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mod bits;
use bits::{
BitStreamReader,
BitStreamWriter
};
use std::collections::HashSet;
use failure::Fail;
use std::{cmp, io};
use crate::hash::SipHasher;
const P_BIP158: u8 = 19;
const M_BIP158: u64 = 784931;
#[derive(Debug, Fail)]
pub enum Error {
#[fail(display = "Limit for the number of elements has been reached")]
LimitReached,
#[fail(display = "Decoding failed due to invalid Golomb-Rice bit sequence")]
Decode,
#[fail(display = "IO error: {}", _0)]
Io(io::Error),
}
impl From<io::Error> for Error {
fn from(err: io::Error) -> Self {
Error::Io(err)
}
}
fn map_to_range(hash: u64, nm: u64) -> u64 {
#[inline]
fn l(n: u64) -> u64 { n & 0xffffffff }
#[inline]
fn h(n: u64) -> u64 { n >> 32 }
let a = h(hash);
let b = l(hash);
let c = h(nm);
let d = l(nm);
a * c + h(a * d + c * b + h(b * d))
}
struct GCSFilter {
k0: u64,
k1: u64,
p: u8
}
impl GCSFilter {
fn new(k0: u64, k1: u64, p: u8) -> GCSFilter {
if p == 0 {
panic!("p cannot be 0");
}
GCSFilter { k0, k1, p }
}
fn golomb_rice_encode(&self, writer: &mut BitStreamWriter, n: u64) -> Result<usize, io::Error> {
let mut wrote = 0;
let mut q = n >> self.p;
while q > 0 {
let nbits = cmp::min(q, 64);
wrote += writer.write(!0u64, nbits as u8)?;
q -= nbits;
}
wrote += writer.write(0, 1)?;
wrote += writer.write(n, self.p)?;
Ok(wrote)
}
fn golomb_rice_decode(&self, reader: &mut BitStreamReader) -> Result<u64, io::Error> {
let mut q = 0u64;
while reader.read(1)? == 1 {
q += 1;
}
let r = reader.read(self.p)?;
return Ok((q << self.p) + r);
}
fn hash(&self, element: &[u8]) -> u64 {
SipHasher::hash_to_u64_with_keys(self.k0, self.k1, element)
}
}
pub struct GCSFilterWriter<'a> {
filter: GCSFilter,
writer: &'a mut dyn io::Write,
elements: HashSet<Vec<u8>>,
m: u64
}
impl<'a> GCSFilterWriter<'a> {
pub fn new(writer: &'a mut dyn io::Write, k0: u64, k1: u64, m: u64, p: u8) -> GCSFilterWriter<'a> {
GCSFilterWriter {
filter: GCSFilter::new(k0, k1, p),
writer,
elements: HashSet::new(),
m
}
}
pub fn add_element(&mut self, element: &[u8]) {
if !element.is_empty() {
self.elements.insert(element.to_vec());
}
}
pub fn finish(&mut self) -> Result<usize, io::Error> {
let nm = self.elements.len() as u64 * self.m;
let mut mapped: Vec<_> = self.elements.iter()
.map(|e| map_to_range(self.filter.hash(e.as_slice()), nm)).collect();
mapped.sort();
let mut encoder = io::Cursor::new(Vec::new());
let varint = mapped.len() as u64;
crate::ser::serialize_default(&mut encoder, &varint).unwrap();
let mut wrote = self.writer.write(encoder.into_inner().as_slice())?;
let mut writer = BitStreamWriter::new(self.writer);
let mut last = 0;
for data in mapped {
wrote += self.filter.golomb_rice_encode(&mut writer, data - last)?;
last = data;
}
wrote += writer.flush()?;
Ok(wrote)
}
}
pub struct GCSFilterReader {
filter: GCSFilter,
m: u64
}
impl GCSFilterReader {
pub fn new(k0: u64, k1: u64, m: u64, p: u8) -> GCSFilterReader {
GCSFilterReader { filter: GCSFilter::new(k0, k1, p), m }
}
pub fn match_any(&self, reader: &mut dyn io::Read, query: &mut dyn Iterator<Item=&[u8]>) -> Result<bool, Error> {
let mut decoder = reader;
let n_elements: u64 = crate::ser::deserialize_default(&mut decoder).unwrap_or(0u64);
let ref mut reader = decoder;
let nm = n_elements * self.m;
let mut mapped = query.map(|e| map_to_range(self.filter.hash(e), nm)).collect::<Vec<_>>();
mapped.sort();
if mapped.is_empty() {
return Ok(true);
}
if n_elements == 0 {
return Ok(false);
}
let mut reader = BitStreamReader::new(reader);
