//! A C representation of Rust's `std::option::Option` used across the FFI
//! boundary for Solana program interfaces
//!
//! This implementation mostly matches `std::option` except iterators since the iteration
//! trait requires returning `std::option::Option`
use std::{
convert, mem,
ops::{Deref, DerefMut},
};
/// A C representation of Rust's `std::option::Option`
#[repr(C)]
#[derive(Copy, PartialEq, PartialOrd, Eq, Ord, Debug, Hash)]
pub enum COption<T> {
/// No value
None,
/// Some value `T`
Some(T),
}
/////////////////////////////////////////////////////////////////////////////
// Type implementation
/////////////////////////////////////////////////////////////////////////////
impl<T> COption<T> {
/////////////////////////////////////////////////////////////////////////
// Querying the contained values
/////////////////////////////////////////////////////////////////////////
/// Returns `true` if the option is a [`COption::Some`] value.
///
/// # Examples
///
/// ```ignore
/// let x: COption<u32> = COption::Some(2);
/// assert_eq!(x.is_some(), true);
///
/// let x: COption<u32> = COption::None;
/// assert_eq!(x.is_some(), false);
/// ```
///
/// [`COption::Some`]: #variant.COption::Some
#[must_use = "if you intended to assert that this has a value, consider `.unwrap()` instead"]
#[inline]
pub fn is_some(&self) -> bool {
match *self {
COption::Some(_) => true,
COption::None => false,
}
}
/// Returns `true` if the option is a [`COption::None`] value.
///
/// # Examples
///
/// ```ignore
/// let x: COption<u32> = COption::Some(2);
/// assert_eq!(x.is_none(), false);
///
/// let x: COption<u32> = COption::None;
/// assert_eq!(x.is_none(), true);
/// ```
///
/// [`COption::None`]: #variant.COption::None
#[must_use = "if you intended to assert that this doesn't have a value, consider \
`.and_then(|| panic!(\"`COption` had a value when expected `COption::None`\"))` instead"]
#[inline]
pub fn is_none(&self) -> bool {
!self.is_some()
}
/// Returns `true` if the option is a [`COption::Some`] value containing the given value.
///
/// # Examples
///
/// ```ignore
/// #![feature(option_result_contains)]
///
/// let x: COption<u32> = COption::Some(2);
/// assert_eq!(x.contains(&2), true);
///
/// let x: COption<u32> = COption::Some(3);
/// assert_eq!(x.contains(&2), false);
///
/// let x: COption<u32> = COption::None;
/// assert_eq!(x.contains(&2), false);
/// ```
#[must_use]
#[inline]
pub fn contains<U>(&self, x: &U) -> bool
where
U: PartialEq<T>,
{
match self {
COption::Some(y) => x == y,
COption::None => false,
}
}
/////////////////////////////////////////////////////////////////////////
// Adapter for working with references
/////////////////////////////////////////////////////////////////////////
/// Converts from `&COption<T>` to `COption<&T>`.
///
/// # Examples
///
/// Converts an `COption<`[`String`]`>` into an `COption<`[`usize`]`>`, preserving the original.
/// The [`map`] method takes the `self` argument by value, consuming the original,
/// so this technique uses `as_ref` to first take an `COption` to a reference
/// to the value inside the original.
///
/// [`map`]: enum.COption.html#method.map
/// [`String`]: ../../std/string/struct.String.html
/// [`usize`]: ../../std/primitive.usize.html
///
/// ```ignore
/// let text: COption<String> = COption::Some("Hello, world!".to_string());
/// // First, cast `COption<String>` to `COption<&String>` with `as_ref`,
/// // then consume *that* with `map`, leaving `text` on the stack.
/// let text_length: COption<usize> = text.as_ref().map(|s| s.len());
/// println!("still can print text: {:?}", text);
/// ```
#[inline]
pub fn as_ref(&self) -> COption<&T> {
match *self {
COption::Some(ref x) => COption::Some(x),
COption::None => COption::None,
}
}
/// Converts from `&mut COption<T>` to `COption<&mut T>`.
