feat: add cuckoofilter to nippy-jar

crates/storage/nippy-jar/Cargo.toml

@@ -20,6 +20,8 @@ thiserror = "1.0"
 bincode = "1.3"
 serde = { version = "1.0",  features = ["derive"] }
 bytes = "1.5"
+cuckoofilter = { version = "0.5.0", features = ["serde_support", "serde_bytes"] }
+tempfile = "3.4"
 
 [features]
 default = []

crates/storage/nippy-jar/src/compression/mod.rs

@@ -29,7 +29,7 @@ pub trait Compression {
 #[derive(Debug, PartialEq, Serialize, Deserialize)]
 pub enum Compressors {
     Zstd(Zstd),
-    // Acoids irrefutable let errors. Remove this after adding another one.
+    // Avoids irrefutable let errors. Remove this after adding another one.
     Unused,
 }
 

crates/storage/nippy-jar/src/filter/cuckoo.rs

@@ -0,0 +1,89 @@
+use super::Filter;
+use crate::NippyJarError;
+use cuckoofilter::{self, CuckooFilter, ExportedCuckooFilter};
+use serde::{Deserialize, Deserializer, Serialize, Serializer};
+use std::collections::hash_map::DefaultHasher;
+
+/// [CuckooFilter](https://www.cs.cmu.edu/~dga/papers/cuckoo-conext2014.pdf). It builds and provides an approximated set-membership filter to answer queries such as "Does this element belong to this set?". Has a theoretical 3% false positive rate.
+pub struct Cuckoo {
+    /// Remaining number of elements that can be added.
+    ///
+    /// This is necessary because the inner implementation will fail on adding an element past capacity, **but it will still add it and remove other**: [source](https://github.com/axiomhq/rust-cuckoofilter/tree/624da891bed1dd5d002c8fa92ce0dcd301975561#notes--todos)
+    remaining: usize,
+
+    /// CuckooFilter.
+    filter: CuckooFilter<DefaultHasher>, // TODO does it need an actual hasher?
+}
+
+impl Cuckoo {
+    pub fn new(max_capacity: usize) -> Self {
+        Cuckoo { remaining: max_capacity, filter: CuckooFilter::with_capacity(max_capacity) }
+    }
+}
+
+impl Filter for Cuckoo {
+    fn add(&mut self, element: &[u8]) -> Result<(), NippyJarError> {
+        if self.remaining == 0 {
+            return Err(NippyJarError::FilterMaxCapacity)
+        }
+
+        self.remaining -= 1;
+
+        Ok(self.filter.add(element)?)
+    }
+
+    fn contains(&self, element: &[u8]) -> Result<bool, NippyJarError> {
+        Ok(self.filter.contains(element))
+    }
+}
+
+impl std::fmt::Debug for Cuckoo {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "Cuckoo {{ remaining_elements: {:?}, filter size: {:?} }}",
+            self.remaining,
+            self.filter.memory_usage(),
+        )
+    }
+}
+
+impl PartialEq for Cuckoo {
+    fn eq(&self, _other: &Self) -> bool {
+        self.remaining == _other.remaining &&
+            {
+                #[cfg(not(test))]
+                {
+                    unimplemented!("No way to figure it out without exporting (expensive), so only allow direct comparison on a test")
+                }
+                #[cfg(test)]
+                {
+                    let f1 = self.filter.export();
+                    let f2 = _other.filter.export();
+                    return f1.length == f2.length && f1.values == f2.values
+                }
+            }
+    }
+}
+
+impl<'de> Deserialize<'de> for Cuckoo {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let (remaining, exported): (usize, ExportedCuckooFilter) =
+            Deserialize::deserialize(deserializer)?;
+
+        Ok(Cuckoo { remaining, filter: exported.into() })
+    }
+}
+
+impl Serialize for Cuckoo {
+    /// Potentially expensive, but should be used only when creating the file.
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        (self.remaining, self.filter.export()).serialize(serializer)
+    }
+}

crates/storage/nippy-jar/src/filter/mod.rs

@@ -0,0 +1,36 @@
+use crate::NippyJarError;
+use serde::{Deserialize, Serialize};
+
+mod cuckoo;
+pub use cuckoo::Cuckoo;
+
+pub trait Filter {
+    /// Add element to the inclusion list.
+    fn add(&mut self, element: &[u8]) -> Result<(), NippyJarError>;
+
+    /// Checks if the element belongs to the inclusion list. There might be false positives.
+    fn contains(&self, element: &[u8]) -> Result<bool, NippyJarError>;
+}
+
+#[derive(Debug, Serialize, Deserialize, PartialEq)]
+pub enum Filters {
+    Cuckoo(Cuckoo),
+    // Avoids irrefutable let errors. Remove this after adding another one.
+    Unused,
+}
+
+impl Filter for Filters {
+    fn add(&mut self, element: &[u8]) -> Result<(), NippyJarError> {
+        match self {
+            Filters::Cuckoo(c) => c.add(element),
+            Filters::Unused => todo!(),
+        }
+    }
+
+    fn contains(&self, element: &[u8]) -> Result<bool, NippyJarError> {
+        match self {
+            Filters::Cuckoo(c) => c.contains(element),
+            Filters::Unused => todo!(),
+        }
+    }
+}