Struct std::str::Utf8Error1.0.0 [] [src]

pub struct Utf8Error { /* fields omitted */ }

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 Strings and &strs make use of this error, for example.


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) => {
            Err(error) => {
                let (valid, after_valid) = input.split_at(error.valid_up_to());
                unsafe {

                if let Some(invalid_sequence_length) = error.error_len() {
                    input = &after_valid[invalid_sequence_length..]
                } else {


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(_).


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());Run

Provide 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) in case of lossy decoding.

Trait Implementations

impl Copy for Utf8Error

impl Debug for Utf8Error

Formats the value using the given formatter. Read more

impl PartialEq<Utf8Error> for Utf8Error

This method tests for self and other values to be equal, and is used by ==. Read more

This method tests for !=.

impl Display for Utf8Error

Formats the value using the given formatter. Read more

impl Clone for Utf8Error

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

impl Eq for Utf8Error

impl Error for Utf8Error

A short description of the error. Read more

The lower-level cause of this error, if any. Read more

Auto Trait Implementations

impl Send for Utf8Error

impl Sync for Utf8Error