///
/// # Examples
///
/// ```ignore
/// let mut x = COption::Some(2);
/// match x.as_mut() {
/// COption::Some(v) => *v = 42,
/// COption::None => {},
/// }
/// assert_eq!(x, COption::Some(42));
/// ```
#[inline]
pub fn as_mut(&mut self) -> COption<&mut T> {
match *self {
COption::Some(ref mut x) => COption::Some(x),
COption::None => COption::None,
}
}
/////////////////////////////////////////////////////////////////////////
// Getting to contained values
/////////////////////////////////////////////////////////////////////////
/// Unwraps an option, yielding the content of a [`COption::Some`].
///
/// # Panics
///
/// Panics if the value is a [`COption::None`] with a custom panic message provided by
/// `msg`.
///
/// [`COption::Some`]: #variant.COption::Some
/// [`COption::None`]: #variant.COption::None
///
/// # Examples
///
/// ```ignore
/// let x = COption::Some("value");
/// assert_eq!(x.expect("the world is ending"), "value");
/// ```
///
/// ```ignore{.should_panic}
/// let x: COption<&str> = COption::None;
/// x.expect("the world is ending"); // panics with `the world is ending`
/// ```
#[inline]
pub fn expect(self, msg: &str) -> T {
match self {
COption::Some(val) => val,
COption::None => expect_failed(msg),
}
}
/// Moves the value `v` out of the `COption<T>` if it is [`COption::Some(v)`].
///
/// In general, because this function may panic, its use is discouraged.
/// Instead, prefer to use pattern matching and handle the [`COption::None`]
/// case explicitly.
///
/// # Panics
///
/// Panics if the self value equals [`COption::None`].
///
/// [`COption::Some(v)`]: #variant.COption::Some
/// [`COption::None`]: #variant.COption::None
///
/// # Examples
///
/// ```ignore
/// let x = COption::Some("air");
/// assert_eq!(x.unwrap(), "air");
/// ```
///
/// ```ignore{.should_panic}
/// let x: COption<&str> = COption::None;
/// assert_eq!(x.unwrap(), "air"); // fails
/// ```
#[inline]
pub fn unwrap(self) -> T {
match self {
COption::Some(val) => val,
COption::None => panic!("called `COption::unwrap()` on a `COption::None` value"),
}
}
/// Returns the contained value or a default.
///
/// Arguments passed to `unwrap_or` are eagerly evaluated; if you are passing
/// the result of a function call, it is recommended to use [`unwrap_or_else`],
/// which is lazily evaluated.
///
/// [`unwrap_or_else`]: #method.unwrap_or_else
///
/// # Examples
///
/// ```ignore
/// assert_eq!(COption::Some("car").unwrap_or("bike"), "car");
/// assert_eq!(COption::None.unwrap_or("bike"), "bike");
/// ```
#[inline]
pub fn unwrap_or(self, def: T) -> T {
match self {
COption::Some(x) => x,
COption::None => def,
}
}
/// Returns the contained value or computes it from a closure.
///
/// # Examples
///
/// ```ignore
/// let k = 10;
/// assert_eq!(COption::Some(4).unwrap_or_else(|| 2 * k), 4);
/// assert_eq!(COption::None.unwrap_or_else(|| 2 * k), 20);
/// ```
#[inline]
pub fn unwrap_or_else<F: FnOnce() -> T>(self, f: F) -> T {
match self {
COption::Some(x) => x,
COption::None => f(),
}
}
/////////////////////////////////////////////////////////////////////////
// Transforming contained values
/////////////////////////////////////////////////////////////////////////
/// Maps an `COption<T>` to `COption<U>` by applying a function to a contained value.
