crates/der/src/bytes_owned.rs

//! Common handling for types backed by byte allocation with enforcement of a
//! library-level length limitation i.e. `Length::max()`.

use crate::{
    referenced::OwnedToRef, BytesRef, DecodeValue, DerOrd, EncodeValue, Error, Header, Length,
    Reader, Result, StrRef, Writer,
};
use alloc::{boxed::Box, vec::Vec};
use core::cmp::Ordering;

/// Byte slice newtype which respects the `Length::max()` limit.
#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
pub(crate) struct BytesOwned {
    /// Precomputed `Length` (avoids possible panicking conversions)
    length: Length,

    /// Inner value
    inner: Box<[u8]>,
}

impl BytesOwned {
    /// Create a new [`BytesOwned`], ensuring that the provided `slice` value
    /// is shorter than `Length::max()`.
    pub fn new(data: impl Into<Box<[u8]>>) -> Result<Self> {
        let inner: Box<[u8]> = data.into();

        Ok(Self {
            length: Length::try_from(inner.len())?,
            inner,
        })
    }

    /// Borrow the inner byte slice
    pub fn as_slice(&self) -> &[u8] {
        &self.inner
    }

    /// Get the [`Length`] of this [`BytesRef`]
    pub fn len(&self) -> Length {
        self.length
    }

    /// Is this [`BytesOwned`] empty?
    pub fn is_empty(&self) -> bool {
        self.len() == Length::ZERO
    }
}

impl AsRef<[u8]> for BytesOwned {
    fn as_ref(&self) -> &[u8] {
        self.as_slice()
    }
}

impl<'a> DecodeValue<'a> for BytesOwned {
    fn decode_value<R: Reader<'a>>(reader: &mut R, header: Header) -> Result<Self> {
        reader.read_vec(header.length).and_then(Self::new)
    }
}

impl EncodeValue for BytesOwned {
    fn value_len(&self) -> Result<Length> {
        Ok(self.length)
    }

    fn encode_value(&self, writer: &mut impl Writer) -> Result<()> {
        writer.write(self.as_ref())
    }
}

impl Default for BytesOwned {
    fn default() -> Self {
        Self {
            length: Length::ZERO,
            inner: Box::new([]),
        }
    }
}

impl DerOrd for BytesOwned {
    fn der_cmp(&self, other: &Self) -> Result<Ordering> {
        Ok(self.as_slice().cmp(other.as_slice()))
    }
}

impl From<BytesOwned> for Box<[u8]> {
    fn from(bytes: BytesOwned) -> Box<[u8]> {
        bytes.inner
    }
}

impl From<StrRef<'_>> for BytesOwned {
    fn from(s: StrRef<'_>) -> BytesOwned {
        let bytes = s.as_bytes();
        debug_assert_eq!(bytes.len(), usize::try_from(s.length).expect("overflow"));

        BytesOwned {
            inner: Box::from(bytes),
            length: s.length,
        }
    }
}

impl OwnedToRef for BytesOwned {
    type Borrowed<'a> = BytesRef<'a>;
    fn owned_to_ref(&self) -> Self::Borrowed<'_> {
        BytesRef {
            length: self.length,
            inner: self.inner.as_ref(),
        }
    }
}

impl From<BytesRef<'_>> for BytesOwned {
    fn from(s: BytesRef<'_>) -> BytesOwned {
        BytesOwned {
            length: s.length,
            inner: Box::from(s.inner),
        }
    }
}

impl TryFrom<&[u8]> for BytesOwned {
    type Error = Error;

    fn try_from(bytes: &[u8]) -> Result<Self> {
        Self::new(bytes)
    }
}

impl TryFrom<Box<[u8]>> for BytesOwned {
    type Error = Error;

    fn try_from(bytes: Box<[u8]>) -> Result<Self> {
        Self::new(bytes)
    }
}

impl TryFrom<Vec<u8>> for BytesOwned {
    type Error = Error;

    fn try_from(bytes: Vec<u8>) -> Result<Self> {
        Self::new(bytes)
    }
}

// Implement by hand because the derive would create invalid values.
// Make sure the length and the inner.len matches.
#[cfg(feature = "arbitrary")]
impl<'a> arbitrary::Arbitrary<'a> for BytesOwned {
    fn arbitrary(u: &mut arbitrary::Unstructured<'a>) -> arbitrary::Result<Self> {
        let length = u.arbitrary()?;
        Ok(Self {
            length,
            inner: Box::from(u.bytes(u32::from(length) as usize)?),
        })
    }

    fn size_hint(depth: usize) -> (usize, Option<usize>) {
        arbitrary::size_hint::and(Length::size_hint(depth), (0, None))
    }
}