pod_read_unaligned and try_pod_read_unaligned (#92)

* pod_read_unaligned and try_pod_read_unaligned

* only do all-features on nightly.

* I forgot we can't use .cast on 1.34

.github/workflows/rust.yml

@@ -35,6 +35,7 @@ jobs:
     - uses: actions/checkout@v2
     - run: cargo test --verbose
     - run: cargo test --verbose --no-default-features
+    - run: cargo test --verbose
     - run: cargo test --verbose --all-features
       if: matrix.rust == 'nightly'
     - run: cargo test --verbose --manifest-path=derive/Cargo.toml --all-features
@@ -54,8 +55,11 @@ jobs:
     - uses: actions/checkout@v2
     - run: cargo install cross
     - run: cross test --verbose --target=${{ matrix.target }} --no-default-features
+    - run: cross test --verbose --target=${{ matrix.target }}
     - run: cross test --verbose --target=${{ matrix.target }} --all-features
+      if: matrix.rust == 'nightly'
     - run: cross test --verbose --target=${{ matrix.target }} --manifest-path=derive/Cargo.toml --all-features
+      if: matrix.rust == 'nightly'
 
   miri-test:
     name: Test with miri

src/lib.rs

@@ -186,6 +186,31 @@ pub fn from_bytes_mut<T: Pod>(s: &mut [u8]) -> &mut T {
   }
 }
 
+/// Reads from the bytes as if they were a `T`.
+///
+/// ## Failure
+/// * If the `bytes` length is not equal to `size_of::<T>()`.
+#[inline]
+pub fn try_pod_read_unaligned<T: Pod>(bytes: &[u8]) -> Result<T, PodCastError> {
+  if bytes.len() != size_of::<T>() {
+    Err(PodCastError::SizeMismatch)
+  } else {
+    Ok(unsafe { (bytes.as_ptr() as *const T).read_unaligned() })
+  }
+}
+
+/// Reads the slice into a `T` value.
+///
+/// ## Panics
+/// * This is like `try_pod_read_unaligned` but will panic on failure.
+#[inline]
+pub fn pod_read_unaligned<T: Pod>(bytes: &[u8]) -> T {
+  match try_pod_read_unaligned(bytes) {
+    Ok(t) => t,
+    Err(e) => something_went_wrong("pod_read_unaligned", e),
+  }
+}
+
 /// Re-interprets `&[u8]` as `&T`.
 ///
 /// ## Failure