Struct lmdb_zero::Unaligned

#[repr(packed)]
pub struct Unaligned<T: LmdbRawIfUnaligned>(_);

Wrapper for arbitrary Copy types which lifts their alignment restrictions.

This allows using values which have non-byte alignment but are otherwise LMDB-safe (as defined by LmdbRaw) to be used with it. It obviously does not make T itself packed, so the same discussion with respect to padding in the LmdbRaw documentation applies here as well.

There is no way to get a reference to the contained value, as Rust currently has no way to express that the reference may be misaligned. (See also https://github.com/rust-lang/rust/issues/27060.)

Example

use lmdb_zero as lmdb;
use lmdb_zero::Unaligned as U;

fn get_a_u64(env: &lmdb::Environment, db: &lmdb::Database,
             key: &str) -> u64 {
  let tx = lmdb::ReadTransaction::new(env).unwrap();
  let access = tx.access();
  access.get::<str, U<u64>>(db, key).unwrap().get()
}

Methods

impl<T: LmdbRawIfUnaligned> Unaligned<T>

pub fn new(t: T) -> Self

Wraps t in an Unaligned marker.

Important traits for &'a mut W

impl<'a, W> Write for &'a mut W where
    W: Write + ?Sized, impl<'a, R> Read for &'a mut R where
    R: Read + ?Sized, impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;

pub fn of_ref(t: &T) -> &Self

Returns t as if it were wrapped by Unaligned.

This is safe because any &T is a valid &Unaligned<T>.

Important traits for &'a mut W

impl<'a, W> Write for &'a mut W where
    W: Write + ?Sized, impl<'a, R> Read for &'a mut R where
    R: Read + ?Sized, impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;

pub fn of_mut(t: &mut T) -> &mut Self

Returns t as if it were wrapped by Unaligned.

This is safe because any &T is a valid &Unaligned<T>.

pub fn get(&self) -> T

Extracts the contained value.

This is safe as the compiler has visibility into the fact that the contained value is misaligned and can copy appropriately.

pub fn set(&mut self, t: T)

Replaces the contained value.

Trait Implementations

impl<T: LmdbRawIfUnaligned> Clone for Unaligned<T>

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: LmdbRawIfUnaligned> Copy for Unaligned<T>

impl<T: LmdbRawIfUnaligned> LmdbRaw for Unaligned<T>

fn reported_type() -> String

Returns the name of this type to report in error messages.

impl<T: LmdbRawIfUnaligned + LmdbOrdKeyIfUnaligned> LmdbOrdKey for Unaligned<T>

fn ordered_by_bytes() -> bool

Returns whether the default LMDB byte-by-byte comparison is correct for valid values of this type.

fn ordered_as_integer() -> bool

Returns whether LMDB will correctly handle this value with the INTEGERKEY or INTEGERDUP flags.

impl<T: LmdbRawIfUnaligned> Binary for Unaligned<T> where
    T: Binary, 

fn fmt(&self, fmt: &mut Formatter) -> Result<(), Error>

Formats the value using the given formatter.

impl<T: LmdbRawIfUnaligned> Debug for Unaligned<T> where
    T: Debug, 

fn fmt(&self, fmt: &mut Formatter) -> Result<(), Error>

Formats the value using the given formatter.

impl<T: LmdbRawIfUnaligned> Display for Unaligned<T> where
    T: Display, 

fn fmt(&self, fmt: &mut Formatter) -> Result<(), Error>

Formats the value using the given formatter.

impl<T: LmdbRawIfUnaligned> LowerExp for Unaligned<T> where
    T: LowerExp, 

fn fmt(&self, fmt: &mut Formatter) -> Result<(), Error>

Formats the value using the given formatter.

impl<T: LmdbRawIfUnaligned> LowerHex for Unaligned<T> where
    T: LowerHex, 

fn fmt(&self, fmt: &mut Formatter) -> Result<(), Error>

Formats the value using the given formatter.

impl<T: LmdbRawIfUnaligned> Octal for Unaligned<T> where
    T: Octal, 

fn fmt(&self, fmt: &mut Formatter) -> Result<(), Error>

Formats the value using the given formatter.

impl<T: LmdbRawIfUnaligned> Pointer for Unaligned<T> where
    T: Pointer, 

fn fmt(&self, fmt: &mut Formatter) -> Result<(), Error>

Formats the value using the given formatter.

impl<T: LmdbRawIfUnaligned> UpperExp for Unaligned<T> where
    T: UpperExp, 

fn fmt(&self, fmt: &mut Formatter) -> Result<(), Error>

Formats the value using the given formatter.

impl<T: LmdbRawIfUnaligned> UpperHex for Unaligned<T> where
    T: UpperHex, 

fn fmt(&self, fmt: &mut Formatter) -> Result<(), Error>

Formats the value using the given formatter.

impl<T: LmdbRawIfUnaligned + PartialEq<T>> PartialEq<Unaligned<T>> for Unaligned<T>

fn eq(&self, other: &Self) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<T: LmdbRawIfUnaligned + Eq> Eq for Unaligned<T>

impl<T: LmdbRawIfUnaligned + PartialOrd<T>> PartialOrd<Unaligned<T>> for Unaligned<T>

fn partial_cmp(&self, other: &Self) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Self) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Self) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Self) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Self) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<T: LmdbRawIfUnaligned + Ord> Ord for Unaligned<T>

fn cmp(&self, other: &Self) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

impl<T: LmdbRawIfUnaligned + Hash> Hash for Unaligned<T>

fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given [Hasher].

