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use std::collections::HashMap;
use std::hash::Hash;
use std::ops::{Deref, DerefMut};
use serde::{Deserialize, Serialize};
use hash32::Hasher;
pub type Count = u8;
pub type Indexer = u32;
/// Represents the content of a cached file.
/// It is stored as a HashMap, because we do not
/// have to store the zeros. With that we save a lot
/// of storage.
#[derive(Default, Clone, Debug, Deserialize, Serialize)]
pub struct FileVector {
data : Vec<FileVectorEntry>
}
#[repr(packed)]
#[derive(Default, Clone, Debug, Deserialize, Serialize)]
pub struct FileVectorEntry {
index: u32,
count: Count,
}
impl Deref for FileVector {
type Target = Vec<FileVectorEntry>;
fn deref(&self) -> &Self::Target {
&self.data
}
}
impl DerefMut for FileVector {
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.data
}
}
impl FileVector {
pub fn new() -> Self {
Self { data : Vec::new() }
}
pub fn to_hashmap(&self) -> HashMap<Indexer, Count> {
let mut map = HashMap::new();
for e in self.data.iter() {
map.insert(e.index, e.count);
}
map
}
pub fn from_words(words: Vec<String>) -> Self {
let mut data : HashMap<Indexer, Count> = HashMap::new();
for word in words {
let mut hasher = hash32::FnvHasher::default();
word.hash(&mut hasher);
let k = hasher.finish32();
match data.entry(k as Indexer) {
std::collections::hash_map::Entry::Occupied(mut e) => {
let i = *e.get();
if i == Count::MAX {
e.insert((i + 1) as Count);
}
}
std::collections::hash_map::Entry::Vacant(e) => {
e.insert(1);
}
}
}
FileVector::from_hashmap(data)
}
pub fn from_hashmap(map : HashMap<Indexer, Count>) -> Self {
Self { data : Vec::from_iter(map.iter().map(|e| {
FileVectorEntry { index: *e.0, count: *e.1 }
}))}
}
}
pub fn scalar_product(a : &FileVector, b : &FileVector) -> u32 {
let a = a.to_hashmap();
let b = b.to_hashmap();
let mut c : u32 = 0;
for (i, x) in a.iter() {
c += (x * (b.get(i).unwrap_or(&0))) as u32;
}
c
}
pub fn match_vector(query : &FileVector, v : &FileVector) -> u32 {
let query = query.to_hashmap();
let v = v.to_hashmap();
let mut c : u32 = 0;
for (i, x) in query.iter() {
let s = x * (v.get(i).unwrap_or(&0));
if s == 0 {
return 0
} else {
c += s as u32;
}
}
c
}
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