///
/// # Examples
///
/// Converts an `COption<`[`String`]`>` into an `COption<`[`usize`]`>`, consuming the original:
///
/// [`String`]: ../../std/string/struct.String.html
/// [`usize`]: ../../std/primitive.usize.html
///
/// ```ignore
/// let maybe_some_string = COption::Some(String::from("Hello, World!"));
/// // `COption::map` takes self *by value*, consuming `maybe_some_string`
/// let maybe_some_len = maybe_some_string.map(|s| s.len());
///
/// assert_eq!(maybe_some_len, COption::Some(13));
/// ```
#[inline]
pub fn map<U, F: FnOnce(T) -> U>(self, f: F) -> COption<U> {
match self {
COption::Some(x) => COption::Some(f(x)),
COption::None => COption::None,
}
}
/// Applies a function to the contained value (if any),
/// or returns the provided default (if not).
///
/// # Examples
///
/// ```ignore
/// let x = COption::Some("foo");
/// assert_eq!(x.map_or(42, |v| v.len()), 3);
///
/// let x: COption<&str> = COption::None;
/// assert_eq!(x.map_or(42, |v| v.len()), 42);
/// ```
#[inline]
pub fn map_or<U, F: FnOnce(T) -> U>(self, default: U, f: F) -> U {
match self {
COption::Some(t) => f(t),
COption::None => default,
}
}
/// Applies a function to the contained value (if any),
/// or computes a default (if not).
///
/// # Examples
///
/// ```ignore
/// let k = 21;
///
/// let x = COption::Some("foo");
/// assert_eq!(x.map_or_else(|| 2 * k, |v| v.len()), 3);
///
/// let x: COption<&str> = COption::None;
/// assert_eq!(x.map_or_else(|| 2 * k, |v| v.len()), 42);
/// ```
#[inline]
pub fn map_or_else<U, D: FnOnce() -> U, F: FnOnce(T) -> U>(self, default: D, f: F) -> U {
match self {
COption::Some(t) => f(t),
COption::None => default(),
}
}
/// Transforms the `COption<T>` into a [`Result<T, E>`], mapping [`COption::Some(v)`] to
/// [`Ok(v)`] and [`COption::None`] to [`Err(err)`].
///
/// Arguments passed to `ok_or` are eagerly evaluated; if you are passing the
/// result of a function call, it is recommended to use [`ok_or_else`], which is
/// lazily evaluated.
///
/// [`Result<T, E>`]: ../../std/result/enum.Result.html
/// [`Ok(v)`]: ../../std/result/enum.Result.html#variant.Ok
/// [`Err(err)`]: ../../std/result/enum.Result.html#variant.Err
/// [`COption::None`]: #variant.COption::None
/// [`COption::Some(v)`]: #variant.COption::Some
/// [`ok_or_else`]: #method.ok_or_else
///
/// # Examples
///
/// ```ignore
/// let x = COption::Some("foo");
/// assert_eq!(x.ok_or(0), Ok("foo"));
///
/// let x: COption<&str> = COption::None;
/// assert_eq!(x.ok_or(0), Err(0));
/// ```
#[inline]
pub fn ok_or<E>(self, err: E) -> Result<T, E> {
match self {
COption::Some(v) => Ok(v),
COption::None => Err(err),
}
}
/// Transforms the `COption<T>` into a [`Result<T, E>`], mapping [`COption::Some(v)`] to
/// [`Ok(v)`] and [`COption::None`] to [`Err(err())`].
