320 lines
8.5 KiB
Rust
320 lines
8.5 KiB
Rust
//! A wrapper around an object that ties it to a physical file
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extern crate serde;
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use anyhow::Context;
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use serde::de::DeserializeOwned;
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use serde::Serialize;
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use std::fs::File;
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use std::path::{Path, PathBuf};
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use thiserror::Error;
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#[derive(Error, Debug)]
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pub enum Error {
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#[error(transparent)]
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Serialization(bincode::Error),
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#[error(transparent)]
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IO(std::io::Error),
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#[error(transparent)]
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Other(#[from] anyhow::Error),
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}
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/// A wrapper around an object `T` that ties the object to a physical file
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#[derive(Debug)]
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pub struct FileLinked<T>
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where
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T: Serialize,
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{
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val: T,
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path: PathBuf,
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}
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impl<T> FileLinked<T>
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where
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T: Serialize,
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{
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/// Returns a readonly reference of `T`
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///
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/// # Examples
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/// ```
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/// # use file_linked::*;
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/// # use serde::{Deserialize, Serialize};
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/// # use std::fmt;
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/// # use std::string::ToString;
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/// # use std::path::PathBuf;
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/// #
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/// # #[derive(Deserialize, Serialize)]
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/// # struct Test {
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/// # pub a: u32,
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/// # pub b: String,
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/// # pub c: f64
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/// # }
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/// #
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/// # fn main() {
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/// let test = Test {
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/// a: 1,
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/// b: String::from("two"),
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/// c: 3.0
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/// };
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///
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/// let linked_test = FileLinked::new(test, &PathBuf::from("./temp"))
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/// .expect("Unable to create file linked object");
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///
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/// assert_eq!(linked_test.readonly().a, 1);
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/// assert_eq!(linked_test.readonly().b, String::from("two"));
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/// assert_eq!(linked_test.readonly().c, 3.0);
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/// #
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/// # std::fs::remove_file("./temp").expect("Unable to remove file");
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/// # }
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/// ```
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pub fn readonly(&self) -> &T {
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&self.val
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}
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/// Creates a new [`FileLinked`] object of type `T` stored to the file given by `path`.
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///
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/// # Examples
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/// ```
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/// # use file_linked::*;
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/// # use serde::{Deserialize, Serialize};
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/// # use std::fmt;
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/// # use std::string::ToString;
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/// # use std::path::PathBuf;
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/// #
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/// #[derive(Deserialize, Serialize)]
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/// struct Test {
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/// pub a: u32,
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/// pub b: String,
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/// pub c: f64
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/// }
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///
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/// # fn main() {
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/// let test = Test {
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/// a: 1,
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/// b: String::from("two"),
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/// c: 3.0
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/// };
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///
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/// let linked_test = FileLinked::new(test, &PathBuf::from("./temp"))
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/// .expect("Unable to create file linked object");
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///
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/// assert_eq!(linked_test.readonly().a, 1);
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/// assert_eq!(linked_test.readonly().b, String::from("two"));
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/// assert_eq!(linked_test.readonly().c, 3.0);
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/// #
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/// # std::fs::remove_file("./temp").expect("Unable to remove file");
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/// # }
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/// ```
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pub fn new(val: T, path: &Path) -> Result<FileLinked<T>, Error> {
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let result = FileLinked {
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val,
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path: path.to_path_buf(),
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};
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result.write_data()?;
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Ok(result)
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}
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fn write_data(&self) -> Result<(), Error> {
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let file = File::create(&self.path)
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.with_context(|| format!("Unable to open path {}", self.path.display()))?;
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bincode::serialize_into(file, &self.val)
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.with_context(|| format!("Unable to write to file {}", self.path.display()))?;
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Ok(())
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}
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/// Modifies the data contained in a `FileLinked` object using a callback `op` that has a mutable reference to the
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/// underlying data. After the mutable operation is performed the data is written to a file to synchronize the state.
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///
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/// # Examples
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/// ```
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/// # use file_linked::*;
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/// # use serde::{Deserialize, Serialize};
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/// # use std::fmt;
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/// # use std::string::ToString;
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/// # use std::path::PathBuf;
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/// #
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/// # #[derive(Deserialize, Serialize)]
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/// # struct Test {
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/// # pub a: u32,
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/// # pub b: String,
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/// # pub c: f64
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/// # }
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/// #
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/// # fn main() -> Result<(), Error> {
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/// let test = Test {
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/// a: 1,
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/// b: String::from(""),
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/// c: 0.0
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/// };
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///
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/// let mut linked_test = FileLinked::new(test, &PathBuf::from("./temp"))
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/// .expect("Unable to create file linked object");
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///
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/// assert_eq!(linked_test.readonly().a, 1);
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///
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/// linked_test.mutate(|t| t.a = 2)?;
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///
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/// assert_eq!(linked_test.readonly().a, 2);
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/// #
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/// # std::fs::remove_file("./temp").expect("Unable to remove file");
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/// #
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/// # Ok(())
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/// # }
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/// ```
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pub fn mutate<U, F: FnOnce(&mut T) -> U>(&mut self, op: F) -> Result<U, Error> {
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let result = op(&mut self.val);
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self.write_data()?;
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Ok(result)
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}
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/// Replaces the value held by the `FileLinked` object with `val`. After replacing the object will be written to a file.
