# 1.0.0[−][src]Struct core::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

## Implementations

### `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]

#### `pub fn clone(&self) -> Utf8Error`[src]

Returns a copy of the value. Read more

#### `pub 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]

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

Formats the value using the given formatter. Read more

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

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

Formats the value using the given formatter. Read more

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

### `impl PartialEq<Utf8Error> for Utf8Error`[src]

#### `pub fn eq(&self, other: &Utf8Error) -> bool`[src]

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

#### `pub 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 Send for Utf8Error`

### `impl Sync for Utf8Error`

### `impl Unpin for Utf8Error`

## Blanket Implementations

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

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

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

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

#### `pub fn borrow(&Self) -> &T`[src]

Immutably borrows from an owned value. Read more

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

#### `pub fn borrow_mut(&mut Self) -> &mut T`[src]

Mutably borrows from an owned value. Read more

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

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

Performs the conversion.

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

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

Performs the conversion.

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

#### `type Error = Infallible`

The type returned in the event of a conversion error.

#### `pub fn try_from(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.

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

Performs the conversion.