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use std::error::Error as StdError; use std::fmt::{self, Debug}; use std::io::{self, Error as IoError, ErrorKind, Read, Seek, SeekFrom, Write}; use super::{Error, Result}; use fs::fnode::{ Fnode, Metadata, Reader as FnodeReader, Version, Writer as FnodeWriter, }; use fs::Handle; use trans::{TxHandle, TxMgr}; /// A reader for a specific vesion of file content. /// /// This reader can be obtained by [`version_reader`] function, and it /// implements [`Read`] trait. /// /// [`version_reader`]: struct.File.html#method.version_reader /// [`Read`]: https://doc.rust-lang.org/std/io/trait.Read.html #[derive(Debug)] pub struct VersionReader { handle: Handle, rdr: FnodeReader, } impl VersionReader { fn new(handle: &Handle, ver: usize) -> Result<Self> { let rdr = FnodeReader::new(handle.fnode.clone(), ver)?; Ok(VersionReader { handle: handle.clone(), rdr, }) } } impl Read for VersionReader { #[inline] fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> { self.rdr.read(buf) } } impl Seek for VersionReader { #[inline] fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> { self.rdr.seek(pos) } } /// A reference to an opened file in the repository. /// /// An instance of a `File` can be read and/or written depending on what options /// it was opened with. Files also implement [`Seek`] to alter the logical /// cursor that the file contains internally. /// /// Files are automatically closed when they go out of scope. /// /// As ZboxFS internally cached file content, it is no need to use buffered /// reader, such as [`BufReader<R>`]. /// /// # Examples /// /// Create a new file and write bytes to it: /// /// ``` /// use std::io::prelude::*; /// # use zbox::{init_env, Result, RepoOpener}; /// /// # fn foo() -> Result<()> { /// # init_env(); /// # let mut repo = RepoOpener::new().create(true).open("mem://foo", "pwd")?; /// let mut file = repo.create_file("/foo.txt")?; /// file.write_all(b"Hello, world!")?; /// file.finish()?; /// # Ok(()) /// # } /// # foo().unwrap(); /// ``` /// /// Read the content of a file into a [`String`]: /// /// ``` /// # use zbox::{init_env, Result, RepoOpener}; /// use std::io::prelude::*; /// # use zbox::OpenOptions; /// /// # fn foo() -> Result<()> { /// # init_env(); /// # let mut repo = RepoOpener::new().create(true).open("mem://foo", "pwd")?; /// # { /// # let mut file = OpenOptions::new() /// # .create(true) /// # .open(&mut repo, "/foo.txt")?; /// # file.write_all(b"Hello, world!")?; /// # file.finish()?; /// # } /// let mut file = repo.open_file("/foo.txt")?; /// let mut content = String::new(); /// file.read_to_string(&mut content)?; /// assert_eq!(content, "Hello, world!"); /// # Ok(()) /// # } /// # foo().unwrap(); /// ``` /// /// # Versioning /// /// `File` contents support up to 255 revision versions. [`Version`] is /// immutable once it is created. /// /// By default, the maximum number of versions of a `File` is `10`, which is /// configurable by [`version_limit`] on both `Repo` and `File` level. File /// level option takes precedence. /// /// After reaching this limit, the oldest [`Version`] will be automatically /// deleted after adding a new one. /// /// Version number starts from `1` and continuously increases by 1. /// /// # Writing /// /// The file content is cached internally for deduplication and will be handled /// automatically, thus calling [`flush`] is **not** recommendated. /// /// `File` is multi-versioned, each time updating its content will create a new /// permanent [`Version`]. There are two ways of writing data to a file: /// /// - **Multi-part Write** /// /// This is done by updating `File` using [`Write`] trait multiple times. /// After all writing operations, [`finish`] must be called to create a new /// version. /// /// ## Examples /// /// ``` /// # use zbox::{init_env, Result, RepoOpener}; /// use std::io::prelude::*; /// use std::io::SeekFrom; /// # use zbox::OpenOptions; /// /// # fn foo() -> Result<()> { /// # init_env(); /// # let mut repo = RepoOpener::new().create(true).open("mem://foo", "pwd")?; /// let mut file = OpenOptions::new() /// .create(true) /// .open(&mut repo, "/foo.txt")?; /// file.write_all(b"foo ")?; /// file.write_all(b"bar")?; /// file.finish()?; /// /// let mut content = String::new(); /// file.seek(SeekFrom::Start(0))?; /// file.read_to_string(&mut content)?; /// assert_eq!