txmap 3.1.2

A concurrent transactional hash map for Rust with fine-grained locking, internal mutability and composable transactions
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73

use crate::{
    custodian::Custodian,
    immediate::{guard::Guard, op::ImmediateOp},
    indexer::Indexer,
    lock_policies::lock_policy::LockPolicy,
    new_types::BitMask,
    result::TxResult,
};
use std::hash::{BuildHasher, Hash};

/// An immediate (one-shot) transaction.
///
/// Built via [`ImmediateTxBuilder`](crate::immediate::tx_builder::ImmediateTxBuilder) and executed immediately.
/// Acquires all needed locks, checks guards, applies operations,
/// then releases locks and returns the final state.
pub struct ImmediateTransaction<'tx, K, V, L, S, STATE>
where
    K: Clone + Hash + Eq,
    L: LockPolicy,
    S: BuildHasher,
    STATE: Default,
{
    pub(crate) custodian: &'tx Custodian<K, V, L>,
    pub(crate) indexer: &'tx Indexer<S>,
    pub(crate) guards: Vec<Guard<'tx, K, V, STATE>>,
    #[allow(clippy::type_complexity)]
    pub(crate) ops: Vec<ImmediateOp<'tx, K, V, STATE>>,
}

impl<'tx, K, V, L, S, STATE> ImmediateTransaction<'tx, K, V, L, S, STATE>
where
    K: Clone + Hash + Eq,
    L: LockPolicy,
    S: BuildHasher,
    STATE: Default,
{
    #[must_use]
    /// Executes the transaction.
    ///
    /// Acquires read/write locks for all involved shards, verifies
    /// all guard conditions, applies the operations, and returns
    /// the final state wrapped in [`TxResult`].
    pub fn execute(&self) -> TxResult<STATE> {
        let mut total_read_bitmask = BitMask::ZERO;
        let mut total_write_bitmask = BitMask::ZERO;

        // get all bitmasks
        for guard in self.guards.iter() {
            total_read_bitmask |= guard.read_bitmask();
        }
        for op in self.ops.iter() {
            let (read_bitmask, write_bitmask) = op.read_write_bitmasks();
            total_read_bitmask |= read_bitmask;
            total_write_bitmask |= write_bitmask;
        }
        // ensure locks are either read or write, not both
        total_read_bitmask &= !total_write_bitmask;

        let mut lock_guards = self
            .custodian
            .lock_guards(total_read_bitmask, total_write_bitmask);
        let mut state = STATE::default();
        for (i, guard) in self.guards.iter().enumerate() {
            if !guard.is_condition_met::<L>(&mut lock_guards, &mut state) {
                return TxResult::RequirementNotMet(i, guard.name.clone(), state);
            }
        }
        for op in self.ops.iter() {
            op.apply::<L, S>(&mut lock_guards, self.indexer, &mut state);
        }
        TxResult::Completed(state)
    }
}