///
/// [`Result<T, E>`]: ../../std/result/enum.Result.html
/// [`Ok(v)`]: ../../std/result/enum.Result.html#variant.Ok
/// [`Err(err())`]: ../../std/result/enum.Result.html#variant.Err
/// [`COption::None`]: #variant.COption::None
/// [`COption::Some(v)`]: #variant.COption::Some
///
/// # Examples
///
/// ```ignore
/// let x = COption::Some("foo");
/// assert_eq!(x.ok_or_else(|| 0), Ok("foo"));
///
/// let x: COption<&str> = COption::None;
/// assert_eq!(x.ok_or_else(|| 0), Err(0));
/// ```
#[inline]
pub fn ok_or_else<E, F: FnOnce() -> E>(self, err: F) -> Result<T, E> {
match self {
COption::Some(v) => Ok(v),
COption::None => Err(err()),
}
}
/////////////////////////////////////////////////////////////////////////
// Boolean operations on the values, eager and lazy
/////////////////////////////////////////////////////////////////////////
/// Returns [`COption::None`] if the option is [`COption::None`], otherwise returns `optb`.
///
/// [`COption::None`]: #variant.COption::None
///
/// # Examples
///
/// ```ignore
/// let x = COption::Some(2);
/// let y: COption<&str> = COption::None;
/// assert_eq!(x.and(y), COption::None);
///
/// let x: COption<u32> = COption::None;
/// let y = COption::Some("foo");
/// assert_eq!(x.and(y), COption::None);
///
/// let x = COption::Some(2);
/// let y = COption::Some("foo");
/// assert_eq!(x.and(y), COption::Some("foo"));
///
/// let x: COption<u32> = COption::None;
/// let y: COption<&str> = COption::None;
/// assert_eq!(x.and(y), COption::None);
/// ```
#[inline]
pub fn and<U>(self, optb: COption<U>) -> COption<U> {
match self {
COption::Some(_) => optb,
COption::None => COption::None,
}
}
/// Returns [`COption::None`] if the option is [`COption::None`], otherwise calls `f` with the
/// wrapped value and returns the result.
///
/// COption::Some languages call this operation flatmap.
///
/// [`COption::None`]: #variant.COption::None
///
/// # Examples
///
/// ```ignore
/// fn sq(x: u32) -> COption<u32> { COption::Some(x * x) }
/// fn nope(_: u32) -> COption<u32> { COption::None }
///
/// assert_eq!(COption::Some(2).and_then(sq).and_then(sq), COption::Some(16));
/// assert_eq!(COption::Some(2).and_then(sq).and_then(nope), COption::None);
/// assert_eq!(COption::Some(2).and_then(nope).and_then(sq), COption::None);
/// assert_eq!(COption::None.and_then(sq).and_then(sq), COption::None);
/// ```
#[inline]
pub fn and_then<U, F: FnOnce(T) -> COption<U>>(self, f: F) -> COption<U> {
match self {
COption::Some(x) => f(x),
COption::None => COption::None,
}
}
/// Returns [`COption::None`] if the option is [`COption::None`], otherwise calls `predicate`
/// with the wrapped value and returns:
///
/// - [`COption::Some(t)`] if `predicate` returns `true` (where `t` is the wrapped
/// value), and
/// - [`COption::None`] if `predicate` returns `false`.
///
/// This function works similar to [`Iterator::filter()`]. You can imagine
/// the `COption<T>` being an iterator over one or zero elements. `filter()`
/// lets you decide which elements to keep.
///
/// # Examples
///
/// ```ignore
/// fn is_even(n: &i32) -> bool {
/// n % 2 == 0
/// }
///
/// assert_eq!(COption::None.filter(is_even), COption::None);
/// assert_eq!(COption::Some(3).filter(is_even), COption::None);
/// assert_eq!(COption::Some(4).filter(is_even), COption::Some(4));
/// ```
///
/// [`COption::None`]: #variant.COption::None
/// [`COption::Some(t)`]: #variant.COption::Some
/// [`Iterator::filter()`]: ../../std/iter/trait.Iterator.html#method.filter
#[inline]
pub fn filter<P: FnOnce(&T) -> bool>(self, predicate: P) -> Self {
if let COption::Some(x) = self {
if predicate(&x) {
return COption::Some(x);
}
}
COption::None
}
/// Returns the option if it contains a value, otherwise returns `optb`.
