diff --git a/src/pod.rs b/src/pod.rs index 6a06457d..d9cf6f80 100644 --- a/src/pod.rs +++ b/src/pod.rs @@ -27,12 +27,12 @@ pub unsafe trait Pod: Copy + 'static {} /// Returns the type and the tail of the slice. #[inline] pub fn from_bytes(data: &[u8]) -> Result<(&T, &[u8])> { + let size = mem::size_of::(); + let tail = data.get(size..).ok_or(())?; let ptr = data.as_ptr(); if (ptr as usize) % mem::align_of::() != 0 { return Err(()); } - let size = mem::size_of::(); - let tail = data.get(size..).ok_or(())?; // Safety: // The alignment and size are checked by this function. // The Pod trait ensures the type is valid to cast from bytes. @@ -40,17 +40,38 @@ pub fn from_bytes(data: &[u8]) -> Result<(&T, &[u8])> { Ok((val, tail)) } +/// Cast a mutable byte slice to a `Pod` type. +/// +/// Returns the type and the tail of the slice. +#[inline] +pub fn from_bytes_mut(data: &mut [u8]) -> Result<(&mut T, &mut [u8])> { + let size = mem::size_of::(); + if size > data.len() { + return Err(()); + } + let (data, tail) = data.split_at_mut(size); + let ptr = data.as_mut_ptr(); + if (ptr as usize) % mem::align_of::() != 0 { + return Err(()); + } + // Safety: + // The alignment and size are checked by this function. + // The Pod trait ensures the type is valid to cast from bytes. + let val = unsafe { &mut *ptr.cast() }; + Ok((val, tail)) +} + /// Cast a byte slice to a slice of a `Pod` type. /// /// Returns the type slice and the tail of the byte slice. #[inline] pub fn slice_from_bytes(data: &[u8], count: usize) -> Result<(&[T], &[u8])> { + let size = count.checked_mul(mem::size_of::()).ok_or(())?; + let tail = data.get(size..).ok_or(())?; let ptr = data.as_ptr(); if (ptr as usize) % mem::align_of::() != 0 { return Err(()); } - let size = count.checked_mul(mem::size_of::()).ok_or(())?; - let tail = data.get(size..).ok_or(())?; // Safety: // The alignment and size are checked by this function. // The Pod trait ensures the type is valid to cast from bytes. @@ -58,6 +79,30 @@ pub fn slice_from_bytes(data: &[u8], count: usize) -> Result<(&[T], &[u8 Ok((slice, tail)) } +/// Cast a mutable byte slice to a slice of a `Pod` type. +/// +/// Returns the type slice and the tail of the byte slice. +#[inline] +pub fn slice_from_bytes_mut( + data: &mut [u8], + count: usize, +) -> Result<(&mut [T], &mut [u8])> { + let size = count.checked_mul(mem::size_of::()).ok_or(())?; + if size > data.len() { + return Err(()); + } + let (data, tail) = data.split_at_mut(size); + let ptr = data.as_mut_ptr(); + if (ptr as usize) % mem::align_of::() != 0 { + return Err(()); + } + // Safety: + // The alignment and size are checked by this function. + // The Pod trait ensures the type is valid to cast from bytes. + let slice = unsafe { slice::from_raw_parts_mut(ptr.cast(), count) }; + Ok((slice, tail)) +} + /// Cast a `Pod` type to a byte slice. #[inline] pub fn bytes_of(val: &T) -> &[u8] {