let mut data = self.filter.golomb_rice_decode(&mut reader)?;
let mut remaining = n_elements - 1;
for p in mapped {
loop {
if data == p {
return Ok(true);
} else if data < p {
if remaining > 0 {
data += self.filter.golomb_rice_decode(&mut reader)?;
remaining -= 1;
} else {
return Ok(false);
}
} else {
break;
}
}
}
Ok(false)
}
pub fn match_all(&self, reader: &mut dyn io::Read, query: &mut dyn Iterator<Item=&[u8]>) -> Result<bool, Error> {
let mut decoder = reader;
let n_elements: u64 = crate::ser::deserialize_default(&mut decoder).unwrap_or(0u64);
let ref mut reader = decoder;
let nm = n_elements * self.m;
let mut mapped = query.map(|e| map_to_range(self.filter.hash(e), nm)).collect::<Vec<_>>();
mapped.sort();
mapped.dedup();
if mapped.is_empty() {
return Ok(true);
}
if n_elements == 0 {
return Ok(false);
}
let mut reader = BitStreamReader::new(reader);
let mut data = self.filter.golomb_rice_decode(&mut reader)?;
let mut remaining = n_elements - 1;
for p in mapped {
loop {
if data == p {
break;
} else if data < p {
if remaining > 0 {
data += self.filter.golomb_rice_decode(&mut reader)?;
remaining -= 1;
} else {
return Ok(false);
}
} else {
return Ok(false);
}
}
}
Ok(true)
}
}
#[test]
fn test_filter () {
use std::io::Cursor;
let mut patterns = HashSet::new();
patterns.insert(hex::decode("000000").unwrap());
patterns.insert(hex::decode("111111").unwrap());
patterns.insert(hex::decode("222222").unwrap());
patterns.insert(hex::decode("333333").unwrap());
patterns.insert(hex::decode("444444").unwrap());
patterns.insert(hex::decode("555555").unwrap());
patterns.insert(hex::decode("666666").unwrap());
patterns.insert(hex::decode("777777").unwrap());
patterns.insert(hex::decode("888888").unwrap());
patterns.insert(hex::decode("999999").unwrap());
patterns.insert(hex::decode("aaaaaa").unwrap());
patterns.insert(hex::decode("bbbbbb").unwrap());
patterns.insert(hex::decode("cccccc").unwrap());
patterns.insert(hex::decode("dddddd").unwrap());
patterns.insert(hex::decode("eeeeee").unwrap());
patterns.insert(hex::decode("ffffff").unwrap());
let mut out = Cursor::new(Vec::new());
{
let mut writer = GCSFilterWriter::new(&mut out, 0, 0, M_BIP158, P_BIP158);
for p in &patterns {
writer.add_element(p.as_slice());
}
writer.finish().unwrap();
}
let bytes = out.into_inner();
{
let mut query = Vec::new();
query.push(hex::decode("abcdef").unwrap());
query.push(hex::decode("eeeeee").unwrap());
let reader = GCSFilterReader::new(0, 0, M_BIP158, P_BIP158);
let mut input = Cursor::new(bytes.clone());
assert!(reader.match_any(&mut input, &mut query.iter().map(|v| v.as_slice())).unwrap());
}
{
let mut query = Vec::new();
query.push(hex::decode("abcdef").unwrap());
query.push(hex::decode("123456").unwrap());
let reader = GCSFilterReader::new(0, 0, M_BIP158, P_BIP158);
let mut input = Cursor::new(bytes.clone());
assert!(!reader.match_any(&mut input, &mut query.iter().map(|v| v.as_slice())).unwrap());
}
{
let reader = GCSFilterReader::new(0, 0, M_BIP158, P_BIP158);
let mut query = Vec::new();
for p in &patterns {
query.push(p.clone());
}
let mut input = Cursor::new(bytes.clone());
assert!(reader.match_all(&mut input, &mut query.iter().map(|v| v.as_slice())).unwrap());
}
{
let reader = GCSFilterReader::new(0, 0, M_BIP158, P_BIP158);
let mut query = Vec::new();
for p in &patterns {
query.push(p.clone());
}
query.push(hex::decode("abcdef").unwrap());
let mut input = Cursor::new(bytes.clone());
assert!(!reader.match_all(&mut input, &mut query.iter().map(|v| v.as_slice())).unwrap());
}
}