const-oid: make ObjectIdentifier::as_bytes a const fn

Also bumps MSRV to 1.71 due to the const use of `[u8]::split_at`.

Additionally makes the internal `Encoder` type const generic around the
size of the output buffer.

.github/workflows/const-oid.yml

@@ -23,7 +23,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - 1.60.0 # MSRV
+          - 1.71.0 # MSRV
           - stable
         target:
           - thumbv7em-none-eabi
@@ -47,7 +47,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - 1.60.0 # MSRV
+          - 1.71.0 # MSRV
           - stable
     steps:
       - uses: actions/checkout@v4

.github/workflows/der.yml

@@ -24,7 +24,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - 1.65.0 # MSRV
+          - 1.71.0 # MSRV
           - stable
         target:
           - thumbv7em-none-eabi
@@ -51,7 +51,7 @@ jobs:
           # 32-bit Linux
           - targets: i686-unknown-linux-gnu
             platform: ubuntu-latest
-            rust: 1.65.0 # MSRV
+            rust: 1.71.0 # MSRV
             deps: sudo apt update && sudo apt install gcc-multilib
           - targets: i686-unknown-linux-gnu
             platform: ubuntu-latest
@@ -61,7 +61,7 @@ jobs:
           # 64-bit Linux
           - targets: x86_64-unknown-linux-gnu
             platform: ubuntu-latest
-            rust: 1.65.0 # MSRV
+            rust: 1.71.0 # MSRV
           - targets: x86_64-unknown-linux-gnu
             platform: ubuntu-latest
             rust: stable
@@ -70,7 +70,7 @@ jobs:
           # 64-bit Windows
           #- targets: x86_64-pc-windows-msvc
           #  platform: windows-latest
-          #  rust: 1.65.0 # MSRV
+          #  rust: 1.71.0 # MSRV
           #- targets: x86_64-pc-windows-msvc
           #  platform: windows-latest
           #  rust: stable
@@ -90,7 +90,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - 1.65.0 # MSRV
+          - 1.71.0 # MSRV
           - stable
     steps:
       - uses: actions/checkout@v4

.github/workflows/pkcs1.yml

@@ -27,7 +27,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - 1.65.0 # MSRV
+          - 1.71.0 # MSRV
           - stable
         target:
           - thumbv7em-none-eabi
@@ -52,7 +52,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - 1.65.0 # MSRV
+          - 1.71.0 # MSRV
           - stable
     steps:
       - uses: actions/checkout@v4

.github/workflows/pkcs5.yml

@@ -26,7 +26,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - 1.65.0 # MSRV
+          - 1.71.0 # MSRV
           - stable
         target:
           - thumbv7em-none-eabi
@@ -51,7 +51,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - 1.65.0 # MSRV
+          - 1.71.0 # MSRV
           - stable
     steps:
       - uses: actions/checkout@v4

.github/workflows/pkcs8.yml

@@ -28,7 +28,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - 1.65.0 # MSRV
+          - 1.71.0 # MSRV
           - stable
         target:
           - thumbv7em-none-eabi
@@ -53,7 +53,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - 1.65.0 # MSRV
+          - 1.71.0 # MSRV
           - stable
     steps:
       - uses: actions/checkout@v4

.github/workflows/sec1.yml

@@ -27,7 +27,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - 1.70.0 # MSRV
+          - 1.71.0 # MSRV
           - stable
         target:
           - thumbv7em-none-eabi
@@ -52,7 +52,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - 1.70.0 # MSRV
+          - 1.71.0 # MSRV
           - stable
     steps:
       - uses: actions/checkout@v4

.github/workflows/spki.yml

@@ -26,7 +26,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - 1.65.0 # MSRV
+          - 1.71.0 # MSRV
           - stable
         target:
           - thumbv7em-none-eabi
@@ -51,7 +51,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - 1.65.0 # MSRV
+          - 1.71.0 # MSRV
           - stable
     steps:
       - uses: actions/checkout@v4

const-oid/Cargo.toml

@@ -14,7 +14,7 @@ categories = ["cryptography", "data-structures", "encoding", "no-std", "parser-i
 keywords = ["iso", "iec", "itu", "oid"]
 readme = "README.md"
 edition = "2021"
-rust-version = "1.60"
+rust-version = "1.71"
 
 [dependencies]
 arbitrary = { version = "1.2", optional = true, features = ["derive"] }

const-oid/README.md

@@ -57,7 +57,7 @@ well as a runtime OID library.
 
