From a59ca28e2cf92b1e4b300f3f5c58e58008f1a0b6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lo=C3=AFc=20Lecrenier?= <loic.lecrenier@me.com>
Date: Sun, 19 Mar 2023 15:14:40 +0100
Subject: [PATCH] Add forgotten file

---
 .../new/ranking_rule_graph/dead_ends_cache.rs | 93 +++++++++++++++++++
 1 file changed, 93 insertions(+)
 create mode 100644 milli/src/search/new/ranking_rule_graph/dead_ends_cache.rs

diff --git a/milli/src/search/new/ranking_rule_graph/dead_ends_cache.rs b/milli/src/search/new/ranking_rule_graph/dead_ends_cache.rs
new file mode 100644
index 000000000..ecb6ae8da
--- /dev/null
+++ b/milli/src/search/new/ranking_rule_graph/dead_ends_cache.rs
@@ -0,0 +1,93 @@
+use crate::search::new::{
+    interner::{FixedSizeInterner, Interned},
+    small_bitmap::SmallBitmap,
+};
+
+pub struct DeadEndsCache<T> {
+    conditions: Vec<Interned<T>>,
+    next: Vec<Self>,
+    pub forbidden: SmallBitmap<T>,
+}
+impl<T> Clone for DeadEndsCache<T> {
+    fn clone(&self) -> Self {
+        Self {
+            conditions: self.conditions.clone(),
+            next: self.next.clone(),
+            forbidden: self.forbidden.clone(),
+        }
+    }
+}
+impl<T> DeadEndsCache<T> {
+    pub fn new(for_interner: &FixedSizeInterner<T>) -> Self {
+        Self {
+            conditions: vec![],
+            next: vec![],
+            forbidden: SmallBitmap::for_interned_values_in(for_interner),
+        }
+    }
+    pub fn forbid_condition(&mut self, condition: Interned<T>) {
+        self.forbidden.insert(condition);
+    }
+
+    pub fn advance(&mut self, condition: Interned<T>) -> Option<&mut Self> {
+        if let Some(idx) = self.conditions.iter().position(|c| *c == condition) {
+            Some(&mut self.next[idx])
+        } else {
+            None
+        }
+    }
+    pub fn forbidden_conditions_for_all_prefixes_up_to(
+        &mut self,
+        prefix: &[Interned<T>],
+    ) -> SmallBitmap<T> {
+        let mut forbidden = self.forbidden.clone();
+        let mut cursor = self;
+        for c in prefix.iter() {
+            if let Some(next) = cursor.advance(*c) {
+                cursor = next;
+                forbidden.union(&cursor.forbidden);
+            } else {
+                break;
+            }
+        }
+        forbidden
+    }
+    pub fn forbidden_conditions_after_prefix(
+        &mut self,
+        prefix: &[Interned<T>],
+    ) -> Option<SmallBitmap<T>> {
+        let mut cursor = self;
+        for c in prefix.iter() {
+            if let Some(next) = cursor.advance(*c) {
+                cursor = next;
+            } else {
+                return None;
+            }
+        }
+        Some(cursor.forbidden.clone())
+    }
+    pub fn forbid_condition_after_prefix(
+        &mut self,
+        mut prefix: impl Iterator<Item = Interned<T>>,
+        forbidden: Interned<T>,
+    ) {
+        match prefix.next() {
+            None => {
+                self.forbidden.insert(forbidden);
+            }
+            Some(first_condition) => {
+                if let Some(idx) = self.conditions.iter().position(|c| *c == first_condition) {
+                    return self.next[idx].forbid_condition_after_prefix(prefix, forbidden);
+                }
+                let mut rest = DeadEndsCache {
+                    conditions: vec![],
+                    next: vec![],
+                    forbidden: SmallBitmap::new(self.forbidden.universe_length()),
+                };
+                rest.forbid_condition_after_prefix(prefix, forbidden);
+                self.conditions.push(first_condition);
+                self.next.push(rest);
+            }
+        }
+    }
+}