, negative use major type 1.
+pub fn cbor_key_bytes(key: i64) -> Vec<u8> {
+    let mut buf = Vec::new();
+    if key >= 0 {
+        let val = key as u64;
+        encode_length(&mut buf, 0, val);
+    } else {
+        let val = (-1 - key) as u64;
+        encode_length(&mut buf, 1, val);
+    }
+    buf
+}
+
+/// Encodes a CBOR type header with major type and length/value.
+/// Uses the minimal encoding based on the value size.
+fn encode_length(buf: &mut Vec<u8>, major: u8, len: u64) {
+    if len < 24 {
+        buf.push(major << 5 | len as u8);
+    } else if len <= 0xFF {
+        buf.push(major << 5 | 24);
+        buf.push(len as u8);
+    } else if len <= 0xFFFF {
+        buf.push(major << 5 | 25);
+        buf.extend_from_slice(&(len as u16).to_be_bytes());
+    } else if len <= 0xFFFFFFFF {
+        buf.push(major << 5 | 26);
+        buf.extend_from_slice(&(len as u32).to_be_bytes());
+    } else {
+        buf.push(major << 5 | 27);
+        buf.extend_from_slice(&len.to_be_bytes());
+    }
+}