1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132

use std::error;
use std::fmt;
use std::str;
use std::string::FromUtf8Error;

use raw::FstType;

/// An error that occurred while using a finite state transducer.
pub enum Error {
    /// A version mismatch occurred while reading a finite state transducer.
    ///
    /// This occurs when the API version (of the crate) does not match the
    /// version encoded in the finite state transducer.
    ///
    /// When this error is encountered, there are only two ways to fix it:
    ///
    /// 1. Change the version of the library to one that is compatible with
    ///    the given finite state transducer.
    /// 2. Rebuild the finite state transducer.
    Version {
        /// The expected version, which is hard-coded into the current version
        /// of this crate.
        expected: u64,
        /// The version read from the finite state transducer.
        got: u64,
    },
    /// An unexpected error occurred while reading a finite state transducer.
    /// Usually this occurs because the data is corrupted or is not actually
    /// a finite state transducer serialized by this library.
    Format,
    /// A duplicate key was inserted into a finite state transducer, which is
    /// not allowed.
    DuplicateKey {
        /// The duplicate key.
        got: Vec<u8>,
    },
    /// A key was inserted out of order into a finite state transducer.
    ///
    /// Keys must always be inserted in lexicographic order.
    OutOfOrder {
        /// The last key successfully inserted.
        previous: Vec<u8>,
        /// The key that caused this error to occur.
        got: Vec<u8>,
    },
    /// A finite state transducer with an unexpected type was found.
    ///
    /// This is not currently used in this crate, but callers may wish to
    /// employ its use for alternative data structures implemented on top of
    /// finite state transducers.
    WrongType {
        /// The expected finite state transducer type.
        expected: FstType,
        /// The type read from a finite state transducer.
        got: FstType,
    },
    /// An error that occurred when trying to decode a UTF-8 byte key.
    FromUtf8(FromUtf8Error),
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        use self::Error::*;
        match *self {
            FromUtf8(ref err) => err.fmt(f),
            Version { expected, got } => {
                write!(f, "\
Error opening FST: expected API version {}, got API version {}.
It looks like the FST you're trying to open is either not an FST file or it
was generated with a different version of the 'fst' crate. You'll either need
to change the version of the 'fst' crate you're using, or re-generate the
FST.", expected, got)
            }
            Format => write!(f, "\
Error opening FST: An unknown error occurred. This usually means you're trying
to read data that isn't actually an encoded FST."),
            DuplicateKey { ref got } => write!(f, "\
Error inserting duplicate key: {}.", format_bytes(&*got)),
            OutOfOrder { ref previous, ref got } => write!(f, "\
Error inserting out-of-order key: {}. (Previous key was {}.) Keys must be
inserted in lexicographic order.",
format_bytes(&*got), format_bytes(&*previous)),
            WrongType { expected, got } => write!(f, "\
Error opening FST: expected type {}, got type {}.", expected, got),
        }
    }
}

impl fmt::Debug for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        fmt::Display::fmt(self, f)
    }
}

impl error::Error for Error {
    fn description(&self) -> &str {
        use self::Error::*;
        match *self {
            FromUtf8(ref err) => err.description(),
            Version { .. } => "incompatible version found when opening FST",
            Format => "unknown invalid format found when opening FST",
            DuplicateKey { .. } => "duplicate key insertion",
            OutOfOrder { .. } => "out-of-order key insertion",
            WrongType { .. } => "incompatible type found when opening FST",
        }
    }

    fn cause(&self) -> Option<&error::Error> {
        match *self {
            Error::FromUtf8(ref err) => Some(err),
            _ => None,
        }
    }
}

impl From<FromUtf8Error> for Error {
    fn from(err: FromUtf8Error) -> Self {
        Error::FromUtf8(err)
    }
}

/// Attempt to convert an arbitrary byte string to a more convenient display
/// form.
///
/// Essentially, try to decode the bytes as UTF-8 and show that. Failing that,
/// just show the sequence of bytes.
fn format_bytes(bytes: &[u8]) -> String {
    match str::from_utf8(bytes) {
        Ok(s) => s.to_owned(),
        Err(_) => format!("{:?}", bytes),
    }
}