Mercurial > lbo > hg > leveldb-rs
view src/env.rs @ 156:94d50060a94a
Introduce RandomAccessFile as abstraction for Table reader.
And TableCache, later.
author | Lewin Bormann <lbo@spheniscida.de> |
---|---|
date | Sun, 09 Jul 2017 17:06:20 +0200 |
parents | 3cc327257435 |
children | de83256f4423 |
line wrap: on
line source
//! An `env` is an abstraction layer that allows the database to run both on different platforms as //! well as persisting data on disk or in memory. use error::{self, Result}; use std::io::{self, Read, Write, Seek}; use std::path::Path; use std::sync::{Arc, Mutex}; /// RandomAccessFile wraps a type implementing read and seek to enable atomic random reads #[derive(Clone)] pub struct RandomAccessFile<F: Read + Seek> { f: Arc<Mutex<F>>, } impl<F: Read + Seek> RandomAccessFile<F> { pub fn new(f: F) -> RandomAccessFile<F> { RandomAccessFile { f: Arc::new(Mutex::new(f)) } } pub fn read_at(&self, off: usize, len: usize) -> Result<Vec<u8>> { let mut f = try!(error::from_lock_result(self.f.lock())); try!(error::from_io_result(f.seek(io::SeekFrom::Start(off as u64)))); let mut buf = Vec::new(); buf.resize(len, 0); error::from_io_result(f.read_exact(&mut buf)).map(|_| buf) } } pub trait Env { type SequentialReader: Read; type RandomReader: Read + Seek; type Writer: Write; type FileLock; fn open_sequential_file(&self, &Path) -> Result<Self::SequentialReader>; fn open_random_access_file(&self, &Path) -> Result<RandomAccessFile<Self::RandomReader>>; fn open_writable_file(&self, &Path) -> Result<Self::Writer>; fn open_appendable_file(&self, &Path) -> Result<Self::Writer>; fn exists(&self, &Path) -> Result<bool>; fn children(&self, &Path) -> Result<Vec<String>>; fn size_of(&self, &Path) -> Result<usize>; fn delete(&self, &Path) -> Result<()>; fn mkdir(&self, &Path) -> Result<()>; fn rmdir(&self, &Path) -> Result<()>; fn rename(&self, &Path, &Path) -> Result<()>; fn lock(&self, &Path) -> Result<Self::FileLock>; fn unlock(&self, l: Self::FileLock); fn new_logger(&self, &Path) -> Result<Logger>; fn micros(&self) -> u64; fn sleep_for(&self, micros: u32); } pub struct Logger { dst: Box<Write>, } impl Logger { pub fn new(w: Box<Write>) -> Logger { Logger { dst: w } } pub fn log(&mut self, message: &String) { let _ = self.dst.write(message.as_bytes()); let _ = self.dst.write("\n".as_bytes()); } }