use super::util::Hash; use std::path::Path; use std::fs::{File, OpenOptions}; use std::mem; use std::io; use std::slice; use std::os::unix::io::AsRawFd; use mmap::{MemoryMap, MapOption, MapError}; const MAGIC: [u8; 7] = *b"zvault\x02"; const VERSION: u8 = 1; pub const MAX_USAGE: f64 = 0.9; pub const MIN_USAGE: f64 = 0.35; pub const INITIAL_SIZE: usize = 1024; quick_error!{ #[derive(Debug)] pub enum IndexError { Io(err: io::Error) { from() cause(err) description("Failed to open index file") display("Index error: failed to open the index file\n\tcaused by: {}", err) } Mmap(err: MapError) { from() cause(err) description("Failed to memory-map the index file") display("Index error: failed to memory-map the index file\n\tcaused by: {}", err) } WrongMagic { description("Wrong header") display("Index error: file has the wrong magic header") } UnsupportedVersion(version: u8) { description("Unsupported version") display("Index error: index file has unsupported version: {}", version) } WrongPosition(key: Hash, should: usize, is: LocateResult) { description("Key at wrong position") display("Index error: key {} has wrong position, expected at: {}, but is at: {:?}", key, should, is) } WrongEntryCount(header: usize, actual: usize) { description("Wrong entry count") display("Index error: index has wrong entry count, expected {}, but is {}", header, actual) } } } #[repr(packed)] pub struct Header { magic: [u8; 7], version: u8, entries: u64, capacity: u64, } #[repr(packed)] #[derive(Clone, Copy, PartialEq, Debug)] pub struct Location { pub bundle: u32, pub chunk: u32 } impl Location { pub fn new(bundle: u32, chunk: u32) -> Self { Location{ bundle: bundle, chunk: chunk } } } #[repr(packed)] #[derive(Clone)] pub struct Entry { pub key: Hash, pub data: Location } impl Entry { #[inline] fn is_used(&self) -> bool { self.key.low != 0 || self.key.high != 0 } fn clear(&mut self) { self.key.low = 0; self.key.high = 0; } } pub struct Index { capacity: usize, entries: usize, max_entries: usize, min_entries: usize, fd: File, mmap: MemoryMap, data: &'static mut [Entry] } #[derive(Debug)] pub enum LocateResult { Found(usize), // Found the key at this position Hole(usize), // Found a hole at this position while searching for a key Steal(usize) // Found a spot to steal at this position while searching for a key } impl Index { pub fn new(path: &Path, create: bool) -> Result { let fd = try!(OpenOptions::new().read(true).write(true).create(create).open(path)); if create { try!(Index::resize_fd(&fd, INITIAL_SIZE)); } let mmap = try!(Index::map_fd(&fd)); if mmap.len() < mem::size_of::
() { return Err(IndexError::WrongMagic); } let data = Index::mmap_as_slice(&mmap, INITIAL_SIZE as usize); let mut index = Index{capacity: 0, max_entries: 0, min_entries: 0, entries: 0, fd: fd, mmap: mmap, data: data}; { let capacity; let entries; { let header = index.header(); if create { header.magic = MAGIC; header.version = VERSION; header.entries = 0; header.capacity = INITIAL_SIZE as u64; } else { if header.magic != MAGIC { return Err(IndexError::WrongMagic); } if header.version != VERSION { return Err(IndexError::UnsupportedVersion(header.version)); } } capacity = header.capacity; entries = header.entries; } index.data = Index::mmap_as_slice(&index.mmap, capacity as usize); index.set_capacity(capacity as usize); index.entries = entries as usize; } debug_assert!(index.check().is_ok(), "Inconsistent after creation"); Ok(index) } #[inline] pub fn open(path: &Path) -> Result { Index::new(path, false) } #[inline] pub fn create(path: &Path) -> Result { Index::new(path, true) } #[inline] fn map_fd(fd: &File) -> Result { MemoryMap::new( try!(fd.metadata().map_err(IndexError::Io)).len() as usize, &[MapOption::MapReadable, MapOption::MapWritable, MapOption::MapFd(fd.as_raw_fd()), MapOption::MapNonStandardFlags(0x0001) //libc::consts::os::posix88::MAP_SHARED ]).map_err(IndexError::Mmap) } #[inline] fn resize_fd(fd: &File, capacity: usize) -> Result<(), IndexError> { fd.set_len((mem::size_of::
