# 1.0.0[−][src]Struct std::str::Utf8Error

    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
                    }
                }
            }
        }
    }Run

## 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());Run

#### `pub fn error_len(&self) -> Option<usize>`1.20.0[src]

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`) 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 Copy for Utf8Error`[src]

### `impl Debug for Utf8Error`[src]

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

Formats the value using the given formatter. Read more

### `impl Display 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 Error for Utf8Error`[src]

#### `fn description(&self) -> &str`[src]

This method is soft-deprecated. Read more

#### `fn cause(&self) -> Option<&dyn Error>`[src]

Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

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

#### `fn source(&self) -> Option<&(dyn Error + 'static)>`1.30.0[src]

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

#### `fn backtrace(&self) -> Option<&Backtrace>`[src]

🔬 This is a nightly-only experimental API. (`backtrace` #53487)

Returns a stack backtrace, if available, of where this error occurred. Read more

### `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 StructuralEq for Utf8Error`[src]

### `impl StructuralPartialEq for Utf8Error`[src]

## Auto Trait Implementations

### `impl RefUnwindSafe for Utf8Error`

### `impl Send for Utf8Error`

### `impl Sync for Utf8Error`

### `impl Unpin for Utf8Error`

### `impl UnwindSafe for Utf8Error`

## Blanket Implementations

### `impl<T> Any for T where
T: 'static + ?Sized,` [src]

#### `fn type_id(&self) -> TypeId`[src]

Gets the `TypeId` of `self`. Read more

### `impl<T> Borrow<T> for T where
T: ?Sized,` [src]

####
ⓘImportant traits for &'_ mut F

### Important traits for &'_ mut F

`impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, R: Read + ?Sized> Read for &'_ mut Rimpl<'_, W: Write + ?Sized> Write for &'_ mut W`
`fn borrow(&self) -> &T`[src]

Immutably borrows from an owned value. Read more

### `impl<T> BorrowMut<T> for T where
T: ?Sized,` [src]

####
ⓘImportant traits for &'_ mut F

### Important traits for &'_ mut F

`impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'_, R: Read + ?Sized> Read for &'_ mut Rimpl<'_, W: Write + ?Sized> Write for &'_ mut W`
`fn borrow_mut(&mut self) -> &mut T`[src]

Mutably borrows from an owned value. Read more

### `impl<T> From<T> for T`[src]

#### `fn from(t: T) -> T`[src]

Performs the conversion.

### `impl<T, U> Into<U> for T where
U: From<T>,` [src]

#### `fn into(self) -> U`[src]

Performs the conversion.

### `impl<T> ToOwned for T where
T: Clone,` [src]

#### `type Owned = T`

The resulting type after obtaining ownership.

#### `fn to_owned(&self) -> T`[src]

Creates owned data from borrowed data, usually by cloning. Read more

#### `fn clone_into(&self, target: &mut T)`[src]

🔬 This is a nightly-only experimental API. (`toowned_clone_into` #41263)

recently added

Uses borrowed data to replace owned data, usually by cloning. Read more

### `impl<T> ToString for T where
T: Display + ?Sized,` [src]

#### `default fn to_string(&self) -> String`[src]

Converts the given value to a `String`. Read more

### `impl<T, U> TryFrom<U> for T where
U: Into<T>,` [src]

#### `type Error = !`

The type returned in the event of a conversion error.

#### `fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>`[src]

Performs the conversion.

### `impl<T, U> TryInto<U> for T where
U: TryFrom<T>,` [src]

#### `type Error = <U as TryFrom<T>>::Error`

The type returned in the event of a conversion error.

#### `fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>`[src]

Performs the conversion.