use std::collections::BTreeMap;
use std::fs;
use std::io::{self, Read, Write};
use super::*;
pub struct RSDB<'a> {
dir_path: &'a str,
log: fs::File,
store: BTreeMap<Vec<u8>, Vec<u8>>,
}
impl<'a> RSDB<'a> {
pub fn new<'l>(dir_path: &'l str) -> io::Result<RSDB<'l>> {
recover(dir_path).map(|(log, store)| {
RSDB {
dir_path: dir_path,
log: log,
store: store,
}
})
}
pub fn get(&self, key: &[u8]) -> io::Result<Option<&Vec<u8>>> {
Ok(self.store.get(key))
}
pub fn set(&mut self, key: &'a [u8], value: &'a [u8]) -> io::Result<()> {
self.log(key.clone(), value.clone())?;
self.store.insert(key.to_vec(), value.to_vec());
Ok(())
}
fn log(&mut self, key: &[u8], value: &[u8]) -> io::Result<()> {
self.log.write_all(&ops::usize_to_array(key.len()))?;
self.log.write_all(&ops::usize_to_array(value.len()))?;
self.log.write_all(key)?;
self.log.write_all(value)?;
Ok(())
}
}
macro_rules! read_or_break {
($file:expr, $buf:expr, $count:expr) => (
match $file.read(&mut $buf) {
Ok(n) if n == $buf.len() => {
$count += n;
},
Ok(_) => {
break;
},
Err(_) => {
break
}
}
)
}
fn recover<'a>(dir_path: &str) -> io::Result<(fs::File, BTreeMap<Vec<u8>, Vec<u8>>)> {
let filename = format!("{}/rsdb.log", dir_path);
fs::create_dir_all(dir_path)?;
let mut file = fs::OpenOptions::new()
.read(true)
.write(true)
.create(true)
.open(filename)?;
let mut store = BTreeMap::new();
let mut read = 0;
loop {
let (mut k_len_buf, mut v_len_buf) = ([0u8; 4], [0u8; 4]);
read_or_break!(file, k_len_buf, read);
read_or_break!(file, v_len_buf, read);
let (klen, vlen) = (ops::array_to_usize(k_len_buf), ops::array_to_usize(v_len_buf));
let (mut k_buf, mut v_buf) = (Vec::with_capacity(klen), Vec::with_capacity(vlen));
read_or_break!(file, k_buf, read);
read_or_break!(file, v_buf, read);
store.insert(k_buf, v_buf);
}
file.set_len(read as u64)?;
Ok((file, store))
}