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use core::{
cmp::Ordering,
fmt,
fmt::Write,
hash, iter, ops,
str::{self, Utf8Error},
};
use crate::Vec;
/// A fixed capacity [`String`](https://doc.rust-lang.org/std/string/struct.String.html)
pub struct String<const N: usize> {
vec: Vec<u8, N>,
}
impl<const N: usize> String<N> {
/// Constructs a new, empty `String` with a fixed capacity of `N` bytes
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use heapless::String;
///
/// // allocate the string on the stack
/// let mut s: String<4> = String::new();
///
/// // allocate the string in a static variable
/// static mut S: String<4> = String::new();
/// ```
#[inline]
pub const fn new() -> Self {
Self { vec: Vec::new() }
}
/// Convert UTF-8 bytes into a `String`.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use heapless::{String, Vec};
///
/// let mut sparkle_heart = Vec::<u8, 4>::new();
/// sparkle_heart.extend_from_slice(&[240, 159, 146, 150]);
///
/// let sparkle_heart: String<4> = String::from_utf8(sparkle_heart)?;
/// assert_eq!("💖", sparkle_heart);
/// # Ok::<(), core::str::Utf8Error>(())
/// ```
///
/// Invalid UTF-8:
///
/// ```
/// use core::str::Utf8Error;
/// use heapless::{String, Vec};
///
/// let mut vec = Vec::<u8, 4>::new();
/// vec.extend_from_slice(&[0, 159, 146, 150]);
///
/// let e: Utf8Error = String::from_utf8(vec).unwrap_err();
/// assert_eq!(e.valid_up_to(), 1);
/// # Ok::<(), core::str::Utf8Error>(())
/// ```
#[inline]
pub fn from_utf8(vec: Vec<u8, N>) -> Result<Self, Utf8Error> {
core::str::from_utf8(&vec)?;
Ok(Self { vec })
}
/// Convert UTF-8 bytes into a `String`, without checking that the string
/// contains valid UTF-8.
///
/// # Safety
///
/// The bytes passed in must be valid UTF-8.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use heapless::{String, Vec};
///
/// let mut sparkle_heart = Vec::<u8, 4>::new();
/// sparkle_heart.extend_from_slice(&[240, 159, 146, 150]);
///
/// // Safety: `sparkle_heart` Vec is known to contain valid UTF-8
/// let sparkle_heart: String<4> = unsafe { String::from_utf8_unchecked(sparkle_heart) };
/// assert_eq!("💖", sparkle_heart);
/// ```
#[inline]
pub unsafe fn from_utf8_unchecked(vec: Vec<u8, N>) -> Self {
Self { vec }
}
/// Converts a `String` into a byte vector.
///
/// This consumes the `String`, so we do not need to copy its contents.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use heapless::String;
///
/// let s: String<4> = String::try_from("ab")?;
/// let b = s.into_bytes();
/// assert!(b.len() == 2);
///
/// assert_eq!(&['a' as u8, 'b' as u8], &b[..]);
/// # Ok::<(), ()>(())
/// ```
#[inline]
pub fn into_bytes(self) -> Vec<u8, N> {
self.vec
}
/// Extracts a string slice containing the entire string.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use heapless::String;
///
/// let mut s: String<4> = String::try_from("ab")?;
/// assert!(s.as_str() == "ab");
///
/// let _s = s.as_str();
/// // s.push('c'); // <- cannot borrow `s` as mutable because it is also borrowed as immutable
/// # Ok::<(), ()>(())
/// ```
#[inline]
pub fn as_str(&self) -> &str {
unsafe { str::from_utf8_unchecked(self.vec.as_slice()) }
}
/// Converts a `String` into a mutable string slice.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use heapless::String;
///
/// let mut s: String<4> = String::try_from("ab")?;
/// let s = s.as_mut_str();
/// s.make_ascii_uppercase();
/// # Ok::<(), ()>(())
/// ```
#[inline]
pub fn as_mut_str(&mut self) -> &mut str {
unsafe { str::from_utf8_unchecked_mut(self.vec.as_mut_slice()) }
}
/// Returns a mutable reference to the contents of this `String`.
