block-buffer: generic implementation of serialization methods

block-buffer/CHANGELOG.md

@@ -7,8 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## UNRELEASED
 ### Added
 - `ReadBuffer` type ([#823])
-- `serialize` and `deserialize` methods ([#823])
 - Optional implementation of the `Zeroize` trait ([#963])
+- Generic `serialize` and `deserialize` methods ([#1200])
 
 ### Changed
 - Block sizes must be bigger than 0 and smaller than 256.
@@ -20,11 +20,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Removed
 - `EagerBuffer::set_data` method. Use the `ReadBuffer` type instead. ([#823])
 
-[#823]: https://github.com/RustCrypto/utils/pull/823
 [#963]: https://github.com/RustCrypto/utils/pull/963
 [#1115]: https://github.com/RustCrypto/utils/pull/1115
 [#1115]: https://github.com/RustCrypto/utils/pull/1116
 [#1149]: https://github.com/RustCrypto/utils/pull/1149
+[#1200]: https://github.com/RustCrypto/utils/pull/1200
 
 ## 0.10.3 (2022-09-04)
 ### Added

block-buffer/src/lib.rs

@@ -42,11 +42,8 @@
 
 pub use hybrid_array as array;
 
-use array::{
-    Array, ArraySize,
-    typenum::{Add1, B1},
-};
-use core::{fmt, mem::MaybeUninit, ops::Add, ptr, slice};
+use array::{Array, ArraySize, typenum::Sum};
+use core::{fmt, mem::MaybeUninit, ptr, slice};
 
 #[cfg(feature = "zeroize")]
 use zeroize::{Zeroize, ZeroizeOnDrop};
@@ -314,6 +311,47 @@ impl<BS: ArraySize, K: BufferKind> BlockBuffer<BS, K> {
     }
 }
 
+/// Size of serialized `BlockBuffer` in bytes.
+pub type SerializedBufferSize<BS, K> = Sum<BS, <K as sealed::Sealed>::Overhead>;
+/// `BlockBuffer` serialized as a byte array.
+pub type SerializedBuffer<BS, K> = Array<u8, SerializedBufferSize<BS, K>>;
+
+impl<BS: ArraySize, K: BufferKind> BlockBuffer<BS, K>
+where
+    BS: core::ops::Add<K::Overhead>,
+    Sum<BS, K::Overhead>: ArraySize,
+{
+    /// Serialize buffer into a byte array.
+    pub fn serialize(&self) -> SerializedBuffer<BS, K> {
+        let mut buf = SerializedBuffer::<BS, K>::default();
+        let data = self.get_data();
+        let (pos, block) = buf.split_at_mut(1);
+        pos[0] = u8::try_from(data.len()).expect("buffer size is smaller than 256");
+        block[..data.len()].copy_from_slice(data);
+        buf
+    }
+
+    /// Deserialize buffer from a byte array.
+    pub fn deserialize(buf: &SerializedBuffer<BS, K>) -> Result<Self, Error> {
+        let (pos, block) = buf.split_at(1);
+        let pos = usize::from(pos[0]);
+
+        if !<K as sealed::Sealed>::invariant(pos, BS::USIZE) {
+            return Err(Error);
+        }
+
+        let (data, tail) = block.split_at(pos);
+
+        if tail.iter().any(|&b| b != 0) {
+            return Err(Error);
+        }
+
+        let mut res = Self::default();
+        unsafe { res.set_data_unchecked(data) };
+        Ok(res)
+    }
+}
+
 impl<BS: ArraySize> BlockBuffer<BS, Eager> {
     /// Compress remaining data after padding it with `delim`, zeros and
     /// the `suffix` bytes. If there is not enough unused space, `compress`
@@ -368,69 +406,6 @@ impl<BS: ArraySize> BlockBuffer<BS, Eager> {
     pub fn len128_padding_be(&mut self, data_len: u128, compress: impl FnMut(&Array<u8, BS>)) {
         self.digest_pad(0x80, &data_len.to_be_bytes(), compress);
     }
-
-    /// Serialize buffer into a byte array.
-    #[inline]
-    pub fn serialize(&self) -> Array<u8, BS> {
-        let mut res = Array::<u8, BS>::default();
-        let data = self.get_data();
-        res[..data.len()].copy_from_slice(data);
-        res[BS::USIZE - 1] = data.len() as u8;
-        res
-    }
-
-    /// Deserialize buffer from a byte array.
-    #[inline]
-    pub fn deserialize(buffer: &Array<u8, BS>) -> Result<Self, Error> {
-        let pos = buffer[BS::USIZE - 1] as usize;
-        if !<Eager as sealed::Sealed>::invariant(pos, BS::USIZE) {
-            return Err(Error);
-        }
-        if buffer[pos..BS::USIZE - 1].iter().any(|&b| b != 0) {
-            return Err(Error);
-        }
-        Ok(Self {
-            buffer: MaybeUninit::new(buffer.clone()),
-            pos: Default::default(),
-        })
-    }
-}
-
-impl<BS: ArraySize> BlockBuffer<BS, Lazy> {
-    /// Serialize buffer into a byte array.
-    #[inline]
-    pub fn serialize(&self) -> Array<u8, Add1<BS>>
-    where
-        BS: Add<B1>,
-        Add1<BS>: ArraySize,
-    {
-        let mut res = Array::<u8, Add1<BS>>::default();
-        res[0] = self.pos;
-        let data = self.get_data();
-        res[1..][..data.len()].copy_from_slice(data);
-        res
-    }
-
-    /// Deserialize buffer from a byte array.
-    #[inline]
-    pub fn deserialize(buffer: &Array<u8, Add1<BS>>) -> Result<Self, Error>
-    where
-        BS: Add<B1>,
-        Add1<BS>: ArraySize,
-    {
-        let pos = buffer[0];
-        if !<Lazy as sealed::Sealed>::invariant(pos as usize, BS::USIZE) {
-            return Err(Error);
-        }
-        if buffer[1..][pos as usize..].iter().any(|&b| b != 0) {
-            return Err(Error);
-        }
-        let buf = Array::try_from(&buffer[1..]).expect("slice has correct length");
-        Ok(Self {
-            buffer: MaybeUninit::new(buf),
-            pos,
-        })
-    }
 }
 
