utf8_parser/
error.rs

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use core::fmt;

/// Error type used for the `utf8-parser` crate
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub enum Utf8ParserError {
    /// Encountered an invalid byte. This is a byte that's invalid no matter the context.
    InvalidByte(u8),
    /// Found a code point that's not valid UTF-8.
    InvalidChar(u32),
    /// Found a start byte in an unexpected place
    UnexpectedStartByte(u8),
    /// Found a continuation byte in an unexpected place
    UnexpectedContinuationByte(u8),
    /// Represented a valid code point in a longer form than necessary.
    ///
    /// From Wikipedia:
    /// > The standard specifies that the correct encoding of a code point uses only the minimum
    /// > number of bytes required to hold the significant bits of the code point. Longer encodings
    /// > are called overlong and are not valid UTF-8 representations of the code point. This rule
    /// > maintains a one-to-one correspondence between code points and their valid encodings, so
    /// > that there is a unique valid encoding for each code point. This ensures that string
    /// > comparisons and searches are well-defined.
    OverlongEncoding,
}

impl fmt::Display for Utf8ParserError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::InvalidByte(byte) => {
                write!(f, "Found invalid byte: 0x{byte:02x}")
            }
            Self::InvalidChar(word) => {
                write!(f, "Parsed invalid UTF-8 code point: 0x{word:04x}")
            }
            Self::UnexpectedStartByte(byte) => {
                write!(
                    f,
                    "Found start byte when a continuation byte was expected: 0x{byte:02x}"
                )
            }
            Self::UnexpectedContinuationByte(byte) => {
                write!(
                    f,
                    "Found continuation byte when a start byte was expected: 0x{byte:02x}"
                )
            }
            Self::OverlongEncoding => {
                write!(f, "Found overlong encoding")
            }
        }
    }
}

impl core::error::Error for Utf8ParserError {}