Mercurial > lbo > hg > leveldb-rs
view src/env.rs @ 165:bb7c31aa2825
Implement bare-bones version of TableCache.
author | Lewin Bormann <lbo@spheniscida.de> |
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date | Mon, 10 Jul 2017 20:01:47 +0200 |
parents | 54f8c4f68b99 |
children | ef5426303667 |
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//! 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::{Cursor, Read, Seek, SeekFrom, Write}; use std::fs::File; use std::os::unix::fs::FileExt; use std::path::Path; use std::sync::Mutex; pub trait RandomAccess { fn read_at(&self, off: usize, len: usize) -> Result<Vec<u8>>; } impl RandomAccess for File { fn read_at(&self, off: usize, len: usize) -> Result<Vec<u8>> { let mut buf = vec![0 as u8; len]; error::from_io_result((self as &FileExt).read_at(buf.as_mut(), off as u64)).map(|_| buf) } } /// BufferBackedFile implements RandomAccess on a cursor. It wraps the cursor in a mutex /// to enable using an immutable receiver, like the File implementation. pub type BufferBackedFile = Mutex<Cursor<Vec<u8>>>; impl RandomAccess for BufferBackedFile { fn read_at(&self, off: usize, len: usize) -> Result<Vec<u8>> { let mut c = self.lock().unwrap(); error::from_io_result(c.seek(SeekFrom::Start(off as u64)))?; let mut buf = vec![0 as u8; len]; error::from_io_result(c.read_exact(&mut buf)).map(|_| buf) } } pub struct FileLock { pub id: String, } pub trait Env { fn open_sequential_file(&self, &Path) -> Result<Box<Read>>; fn open_random_access_file(&self, &Path) -> Result<Box<RandomAccess>>; fn open_writable_file(&self, &Path) -> Result<Box<Write>>; fn open_appendable_file(&self, &Path) -> Result<Box<Write>>; 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<FileLock>; fn unlock(&self, l: 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()); } }