///
/// # Safety
///
/// This function is unsafe because it does not check that the bytes passed
/// to it are valid UTF-8. If this constraint is violated, it may cause
/// memory unsafety issues with future users of the `String`, as the rest of
/// the library assumes that `String`s are valid UTF-8.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use heapless::String;
///
/// let mut s: String<8> = String::try_from("hello")?;
///
/// unsafe {
/// let vec = s.as_mut_vec();
/// assert_eq!(&[104, 101, 108, 108, 111][..], &vec[..]);
///
/// vec.reverse();
/// }
/// assert_eq!(s, "olleh");
/// # Ok::<(), ()>(())
/// ```
pub unsafe fn as_mut_vec(&mut self) -> &mut Vec<u8, N> {
&mut self.vec
}
/// Appends a given string slice onto the end of this `String`.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use heapless::String;
///
/// let mut s: String<8> = String::try_from("foo")?;
///
/// assert!(s.push_str("bar").is_ok());
///
/// assert_eq!("foobar", s);
///
/// assert!(s.push_str("tender").is_err());
/// # Ok::<(), ()>(())
/// ```
#[inline]
pub fn push_str(&mut self, string: &str) -> Result<(), ()> {
self.vec.extend_from_slice(string.as_bytes())
}
/// Returns the maximum number of elements the String can hold
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use heapless::String;
///
/// let mut s: String<4> = String::new();
/// assert!(s.capacity() == 4);
/// ```
#[inline]
pub fn capacity(&self) -> usize {
self.vec.capacity()
}
/// Appends the given [`char`] to the end of this `String`.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use heapless::String;
///
/// let mut s: String<8> = String::try_from("abc")?;
///
/// s.push('1').unwrap();
/// s.push('2').unwrap();
/// s.push('3').unwrap();
///
/// assert!("abc123" == s.as_str());
///
/// assert_eq!("abc123", s);
/// # Ok::<(), ()>(())
/// ```
#[inline]
pub fn push(&mut self, c: char) -> Result<(), ()> {
match c.len_utf8() {
1 => self.vec.push(c as u8).map_err(|_| {}),
_ => self
.vec
.extend_from_slice(c.encode_utf8(&mut [0; 4]).as_bytes()),
}
}
/// Shortens this `String` to the specified length.
///
/// If `new_len` is greater than the string's current length, this has no
/// effect.
///
/// Note that this method has no effect on the allocated capacity
/// of the string
///
/// # Panics
///
/// Panics if `new_len` does not lie on a [`char`] boundary.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use heapless::String;
///
/// let mut s: String<8> = String::try_from("hello")?;
///
/// s.truncate(2);
///
/// assert_eq!("he", s);
/// # Ok::<(), ()>(())
/// ```
#[inline]
pub fn truncate(&mut self, new_len: usize) {
if new_len <= self.len() {
assert!(self.is_char_boundary(new_len));
self.vec.truncate(new_len)
}
}
/// Removes the last character from the string buffer and returns it.
///
/// Returns [`None`] if this `String` is empty.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use heapless::String;
///
/// let mut s: String<8> = String::try_from("foo")?;
///
/// assert_eq!(s.pop(), Some('o'));
/// assert_eq!(s.pop(), Some('o'));
/// assert_eq!(s.pop(), Some('f'));
///
/// assert_eq!(s.pop(), None);
/// Ok::<(), ()>(())
/// ```
pub fn pop(&mut self) -> Option<char> {
let ch = self.chars().rev().next()?;
// pop bytes that correspond to `ch`
for _ in 0..ch.len_utf8() {
unsafe {
self.vec.pop_unchecked();
}
}
Some(ch)
}
/// Removes a [`char`] from this `String` at a byte position and returns it.
///
/// Note: Because this shifts over the remaining elements, it has a
/// worst-case performance of *O*(*n*).
///
/// # Panics
///
/// Panics if `idx` is larger than or equal to the `String`'s length,
/// or if it does not lie on a [`char`] boundary.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use heapless::String;
///
/// let mut s: String<8> = String::try_from("foo").unwrap();
///
/// assert_eq!(s.remove(0), 'f');
/// assert_eq!(s.remove(1), 'o');
/// assert_eq!(s.remove(0), 'o');
/// ```
#[inline]
pub fn remove(&mut self, index: usize) -> char {
let ch = match self[index..].chars().next() {
Some(ch) => ch,
None => panic!("cannot remove a char from the end of a string"),
};
let next = index + ch.len_utf8();
let len = self.len();
let ptr = self.vec.as_mut_ptr();
unsafe {
core::ptr::copy(ptr.add(next), ptr.add(index), len - next);
self.vec.set_len(len - (next - index));
}
ch
}
/// Truncates this `String`, removing all contents.