(content, "foo bar"); /// /// # Ok(()) /// # } /// # foo().unwrap(); /// ``` /// /// - **Single-part Write** /// /// This can be done by calling [`write_once`], which will call [`finish`] /// internally to create a new version. /// /// ## Examples /// /// ``` /// # #![allow(unused_mut, unused_variables)] /// # use zbox::{init_env, Result, RepoOpener}; /// use std::io::{Read, Seek, SeekFrom}; /// # use zbox::OpenOptions; /// /// # fn foo() -> Result<()> { /// # init_env(); /// # let mut repo = RepoOpener::new().create(true).open("mem://foo", "pwd")?; /// let mut file = OpenOptions::new() /// .create(true) /// .open(&mut repo, "/foo.txt")?; /// file.write_once(b"foo bar")?; /// /// let mut content = String::new(); /// file.seek(SeekFrom::Start(0))?; /// file.read_to_string(&mut content)?; /// assert_eq!(content, "foo bar"); /// /// # Ok(()) /// # } /// # foo().unwrap(); /// ``` /// /// # Reading /// /// As `File` can contain multiple versions, [`Read`] operation can be /// associated with different versions. By default, reading on `File` object is /// always binded to the latest version. To read a specific version, a /// [`VersionReader`], which supports [`Read`] trait as well, can be used. /// /// ## Examples /// /// Read the file content while it is in writing, notice that reading is always /// binded to latest content version. /// /// ``` /// use std::io::prelude::*; /// use std::io::SeekFrom; /// # use zbox::{init_env, Result, RepoOpener}; /// # use zbox::OpenOptions; /// /// # fn foo() -> Result<()> { /// # init_env(); /// # let mut repo = RepoOpener::new().create(true).open("mem://foo", "pwd")?; /// // create a file and write data to it /// let mut file = OpenOptions::new().create(true).open(&mut repo, "/foo.txt")?; /// file.write_once(&[1, 2, 3, 4, 5, 6])?; /// /// // read the first 2 bytes /// let mut buf = [0; 2]; /// file.seek(SeekFrom::Start(0))?; /// file.read_exact(&mut buf)?; /// assert_eq!(&buf[..], &[1, 2]); /// /// // create a new version, now the file content is [1, 2, 7, 8, 5, 6] /// file.write_once(&[7, 8])?; /// /// // notice that reading is on the latest version /// file.seek(SeekFrom::Current(-2))?; /// file.read_exact(&mut buf)?; /// assert_eq!(&buf[..], &[7, 8]); /// /// # Ok(()) /// # } /// # foo().unwrap(); /// ``` /// /// Read multiple versions using [`VersionReader`]. /// /// ``` /// use std::io::prelude::*; /// # use zbox::{init_env, Result, RepoOpener}; /// # use zbox::OpenOptions; /// /// # fn foo() -> Result<()> { /// # init_env(); /// # let mut repo = RepoOpener::new().create(true).open("mem://foo", "pwd")?; /// // create a file and write 2 versions /// let mut file = OpenOptions::new().create(true).open(&mut repo, "/foo.txt")?; /// file.write_once(b"foo")?; /// file.write_once(b"bar")?; /// /// // get latest version number /// let curr_ver = file.curr_version()?; /// /// // create a version reader and read latest version of content /// let mut rdr = file.version_reader(curr_ver)?; /// let mut content = String::new(); /// rdr.read_to_string(&mut content)?; /// assert_eq!(content, "foobar"); /// /// // create another version reader and read previous version of content /// let mut rdr = file.version_reader(curr_ver - 1)?; /// let mut content = String::new(); /// rdr.read_to_string(&mut content)?; /// assert_eq!