error.rs - source
Description: Source of the Rust file `library/core/src/str/error.rs`.

#
core/str/
error.rs

    1//! Defines utf8 error type.
    2
    3use crate::error::Error;
    4use crate::fmt;
    5
    6/// Errors which can occur when attempting to interpret a sequence of [`u8`]
    7/// as a string.
    8///
    9/// As such, the `from_utf8` family of functions and methods for both [`String`]s
    10/// and [`&str`]s make use of this error, for example.
    11///
    12/// [`String`]: ../../std/string/struct.String.html#method.from_utf8
    13/// [`&str`]: super::from_utf8
    14///
    15/// # Examples
    16///
    17/// This error type’s methods can be used to create functionality
    18/// similar to `String::from_utf8_lossy` without allocating heap memory:
    19///
    20/// ```
    21/// fn from_utf8_lossy<F>(mut input: &[u8], mut push: F) where F: FnMut(&str) {
    22///     loop {
    23///         match std::str::from_utf8(input) {
    24///             Ok(valid) => {
    25///                 push(valid);
    26///                 break
    27///             }
    28///             Err(error) => {
    29///                 let (valid, after_valid) = input.split_at(error.valid_up_to());
    30///                 unsafe {
    31///                     push(std::str::from_utf8_unchecked(valid))
    32///                 }
    33///                 push("\u{FFFD}");
    34///
    35///                 if let Some(invalid_sequence_length) = error.error_len() {
    36///                     input = &after_valid[invalid_sequence_length..]
    37///                 } else {
    38///                     break
    39///                 }
    40///             }
    41///         }
    42///     }
    43/// }
    44/// ```
    45#[derive(Copy, Eq, PartialEq, Clone, Debug)]
    46#[stable(feature = "rust1", since = "1.0.0")]
    47pub struct Utf8Error {
    48    pub(super) valid_up_to: usize,
    49    pub(super) error_len: Option<u8>,
    50}
    51
    52impl Utf8Error {
    53    /// Returns the index in the given string up to which valid UTF-8 was
    54    /// verified.
    55    ///
    56    /// It is the maximum index such that `from_utf8(&input[..index])`
    57    /// would return `Ok(_)`.
    58    ///
    59    /// # Examples
    60    ///
    61    /// Basic usage:
    62    ///
    63    /// ```
    64    /// use std::str;
    65    ///
    66    /// // some invalid bytes, in a vector
    67    /// let sparkle_heart = vec![0, 159, 146, 150];
    68    ///
    69    /// // std::str::from_utf8 returns a Utf8Error
    70    /// let error = str::from_utf8(&sparkle_heart).unwrap_err();
    71    ///
    72    /// // the second byte is invalid here
    73    /// assert_eq!(1, error.valid_up_to());
    74    /// ```
    75    #[stable(feature = "utf8_error", since = "1.5.0")]
    76    #[rustc_const_stable(feature = "const_str_from_utf8_shared", since = "1.63.0")]
    77    #[must_use]
    78    #[inline]
    79    pub const fn valid_up_to(&self) -> usize {
    80        self.valid_up_to
    81    }
    82
    83    /// Provides more information about the failure:
    84    ///
    85    /// * `None`: the end of the input was reached unexpectedly.
    86    ///   `self.valid_up_to()` is 1 to 3 bytes from the end of the input.
    87    ///   If a byte stream (such as a file or a network socket) is being decoded incrementally,
    88    ///   this could be a valid `char` whose UTF-8 byte sequence is spanning multiple chunks.
    89    ///
    90    /// * `Some(len)`: an unexpected byte was encountered.
    91    ///   The length provided is that of the invalid byte sequence
    92    ///   that starts at the index given by `valid_up_to()`.
    93    ///   Decoding should resume after that sequence
    94    ///   (after inserting a [`U+FFFD REPLACEMENT CHARACTER`][U+FFFD]) in case of
    95    ///   lossy decoding.
    96    ///
    97    /// [U+FFFD]: ../../std/char/constant.REPLACEMENT_CHARACTER.html
    98    #[stable(feature = "utf8_error_error_len", since = "1.20.0")]
    99    #[rustc_const_stable(feature = "const_str_from_utf8_shared", since = "1.63.0")]
    100    #[must_use]
    101    #[inline]
    102    pub const fn error_len(&self) -> Option<usize> {
    103        // FIXME(const-hack): This should become `map` again, once it's `const`
    104        match self.error_len {
    105            Some(len) => Some(len as usize),
    106            None => None,
    107        }
    108    }
    109}
    110
    111#[stable(feature = "rust1", since = "1.0.0")]
    112impl fmt::Display for Utf8Error {
    113    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
    114        if let Some(error_len) = self.error_len {
    115            write!(
    116                f,
    117                "invalid utf-8 sequence of {} bytes from index {}",
    118                error_len, self.valid_up_to
    119            )
    120        } else {
    121            write!(f, "incomplete utf-8 byte sequence from index {}", self.valid_up_to)
    122        }
    123    }
    124}
    125
    126#[stable(feature = "rust1", since = "1.0.0")]
    127impl Error for Utf8Error {}
    128
    129/// An error returned when parsing a `bool` using [`from_str`] fails
    130///
    131/// [`from_str`]: super::FromStr::from_str
    132#[derive(Debug, Clone, PartialEq, Eq)]
    133#[non_exhaustive]
    134#[stable(feature = "rust1", since = "1.0.0")]
    135pub struct ParseBoolError;
    136
    137#[stable(feature = "rust1", since = "1.0.0")]
    138impl fmt::Display for ParseBoolError {
    139    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
    140        "provided string was not `true` or `false`".fmt(f)
    141    }
    142}
    143
    144#[stable(feature = "rust1", since = "1.0.0")]
    145impl Error for ParseBoolError {}