///
/// While this means the `String` will have a length of zero, it does not
/// touch its capacity.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use heapless::String;
///
/// let mut s: String<8> = String::try_from("foo")?;
///
/// s.clear();
///
/// assert!(s.is_empty());
/// assert_eq!(0, s.len());
/// assert_eq!(8, s.capacity());
/// Ok::<(), ()>(())
/// ```
#[inline]
pub fn clear(&mut self) {
self.vec.clear()
}
}
impl<const N: usize> Default for String<N> {
fn default() -> Self {
Self::new()
}
}
impl<'a, const N: usize> TryFrom<&'a str> for String<N> {
type Error = ();
fn try_from(s: &'a str) -> Result<Self, Self::Error> {
let mut new = String::new();
new.push_str(s)?;
Ok(new)
}
}
impl<const N: usize> str::FromStr for String<N> {
type Err = ();
fn from_str(s: &str) -> Result<Self, Self::Err> {
let mut new = String::new();
new.push_str(s)?;
Ok(new)
}
}
impl<const N: usize> iter::FromIterator<char> for String<N> {
fn from_iter<T: IntoIterator<Item = char>>(iter: T) -> Self {
let mut new = String::new();
for c in iter {
new.push(c).unwrap();
}
new
}
}
impl<'a, const N: usize> iter::FromIterator<&'a char> for String<N> {
fn from_iter<T: IntoIterator<Item = &'a char>>(iter: T) -> Self {
let mut new = String::new();
for c in iter {
new.push(*c).unwrap();
}
new
}
}
impl<'a, const N: usize> iter::FromIterator<&'a str> for String<N> {
fn from_iter<T: IntoIterator<Item = &'a str>>(iter: T) -> Self {
let mut new = String::new();
for c in iter {
new.push_str(c).unwrap();
}
new
}
}
impl<const N: usize> Clone for String<N> {
fn clone(&self) -> Self {
Self {
vec: self.vec.clone(),
}
}
}
impl<const N: usize> fmt::Debug for String<N> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
<str as fmt::Debug>::fmt(self, f)
}
}
impl<const N: usize> fmt::Display for String<N> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
<str as fmt::Display>::fmt(self, f)
}
}
impl<const N: usize> hash::Hash for String<N> {
#[inline]
fn hash<H: hash::Hasher>(&self, hasher: &mut H) {
<str as hash::Hash>::hash(self, hasher)
}
}
impl<const N: usize> fmt::Write for String<N> {
fn write_str(&mut self, s: &str) -> Result<(), fmt::Error> {
self.push_str(s).map_err(|_| fmt::Error)
}
fn write_char(&mut self, c: char) -> Result<(), fmt::Error> {
self.push(c).map_err(|_| fmt::Error)
}
}
impl<const N: usize> ops::Deref for String<N> {
type Target = str;
fn deref(&self) -> &str {
self.as_str()
}
}
impl<const N: usize> ops::DerefMut for String<N> {
fn deref_mut(&mut self) -> &mut str {
self.as_mut_str()
}
}
impl<const N: usize> AsRef<str> for String<N> {
#[inline]
fn as_ref(&self) -> &str {
self
}
}
impl<const N: usize> AsRef<[u8]> for String<N> {
#[inline]
fn as_ref(&self) -> &[u8] {
self.as_bytes()
}
}
impl<const N1: usize, const N2: usize> PartialEq<String<N2>> for String<N1> {
fn eq(&self, rhs: &String<N2>) -> bool {
str::eq(&**self, &**rhs)
}
fn ne(&self, rhs: &String<N2>) -> bool {
str::ne(&**self, &**rhs)
}
}
// String<N> == str
impl<const N: usize> PartialEq<str> for String<N> {
#[inline]
fn eq(&self, other: &str) -> bool {
str::eq(&self[..], &other[..])
}
#[inline]
fn ne(&self, other: &str) -> bool {
str::ne(&self[..], &other[..])
}
}
// String<N> == &'str
impl<const N: usize> PartialEq<&str> for String<N> {
#[inline]
fn eq(&self, other: &&str) -> bool {
str::eq(&self[..], &other[..])