(content, "foo"); /// /// # Ok(()) /// # } /// # foo().unwrap(); /// ``` /// /// [`Seek`]: https://doc.rust-lang.org/std/io/trait.Seek.html /// [`BufReader<R>`]: https://doc.rust-lang.org/std/io/struct.BufReader.html /// [`flush`]: https://doc.rust-lang.org/std/io/trait.Write.html#tymethod.flush /// [`String`]: https://doc.rust-lang.org/std/string/struct.String.html /// [`Read`]: https://doc.rust-lang.org/std/io/trait.Read.html /// [`Write`]: https://doc.rust-lang.org/std/io/trait.Write.html /// [`Version`]: struct.Version.html /// [`VersionReader`]: struct.VersionReader.html /// [`version_limit`]: struct.OpenOptions.html#method.version_limit /// [`finish`]: struct.File.html#method.finish /// [`write_once`]: struct.File.html#method.write_once pub struct File { handle: Handle, pos: SeekFrom, // must always be SeekFrom::Start rdr: Option<FnodeReader>, wtr: Option<FnodeWriter>, tx_handle: Option<TxHandle>, can_read: bool, can_write: bool, } impl File { pub(super) fn new( handle: Handle, pos: SeekFrom, can_read: bool, can_write: bool, ) -> Self { File { handle, pos, rdr: None, wtr: None, tx_handle: None, can_read, can_write, } } /// Check if file system is closed fn check_closed(&self) -> Result<()> { let shutter = self.handle.shutter.read().unwrap(); if shutter.is_closed() { return Err(Error::RepoClosed); } Ok(()) } /// Queries metadata about the file. pub fn metadata(&self) -> Result<Metadata> { self.check_closed()?; let fnode = self.handle.fnode.read().unwrap(); Ok(fnode.metadata()) } /// Returns a list of all the file content versions. pub fn history(&self) -> Result<Vec<Version>> { self.check_closed()?; let fnode = self.handle.fnode.read().unwrap(); Ok(fnode.history()) } /// Returns the current content version number. pub fn curr_version(&self) -> Result<usize> { self.check_closed()?; let fnode = self.handle.fnode.read().unwrap(); Ok(fnode.curr_ver_num()) } /// Returns content byte size of the current version. fn curr_len(&self) -> usize { let fnode = self.handle.fnode.read().unwrap(); fnode.curr_len() } /// Get a reader of the specified version. /// /// The returned reader implements [`Read`] trait. To get the version /// number, first call [`history`] to get the list of all versions and /// then choose the version number from it. /// /// [`Read`]: https://doc.rust-lang.org/std/io/trait.Read.html /// [`history`]: struct.File.html#method.history pub fn version_reader(&self, ver_num: usize) -> Result<VersionReader> { self.check_closed()?; if !self.can_read { return Err(Error::CannotRead); } VersionReader::new(&self.handle, ver_num) } // calculate the seek position from the start based on file current size fn seek_pos(&self, pos: SeekFrom) -> SeekFrom { let curr_len = self.curr_len(); let pos: i64 = match pos { SeekFrom::Start(p) => p as i64, SeekFrom::End(p) => curr_len as i64 + p, SeekFrom::Current(p) => match self.pos { SeekFrom::Start(q) => p + q as i64, SeekFrom::End(_) => unreachable!(), SeekFrom::Current(_) => unreachable!(), }, }; SeekFrom::Start(pos as u64) } fn begin_write(&mut self) -> Result<()> { if self.wtr.is_some() { return Err(Error::NotFinish); } if !self.can_write { return Err(Error::CannotWrite); } assert!(self.tx_handle.is_none()); // append zeros if current position is beyond EOF let curr_len = self.curr_len(); match self.pos { SeekFrom::Start(pos) => { let pos = pos as usize; if pos > curr_len { // append zeros by setting file length self.set_len(pos)?; // then seek to new EOF self.pos = self.seek_pos(SeekFrom::End(0)); } } _ => unreachable!(), } // begin write let tx_handle = TxMgr::begin_trans(&self.handle.txmgr)?; tx_handle.run(|| { let mut wtr = FnodeWriter::new(self.handle.clone(), tx_handle.txid); wtr.seek(self.seek_pos(self.pos))?; self.wtr = Some(wtr); Ok(()) })?; self.tx_handle = Some(tx_handle); Ok(()) } // re-create reader on latest version fn renew_reader(&mut self) -> Result<()> { let mut rdr = FnodeReader::new_current(self.handle.fnode.clone())?; rdr.seek(self.pos)?; self.rdr = Some(rdr); Ok(()) } /// Complete multi-part write to file and create a new version. /// /// # Errors /// /// Calling this function without writing data before will return /// [`Error::NotWrite`] error. /// /// [`Error::NotWrite`]: enum.Error.html pub fn finish(&mut