() + capacity * mem::size_of::()) as u64).map_err(IndexError::Io) } #[inline] fn mmap_as_slice(mmap: &MemoryMap, len: usize) -> &'static mut [Entry] { if mmap.len() < mem::size_of::
() + len * mem::size_of::() { panic!("Memory map too small"); } let ptr = unsafe { mmap.data().offset(mem::size_of::
() as isize) as *mut Entry }; unsafe { slice::from_raw_parts_mut(ptr, len) } } #[inline] fn header(&mut self) -> &mut Header { if self.mmap.len() < mem::size_of::
() { panic!("Failed to read beyond end"); } unsafe { &mut *(self.mmap.data() as *mut Header) } } #[inline] fn set_capacity(&mut self, capacity: usize) { self.capacity = capacity; self.min_entries = (capacity as f64 * MIN_USAGE) as usize; self.max_entries = (capacity as f64 * MAX_USAGE) as usize; } fn reinsert(&mut self, start: usize, end: usize) -> Result<(), IndexError> { for pos in start..end { let key; let data; { let entry = &mut self.data[pos]; if !entry.is_used() { continue; } key = entry.key; data = entry.data; entry.clear(); } self.entries -= 1; try!(self.set(&key, &data)); } Ok(()) } fn shrink(&mut self) -> Result { if self.entries >= self.min_entries || self.capacity <= INITIAL_SIZE { return Ok(false) } let old_capacity = self.capacity; let new_capacity = self.capacity / 2; self.set_capacity(new_capacity); try!(self.reinsert(new_capacity, old_capacity)); try!(Index::resize_fd(&self.fd, new_capacity)); self.mmap = try!(Index::map_fd(&self.fd)); self.data = Index::mmap_as_slice(&self.mmap, new_capacity); assert_eq!(self.data.len(), self.capacity); Ok(true) } fn extend(&mut self) -> Result { if self.entries <= self.max_entries { return Ok(false) } let new_capacity = 2 * self.capacity; try!(Index::resize_fd(&self.fd, new_capacity)); self.mmap = try!(Index::map_fd(&self.fd)); self.data = Index::mmap_as_slice(&self.mmap, new_capacity); self.set_capacity(new_capacity); assert_eq!(self.data.len(), self.capacity); try!(self.reinsert(0, new_capacity)); Ok(true) } pub fn check(&self) -> Result<(), IndexError> { let mut entries = 0; for pos in 0..self.capacity { let entry = &self.data[pos]; if !entry.is_used() { continue; } entries += 1; match self.locate(&entry.key) { LocateResult::Found(p) if p == pos => true, found => return Err(IndexError::WrongPosition(entry.key, pos, found)) }; } if entries != self.entries { return Err(IndexError::WrongEntryCount(self.entries, entries)); } Ok(()) } #[inline] fn increase_count(&mut self) -> Result<(), IndexError> { self.entries += 1; try!(self.extend()); self.write_header(); Ok(()) } #[inline] fn decrease_count(&mut self) -> Result<(), IndexError> { self.entries -= 1; try!(self.shrink()); self.write_header(); Ok(()) } #[inline] fn write_header(&mut self) { let entries = self.entries; let capacity = self.capacity; let header = self.header(); header.entries = entries as u64; header.capacity = capacity as u64; } /// Finds the position for this key /// If the key is in the table, it will be the position of the key, /// otherwise it will be the position where this key should be inserted fn locate(&self, key: &Hash) -> LocateResult { let mut pos = key.hash() as usize % self.capacity; let mut dist = 0; loop { let entry = &self.data[pos]; if !entry.is_used() { return LocateResult::Hole(pos); } if entry.key == *key { return LocateResult::Found(pos); } let odist = (pos + self.capacity - entry.key.hash() as usize % self.capacity) % self.capacity; if dist > odist { return LocateResult::Steal(pos); } pos = (pos + 1) % self.capacity ; dist += 1; } } /// Shifts all following entries towards the left if they can get closer to their ideal position. /// The entry at the given position will be lost. fn backshift(&mut self, start: usize) { let mut pos = start; let mut last_pos; loop { last_pos = pos; pos = (pos + 1) % self.capacity; { let entry = &self.data[pos]; if !entry.is_used() { // we found a hole, stop shifting here break; } if entry.key.hash() as usize % self.capacity == pos { // we found an entry at the right position, stop shifting here break; } } self.data[last_pos] = self.data[pos].clone(); } self.data[last_pos].clear(); } /// Adds the key, data pair into the table. /// If the key existed in the table before, it is overwritten and false is returned. /// Otherwise it will be added to the table and true is returned. pub fn set(&mut self, key: &Hash, data: &Location) -> Result { match self.locate(key) { LocateResult::Found(pos) => { self.data[pos].data = *data; Ok(false) }, LocateResult::Hole(pos) => { { let entry = &mut self.data[pos]; entry.key = *key; entry.data = *data; } try!(self.increase_count()); Ok(true) }, LocateResult::Steal(pos) => { let mut stolen_key; let mut stolen_data; let mut cur_pos = pos; { let entry = &mut self.data[pos]; stolen_key = entry.key; stolen_data = entry.data; entry.key = *key; entry.data = *data; } loop { cur_pos = (cur_pos + 1) % self.capacity; let entry = &mut self.data[cur_pos]; if entry.is_used() { mem::swap(&mut stolen_key, &mut entry.key); mem::swap(&mut stolen_data, &mut entry.data); } else { entry.key = stolen_key; entry.data = stolen_data; break; } } try!(self.increase_count()); Ok(true) } } } #[inline] pub fn contains(&self, key: &Hash) -> bool { debug_assert!(self.check().is_ok(), "Inconsistent before get"); match self.locate(key) { LocateResult::Found(_) => true, _ => false } } #[inline] pub fn pos(&self, key: &Hash) -> Option { debug_assert!(self.check().is_ok(), "Inconsistent before get"); match self.locate(key) { LocateResult::Found(pos) => Some(pos), _ => None } } #[inline] pub fn get(&self, key: &Hash) -> Option { debug_assert!(self.check().is_ok(), "Inconsistent before get"); match self.locate(key) { LocateResult::Found(pos) => Some(self.data[pos].data), _ => None } } #[inline] pub fn modify(&mut self, key: &Hash, mut f: F) -> bool where F: FnMut(&mut Location) { debug_assert!(self.check().is_ok(), "Inconsistent before get"); match self.locate(key) { LocateResult::Found(pos) => { f(&mut self.data[pos].data); true }, _ => false } } #[inline] pub fn delete(&mut self, key: &Hash) -> Result { match self.locate(key) { LocateResult::Found(pos) => { self.backshift(pos); try!(self.decrease_count()); Ok(true) }, _ => Ok(false) } } pub fn filter(&mut self, mut f: F) -> Result where F: FnMut(&Hash, &Location) -> bool { //TODO: is it faster to walk in reverse direction? let mut deleted = 0; let mut pos = 0; while pos < self.capacity { { let entry = &mut self.data[pos]; if !entry.is_used() || f(&entry.key, &entry.data) { pos += 1; continue; } } self.backshift(pos); deleted += 1; } self.entries -= deleted; while try!(self.shrink()) {} self.write_header(); Ok(deleted) } #[inline] pub fn walk(&self, mut f: F) -> Result<(), E> where F: FnMut(&Hash, &Location) -> Result<(), E> { for pos in 0..self.capacity { let entry = &self.data[pos]; if entry.is_used() { try!(f(&entry.key, &entry.data)); } } Ok(()) } #[inline] pub fn walk_mut(&mut self, mut f: F) -> Result<(), E> where F: FnMut(&Hash, &mut Location) -> Result<(), E> { for pos in 0..self.capacity { let entry = &mut self.data[pos]; if entry.is_used() { try!(f(&entry.key, &mut entry.data)); } } Ok(()) } #[inline] pub fn next_entry(&self, index: usize) -> Option { let mut i = index; while i < self.capacity && !self.data[i].is_used() { i += 1; } if i == self.capacity { None } else { Some(i) } } #[inline] pub fn get_entry(&self, index: usize) -> Option<&Entry> { let entry = &self.data[index]; if entry.is_used() { Some(entry) } else { None } } #[inline] pub fn len(&self) -> usize { self.entries } #[inline] pub fn size(&self) -> usize { self.mmap.len() } #[inline] pub fn is_empty(&self) -> bool { self.entries == 0 } #[inline] pub fn capacity(&self) -> usize { self.capacity } }