1 files changed, 74 insertions, 0 deletions
diff --git a/vendor/varisat-checker/src/hash.rs b/vendor/varisat-checker/src/hash.rs
new file mode 100644
index 000000000..40474ff8e
--- /dev/null
+++ b/vendor/varisat-checker/src/hash.rs
@@ -0,0 +1,74 @@
+//! Computation of clause hashes.
+use std::mem::take;
+
+use partial_ref::{partial, PartialRef};
+use rustc_hash::FxHashMap as HashMap;
+
+use varisat_formula::{Lit, Var};
+use varisat_internal_proof::{lit_code_hash, lit_hash, ClauseHash};
+
+use crate::context::{parts::*, Context};
+
+pub struct ClauseHasher {
+    /// How many bits are used for storing clause hashes.
+    pub hash_bits: u32,
+    /// Changed solver names that are not yet reflected in the checkers current clause hashes.
+    pub buffered_solver_var_names: Vec<(Var, Option<Var>)>,
+    /// Does buffered_solver_var_names contain a new name?
+    ///
+    /// If it contains only deletes, there is no need to rehash
+    pub rename_in_buffered_solver_var_names: bool,
+    /// Current mapping from global var names to solver var names, used for hashing.
+    solver_var_names: HashMap<Var, Var>,
+}
+
+impl Default for ClauseHasher {
+    fn default() -> ClauseHasher {
+        ClauseHasher {
+            hash_bits: 64,
+            buffered_solver_var_names: vec![],
+            rename_in_buffered_solver_var_names: false,
+            solver_var_names: Default::default(),
+        }
+    }
+}
+
+impl ClauseHasher {
+    /// Compute a clause hash of the current bit size
+    pub fn clause_hash(&self, lits: &[Lit]) -> ClauseHash {
+        let shift_bits = ClauseHash::max_value().count_ones() - self.hash_bits;
+        let mut hash = 0;
+        for &lit in lits.iter() {
+            match self.solver_var_names.get(&lit.var()) {
+                Some(var) => hash ^= lit_hash(var.lit(lit.is_positive())),
+                None => hash ^= lit_code_hash(lit.code() + Var::max_count() * 2),
+            }
+        }
+        hash >> shift_bits
+    }
+}
+
+/// Recompute all clause hashes if necessary
+pub fn rehash(mut ctx: partial!(Context, mut ClauseHasherP, mut ClausesP)) {
+    let (hasher, mut ctx) = ctx.split_part_mut(ClauseHasherP);
+    let clauses = ctx.part_mut(ClausesP);
+
+    for (global, solver) in hasher.buffered_solver_var_names.drain(..) {
+        if let Some(solver) = solver {
+            hasher.solver_var_names.insert(global, solver);
+        } else {
+            hasher.solver_var_names.remove(&global);
+        }
+    }
+    hasher.rename_in_buffered_solver_var_names = false;
+
+    let mut old_clauses = take(&mut clauses.clauses);
+
+    for (_, mut candidates) in old_clauses.drain() {
+        for clause in candidates.drain(..) {
+            let hash = hasher.clause_hash(clause.lits.slice(&clauses.literal_buffer));
+            let candidates = clauses.clauses.entry(hash).or_default();
+            candidates.push(clause);
+        }
+    }
+}