///
/// Arguments passed to `or` are eagerly evaluated; if you are passing the
/// result of a function call, it is recommended to use [`or_else`], which is
/// lazily evaluated.
///
/// [`or_else`]: #method.or_else
///
/// # Examples
///
/// ```ignore
/// let x = COption::Some(2);
/// let y = COption::None;
/// assert_eq!(x.or(y), COption::Some(2));
///
/// let x = COption::None;
/// let y = COption::Some(100);
/// assert_eq!(x.or(y), COption::Some(100));
///
/// let x = COption::Some(2);
/// let y = COption::Some(100);
/// assert_eq!(x.or(y), COption::Some(2));
///
/// let x: COption<u32> = COption::None;
/// let y = COption::None;
/// assert_eq!(x.or(y), COption::None);
/// ```
#[inline]
pub fn or(self, optb: COption<T>) -> COption<T> {
match self {
COption::Some(_) => self,
COption::None => optb,
}
}
/// Returns the option if it contains a value, otherwise calls `f` and
/// returns the result.
///
/// # Examples
///
/// ```ignore
/// fn nobody() -> COption<&'static str> { COption::None }
/// fn vikings() -> COption<&'static str> { COption::Some("vikings") }
///
/// assert_eq!(COption::Some("barbarians").or_else(vikings), COption::Some("barbarians"));
/// assert_eq!(COption::None.or_else(vikings), COption::Some("vikings"));
/// assert_eq!(COption::None.or_else(nobody), COption::None);
/// ```
#[inline]
pub fn or_else<F: FnOnce() -> COption<T>>(self, f: F) -> COption<T> {
match self {
COption::Some(_) => self,
COption::None => f(),
}
}
/// Returns [`COption::Some`] if exactly one of `self`, `optb` is [`COption::Some`], otherwise returns [`COption::None`].
///
/// [`COption::Some`]: #variant.COption::Some
/// [`COption::None`]: #variant.COption::None
///
/// # Examples
///
/// ```ignore
/// let x = COption::Some(2);
/// let y: COption<u32> = COption::None;
/// assert_eq!(x.xor(y), COption::Some(2));
///
/// let x: COption<u32> = COption::None;
/// let y = COption::Some(2);
/// assert_eq!(x.xor(y), COption::Some(2));
///
/// let x = COption::Some(2);
/// let y = COption::Some(2);
/// assert_eq!(x.xor(y), COption::None);
///
/// let x: COption<u32> = COption::None;
/// let y: COption<u32> = COption::None;
/// assert_eq!(x.xor(y), COption::None);
/// ```
#[inline]
pub fn xor(self, optb: COption<T>) -> COption<T> {
match (self, optb) {
(COption::Some(a), COption::None) => COption::Some(a),
(COption::None, COption::Some(b)) => COption::Some(b),
_ => COption::None,
}
}
/////////////////////////////////////////////////////////////////////////
// Entry-like operations to insert if COption::None and return a reference
/////////////////////////////////////////////////////////////////////////
/// Inserts `v` into the option if it is [`COption::None`], then
/// returns a mutable reference to the contained value.
///
/// [`COption::None`]: #variant.COption::None
///
/// # Examples
///
/// ```ignore
/// let mut x = COption::None;
///
/// {
/// let y: &mut u32 = x.get_or_insert(5);
/// assert_eq!(y, &5);
///
/// *y = 7;
/// }
///
/// assert_eq!(x, COption::Some(7));
/// ```
#[inline]
pub fn get_or_insert(&mut self, v: T) -> &mut T {
self.get_or_insert_with(|| v)
}
/// Inserts a value computed from `f` into the option if it is [`COption::None`], then
/// returns a mutable reference to the contained value.
