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use crate::{
nd, Arc, BTreeMap, CompactFile, Data, HashMap, HashSet, Mutex, RwLock, SaveOp, Storage,
};
use std::ops::Bound::Included;
type PageInfoPtr = Arc<Mutex<PageInfo>>;
struct PageInfo {
current: Option<Data>,
history: BTreeMap<u64, Data>,
}
impl PageInfo {
fn new() -> PageInfoPtr {
Arc::new(Mutex::new(Self {
current: None,
history: BTreeMap::new(),
}))
}
fn get(&mut self, lpnum: u64, a: &AccessPagedData) -> Data {
if !a.writer {
if let Some((_k, v)) = self
.history
.range((Included(&a.time), Included(&u64::MAX)))
.next()
{
return v.clone();
}
}
if let Some(p) = &self.current {
return p.clone();
}
let file = a.spd.file.read().unwrap();
let data = file.get_page(lpnum);
self.current = Some(data.clone());
data
}
fn set(&mut self, time: u64, data: Data) {
if let Some(old) = self.current.take() {
self.history.insert(time, old);
}
self.current = Some(data);
}
fn trim(&mut self, to: u64) {
while let Some(&f) = self.history.keys().next() {
if f >= to {
break;
}
self.history.remove(&f);
}
}
}
#[derive(Default)]
pub struct Stash {
time: u64,
pages: HashMap<u64, PageInfoPtr>,
readers: BTreeMap<u64, usize>,
updates: BTreeMap<u64, HashSet<u64>>,
}
impl Stash {
fn set(&mut self, lpnum: u64, data: Data) {
let time = self.time;
let u = self.updates.entry(time).or_insert_with(HashSet::default);
if u.insert(lpnum) {
let p = self.pages.entry(lpnum).or_insert_with(PageInfo::new);
p.lock().unwrap().set(time, data);
}
}
fn get(&mut self, lpnum: u64) -> PageInfoPtr {
let p = self.pages.entry(lpnum).or_insert_with(PageInfo::new);
p.clone()
}
fn begin_read(&mut self) -> u64 {
let time = self.time;
let n = self.readers.entry(time).or_insert(0);
*n += 1;
time
}
fn end_read(&mut self, time: u64) {
let n = self.readers.get_mut(&time).unwrap();
*n -= 1;
if *n == 0 {
self.readers.remove(&time);
self.trim();
}
}
fn end_write(&mut self) -> usize {
let result = if let Some(u) = self.updates.get(&self.time) {
u.len()
} else {
0
};
self.time += 1;
self.trim();
result
}
fn trim(&mut self) {
let rt = *self.readers.keys().next().unwrap_or(&self.time);
while let Some(&wt) = self.updates.keys().next() {
if wt >= rt {
break;
}
for lpnum in self.updates.remove(&wt).unwrap() {
let p = self.pages.get(&lpnum).unwrap();
p.lock().unwrap().trim(rt);
}
}
}
}
pub struct SharedPagedData {
pub file: RwLock<CompactFile>,
pub sp_size: usize,
pub ep_size: usize,
pub stash: RwLock<Stash>,
}
const EP_SIZE: usize = 1024;
const EP_MAX: usize = 16;
const SP_SIZE: usize = (EP_MAX + 1) * 8;
impl SharedPagedData {
pub fn new(file: Box<dyn Storage>) -> Self {
let file = CompactFile::new(file, SP_SIZE, EP_SIZE);
let sp_size = file.sp_size;
let ep_size = file.ep_size;
Self {
stash: RwLock::new(Stash::default()),
file: RwLock::new(file),
sp_size,
ep_size,
}
}
pub fn page_size_max(&self) -> usize {
let ep_max = (self.sp_size - 2) / 8;
(self.ep_size - 16) * ep_max + (self.sp_size - 2)
}
}
pub struct AccessPagedData {
writer: bool,
time: u64,
pub spd: Arc<SharedPagedData>,
}
impl AccessPagedData {
pub fn new_reader(spd: Arc<SharedPagedData>) -> Self {
let time = spd.stash.write().unwrap().begin_read();
AccessPagedData {
writer: false,
time,
spd,
}
}
pub fn new_writer(spd: Arc<SharedPagedData>) -> Self {
AccessPagedData {
writer: true,
time: 0,
spd,
}
}
pub fn get_page(&self, lpnum: u64) -> Data {
let pinfo = self.spd.stash.write().unwrap().get(lpnum);
let mut pinfo = pinfo.lock().unwrap();
pinfo.get(lpnum, self)
}
pub fn set_page(&self, lpnum: u64, data: Data) {
debug_assert!(self.writer);
self.spd.stash.write().unwrap().set(lpnum, data.clone());
self.spd.file.write().unwrap().set_page(lpnum, data);
}
pub fn is_new(&self) -> bool {
self.writer && self.spd.file.read().unwrap().is_new()
}
pub fn compress(&self, size: usize, saving: usize) -> bool {
debug_assert!(self.writer);
CompactFile::compress(self.spd.sp_size, self.spd.ep_size, size, saving)
}
pub fn alloc_page(&self) -> u64 {
debug_assert!(self.writer);
self.spd.file.write().unwrap().alloc_page()
}
pub fn free_page(&self, lpnum: u64) {
debug_assert!(self.writer);
self.spd.stash.write().unwrap().set(lpnum, nd());
self.spd.file.write().unwrap().free_page(lpnum);
}
pub fn save(&self, op: SaveOp) -> usize {
debug_assert!(self.writer);
match op {
SaveOp::Save => {
self.spd.file.write().unwrap().save();
self.spd.stash.write().unwrap().end_write()
}
SaveOp::RollBack => {
self.spd.file.write().unwrap().rollback();
0
}
}
}
}
impl Drop for AccessPagedData {
fn drop(&mut self) {
if !self.writer {
self.spd.stash.write().unwrap().end_read(self.time);
}
}
}