Enum LockMode 

pub enum LockMode {
    Shared,
    Exclusive,
}

The mode in which a transaction holds, or wants to hold, a lock.

Examples

use lock_db::LockMode;

// Two readers coexist; a writer excludes everyone.
assert!(LockMode::Shared.compatible_with(LockMode::Shared));
assert!(!LockMode::Shared.compatible_with(LockMode::Exclusive));
assert!(!LockMode::Exclusive.compatible_with(LockMode::Exclusive));

Variants

Shared

A read lock. Any number of transactions may hold a resource Shared at the same time, but none may hold it Exclusive while they do.

Exclusive

A write lock. Held by at most one transaction, and only when no other transaction holds the resource in any mode.

Implementations

impl LockMode

pub const fn compatible_with(self, other: LockMode) -> bool

Returns true if a lock in self mode and a lock in other mode may be held on the same resource by two different transactions at once.

This is the symmetric compatibility relation: a.compatible_with(b) always equals b.compatible_with(a). The only compatible pair is shared/shared.

Examples

use lock_db::LockMode;

for a in [LockMode::Shared, LockMode::Exclusive] {
    for b in [LockMode::Shared, LockMode::Exclusive] {
        // Symmetry holds for every pair.
        assert_eq!(a.compatible_with(b), b.compatible_with(a));
    }
}

pub const fn covers(self, other: LockMode) -> bool

Returns true if holding self already grants everything other would.

A transaction that already holds a resource exclusively does not need to re-acquire it to read; a transaction holding it shared still needs an upgrade to write. This drives the idempotent and upgrade paths of LockManager::try_acquire.

Examples

use lock_db::LockMode;

assert!(LockMode::Exclusive.covers(LockMode::Shared));
assert!(LockMode::Exclusive.covers(LockMode::Exclusive));
assert!(LockMode::Shared.covers(LockMode::Shared));
assert!(!LockMode::Shared.covers(LockMode::Exclusive));

pub const fn is_exclusive(self) -> bool

Returns true for LockMode::Exclusive.

Examples

use lock_db::LockMode;

assert!(LockMode::Exclusive.is_exclusive());
assert!(!LockMode::Shared.is_exclusive());

Trait Implementations

impl Clone for LockMode

fn clone(&self) -> LockMode

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for LockMode

impl Debug for LockMode

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for LockMode

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Eq for LockMode

impl Hash for LockMode

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, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for LockMode

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

This method returns an Ordering between self and other.

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

where Self: Sized,

Compares and returns the maximum of two values.

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

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for LockMode

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for LockMode

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

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

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

Tests less than (for self and other) and is used by the < operator.

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

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

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

Tests greater than (for self and other) and is used by the > operator.

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

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

impl Serialize for LockMode

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for LockMode