 #[cfg(feature = "zeroize")]

block-buffer/src/sealed.rs

@@ -1,3 +1,5 @@
+use hybrid_array::sizes::{U0, U1};
+
 use super::{Array, ArraySize};
 use core::{mem::MaybeUninit, ptr, slice};
 
@@ -10,6 +12,8 @@ pub trait Sealed {
     #[cfg(feature = "zeroize")]
     type Pos: Default + Clone + zeroize::Zeroize;
 
+    type Overhead: ArraySize;
+
     const NAME: &'static str;
 
     fn get_pos<N: ArraySize>(buf: &Block<N>, pos: &Self::Pos) -> usize;
@@ -26,6 +30,7 @@ pub trait Sealed {
 
 impl Sealed for super::Eager {
     type Pos = ();
+    type Overhead = U0;
     const NAME: &'static str = "BlockBuffer<Eager>";
 
     fn get_pos<N: ArraySize>(buf: &Block<N>, _pos: &Self::Pos) -> usize {
@@ -72,6 +77,7 @@ impl Sealed for super::Eager {
 
 impl Sealed for super::Lazy {
     type Pos = u8;
+    type Overhead = U1;
     const NAME: &'static str = "BlockBuffer<Lazy>";
 
     fn get_pos<N: ArraySize>(_buf_val: &Block<N>, pos: &Self::Pos) -> usize {

block-buffer/tests/mod.rs

@@ -183,7 +183,7 @@ fn test_eager_serialize() {
     buf1.digest_blocks(&[41, 42], |_| {});
 
     let ser1 = buf1.serialize();
-    assert_eq!(&ser1[..], &[41, 42, 0, 2]);
+    assert_eq!(&ser1[..], &[2, 41, 42, 0]);
 
     let mut buf2 = Buf::deserialize(&ser1).unwrap();
     assert_eq!(buf1.serialize(), ser1);
@@ -192,7 +192,7 @@ fn test_eager_serialize() {
     buf2.digest_blocks(&[43], |_| {});
 
     let ser2 = buf1.serialize();
-    assert_eq!(&ser2[..], &[41, 42, 43, 3]);
+    assert_eq!(&ser2[..], &[3, 41, 42, 43]);
     assert_eq!(buf1.serialize(), ser2);
 
     let mut buf3 = Buf::deserialize(&ser2).unwrap();
@@ -213,11 +213,11 @@ fn test_eager_serialize() {
     let buf = Array([0, 0, 0, 10]);
     assert!(Buf::deserialize(&buf).is_err());
     // "Garbage" bytes are not zeroized
-    let buf = Array([1, 0, 0, 0]);
+    let buf = Array([0, 1, 0, 0]);
     assert!(Buf::deserialize(&buf).is_err());
-    let buf = Array([0, 1, 0, 1]);
+    let buf = Array([1, 0, 1, 0]);
     assert!(Buf::deserialize(&buf).is_err());
-    let buf = Array([0, 0, 1, 2]);
+    let buf = Array([2, 0, 0, 1]);
     assert!(Buf::deserialize(&buf).is_err());
 }