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