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pub mod disk_log {
use std::sync::Mutex;
use std::sync::Arc;
use std::{path::Path, fs};
use std::io::Error;
use simple_wal::LogFile;
use simple_wal::LogError;
use tokio::sync::{mpsc, oneshot};
struct TmpLogStruct {
path: String,
log: LogFile,
current_segment_index: usize
}
pub enum Job {
WriteLog {
data: Vec<u8>,
dst: Option<oneshot::Sender<Result<(), StatusResult>>>
},
GetSegment {
segment_index: usize,
dst: oneshot::Sender<Result<LogFile, StatusResult>>,
},
}
pub enum StatusResult {
LogErr(LogError),
IoError(Error),
End
}
pub fn start(path: String, table_name: String, total_segment_size: usize)
-> mpsc::Sender<Job>
{
let (sx, mut rx) = mpsc::channel::<Job>(20);
tokio::task::spawn(async move {
let ctx = Arc::new(Mutex::new(Context::open(&path, &table_name, total_segment_size).unwrap()));
while let Some(job) = rx.recv().await {
match job {
Job::WriteLog { mut data,
dst } => {
let ctx_copy = ctx.clone();
let resp = tokio::task::spawn_blocking(move || {
let mut ctx = ctx_copy.lock().unwrap();
ctx.write_to_disk(&mut data)
});
match dst {
Some(dst) => {
let resp = resp.await.unwrap();
let _ = dst.send(resp);
}
None => (),
}
}
Job::GetSegment { segment_index, dst } => {
let cx = ctx.lock().unwrap();
let filename = cx.find_filename(segment_index);
if Path::new(&filename).is_file() {
match LogFile::open(filename) {
Ok(log) => {
let _ = dst.send(Ok(log));
}
Err(e) => {
let _ = dst.send(Err(StatusResult::LogErr(e)));
}
}
} else {
let _ = dst.send(Err(StatusResult::End));
}
}
}
}
});
sx
}
// -----------------------------------------
struct Context {
log: LogFile,
path: String,
// total_segment_size is total len of query list per file.LOG
total_segment_size: usize,
// used_segment is len of reocrd in current_file.LOG
used_segment: usize,
// current_segment is pointer to current_segment
current_segment_index: usize
}
impl Context {
pub fn open(path: &str,
table_name: &str,
mut total_segment_size: usize) -> Result<Self, LogError>
{
// at-least 200 Record
total_segment_size = if total_segment_size < 200 { 200 } else { total_segment_size };
let mut slog = open_last_segment(path, table_name, total_segment_size);
let used_segment = used_segment(&mut slog.log);
Ok(Context{
log: slog.log,
path: slog.path,
total_segment_size,
used_segment,
// current_segment is pointer to current_segment and when move to new segment change
current_segment_index: 1
})
}
#[inline]
fn write_to_disk(&mut self, bytes: &mut Vec<u8>) -> Result<(), StatusResult> {
let sum = self.used_segment + 1;
// if segment have free space
if sum < self.total_segment_size {
let _ = self.log.write(bytes);
// flush to disk
match self.log.flush() {
Ok(_) => {
self.used_segment = sum;
Ok(())
}
Err(err) => {
return Err(StatusResult::IoError(err))
}
}
}
// if segment with this become full
else if sum == self.total_segment_size {
// write buffer to segment
let _ = self.log.write(bytes);
// flush to disk
match self.log.flush() {
Ok(_) => {
// ----- move to new segment -----
self.current_segment_index += 1;
// create filename for new segment
let curr_filename = filename_factory(&self.path, self.current_segment_index * self.total_segment_size);
// create new segment
let log = match LogFile::open(&curr_filename) {
Ok(lf) => lf,
Err(err) => {
return Err(StatusResult::LogErr(err))
}
};
self.used_segment = 0;
self.log = log;
Ok(())
}
Err(err) => {
return Err(StatusResult::IoError(err))
}
}
}
// if segment is full
else {
// ----- move to new segment -----
self.current_segment_index += 1;
// create filename for new segment
let curr_filename = filename_factory(&self.path, self.current_segment_index * self.total_segment_size);
// create new segment
let log = match LogFile::open(&curr_filename) {
Ok(lf) => lf,
Err(err) => {
return Err(StatusResult::LogErr(err))
}
};
self.log = log;
// write buffer to segment
let _ = self.log.write(bytes);
// flush to disk
match self.log.flush() {
Ok(_) => {
self.used_segment = 1;
Ok(())
}
Err(err) => {
return Err(StatusResult::IoError(err))
}
}
}
}
#[inline]
fn find_filename(&self, segment_index: usize) -> String {
let s = filename_factory(&self.path, self.total_segment_size * segment_index);
println!("{}", &s);
s
}
}
// -------------------------------------------------
#[inline]
fn filename_factory(path: &str, segment_pointer: usize) -> String {
format!("{}/segment-{}.LOG", &path, segment_pointer)
}
// if not exist directory then is first time run, create dir and a segment-1 and open it
// else open latest segment exist
fn used_segment(log: &mut LogFile) -> usize {
let mut counter = 0;
let iter = log.iter(..).unwrap();
iter.for_each(|_| counter += 1);
return counter
}
fn open_last_segment(path: &str, table_name: &str, total_segment_size: usize) -> TmpLogStruct {
let path = format!("{}/{}", path, table_name);
// if not exist, (First times is started_service)
if !Path::new(&path).is_dir() {
let curr_filename = filename_factory(&path, total_segment_size);
fs::create_dir(&path).unwrap();
return TmpLogStruct {
path: path,
log: LogFile::open(&curr_filename).unwrap(),
current_segment_index: 1
}
}
else {
// -----------------------------------------
let mut segment_index = 2;
let mut latest_segment = filename_factory(&path, total_segment_size);
loop {
let segment_pointer = total_segment_size * segment_index;
let filename = filename_factory(&path, segment_pointer);
if Path::new(&filename).is_file() {
latest_segment = filename;
segment_index += 1;
}
else {
// if not exist segment_2
if segment_index == 2 {
return TmpLogStruct {
path,
log: LogFile::open(latest_segment).unwrap(),
current_segment_index: 1
}
}
else {
return TmpLogStruct {
path,
log: LogFile::open(latest_segment).unwrap(),
current_segment_index: (segment_index - 1)
}
}
}
}
}
}
}