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
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185

#[cfg(feature = "std")]
use alloc::boxed::Box;
use core::fmt::{self, Display, Formatter};

#[cfg(feature = "std")]
use std::error::Error as StdError;

/// The possible kinds of error produced by the crate
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum ErrorKind {
    /// An encryption or decryption operation failed
    Encryption,

    /// Out of space in provided buffer
    ExceededBuffer,

    /// The provided input was invalid
    InvalidData,

    /// The provided key was invalid
    InvalidKeyData,

    /// The provided nonce was invalid (bad length)
    InvalidNonce,

    /// A secret key is required but not present
    MissingSecretKey,

    /// An unexpected error occurred
    Unexpected,

    /// The input parameters to the method were incorrect
    Usage,

    /// An unsupported operation was requested
    Unsupported,
}

impl ErrorKind {
    /// Convert the error kind to a string reference
    pub fn as_str(&self) -> &'static str {
        match self {
            Self::Encryption => "Encryption error",
            Self::ExceededBuffer => "Exceeded allocated buffer",
            Self::InvalidData => "Invalid data",
            Self::InvalidNonce => "Invalid encryption nonce",
            Self::InvalidKeyData => "Invalid key data",
            Self::MissingSecretKey => "Missing secret key",
            Self::Unexpected => "Unexpected error",
            Self::Usage => "Usage error",
            Self::Unsupported => "Unsupported",
        }
    }
}

impl Display for ErrorKind {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str(self.as_str())
    }
}

/// The standard crate error type
#[derive(Debug)]
pub struct Error {
    pub(crate) kind: ErrorKind,
    #[cfg(feature = "std")]
    pub(crate) cause: Option<Box<dyn StdError + Send + Sync + 'static>>,
    pub(crate) message: Option<&'static str>,
}

impl Error {
    /// Create a new error instance with message text
    pub fn from_msg(kind: ErrorKind, msg: &'static str) -> Self {
        Self {
            kind,
            #[cfg(feature = "std")]
            cause: None,
            message: Some(msg),
        }
    }

    /// Accessor for the error kind
    pub fn kind(&self) -> ErrorKind {
        self.kind
    }

    /// Accessor for the error message
    pub fn message(&self) -> &'static str {
        self.message.unwrap_or_else(|| self.kind.as_str())
    }

    #[cfg(feature = "std")]
    pub(crate) fn with_cause<T: Into<Box<dyn StdError + Send + Sync>>>(mut self, err: T) -> Self {
        self.cause = Some(err.into());
        self
    }
}

impl Display for Error {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        if let Some(msg) = self.message {
            f.write_str(msg)?;
        } else {
            f.write_str(self.kind.as_str())?;
        }
        #[cfg(feature = "std")]
        if let Some(cause) = self.cause.as_ref() {
            write!(f, "\nCaused by: {}", cause)?;
        }
        Ok(())
    }
}

#[cfg(feature = "std")]
impl StdError for Error {
    fn source(&self) -> Option<&(dyn StdError + 'static)> {
        self.cause.as_ref().map(|err| {
            // &<Error + ?Sized> implements Error, which lets us
            // create a new trait object
            (&**err) as &dyn StdError
        })
    }
}

impl PartialEq for Error {
    fn eq(&self, other: &Self) -> bool {
        self.kind == other.kind && self.message == other.message
    }
}

impl From<ErrorKind> for Error {
    fn from(kind: ErrorKind) -> Self {
        Self {
            kind,
            #[cfg(feature = "std")]
            cause: None,
            message: None,
        }
    }
}

macro_rules! err_msg {
    ($kind:ident) => {
        $crate::error::Error::from($crate::error::ErrorKind::$kind)
    };
    ($kind:ident, $msg:expr) => {
        $crate::error::Error::from_msg($crate::error::ErrorKind::$kind, $msg)
    };
}

#[cfg(feature = "std")]
macro_rules! err_map {
    ($($params:tt)*) => {
        |err| err_msg!($($params)*).with_cause(err)
    };
}

#[cfg(not(feature = "std"))]
macro_rules! err_map {
    ($($params:tt)*) => {
        |_| err_msg!($($params)*)
    };
}

#[cfg(all(test, feature = "std"))]
mod tests {
    use super::*;

    #[test]
    // ensure that the source can still be downcast
    fn downcast_err() {
        #[derive(Debug)]
        struct E;
        impl Display for E {
            fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
                write!(f, "E")
            }
        }
        impl StdError for E {}

        let err = Error::from(ErrorKind::Unexpected).with_cause(E);
        let e = err.source().unwrap().downcast_ref::<E>();
        assert!(e.is_some());
    }
}