///
/// [`COption::None`]: #variant.COption::None
///
/// # Examples
///
/// ```ignore
/// let mut x = COption::None;
///
/// {
/// let y: &mut u32 = x.get_or_insert_with(|| 5);
/// assert_eq!(y, &5);
///
/// *y = 7;
/// }
///
/// assert_eq!(x, COption::Some(7));
/// ```
#[inline]
pub fn get_or_insert_with<F: FnOnce() -> T>(&mut self, f: F) -> &mut T {
if let COption::None = *self {
*self = COption::Some(f())
}
match *self {
COption::Some(ref mut v) => v,
COption::None => unreachable!(),
}
}
/////////////////////////////////////////////////////////////////////////
// Misc
/////////////////////////////////////////////////////////////////////////
/// Replaces the actual value in the option by the value given in parameter,
/// returning the old value if present,
/// leaving a [`COption::Some`] in its place without deinitializing either one.
///
/// [`COption::Some`]: #variant.COption::Some
///
/// # Examples
///
/// ```ignore
/// let mut x = COption::Some(2);
/// let old = x.replace(5);
/// assert_eq!(x, COption::Some(5));
/// assert_eq!(old, COption::Some(2));
///
/// let mut x = COption::None;
/// let old = x.replace(3);
/// assert_eq!(x, COption::Some(3));
/// assert_eq!(old, COption::None);
/// ```
#[inline]
pub fn replace(&mut self, value: T) -> COption<T> {
mem::replace(self, COption::Some(value))
}
}
impl<T: Copy> COption<&T> {
/// Maps an `COption<&T>` to an `COption<T>` by copying the contents of the
/// option.
///
/// # Examples
///
/// ```ignore
/// let x = 12;
/// let opt_x = COption::Some(&x);
/// assert_eq!(opt_x, COption::Some(&12));
/// let copied = opt_x.copied();
/// assert_eq!(copied, COption::Some(12));
/// ```
pub fn copied(self) -> COption<T> {
self.map(|&t| t)
}
}
impl<T: Copy> COption<&mut T> {
/// Maps an `COption<&mut T>` to an `COption<T>` by copying the contents of the
/// option.
///
/// # Examples
///
/// ```ignore
/// let mut x = 12;
/// let opt_x = COption::Some(&mut x);
/// assert_eq!(opt_x, COption::Some(&mut 12));
/// let copied = opt_x.copied();
/// assert_eq!(copied, COption::Some(12));
/// ```
pub fn copied(self) -> COption<T> {
self.map(|&mut t| t)
}
}
impl<T: Clone> COption<&T> {
/// Maps an `COption<&T>` to an `COption<T>` by cloning the contents of the
/// option.
///
/// # Examples
///
/// ```ignore
/// let x = 12;
/// let opt_x = COption::Some(&x);
/// assert_eq!(opt_x, COption::Some(&12));
/// let cloned = opt_x.cloned();
/// assert_eq!(cloned, COption::Some(12));
/// ```
pub fn cloned(self) -> COption<T> {
self.map(|t| t.clone())
}
}
impl<T: Clone> COption<&mut T> {
/// Maps an `COption<&mut T>` to an `COption<T>` by cloning the contents of the
/// option.
///
/// # Examples
///
/// ```ignore
/// let mut x = 12;
/// let opt_x = COption::Some(&mut x);
/// assert_eq!(opt_x, COption::Some(&mut 12));
/// let cloned = opt_x.cloned();
/// assert_eq!(cloned, COption::Some(12));
/// ```
pub fn cloned(self) -> COption<T> {
self.map(|t| t.clone())
}
}
impl<T: Default> COption<T> {
/// Returns the contained value or a default
///
/// Consumes the `self` argument then, if [`COption::Some`], returns the contained
/// value, otherwise if [`COption::None`], returns the [default value] for that
/// type.
///
/// # Examples
///
/// Converts a string to an integer, turning poorly-formed strings
/// into 0 (the default value for integers). [`parse`] converts
/// a string to any other type that implements [`FromStr`], returning
/// [`COption::None`] on error.