self) -> Result<()> { self.check_closed()?; match self.wtr.take() { Some(wtr) => { let tx_handle = self.tx_handle.take().unwrap(); let mut end_pos = 0; tx_handle.run(|| { end_pos = wtr.finish()?; Ok(()) })?; tx_handle.commit()?; // set position self.pos = SeekFrom::Start(end_pos as u64); } None => return Err(Error::NotWrite), } // re-create reader if there is an existing reader if self.rdr.is_some() { self.renew_reader()?; } Ok(()) } /// Single-part write to file and create a new version. /// /// This function provides a convenient way of combining [`Write`] and /// [`finish`]. /// /// [`Write`]: https://doc.rust-lang.org/std/io/trait.Write.html /// [`finish`]: struct.File.html#method.finish pub fn write_once(&mut self, buf: &[u8]) -> Result<()> { self.check_closed()?; match self.wtr { Some(_) => Err(Error::NotFinish), None => { self.begin_write()?; match self.wtr { Some(ref mut wtr) => match self.tx_handle { Some(ref tx_handle) => { tx_handle.run(|| { wtr.write_all(buf)?; Ok(()) })?; } None => unreachable!(), }, None => unreachable!(), } self.finish() } } } /// Truncates or extends the underlying file, create a new version of /// content which size to become `size`. /// /// If the size is less than the current content size, then the new /// content will be shrunk. If it is greater than the current content size, /// then the content will be extended to `size` and have all of the /// intermediate data filled in with 0s. /// /// # Errors /// /// This function will return an error if the file is not opened for /// writing or not finished writing. pub fn set_len(&mut self, len: usize) -> Result<()> { self.check_closed()?; if self.wtr.is_some() { return Err(Error::NotFinish); } if !self.can_write { return Err(Error::CannotWrite); } let tx_handle = TxMgr::begin_trans(&self.handle.txmgr)?; tx_handle.run_all(|| { Fnode::set_len(self.handle.clone(), len, tx_handle.txid) })?; // re-create reader if there is an existing reader if self.rdr.is_some() { self.renew_reader()?; } Ok(()) } } impl Read for File { fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> { map_io_err!(self.check_closed())?; if !self.can_read { return Err(IoError::new( ErrorKind::Other, Error::CannotRead.description(), )); } // if reader is not created yet, create a new reader and seek to // the current file position if self.rdr.is_none() { map_io_err!(self.renew_reader())?; } match self.rdr { Some(ref mut rdr) => { let read = rdr.read(buf)?; let new_pos = rdr.seek(SeekFrom::Current(0)).unwrap(); self.pos = SeekFrom::Start(new_pos); Ok(read) } None => unreachable!(), } } } impl Write for File { fn write(&mut self, buf: &[u8]) -> io::Result<usize> { map_io_err!(self.check_closed())?; if self.wtr.is_none() { map_io_err!(self.begin_write())?; } match self.wtr { Some(ref mut wtr) => match self.tx_handle { Some(ref tx_handle) => { let mut ret = 0; map_io_err!(tx_handle.run(|| { ret = wtr.write(buf)?; Ok(()) }))?; Ok(ret) } None => unreachable!(), }, None => unreachable!(), } } fn flush(&mut self) -> io::Result<()> { map_io_err!(self.check_closed())?; match self.wtr { Some(ref mut wtr) => match self.tx_handle { Some(ref tx_handle) => { map_io_err!(tx_handle.run(|| { wtr.flush()?; Ok(()) }))?; Ok(()) } None => unreachable!(), }, None => Err(IoError::new( ErrorKind::PermissionDenied, Error::CannotWrite.description(), )), } } } impl Seek for File { fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> { map_io_err!(self.check_closed())?; if self.wtr.is_some() { return Err(IoError::new( ErrorKind::Other, Error::NotFinish.description(), )); } self.pos = match self.rdr { Some(ref mut rdr) => SeekFrom::Start(rdr.seek(pos)?), None => self.seek_pos(pos), }; match self.pos { SeekFrom::Start(pos) => Ok(pos), _ => unreachable!(), } } } impl Debug for File { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { f.debug_struct("File") .field("pos", &self.pos) .field("rdr", &self.rdr) .field("wtr", &self.wtr) .field("can_read", &self.can_read) .field("can_write", &self.can_write) .finish() } }