Struct FromUtf8Error 

pub struct FromUtf8Error {
    bytes: Vec<u8>,
    error: Utf8Error,
}

A possible error value when converting a String from a UTF-8 byte vector.

This type is the error type for the from_utf8 method on String. It is designed in such a way to carefully avoid reallocations: the into_bytes method will give back the byte vector that was used in the conversion attempt.

The Utf8Error type provided by std::str represents an error that may occur when converting a slice of u8s to a &str. In this sense, it’s an analogue to FromUtf8Error, and you can get one from a FromUtf8Error through the utf8_error method.

Examples

// some invalid bytes, in a vector
let bytes = vec![0, 159];

let value = String::from_utf8(bytes);

assert!(value.is_err());
assert_eq!(vec![0, 159], value.unwrap_err().into_bytes());

Fields

bytes: Vec<u8>

error: Utf8Error

Implementations

impl FromUtf8Error

pub fn as_bytes(&self) -> &[u8]

Returns a slice of u8s bytes that were attempted to convert to a String.

Examples

// some invalid bytes, in a vector
let bytes = vec![0, 159];

let value = String::from_utf8(bytes);

assert_eq!(&[0, 159], value.unwrap_err().as_bytes());

pub fn into_utf8_lossy(self) -> String

Converts the bytes into a String lossily, substituting invalid UTF-8 sequences with replacement characters.

See String::from_utf8_lossy for more details on replacement of invalid sequences, and String::from_utf8_lossy_owned for the String function which corresponds to this function.

This is useful in conjunction with String::from_utf8 when you need to branch on whether the bytes are valid UTF-8, but still want to recover a lossily converted String in the error case. Use String::from_utf8_lossy_owned if you always need a lossily converted String.

Since the original String::from_utf8 error records where validation stopped, this method does not need to re-check the already valid prefix of the byte sequence.

Examples

// some invalid bytes
let input: Vec<u8> = b"Hello \xF0\x90\x80World".into();

let (output, had_invalid_utf8) = match String::from_utf8(input) {
    Ok(output) => (output, false),
    Err(error) => {
        // The bytes were not valid UTF-8, but we can still recover a string.
        (error.into_utf8_lossy(), true)
    }
};

assert_eq!(String::from("Hello �World"), output);
assert!(had_invalid_utf8);

pub fn into_bytes(self) -> Vec<u8>

Returns the bytes that were attempted to convert to a String.

This method is carefully constructed to avoid allocation. It will consume the error, moving out the bytes, so that a copy of the bytes does not need to be made.

Examples

// some invalid bytes, in a vector
let bytes = vec![0, 159];

let value = String::from_utf8(bytes);

assert_eq!(vec![0, 159], value.unwrap_err().into_bytes());

pub fn utf8_error(&self) -> Utf8Error

Fetch a Utf8Error to get more details about the conversion failure.

The Utf8Error type provided by std::str represents an error that may occur when converting a slice of u8s to a &str. In this sense, it’s an analogue to FromUtf8Error. See its documentation for more details on using it.

Examples

// some invalid bytes, in a vector
let bytes = vec![0, 159];

let error = String::from_utf8(bytes).unwrap_err().utf8_error();

// the first byte is invalid here
assert_eq!(1, error.valid_up_to());

Trait Implementations

impl Clone for FromUtf8Error

fn clone(&self) -> FromUtf8Error

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for FromUtf8Error

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for FromUtf8Error

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for FromUtf8Error

#[doc(hidden)]

fn assert_fields_are_eq(&self)

🔬This is a nightly-only experimental API. (derive_eq_internals)

#[doc(hidden)]

fn assert_receiver_is_total_eq(&self)

👎Deprecated since 1.95.0:

implementation detail of #[derive(Eq)]

impl Error for FromUtf8Error

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

#[doc(hidden)]

fn type_id(&self, _: Internal) -> TypeId

where Self: 'static,

🔬This is a nightly-only experimental API. (error_type_id #60784)

Gets the TypeId of self.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access #99301)

Provides type-based access to context intended for error reports.

impl PartialEq for FromUtf8Error

fn eq(&self, other: &FromUtf8Error) -> bool

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for FromUtf8Error