Struct `FromUtf8Error`

pub struct FromUtf8Error { pub(in ::string) bytes: Vec<u8>, pub(in ::string) 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`

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());

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);

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());

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());