///
/// ```ignore
/// let good_year_from_input = "1909";
/// let bad_year_from_input = "190blarg";
/// let good_year = good_year_from_input.parse().ok().unwrap_or_default();
/// let bad_year = bad_year_from_input.parse().ok().unwrap_or_default();
///
/// assert_eq!(1909, good_year);
/// assert_eq!(0, bad_year);
/// ```
///
/// [`COption::Some`]: #variant.COption::Some
/// [`COption::None`]: #variant.COption::None
/// [default value]: ../default/trait.Default.html#tymethod.default
/// [`parse`]: ../../std/primitive.str.html#method.parse
/// [`FromStr`]: ../../std/str/trait.FromStr.html
#[inline]
pub fn unwrap_or_default(self) -> T {
match self {
COption::Some(x) => x,
COption::None => T::default(),
}
}
}
impl<T: Deref> COption<T> {
/// Converts from `COption<T>` (or `&COption<T>`) to `COption<&T::Target>`.
///
/// Leaves the original COption in-place, creating a new one with a reference
/// to the original one, additionally coercing the contents via [`Deref`].
///
/// [`Deref`]: ../../std/ops/trait.Deref.html
///
/// # Examples
///
/// ```ignore
/// #![feature(inner_deref)]
///
/// let x: COption<String> = COption::Some("hey".to_owned());
/// assert_eq!(x.as_deref(), COption::Some("hey"));
///
/// let x: COption<String> = COption::None;
/// assert_eq!(x.as_deref(), COption::None);
/// ```
pub fn as_deref(&self) -> COption<&T::Target> {
self.as_ref().map(|t| t.deref())
}
}
impl<T: DerefMut> COption<T> {
/// Converts from `COption<T>` (or `&mut COption<T>`) to `COption<&mut T::Target>`.
///
/// Leaves the original `COption` in-place, creating a new one containing a mutable reference to
/// the inner type's `Deref::Target` type.
///
/// # Examples
///
/// ```ignore
/// #![feature(inner_deref)]
///
/// let mut x: COption<String> = COption::Some("hey".to_owned());
/// assert_eq!(x.as_deref_mut().map(|x| {
/// x.make_ascii_uppercase();
/// x
/// }), COption::Some("HEY".to_owned().as_mut_str()));
/// ```
pub fn as_deref_mut(&mut self) -> COption<&mut T::Target> {
self.as_mut().map(|t| t.deref_mut())
}
}
impl<T, E> COption<Result<T, E>> {
/// Transposes an `COption` of a [`Result`] into a [`Result`] of an `COption`.
///
/// [`COption::None`] will be mapped to [`Ok`]`(`[`COption::None`]`)`.
/// [`COption::Some`]`(`[`Ok`]`(_))` and [`COption::Some`]`(`[`Err`]`(_))` will be mapped to
/// [`Ok`]`(`[`COption::Some`]`(_))` and [`Err`]`(_)`.
///
/// [`COption::None`]: #variant.COption::None
/// [`Ok`]: ../../std/result/enum.Result.html#variant.Ok
/// [`COption::Some`]: #variant.COption::Some
/// [`Err`]: ../../std/result/enum.Result.html#variant.Err
///
/// # Examples
///
/// ```ignore
/// #[derive(Debug, Eq, PartialEq)]
/// struct COption::SomeErr;
///
/// let x: Result<COption<i32>, COption::SomeErr> = Ok(COption::Some(5));
/// let y: COption<Result<i32, COption::SomeErr>> = COption::Some(Ok(5));
/// assert_eq!(x, y.transpose());
/// ```
#[inline]
pub fn transpose(self) -> Result<COption<T>, E> {
match self {
COption::Some(Ok(x)) => Ok(COption::Some(x)),
COption::Some(Err(e)) => Err(e),
COption::None => Ok(COption::None),
}
}
}
// This is a separate function to reduce the code size of .expect() itself.
