std::string::FromUtf8Error - Rust
Description: API documentation for the Rust `FromUtf8Error` struct in crate `std`.
Keywords: rust, rustlang, rust-lang, FromUtf8Error

# Struct std::string::FromUtf8Error 1.0.0 [−] [src]

    pub struct FromUtf8Error { /* fields omitted */ }

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 `u8`s 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

Basic usage:

    // 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());Run

## Methods

### `impl FromUtf8Error`
[src]

#### `fn as_bytes(&self) -> &[u8]`

🔬 This is a nightly-only experimental API. (`from_utf8_error_as_bytes` #40895)

recently added

Returns a slice of [`u8`]s bytes that were attempted to convert to a `String`.

# Examples

Basic usage:

    #![feature(from_utf8_error_as_bytes)]
    // 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());Run

#### `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

Basic usage:

    // 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());Run

#### `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 `u8`s to a `&str`. In this sense, it's an analogue to `FromUtf8Error`. See its documentation for more details on using it.

# Examples

Basic usage:

    // 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());Run

## Trait Implementations

### `impl Debug for FromUtf8Error`
[src]

#### `fn fmt(&self, __arg_0: &mut Formatter) -> Result<(), Error>`

Formats the value using the given formatter.

### `impl Display for FromUtf8Error`
[src]

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

Formats the value using the given formatter. Read more

### `impl Error for FromUtf8Error`
[src]

#### `fn description(&self) -> &str`

A short description of the error. Read more

#### `fn cause(&self) -> Option<&Error>`

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

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