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//! Defines utf8 error type.
use crate::fmt;
/// Errors which can occur when attempting to interpret a sequence of [`u8`]
/// as a string.
///
/// As such, the `from_utf8` family of functions and methods for both [`String`]s
/// and [`&str`]s make use of this error, for example.
///
/// [`String`]: ../../std/string/struct.String.html#method.from_utf8
/// [`&str`]: super::from_utf8
///
/// # Examples
///
/// This error type’s methods can be used to create functionality
/// similar to `String::from_utf8_lossy` without allocating heap memory:
///
/// ```
/// fn from_utf8_lossy<F>(mut input: &[u8], mut push: F) where F: FnMut(&str) {
/// loop {
/// match std::str::from_utf8(input) {
/// Ok(valid) => {
/// push(valid);
/// break
/// }
/// Err(error) => {
/// let (valid, after_valid) = input.split_at(error.valid_up_to());
/// unsafe {
/// push(std::str::from_utf8_unchecked(valid))
/// }
/// push("\u{FFFD}");
///
/// if let Some(invalid_sequence_length) = error.error_len() {
/// input = &after_valid[invalid_sequence_length..]
/// } else {
/// break
/// }
/// }
/// }
/// }
/// }
/// ```
#[derive(Copy, Eq, PartialEq, Clone, Debug)]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Utf8Error {
pub(super) valid_up_to: usize,
pub(super) error_len: Option<u8>,
}
impl Utf8Error {
/// Returns the index in the given string up to which valid UTF-8 was
/// verified.
///
/// It is the maximum index such that `from_utf8(&input[..index])`
/// would return `Ok(_)`.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use std::str;
///
/// // some invalid bytes, in a vector
/// let sparkle_heart = vec![0, 159, 146, 150];
///
/// // std::str::from_utf8 returns a Utf8Error
/// let error = str::from_utf8(&sparkle_heart).unwrap_err();
///
/// // the second byte is invalid here
/// assert_eq!(1, error.valid_up_to());
/// ```
#[stable(feature = "utf8_error", since = "1.5.0")]
#[rustc_const_stable(feature = "const_str_from_utf8_shared", since = "1.63.0")]
#[must_use]
#[inline]
pub const fn valid_up_to(&self) -> usize {
self.valid_up_to
}
/// Provides more information about the failure:
///
/// * `None`: the end of the input was reached unexpectedly.
/// `self.valid_up_to()` is 1 to 3 bytes from the end of the input.
/// If a byte stream (such as a file or a network socket) is being decoded incrementally,
/// this could be a valid `char` whose UTF-8 byte sequence is spanning multiple chunks.
///
/// * `Some(len)`: an unexpected byte was encountered.
/// The length provided is that of the invalid byte sequence
/// that starts at the index given by `valid_up_to()`.
/// Decoding should resume after that sequence
/// (after inserting a [`U+FFFD REPLACEMENT CHARACTER`][U+FFFD]) in case of
/// lossy decoding.
///
/// [U+FFFD]: ../../std/char/constant.REPLACEMENT_CHARACTER.html
#[stable(feature = "utf8_error_error_len", since = "1.20.0")]
#[rustc_const_stable(feature = "const_str_from_utf8_shared", since = "1.63.0")]
#[must_use]
#[inline]
pub const fn error_len(&self) -> Option<usize> {
// FIXME: This should become `map` again, once it's `const`
match self.error_len {
Some(len) => Some(len as usize),
None => None,
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl fmt::Display for Utf8Error {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
if let Some(error_len) = self.error_len {
write!(
f,
"invalid utf-8 sequence of {} bytes from index {}",
error_len, self.valid_up_to
)
} else {
write!(f, "incomplete utf-8 byte sequence from index {}", self.valid_up_to)
}
}
}
/// An error returned when parsing a `bool` using [`from_str`] fails
///
/// [`from_str`]: super::FromStr::from_str
#[derive(Debug, Clone, PartialEq, Eq)]
#[non_exhaustive]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct ParseBoolError;
#[stable(feature = "rust1", since = "1.0.0")]
impl fmt::Display for ParseBoolError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
"provided string was not `true` or `false`".fmt(f)
}
}