}
#[inline]
fn ne(&self, other: &&str) -> bool {
str::ne(&self[..], &other[..])
}
}
// str == String<N>
impl<const N: usize> PartialEq<String<N>> for str {
#[inline]
fn eq(&self, other: &String<N>) -> bool {
str::eq(&self[..], &other[..])
}
#[inline]
fn ne(&self, other: &String<N>) -> bool {
str::ne(&self[..], &other[..])
}
}
// &'str == String<N>
impl<const N: usize> PartialEq<String<N>> for &str {
#[inline]
fn eq(&self, other: &String<N>) -> bool {
str::eq(&self[..], &other[..])
}
#[inline]
fn ne(&self, other: &String<N>) -> bool {
str::ne(&self[..], &other[..])
}
}
impl<const N: usize> Eq for String<N> {}
impl<const N1: usize, const N2: usize> PartialOrd<String<N2>> for String<N1> {
#[inline]
fn partial_cmp(&self, other: &String<N2>) -> Option<Ordering> {
PartialOrd::partial_cmp(&**self, &**other)
}
}
impl<const N: usize> Ord for String<N> {
#[inline]
fn cmp(&self, other: &Self) -> Ordering {
Ord::cmp(&**self, &**other)
}
}
macro_rules! impl_try_from_num {
($num:ty, $size:expr) => {
impl<const N: usize> core::convert::TryFrom<$num> for String<N> {
type Error = ();
fn try_from(s: $num) -> Result<Self, Self::Error> {
let mut new = String::new();
write!(&mut new, "{}", s).map_err(|_| ())?;
Ok(new)
}
}
};
}
impl_try_from_num!(i8, 4);
impl_try_from_num!(i16, 6);
impl_try_from_num!(i32, 11);
impl_try_from_num!(i64, 20);
impl_try_from_num!(u8, 3);
impl_try_from_num!(u16, 5);
impl_try_from_num!(u32, 10);
impl_try_from_num!(u64, 20);
#[cfg(test)]
mod tests {
use crate::{String, Vec};
use core::convert::TryFrom;
#[test]
fn static_new() {
static mut _S: String<8> = String::new();
}
#[test]
fn clone() {
let s1: String<20> = String::try_from("abcd").unwrap();
let mut s2 = s1.clone();
s2.push_str(" efgh").unwrap();
assert_eq!(s1, "abcd");
assert_eq!(s2, "abcd efgh");
}
#[test]
fn cmp() {
let s1: String<4> = String::try_from("abcd").unwrap();
let s2: String<4> = String::try_from("zzzz").unwrap();
assert!(s1 < s2);
}
#[test]
fn cmp_heterogenous_size() {
let s1: String<4> = String::try_from("abcd").unwrap();
let s2: String<8> = String::try_from("zzzz").unwrap();
assert!(s1 < s2);
}
#[test]
fn debug() {
use core::fmt::Write;
let s: String<8> = String::try_from("abcd").unwrap();
let mut std_s = std::string::String::new();
write!(std_s, "{:?}", s).unwrap();
assert_eq!("\"abcd\"", std_s);
}
#[test]
fn display() {
use core::fmt::Write;
let s: String<8> = String::try_from("abcd").unwrap();
let mut std_s = std::string::String::new();
write!(std_s, "{}", s).unwrap();
assert_eq!("abcd", std_s);
}
#[test]
fn empty() {
let s: String<4> = String::new();
assert!(s.capacity() == 4);
assert_eq!(s, "");
assert_eq!(s.len(), 0);
assert_ne!(s.len(), 4);
}
#[test]
fn try_from() {
let s: String<4> = String::try_from("123").unwrap();
assert!(s.len() == 3);
assert_eq!(s, "123");
let e: () = String::<2>::try_from("123").unwrap_err();
assert_eq!(e, ());
}
#[test]
fn from_str() {
use core::str::FromStr;
let s: String<4> = String::<4>::from_str("123").unwrap();
assert!(s.len() == 3);
assert_eq!(s, "123");
let e: () = String::<2>::from_str("123").unwrap_err();
assert_eq!(e, ());
}
#[test]
fn from_iter() {
let mut v: Vec<char, 5> = Vec::new();
v.push('h').unwrap();
v.push('e').unwrap();
v.push('l').unwrap();
