alloc::str::Utf8Error - Rust
Description: API documentation for the Rust `Utf8Error` struct in crate `alloc`.
Keywords: rust, rustlang, rust-lang, Utf8Error

# Struct alloc::str::Utf8Error 1.0.0[−][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 `String`s and `&str`s make use of this error, for example.

# 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
                    }
                }
            }
        }
    }

## Methods

###

`impl Utf8Error`

[src]

####

`pub fn valid_up_to(&self) -> usize`

1.5.0
[src]

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());

####

`pub fn error_len(&self) -> Option<usize>`

1.20.0
[src]

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 Clone for Utf8Error`

[src]

####

`fn clone(&self) -> Utf8Error`

[src]

Returns a copy of the value. Read more

####

`fn clone_from(&mut self, source: &Self)`

[src]

Performs copy-assignment from `source`. Read more

###

`impl Debug for Utf8Error`

[src]

####

`fn fmt(&self, f: &mut Formatter) -> Result<(), Error>`

[src]

Formats the value using the given formatter. Read more

###

`impl Eq for Utf8Error`

[src]

###

`impl PartialEq<Utf8Error> for Utf8Error`

[src]

####

`fn eq(&self, other: &Utf8Error) -> bool`

[src]

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

####

`fn ne(&self, other: &Utf8Error) -> bool`

[src]

This method tests for `!=`.

###

`impl Copy for Utf8Error`

[src]

###

`impl Display for Utf8Error`

[src]

####

`fn fmt(&self, f: &mut Formatter) -> Result<(), Error>`

[src]

Formats the value using the given formatter. Read more

## Auto Trait Implementations

###

`impl Send for Utf8Error`

###

`impl Sync for Utf8Error`

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