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use crate::{utils::RangedBytes, FmtArg, PanicFmt, PanicVal};
use core::{
cmp::PartialEq,
fmt::{self, Debug},
};
/// For precomputing a panic message.
///
#[cfg_attr(feature = "docsrs", doc(cfg(feature = "non_basic")))]
#[derive(Copy, Clone)]
pub struct ArrayString<const CAP: usize> {
pub(crate) len: u32,
pub(crate) buffer: [u8; CAP],
}
/// Equivalent of `ArrayString` which can only be up to 255 bytes long.
///
/// This stores the length as a `u8`, while `ArrayString` stores it as a `u32`,
/// making this 3 bytes smaller and 1-aligned (while ArrayString is aligned to a `u32`).
#[derive(Copy, Clone)]
pub(crate) struct TinyString<const CAP: usize> {
len: u8,
buffer: [u8; CAP],
}
const fn add_up_lengths(mut strings: &[&str]) -> usize {
let mut len = 0;
while let [x, rem @ ..] = strings {
len += x.len();
strings = rem;
}
len
}
impl<const CAP: usize> ArrayString<CAP> {
/// Constructs an `ArrayString` from a `&str`
///
/// # Panics
///
/// Panics if `string` is larger than `CAP`.
///
/// # Example
///
/// ```rust
/// use const_panic::ArrayString;
///
/// assert_eq!(ArrayString::<16>::new("Hello, world!"), "Hello, world!");
/// ```
pub const fn new(string: &str) -> Self {
Self::concat(&[string])
}
/// Constructs an `ArrayString` by concatenating zero or more `&str`s
///
/// # Panics
///
/// Panics if the concatenated string would be longer than `CAP`.
///
/// # Example
///
/// ```rust
/// use const_panic::ArrayString;
///
/// assert_eq!(
/// ArrayString::<99>::concat(&["This ", "is ", "a string"]),
/// "This is a string"
/// );
/// ```
pub const fn concat(strings: &[&str]) -> Self {
let mut len = 0u32;
let mut buffer = [0u8; CAP];
let mut mstrings = strings;
while let [string, ref rem @ ..] = *mstrings {
mstrings = rem;
let mut bytes = string.as_bytes();
while let [x, ref rem @ ..] = *bytes {
if len == u32::MAX || len as usize >= CAP {
crate::concat_panic(&[&[
PanicVal::write_str("The input strings were longer than "),
PanicVal::from_usize(CAP, FmtArg::DISPLAY),
PanicVal::write_str(", concatenated length: "),
PanicVal::from_usize(add_up_lengths(strings), FmtArg::DISPLAY),
PanicVal::write_str(", strings: "),
PanicVal::from_slice_str(strings, FmtArg::DEBUG),
]])
}
bytes = rem;
buffer[len as usize] = x;
len += 1;
}
}
Self { len, buffer }
}
/// Constructs this string from a `&[&[PanicVal<'_>]]`.
///
/// Returns `None` if the formatted args would be larger than `CAP`.
///
/// # Example
///
/// ```rust
/// use const_panic::{ArrayString, FmtArg, flatten_panicvals};
///
/// assert_eq!(
/// ArrayString::<17>::concat_panicvals(&[
/// &flatten_panicvals!(FmtArg::DEBUG; 1u8, ("hello")),
/// &flatten_panicvals!(FmtArg::DEBUG; &[3u8, 5, 8]),
/// ]).unwrap(),
/// "1\"hello\"[3, 5, 8]",
/// );
///
/// assert!(
/// ArrayString::<16>::concat_panicvals(&[
/// &flatten_panicvals!(FmtArg::DEBUG; 1u8, ("hello")),
/// &flatten_panicvals!(FmtArg::DEBUG; &[3u8, 5, 8]),
/// ]).is_none(),
/// );
///
/// ```
///
pub const fn concat_panicvals(args: &[&[PanicVal<'_>]]) -> Option<Self> {
match crate::concat_panic_::make_panic_string::<CAP>(args) {
Ok(x) => Some(x),
Err(_) => None,
}
}
/// Constructs this string from a `&[PanicVal<'_>]`.
///
/// Returns `None` if the formatted args would be larger than `CAP`.
///
/// # Example
///
/// ```rust
/// use const_panic::{ArrayString, FmtArg, flatten_panicvals};
///
/// assert_eq!(
/// ArrayString::<8>::from_panicvals(
/// &flatten_panicvals!(FmtArg::DEBUG; 100u8, "hello")
/// ).unwrap(),
/// "100hello",
/// );
///
/// // trying to format panicvals into too small an ArrayString
/// assert!(
/// ArrayString::<7>::from_panicvals(
/// &flatten_panicvals!(FmtArg::DEBUG; 100u8, "hello")
/// ).is_none(),
/// );
///
/// ```
pub const fn from_panicvals(args: &[PanicVal<'_>]) -> Option<Self> {
Self::concat_panicvals(&[args])
}
/// How long the string is in bytes.