v.push('l').unwrap();
v.push('o').unwrap();
let string1: String<5> = v.iter().collect(); //&char
let string2: String<5> = "hello".chars().collect(); //char
assert_eq!(string1, "hello");
assert_eq!(string2, "hello");
}
#[test]
#[should_panic]
fn from_panic() {
let _: String<4> = String::try_from("12345").unwrap();
}
#[test]
fn try_from_num() {
let v: String<20> = String::try_from(18446744073709551615 as u64).unwrap();
assert_eq!(v, "18446744073709551615");
let e: () = String::<2>::try_from(18446744073709551615 as u64).unwrap_err();
assert_eq!(e, ());
}
#[test]
fn into_bytes() {
let s: String<4> = String::try_from("ab").unwrap();
let b: Vec<u8, 4> = s.into_bytes();
assert_eq!(b.len(), 2);
assert_eq!(&['a' as u8, 'b' as u8], &b[..]);
}
#[test]
fn as_str() {
let s: String<4> = String::try_from("ab").unwrap();
assert_eq!(s.as_str(), "ab");
// should be moved to fail test
// let _s = s.as_str();
// s.push('c'); // <- cannot borrow `s` as mutable because it is also borrowed as immutable
}
#[test]
fn as_mut_str() {
let mut s: String<4> = String::try_from("ab").unwrap();
let s = s.as_mut_str();
s.make_ascii_uppercase();
assert_eq!(s, "AB");
}
#[test]
fn push_str() {
let mut s: String<8> = String::try_from("foo").unwrap();
assert!(s.push_str("bar").is_ok());
assert_eq!("foobar", s);
assert_eq!(s, "foobar");
assert!(s.push_str("tender").is_err());
assert_eq!("foobar", s);
assert_eq!(s, "foobar");
}
#[test]
fn push() {
let mut s: String<6> = String::try_from("abc").unwrap();
assert!(s.push('1').is_ok());
assert!(s.push('2').is_ok());
assert!(s.push('3').is_ok());
assert!(s.push('4').is_err());
assert!("abc123" == s.as_str());
}
#[test]
fn as_bytes() {
let s: String<8> = String::try_from("hello").unwrap();
assert_eq!(&[104, 101, 108, 108, 111], s.as_bytes());
}
#[test]
fn truncate() {
let mut s: String<8> = String::try_from("hello").unwrap();
s.truncate(6);
assert_eq!(s.len(), 5);
s.truncate(2);
assert_eq!(s.len(), 2);
assert_eq!("he", s);
assert_eq!(s, "he");
}
#[test]
fn pop() {
let mut s: String<8> = String::try_from("foo").unwrap();
assert_eq!(s.pop(), Some('o'));
assert_eq!(s.pop(), Some('o'));
assert_eq!(s.pop(), Some('f'));
assert_eq!(s.pop(), None);
}
#[test]
fn pop_uenc() {
let mut s: String<8> = String::try_from("é").unwrap();
assert_eq!(s.len(), 3);
match s.pop() {
Some(c) => {
assert_eq!(s.len(), 1);
assert_eq!(c, '\u{0301}'); // accute accent of e
()
}
None => assert!(false),
};
}
#[test]
fn is_empty() {
let mut v: String<8> = String::new();
assert!(v.is_empty());
let _ = v.push('a');
assert!(!v.is_empty());
}
#[test]
fn clear() {
let mut s: String<8> = String::try_from("foo").unwrap();
s.clear();
assert!(s.is_empty());
assert_eq!(0, s.len());
assert_eq!(8, s.capacity());
}
#[test]
fn remove() {
let mut s: String<8> = String::try_from("foo").unwrap();
assert_eq!(s.remove(0), 'f');
assert_eq!(s.as_str(), "oo");
}
#[test]
fn remove_uenc() {
let mut s: String<8> = String::try_from("ĝėēƶ").unwrap();
assert_eq!(s.remove(2), 'ė');
assert_eq!(s.remove(2), 'ē');
assert_eq!(s.remove(2), 'ƶ');
assert_eq!(s.as_str(), "ĝ");
}
#[test]
fn remove_uenc_combo_characters() {
let mut s: String<8> = String::try_from("héy").unwrap();
assert_eq!(s.remove(2), '\u{0301}');
assert_eq!(s.as_str(), "hey");
}
}