imag/libimagstore/src/lazyfile.rs

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use error::{StoreError, StoreErrorKind};
use std::io::{Seek, SeekFrom};
use std::path::{Path, PathBuf};
use std::fs::{File, OpenOptions, create_dir_all};
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/**
* LazyFile type
*
* A lazy file is either absent, but a path to it is available, or it is present.
*/
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#[derive(Debug)]
pub enum LazyFile {
Absent(PathBuf),
File(File)
}
fn open_file<A: AsRef<Path>>(p: A) -> ::std::io::Result<File> {
OpenOptions::new().write(true).read(true).open(p)
}
fn create_file<A: AsRef<Path>>(p: A) -> ::std::io::Result<File> {
if let Some(parent) = p.as_ref().parent() {
debug!("Implicitely creating directory: {:?}", parent);
if let Err(e) = create_dir_all(parent) {
return Err(e);
}
}
OpenOptions::new().write(true).read(true).create(true).open(p)
}
impl LazyFile {
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/**
* Get the mutable file behind a LazyFile object
*/
pub fn get_file_mut(&mut self) -> Result<&mut File, StoreError> {
debug!("Getting lazy file: {:?}", self);
let file = match *self {
LazyFile::File(ref mut f) => return {
// We seek to the beginning of the file since we expect each
// access to the file to be in a different context
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f.seek(SeekFrom::Start(0))
.map_err(|e| StoreError::new(StoreErrorKind::FileNotCreated, Some(Box::new(e))))
.map(|_| f)
},
LazyFile::Absent(ref p) => {
try!(open_file(p).map_err(|e| {
StoreError::new(StoreErrorKind::FileNotFound,
Some(Box::new(e)))
}))
}
};
*self = LazyFile::File(file);
if let LazyFile::File(ref mut f) = *self {
return Ok(f);
}
unreachable!()
}
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/**
* Create a file out of this LazyFile object
*/
pub fn create_file(&mut self) -> Result<&mut File, StoreError> {
debug!("Creating lazy file: {:?}", self);
let file = match *self {
LazyFile::File(ref mut f) => return Ok(f),
LazyFile::Absent(ref p) => {
try!(create_file(p).map_err(|e| {
StoreError::new(StoreErrorKind::FileNotFound,
Some(Box::new(e)))
}))
}
};
*self = LazyFile::File(file);
if let LazyFile::File(ref mut f) = *self {
return Ok(f);
}
unreachable!()
}
}
#[cfg(test)]
mod test {
use super::LazyFile;
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use std::io::{Read, Write};
use std::path::PathBuf;
use tempdir::TempDir;
fn get_dir() -> TempDir {
TempDir::new("test-image").unwrap()
}
#[test]
fn lazy_file() {
let dir = get_dir();
let mut path = PathBuf::from(dir.path());
path.set_file_name("test1");
let mut lf = LazyFile::Absent(path);
write!(lf.create_file().unwrap(), "Hello World").unwrap();
dir.close().unwrap();
}
#[test]
fn lazy_file_with_file() {
let dir = get_dir();
let mut path = PathBuf::from(dir.path());
path.set_file_name("test2");
let mut lf = LazyFile::Absent(path.clone());
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{
let mut file = lf.create_file().unwrap();
file.write(b"Hello World").unwrap();
file.sync_all().unwrap();
}
{
let mut file = lf.get_file_mut().unwrap();
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let mut s = Vec::new();
file.read_to_end(&mut s).unwrap();
assert_eq!(s, "Hello World".to_string().into_bytes());
}
dir.close().unwrap();
}
}