 ## Minimum Supported Rust Version
 
-This crate requires **Rust 1.65** at a minimum.
+This crate requires **Rust 1.71** at a minimum.
 
 We may change the MSRV in the future, but it will be accompanied by a minor
 version bump.
@@ -84,7 +84,7 @@ dual licensed as above, without any additional terms or conditions.
 [docs-image]: https://docs.rs/const-oid/badge.svg
 [docs-link]: https://docs.rs/const-oid/
 [license-image]: https://img.shields.io/badge/license-Apache2.0/MIT-blue.svg
-[rustc-image]: https://img.shields.io/badge/rustc-1.65+-blue.svg
+[rustc-image]: https://img.shields.io/badge/rustc-1.71+-blue.svg
 [chat-image]: https://img.shields.io/badge/zulip-join_chat-blue.svg
 [chat-link]: https://rustcrypto.zulipchat.com/#narrow/stream/300570-formats
 [build-image]: https://github.com/RustCrypto/formats/workflows/const-oid/badge.svg?branch=master&event=push

const-oid/src/buffer.rs

@@ -12,8 +12,8 @@ pub struct Buffer<const SIZE: usize> {
 
 impl<const SIZE: usize> Buffer<SIZE> {
     /// Borrow the inner byte slice.
-    pub fn as_bytes(&self) -> &[u8] {
-        &self.bytes[..self.length as usize]
+    pub const fn as_bytes(&self) -> &[u8] {
+        self.bytes.split_at(self.length as usize).0
     }
 
     /// Get the length of the BER message.

const-oid/src/encoder.rs

@@ -7,12 +7,12 @@ use crate::{
 
 /// BER/DER encoder
 #[derive(Debug)]
-pub(crate) struct Encoder {
+pub(crate) struct Encoder<const MAX_SIZE: usize> {
     /// Current state
     state: State,
 
     /// Bytes of the OID being encoded in-progress
-    bytes: [u8; ObjectIdentifier::MAX_SIZE],
+    bytes: [u8; MAX_SIZE],
 
     /// Current position within the byte buffer
     cursor: usize,
@@ -31,18 +31,18 @@ enum State {
     Body,
 }
 
-impl Encoder {
+impl<const MAX_SIZE: usize> Encoder<MAX_SIZE> {
     /// Create a new encoder initialized to an empty default state.
     pub(crate) const fn new() -> Self {
         Self {
             state: State::Initial,
-            bytes: [0u8; ObjectIdentifier::MAX_SIZE],
+            bytes: [0u8; MAX_SIZE],
             cursor: 0,
         }
     }
 
     /// Extend an existing OID.
-    pub(crate) const fn extend(oid: ObjectIdentifier) -> Self {
+    pub(crate) const fn extend(oid: ObjectIdentifier<MAX_SIZE>) -> Self {
         Self {
             state: State::Body,
             bytes: oid.buffer.bytes,
@@ -99,7 +99,7 @@ impl Encoder {
     }
 
     /// Finish encoding an OID.
-    pub(crate) const fn finish(self) -> Result<ObjectIdentifier> {
+    pub(crate) const fn finish(self) -> Result<ObjectIdentifier<MAX_SIZE>> {
         if self.cursor >= 2 {
             let bytes = Buffer {
                 bytes: self.bytes,
@@ -156,7 +156,7 @@ mod tests {
 