#[inline(never)]
#[cold]
fn expect_failed(msg: &str) -> ! {
panic!("{}", msg)
}
// // This is a separate function to reduce the code size of .expect_none() itself.
// #[inline(never)]
// #[cold]
// fn expect_none_failed(msg: &str, value: &dyn fmt::Debug) -> ! {
// panic!("{}: {:?}", msg, value)
// }
/////////////////////////////////////////////////////////////////////////////
// Trait implementations
/////////////////////////////////////////////////////////////////////////////
impl<T: Clone> Clone for COption<T> {
#[inline]
fn clone(&self) -> Self {
match self {
COption::Some(x) => COption::Some(x.clone()),
COption::None => COption::None,
}
}
#[inline]
fn clone_from(&mut self, source: &Self) {
match (self, source) {
(COption::Some(to), COption::Some(from)) => to.clone_from(from),
(to, from) => *to = from.clone(),
}
}
}
impl<T> Default for COption<T> {
/// Returns [`COption::None`][COption::None].
///
/// # Examples
///
/// ```ignore
/// let opt: COption<u32> = COption::default();
/// assert!(opt.is_none());
/// ```
#[inline]
fn default() -> COption<T> {
COption::None
}
}
impl<T> From<T> for COption<T> {
fn from(val: T) -> COption<T> {
COption::Some(val)
}
}
impl<'a, T> From<&'a COption<T>> for COption<&'a T> {
fn from(o: &'a COption<T>) -> COption<&'a T> {
o.as_ref()
}
}
impl<'a, T> From<&'a mut COption<T>> for COption<&'a mut T> {
fn from(o: &'a mut COption<T>) -> COption<&'a mut T> {
o.as_mut()
}
}
impl<T> COption<COption<T>> {
/// Converts from `COption<COption<T>>` to `COption<T>`
///
/// # Examples
/// Basic usage:
/// ```ignore
/// #![feature(option_flattening)]
/// let x: COption<COption<u32>> = COption::Some(COption::Some(6));
/// assert_eq!(COption::Some(6), x.flatten());
///
/// let x: COption<COption<u32>> = COption::Some(COption::None);
/// assert_eq!(COption::None, x.flatten());
///
/// let x: COption<COption<u32>> = COption::None;
/// assert_eq!(COption::None, x.flatten());
/// ```
/// Flattening once only removes one level of nesting:
/// ```ignore
/// #![feature(option_flattening)]
/// let x: COption<COption<COption<u32>>> = COption::Some(COption::Some(COption::Some(6)));
/// assert_eq!(COption::Some(COption::Some(6)), x.flatten());
/// assert_eq!(COption::Some(6), x.flatten().flatten());
/// ```
#[inline]
pub fn flatten(self) -> COption<T> {
self.and_then(convert::identity)
}
}
impl<T> From<Option<T>> for COption<T> {
fn from(option: Option<T>) -> Self {
match option {
Some(value) => COption::Some(value),
None => COption::None,
}
}
}
#[rustversion::since(1.49.0)]
impl<T> From<COption<T>> for Option<T> {
fn from(coption: COption<T>) -> Self {
match coption {
COption::Some(value) => Some(value),
COption::None => None,
}
}
}
#[rustversion::before(1.49.0)] // Remove `Into` once the BPF toolchain upgrades to 1.49.0 or newer
impl<T> Into<Option<T>> for COption<T> {
fn into(self) -> Option<T> {
match self {
COption::Some(value) => Some(value),
COption::None => None,
}
}
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn test_from_rust_option() {
let option = Some(99u64);
let c_option: COption<u64> = option.into();
assert_eq!(c_option, COption::Some(99u64));
let expected = c_option.into();
assert_eq!(option, expected);
let option = None;
let c_option: COption<u64> = option.into();
assert_eq!(c_option, COption::None);
let expected = c_option.into();
assert_eq!(option, expected);
}
}