fn hash_slice<H>(data: &[Self], state: &mut H) where
    H: Hasher, 

Feeds a slice of this type into the given [Hasher].

impl<T: LmdbRawIfUnaligned + Add<T>> Add<Unaligned<T>> for Unaligned<T> where
    T::Output: LmdbRawIfUnaligned, 

type Output = Unaligned<T::Output>

The resulting type after applying the + operator.

fn add(self, rhs: Self) -> Self::Output

Performs the + operation.

impl<T: LmdbRawIfUnaligned + BitAnd<T>> BitAnd<Unaligned<T>> for Unaligned<T> where
    T::Output: LmdbRawIfUnaligned, 

type Output = Unaligned<T::Output>

The resulting type after applying the & operator.

fn bitand(self, rhs: Self) -> Self::Output

Performs the & operation.

impl<T: LmdbRawIfUnaligned + BitOr<T>> BitOr<Unaligned<T>> for Unaligned<T> where
    T::Output: LmdbRawIfUnaligned, 

type Output = Unaligned<T::Output>

The resulting type after applying the | operator.

fn bitor(self, rhs: Self) -> Self::Output

Performs the | operation.

impl<T: LmdbRawIfUnaligned + BitXor<T>> BitXor<Unaligned<T>> for Unaligned<T> where
    T::Output: LmdbRawIfUnaligned, 

type Output = Unaligned<T::Output>

The resulting type after applying the ^ operator.

fn bitxor(self, rhs: Self) -> Self::Output

Performs the ^ operation.

impl<T: LmdbRawIfUnaligned + Div<T>> Div<Unaligned<T>> for Unaligned<T> where
    T::Output: LmdbRawIfUnaligned, 

type Output = Unaligned<T::Output>

The resulting type after applying the / operator.

fn div(self, rhs: Self) -> Self::Output

Performs the / operation.

impl<T: LmdbRawIfUnaligned + Mul<T>> Mul<Unaligned<T>> for Unaligned<T> where
    T::Output: LmdbRawIfUnaligned, 

type Output = Unaligned<T::Output>

The resulting type after applying the * operator.

fn mul(self, rhs: Self) -> Self::Output

Performs the * operation.

impl<T: LmdbRawIfUnaligned + Rem<T>> Rem<Unaligned<T>> for Unaligned<T> where
    T::Output: LmdbRawIfUnaligned, 

type Output = Unaligned<T::Output>

The resulting type after applying the % operator.

fn rem(self, rhs: Self) -> Self::Output

Performs the % operation.

impl<T: LmdbRawIfUnaligned + Shl<T>> Shl<Unaligned<T>> for Unaligned<T> where
    T::Output: LmdbRawIfUnaligned, 

type Output = Unaligned<T::Output>

The resulting type after applying the << operator.

fn shl(self, rhs: Self) -> Self::Output

Performs the << operation.

impl<T: LmdbRawIfUnaligned + Shr<T>> Shr<Unaligned<T>> for Unaligned<T> where
    T::Output: LmdbRawIfUnaligned, 

type Output = Unaligned<T::Output>

The resulting type after applying the >> operator.

fn shr(self, rhs: Self) -> Self::Output

Performs the >> operation.

impl<T: LmdbRawIfUnaligned + Sub<T>> Sub<Unaligned<T>> for Unaligned<T> where
    T::Output: LmdbRawIfUnaligned, 

type Output = Unaligned<T::Output>

The resulting type after applying the - operator.

fn sub(self, rhs: Self) -> Self::Output

Performs the - operation.

impl<T: LmdbRawIfUnaligned + AddAssign<T>> AddAssign<Unaligned<T>> for Unaligned<T>

fn add_assign(&mut self, rhs: Self)

Performs the += operation.

impl<T: LmdbRawIfUnaligned + BitAndAssign<T>> BitAndAssign<Unaligned<T>> for Unaligned<T>

fn bitand_assign(&mut self, rhs: Self)

Performs the &= operation.

impl<T: LmdbRawIfUnaligned + BitOrAssign<T>> BitOrAssign<Unaligned<T>> for Unaligned<T>

fn bitor_assign(&mut self, rhs: Self)

Performs the |= operation.

impl<T: LmdbRawIfUnaligned + BitXorAssign<T>> BitXorAssign<Unaligned<T>> for Unaligned<T>

fn bitxor_assign(&mut self, rhs: Self)

Performs the ^= operation.

impl<T: LmdbRawIfUnaligned + DivAssign<T>> DivAssign<Unaligned<T>> for Unaligned<T>

fn div_assign(&mut self, rhs: Self)

Performs the /= operation.

impl<T: LmdbRawIfUnaligned + MulAssign<T>> MulAssign<Unaligned<T>> for Unaligned<T>

fn mul_assign(&mut self, rhs: Self)

Performs the *= operation.

impl<T: LmdbRawIfUnaligned + RemAssign<T>> RemAssign<Unaligned<T>> for Unaligned<T>

fn rem_assign(&mut self, rhs: Self)

Performs the %= operation.

impl<T: LmdbRawIfUnaligned + ShlAssign<T>> ShlAssign<Unaligned<T>> for Unaligned<T>

fn shl_assign(&mut self, rhs: Self)

Performs the <<= operation.

impl<T: LmdbRawIfUnaligned + ShrAssign<T>> ShrAssign<Unaligned<T>> for Unaligned<T>

fn shr_assign(&mut self, rhs: Self)

Performs the >>= operation.

impl<T: LmdbRawIfUnaligned + SubAssign<T>> SubAssign<Unaligned<T>> for Unaligned<T>

fn sub_assign(&mut self, rhs: Self)

Performs the -= operation.