///
/// # Example
///
/// ```rust
/// use const_panic::ArrayString;
///
/// assert_eq!(ArrayString::<16>::new("foo").len(), 3);
/// assert_eq!(ArrayString::<16>::new("foo bar").len(), 7);
/// assert_eq!(ArrayString::<16>::new("Hello, world!").len(), 13);
/// ```
pub const fn len(&self) -> usize {
self.len as usize
}
/// Accesses the string as a byte slice.
///
/// # Performance
///
/// When the "rust_1_64" feature is disabled,
/// this takes a linear amount of time to run, proportional to `CAP - self.len()`.
///
/// When the "rust_1_64" feature is enabled,
/// this takes a constant amount of time to run.
///
/// # Example
///
/// ```rust
/// use const_panic::ArrayString;
///
/// assert_eq!(ArrayString::<16>::new("foo").as_bytes(), b"foo");
/// assert_eq!(ArrayString::<16>::new("foo bar").as_bytes(), b"foo bar");
/// assert_eq!(ArrayString::<16>::new("Hello, world!").as_bytes(), b"Hello, world!");
/// ```
pub const fn as_bytes(&self) -> &[u8] {
bytes_up_to(&self.buffer, self.len())
}
/// Gets the string.
///
/// # Performance
///
/// This takes a linear amount of time to run.
///
/// # Example
///
/// ```rust
/// use const_panic::ArrayString;
///
/// assert_eq!(ArrayString::<16>::new("foo").to_str(), "foo");
/// assert_eq!(ArrayString::<16>::new("foo bar").to_str(), "foo bar");
/// assert_eq!(ArrayString::<16>::new("Hello, world!").to_str(), "Hello, world!");
/// ```
pub const fn to_str(&self) -> &str {
#[cfg(not(feature = "rust_1_64"))]
{
// safety: make_panic_string delegates formatting to the `write_to_buffer` macro,
// which is tested as producing valid utf8.
unsafe { core::str::from_utf8_unchecked(self.as_bytes()) }
}
#[cfg(feature = "rust_1_64")]
match core::str::from_utf8(self.as_bytes()) {
Ok(x) => x,
Err(_) => panic!("INTERNAL BUG: the string isn't valid utf-8"),
}
}
/// Creates a single element `PanicVal` borrowing from this string.
pub const fn to_panicvals(&self, f: FmtArg) -> [PanicVal<'_>; 1] {
[PanicVal::from_str(self.to_str(), f)]
}
/// Creates a `PanicVal` borrowing from this string.
pub const fn to_panicval(&self, f: FmtArg) -> PanicVal<'_> {
PanicVal::from_str(self.to_str(), f)
}
}
impl<const CAP: usize> ArrayString<CAP> {
pub(crate) const fn to_compact(self) -> TinyString<CAP> {
if self.len() <= 255 {
TinyString {
len: self.len as u8,
buffer: self.buffer,
}
} else {
crate::concat_panic(&[&[
PanicVal::write_str(
"The input string is too long, expected `length <= 255`, found length: ",
),
PanicVal::from_usize(self.len(), FmtArg::DISPLAY),
]])
}
}
}
impl<const CAP: usize> Debug for ArrayString<CAP> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
Debug::fmt(self.to_str(), f)
}
}
impl<const CAP: usize> PartialEq<str> for ArrayString<CAP> {
fn eq(&self, str: &str) -> bool {
self.to_str() == str
}
}
impl<const CAP: usize> PartialEq<&str> for ArrayString<CAP> {
fn eq(&self, str: &&str) -> bool {
self == *str
}
}
impl<const CAP: usize> PanicFmt for ArrayString<CAP> {
type This = Self;
type Kind = crate::fmt::IsCustomType;
const PV_COUNT: usize = 1;
}
////////////////////////////////////////////////////////////////////////////////
impl<const CAP: usize> TinyString<CAP> {
pub(crate) const fn ranged(&self) -> RangedBytes<&[u8]> {
RangedBytes {
start: 0,
end: self.len as usize,
bytes: &self.buffer,
}
}
}
////////////////////////////////////////////////////////////////////////////////
#[cfg(not(feature = "rust_1_64"))]
const fn bytes_up_to(buffer: &[u8], upto: usize) -> &[u8] {
let mut to_truncate = buffer.len() - upto;
let mut out: &[u8] = buffer;
while to_truncate != 0 {
if let [rem @ .., _] = out {
out = rem;
}
to_truncate -= 1;
}
if out.len() != upto {
panic!("BUG!")
}
out
}
#[cfg(feature = "rust_1_64")]
const fn bytes_up_to(buffer: &[u8], upto: usize) -> &[u8] {
if upto > buffer.len() {
return buffer;
}
// SAFETY: the above conditional ensures that `upto` doesn't
// create a partially-dangling slice
unsafe { core::slice::from_raw_parts(buffer.as_ptr(), upto) }
}