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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")] pub 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")] pub fn error_len(&self) -> Option<usize> { self.error_len.map(|len| len as usize) } } #[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)] #[stable(feature = "rust1", since = "1.0.0")] pub struct ParseBoolError { pub(super) _priv: (), } #[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) } }