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///
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/// # Examples
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/// ```
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/// # use file_linked::*;
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/// # use serde::{Deserialize, Serialize};
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/// # use std::fmt;
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/// # use std::string::ToString;
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/// # use std::path::PathBuf;
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/// #
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/// # #[derive(Deserialize, Serialize)]
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/// # struct Test {
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/// # pub a: u32,
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/// # pub b: String,
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/// # pub c: f64
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/// # }
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/// #
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/// # fn main() -> Result<(), Error> {
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/// let test = Test {
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/// a: 1,
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/// b: String::from(""),
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/// c: 0.0
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/// };
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///
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/// let mut linked_test = FileLinked::new(test, &PathBuf::from("./temp"))
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/// .expect("Unable to create file linked object");
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///
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/// assert_eq!(linked_test.readonly().a, 1);
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///
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/// linked_test.replace(Test {
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/// a: 2,
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/// b: String::from(""),
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/// c: 0.0
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/// })?;
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///
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/// assert_eq!(linked_test.readonly().a, 2);
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/// #
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/// # std::fs::remove_file("./temp").expect("Unable to remove file");
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/// #
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/// # Ok(())
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/// # }
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/// ```
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pub fn replace(&mut self, val: T) -> Result<(), Error> {
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self.val = val;
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self.write_data()
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}
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}
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impl<T> FileLinked<T>
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where
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T: Serialize + DeserializeOwned,
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{
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/// Deserializes an object `T` from the file given by `path`
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///
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/// # Examples
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/// ```
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/// # use file_linked::*;
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/// # use serde::{Deserialize, Serialize};
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/// # use std::fmt;
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/// # use std::string::ToString;
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/// # use std::fs;
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/// # use std::fs::OpenOptions;
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/// # use std::io::Write;
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/// # use std::path::PathBuf;
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/// #
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/// # #[derive(Deserialize, Serialize)]
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/// # struct Test {
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/// # pub a: u32,
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/// # pub b: String,
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/// # pub c: f64
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/// # }
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/// #
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/// # fn main() -> Result<(), Error> {
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/// let test = Test {
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/// a: 1,
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/// b: String::from("2"),
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/// c: 3.0
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/// };
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///
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/// let path = PathBuf::from("./temp");
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///
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/// let mut file = OpenOptions::new()
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/// .write(true)
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/// .create(true)
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/// .open(&path)
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/// .expect("Unable to create file");
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///
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/// bincode::serialize_into(file, &test).expect("Unable to serialize object");
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///
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/// let mut linked_test = FileLinked::<Test>::from_file(&path)
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/// .expect("Unable to create file linked object");
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///
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/// assert_eq!(linked_test.readonly().a, test.a);
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/// assert_eq!(linked_test.readonly().b, test.b);
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/// assert_eq!(linked_test.readonly().c, test.c);
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/// #
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/// # std::fs::remove_file("./temp").expect("Unable to remove file");
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/// #
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/// # Ok(())
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/// # }
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/// ```
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pub fn from_file(path: &Path) -> Result<FileLinked<T>, Error> {
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let file =
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File::open(path).with_context(|| format!("Unable to open file {}", path.display()))?;
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let val = bincode::deserialize_from(file)
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.with_context(|| String::from("Unable to parse value from file."))?;
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Ok(FileLinked {
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val,
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path: path.to_path_buf(),
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})
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use std::fs;
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#[test]
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fn test_mutate() -> Result<(), Error> {
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let list = vec![1, 2, 3, 4];
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let mut file_linked_list = FileLinked::new(list, &PathBuf::from("test.txt"))?;
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assert_eq!(format!("{:?}", file_linked_list.readonly()), "[1, 2, 3, 4]");
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file_linked_list.mutate(|v1| v1.push(5))?;
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assert_eq!(
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format!("{:?}", file_linked_list.readonly()),
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"[1, 2, 3, 4, 5]"
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);
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file_linked_list.mutate(|v1| v1[1] = 1)?;
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assert_eq!(
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format!("{:?}", file_linked_list.readonly()),
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"[1, 1, 3, 4, 5]"
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);
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fs::remove_file("test.txt").expect("Unable to remove file");
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Ok(())
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}
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}
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