     #[test]
     fn encode() {
-        let encoder = Encoder::new();
+        let encoder = Encoder::<7>::new();
         let encoder = encoder.arc(1).unwrap();
         let encoder = encoder.arc(2).unwrap();
         let encoder = encoder.arc(840).unwrap();

const-oid/src/lib.rs

@@ -146,50 +146,15 @@ impl ObjectIdentifier {
 
         Ok(oid)
     }
-
-    /// Get the parent OID of this one (if applicable).
-    pub fn parent(&self) -> Option<Self> {
-        let num_arcs = self.len().checked_sub(1)?;
-        Self::from_arcs(self.arcs().take(num_arcs)).ok()
-    }
-
-    /// Push an additional arc onto this OID, returning the child OID.
-    pub const fn push_arc(self, arc: Arc) -> Result<Self> {
-        // TODO(tarcieri): use `?` when stable in `const fn`
-        match Encoder::extend(self).arc(arc) {
-            Ok(encoder) => encoder.finish(),
-            Err(err) => Err(err),
-        }
-    }
-
-    /// Does this OID start with the other OID?
-    pub fn starts_with(&self, other: ObjectIdentifier) -> bool {
-        let mut self_arcs = self.arcs();
-
-        for other_arc in other.arcs() {
-            match self_arcs.next() {
-                Some(arc) => {
-                    if arc != other_arc {
-                        return false;
-                    }
-                }
-                None => {
-                    return false;
-                }
-            }
-        }
-
-        true
-    }
 }
 
 impl<const MAX_SIZE: usize> ObjectIdentifier<MAX_SIZE> {
     /// Get the BER/DER serialization of this OID as bytes.
     ///
-    /// Note that this encoding omits the tag/length, and only contains the
-    /// value portion of the encoded OID.
-    pub fn as_bytes(&self) -> &[u8] {
-        self.buffer.as_ref()
+    /// Note that this encoding omits the tag/length, and only contains the value portion of the
+    /// encoded OID.
+    pub const fn as_bytes(&self) -> &[u8] {
+        self.buffer.as_bytes()
     }
 
     /// Return the arc with the given index, if it exists.
@@ -208,11 +173,55 @@ impl<const MAX_SIZE: usize> ObjectIdentifier<MAX_SIZE> {
     pub fn len(&self) -> usize {
         self.arcs().count()
     }
+
+    /// Get the parent OID of this one (if applicable).
+    pub fn parent(&self) -> Option<Self> {
+        let num_arcs = self.len().checked_sub(1)?;
+        let mut encoder = Encoder::new();
+
+        for arc in self.arcs().take(num_arcs) {
+            encoder = encoder.arc(arc).ok()?;
+        }
+
+        encoder.finish().ok()
+    }
+
+    /// Push an additional arc onto this OID, returning the child OID.
+    pub const fn push_arc(self, arc: Arc) -> Result<Self> {
+        // TODO(tarcieri): use `?` when stable in `const fn`
+        match Encoder::extend(self).arc(arc) {
+            Ok(encoder) => encoder.finish(),
+            Err(err) => Err(err),
+        }
+    }
+
+    /// Does this OID start with the other OID?
+    pub const fn starts_with(&self, other: ObjectIdentifier) -> bool {
+        let len = other.as_bytes().len();
+
+        if self.as_bytes().len() < len {
+            return false;
+        }
+
+        let mut i = 0;
+        while i < len {
+            if self.as_bytes()[i] != other.as_bytes()[i] {
+                return false;
+            }
+
+            match i.checked_add(1) {
+                Some(succ) => i = succ,
+                None => return false,
+            }
+        }
+
+        true
+    }
 }
 
 impl<const MAX_SIZE: usize> AsRef<[u8]> for ObjectIdentifier<MAX_SIZE> {
     fn as_ref(&self) -> &[u8] {
-        self.as_bytes()
+        self.buffer.as_bytes()
     }
 }
 

const-oid/src/parser.rs

@@ -11,7 +11,7 @@ pub(crate) struct Parser {
     current_arc: Arc,
 
     /// BER/DER encoder
-    encoder: Encoder,
+    encoder: Encoder<{ ObjectIdentifier::MAX_SIZE }>,
 }
 
 impl Parser {

der/Cargo.toml

@@ -13,7 +13,7 @@ categories = ["cryptography", "data-structures", "encoding", "no-std", "parser-i
 keywords = ["asn1", "crypto", "itu", "pkcs"]
 readme = "README.md"
 edition = "2021"
-rust-version = "1.65"
+rust-version = "1.71"
 
 [dependencies]
 arbitrary = { version = "1.3", features = ["derive"], optional = true }