Merge pull request #1 from CeresDB/remove-collect

remove unnecessary collect

Author: Rachelint

README.md

@@ -22,24 +22,28 @@ or
 
 ```toml
 [dependencies]
-xorfilter-rs = { git = "https://github.com/bnclabs/xorfilter" }
+xorfilter-rs = { git = "https://github.com/prataprc/xorfilter" }
 ```
 
 ```rust
-use xorfilter::Xor8;
-
-let mut keys: Vec<u64> = vec![];
-for _ in 0..num_keys {
-    keys.push(rng.gen());
-}
-
-let mut filter = Xor8::new(); // new filter.
-filter.populate_keys(&keys); // populate keys.
-filter.build(); // build bitmap.
-
-for key in 0..lookup {
-    // there can be false positives, but no false negatives.
-    filter.contains_key(key);
+use xorfilter::{xor8::Xor8Builder, BuildHasherDefault};
+
+fn main() {
+    let num_keys = 1000;
+    let lookup = 10;
+    let mut b = Xor8Builder::<BuildHasherDefault>::default();
+    for i in 0..num_keys {
+        if i % 2 == 0 {
+            b.insert(&i);
+        }
+    }
+
+    // build bitmap.
+    let filter = b.build().unwrap();
+    for key in 0..lookup {
+        // there can be false positives, but no false negatives.
+        println!("{key}: {}", filter.contains(&key));
+    }
 }
 ```
 

src/xor8/builder.rs

@@ -1,13 +1,15 @@
-use std::hash::BuildHasher;
-use std::hash::Hash;
-use std::hash::Hasher;
-use std::sync::Arc;
-
-use crate::xor8::filter::fingerprint;
-use crate::xor8::filter::splitmix64;
-use crate::xor8::filter::XorSet;
-use crate::xor8::Xor8;
-use crate::BuildHasherDefault;
+use std::{
+    hash::{BuildHasher, Hash, Hasher},
+    sync::Arc,
+};
+
+use crate::{
+    xor8::{
+        filter::{fingerprint, splitmix64, XorSet},
+        Xor8,
+    },
+    BuildHasherDefault,
+};
 
 #[derive(Clone, Copy, Default)]
 struct KeyIndex {
@@ -56,15 +58,17 @@ type U64HashSet = ::std::collections::HashSet<u64, U64IdentifyBuildHasher>;
 /// ```
 #[derive(Clone, Debug)]
 pub struct Xor8Builder<H = BuildHasherDefault>
-where H: BuildHasher + Clone
+where
+    H: BuildHasher + Clone,
 {
     digests: U64HashSet,
     pub num_digests: usize,
     pub hash_builder: H,
 }
 
 impl<H> Default for Xor8Builder<H>
-where H: BuildHasher + Clone + Default
+where
+    H: BuildHasher + Clone + Default,
 {
     fn default() -> Self {
         Self {
@@ -76,11 +80,14 @@ where H: BuildHasher + Clone + Default
 }
 
 impl<H> Xor8Builder<H>
-where H: BuildHasher + Clone
+where
+    H: BuildHasher + Clone,
 {
     /// New Xor8 builder initialized with [BuildHasherDefault].
     pub fn new() -> Self
-    where H: Default {
+    where
+        H: Default,
+    {
         Self::default()
     }
 
@@ -107,8 +114,8 @@ where H: BuildHasher + Clone
 
     /// Insert 64-bit digest of a single key.
     ///
-    /// Digest for the key shall be generated using the default-hasher or via hasher
-    /// supplied via [Xor8Builder::with_hasher] method.
+    /// Digest for the key shall be generated using the default-hasher or via
+    /// hasher supplied via [Xor8Builder::with_hasher] method.
     pub fn insert<K: ?Sized + Hash>(&mut self, key: &K) {
         let digest = self.hash(key);
 
@@ -118,8 +125,8 @@ where H: BuildHasher + Clone
 
     /// Populate with 64-bit digests for a collection of keys of type `K`.
     ///
-    /// Digest for key shall be generated using the default-hasher or via hasher supplied
-    /// via [Xor8Builder::with_hasher] method.
+    /// Digest for key shall be generated using the default-hasher or via hasher
+    /// supplied via [Xor8Builder::with_hasher] method.
     pub fn populate<'i, K: Hash + 'i, I: IntoIterator<Item = &'i K>>(&mut self, keys: I) {
         let mut n = 0;
 
@@ -145,28 +152,49 @@ where H: BuildHasher + Clone
         self.num_digests += n;
     }
 
-    /// Build bitmap for keys that where previously inserted using [Xor8Builder::insert],
-    /// [Xor8Builder::populate] and [Xor8Builder::populate_digests] method.
+    /// Build bitmap for keys that where previously inserted using
+    /// [Xor8Builder::insert], [Xor8Builder::populate] and
+    /// [Xor8Builder::populate_digests] method.
     pub fn build(&mut self) -> Result<Xor8<H>, crate::Error> {
-        let digests = self.digests.iter().copied().collect::<Vec<u64>>();
-        self.build_from_digests(&digests)
+        let digest_len = self.digests.len();
+        Self::build_inner(
+            self.hash_builder.clone(),
+            self.digests.iter().copied(),
+            digest_len,
+        )
     }
 
     /// Build a bitmap for pre-computed 64-bit digests for keys.
     ///
     /// If keys where previously inserted using [Xor8Builder::insert] or
-    /// [Xor8Builder::populate] or [Xor8Builder::populate_digests] methods, they shall be
-    /// ignored.
+    /// [Xor8Builder::populate] or [Xor8Builder::populate_digests] methods, they
+    /// shall be ignored.
     ///
-    /// It is upto the caller to ensure that digests are unique, that there no duplicates.
+    /// It is upto the caller to ensure that digests are unique, that there no
+    /// duplicates.
     pub fn build_from_digests(
         &mut self,
         digests: &[u64],
     ) -> Result<Xor8<H>, crate::Error> {
-        let mut ff = Xor8::<H>::new(self.hash_builder.clone());
+        Self::build_inner(
+            self.hash_builder.clone(),
+            digests.iter().copied(),
+            digests.len(),
+        )
+    }
 
-        ff.num_keys = Some(digests.len());
-        let (size, mut rngcounter) = (digests.len(), 1_u64);
+    fn build_inner<It>(
+        hash_builder: H,
+        digest_iter: It,
+        digest_len: usize,
+    ) -> Result<Xor8<H>, crate::Error>
+    where
+        It: Iterator<Item = u64> + Clone,
+    {
+        let mut ff = Xor8::<H>::new(hash_builder);
+
+        ff.num_keys = Some(digest_len);
+        let (size, mut rngcounter) = (digest_len, 1_u64);
         let capacity = {
             let capacity = 32 + ((1.23 * (size as f64)).ceil() as u32);
             capacity / 3 * 3 // round it down to a multiple of 3
@@ -185,8 +213,8 @@ where H: BuildHasher + Clone
         let mut sets2: Vec<XorSet> = vec![XorSet::default(); block_length];
 
         loop {
-            for key in digests.iter() {
-                let hs = ff.get_h0h1h2(*key);
+            for key in digest_iter.clone() {
+                let hs = ff.get_h0h1h2(key);
                 sets0[hs.h0 as usize].xor_mask ^= hs.h;
                 sets0[hs.h0 as usize].count += 1;
                 sets1[hs.h1 as usize].xor_mask ^= hs.h;