1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249
//! Types dealing with the data of a state
#![deny(unsafe_code)]
use std::borrow::{Borrow, BorrowMut};
use std::fmt;
use std::fmt::{Display, Formatter};
/// A placeholder for state data whose content is irrelevant
///
/// This type can be "read" from any state regardless of the size of the state data. It doesn't contain the actual data
/// but just their size, which can be obtained via the [`OpaqueData::size`] method. This is useful on different
/// occasions, for instance:
/// - If you want to query the size of state data without querying the actual data:
/// ```
/// # use std::io;
/// # use wnf::{AsState, OwnedState, OpaqueData};
/// #
/// # fn main() -> Result<(), Box<dyn std::error::Error>> {
/// let state = OwnedState::<u32>::create_temporary()?;
/// state.set(&42)?;
///
/// assert_eq!(state.as_state().cast::<OpaqueData>().get()?.size(), 4);
///
/// // Less efficient alternative:
/// assert_eq!(state.as_state().cast::<[u8]>().get_boxed()?.len(), 4);
/// # Ok(()) }
/// ```
/// - If you want to check if a state can be read without querying its actual data:
/// ```
/// # use std::io;
/// # use wnf::{OwnedState, OpaqueData};
/// #
/// # fn main() -> Result<(), Box<dyn std::error::Error>> {
/// // Here we could have used any type `T: NoUninit` in place of `u32`
/// let state = OwnedState::<u32>::create_temporary()?;
/// state.set(&42)?;
///
/// let can_read = state.cast::<OpaqueData>().get().is_ok();
///
/// assert!(can_read);
/// # Ok(()) }
/// ```
///
/// Another use case is reading the change stamp of a state without knowing what the actual data look like, but that is
/// already implemented in [`OwnedState::change_stamp`](crate::state::OwnedState::change_stamp).
#[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
pub struct OpaqueData {
size: usize,
}
impl OpaqueData {
/// Creates a new [`OpaqueData`]
pub(crate) const fn new(size: usize) -> Self {
Self { size }
}
/// Returns the size in bytes of this [`OpaqueData`]
pub const fn size(self) -> usize {
self.size
}
}
/// The change stamp of a state
///
/// This is `0` when the state is created and is increased by `1` on every update to the state.
///
/// Several methods on other types deal with change stamps. See their documentations for details:
/// - [`OwnedState::change_stamp`](crate::state::OwnedState::change_stamp)
/// - [`OwnedState::query`](crate::state::OwnedState::query) and
/// [`OwnedState::query_boxed`](crate::state::OwnedState::query_boxed)
/// - [`OwnedState::update`](crate::state::OwnedState::update)
/// - [`DataAccessor::change_stamp`](crate::subscribe::DataAccessor::change_stamp)
/// - [`DataAccessor::query`](crate::subscribe::DataAccessor::query) and
/// [`DataAccessor::query_boxed`](crate::subscribe::DataAccessor::query_boxed)
#[derive(Clone, Copy, Debug, Default, Eq, Hash, Ord, PartialEq, PartialOrd)]
pub struct ChangeStamp(u32);
impl ChangeStamp {
/// Creates a new [`ChangeStamp`] with the given value
pub const fn new(value: u32) -> Self {
Self(value)
}
/// Returns the initial change stamp of every state, which is `0`:
///
/// ```
/// # use wnf::ChangeStamp;
/// #
/// assert_eq!(ChangeStamp::initial().value(), 0);
/// ```
pub const fn initial() -> Self {
Self(0)
}
/// Returns the inner value
pub const fn value(self) -> u32 {
self.0
}
/// Returns a mutable raw pointer to the inner value for use in FFI
pub(crate) fn as_mut_ptr(&mut self) -> *mut u32 {
&mut self.0
}
}
impl From<u32> for ChangeStamp {
fn from(value: u32) -> Self {
Self(value)
}
}
impl From<ChangeStamp> for u32 {
fn from(ChangeStamp(value): ChangeStamp) -> Self {
value
}
}
impl Display for ChangeStamp {
fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
self.0.fmt(f)
}
}
impl PartialEq<u32> for ChangeStamp {
fn eq(&self, other: &u32) -> bool {
self.0 == *other
}
}
impl PartialEq<ChangeStamp> for u32 {
fn eq(&self, other: &ChangeStamp) -> bool {
*self == other.0
}
}
impl AsRef<u32> for ChangeStamp {
fn as_ref(&self) -> &u32 {
&self.0
}
}
impl AsMut<u32> for ChangeStamp {
fn as_mut(&mut self) -> &mut u32 {
&mut self.0
}
}
impl Borrow<u32> for ChangeStamp {
fn borrow(&self) -> &u32 {
&self.0
}
}
impl BorrowMut<u32> for ChangeStamp {
fn borrow_mut(&mut self) -> &mut u32 {
&mut self.0
}
}
/// State data together with a change stamp
#[derive(Clone, Copy, Debug, Default, Eq, Hash, PartialEq)]
pub struct StampedData<T> {
data: T,
change_stamp: ChangeStamp,
}
impl<T> StampedData<T> {
/// Creates a new [`StampedData`] from the given data and change stamp
pub fn from_data_change_stamp(data: T, change_stamp: impl Into<ChangeStamp>) -> Self {
Self {
data,
change_stamp: change_stamp.into(),
}
}
/// Moves the contained data and change stamp out of this [`StampedData`]
pub fn into_data_change_stamp(self) -> (T, ChangeStamp) {
(self.data, self.change_stamp)
}
/// Moves the contained data out of this [`StampedData`], discarding the change stamp
pub fn into_data(self) -> T {
self.data
}
/// Returns a reference to the data contained in this [`StampedData`]
pub const fn data(&self) -> &T {
&self.data
}
/// Returns the change stamp contained in this [`StampedData`]
pub const fn change_stamp(&self) -> ChangeStamp {
self.change_stamp
}
/// Returns a new [`StampedData`] obtained by applying a given closure to the contained data
pub fn map<U, F>(self, op: F) -> StampedData<U>
where
F: FnOnce(T) -> U,
{
StampedData {
data: op(self.data),
change_stamp: self.change_stamp,
}
}
}
impl<T> From<(T, ChangeStamp)> for StampedData<T> {
fn from((data, change_stamp): (T, ChangeStamp)) -> Self {
Self { data, change_stamp }
}
}
impl<T> From<StampedData<T>> for (T, ChangeStamp) {
fn from(stamped_data: StampedData<T>) -> Self {
(stamped_data.data, stamped_data.change_stamp)
}
}
impl<T> AsRef<T> for StampedData<T> {
fn as_ref(&self) -> &T {
&self.data
}
}
impl<T> AsMut<T> for StampedData<T> {
fn as_mut(&mut self) -> &mut T {
&mut self.data
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn change_stamp_display() {
assert_eq!(ChangeStamp::from(42).to_string(), "42");
}
#[test]
fn stamped_data_map() {
assert_eq!(
StampedData::from_data_change_stamp(42, 1).map(|x| x.to_string()),
StampedData::from_data_change_stamp(String::from("42"), 1)
);
}
}