# error.rs - source
Source of the Rust file `/home/key/.cargo/registry/src/github.com-1ecc6299db9ec823/rand_core-0.6.3/src/error.rs`.
Keywords: rust, rustlang, rust-lang

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    // Copyright 2018 Developers of the Rand project.
    //
    // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
    // https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
    // <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
    // option. This file may not be copied, modified, or distributed
    // except according to those terms.

    //! Error types

    use core::fmt;
    use core::num::NonZeroU32;

    #[cfg(feature = "std")] use std::boxed::Box;

    /// Error type of random number generators
    ///
    /// In order to be compatible with `std` and `no_std`, this type has two
    /// possible implementations: with `std` a boxed `Error` trait object is stored,
    /// while with `no_std` we merely store an error code.
    pub struct Error {
        #[cfg(feature = "std")]
        inner: Box<dyn std::error::Error + Send + Sync + 'static>,
        #[cfg(not(feature = "std"))]
        code: NonZeroU32,
    }

    impl Error {
        /// Codes at or above this point can be used by users to define their own
        /// custom errors.
        ///
        /// This has a fixed value of `(1 << 31) + (1 << 30) = 0xC000_0000`,
        /// therefore the number of values available for custom codes is `1 << 30`.
        ///
        /// This is identical to [`getrandom::Error::CUSTOM_START`](https://docs.rs/getrandom/latest/getrandom/struct.Error.html#associatedconstant.CUSTOM_START).
        pub const CUSTOM_START: u32 = (1 << 31) + (1 << 30);
        /// Codes below this point represent OS Errors (i.e. positive i32 values).
        /// Codes at or above this point, but below [`Error::CUSTOM_START`] are
        /// reserved for use by the `rand` and `getrandom` crates.
        ///
        /// This is identical to [`getrandom::Error::INTERNAL_START`](https://docs.rs/getrandom/latest/getrandom/struct.Error.html#associatedconstant.INTERNAL_START).
        pub const INTERNAL_START: u32 = 1 << 31;

        /// Construct from any type supporting `std::error::Error`
        ///
        /// Available only when configured with `std`.
        ///
        /// See also `From<NonZeroU32>`, which is available with and without `std`.
        #[cfg(feature = "std")]
        #[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
        #[inline]
        pub fn new<E>(err: E) -> Self
        where
            E: Into<Box<dyn std::error::Error + Send + Sync + 'static>>,
        {
            Error { inner: err.into() }
        }

        /// Reference the inner error (`std` only)
        ///
        /// When configured with `std`, this is a trivial operation and never
        /// panics. Without `std`, this method is simply unavailable.
        #[cfg(feature = "std")]
        #[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
        #[inline]
        pub fn inner(&self) -> &(dyn std::error::Error + Send + Sync + 'static) {
            &*self.inner
        }

        /// Unwrap the inner error (`std` only)
        ///
        /// When configured with `std`, this is a trivial operation and never
        /// panics. Without `std`, this method is simply unavailable.
        #[cfg(feature = "std")]
        #[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
        #[inline]
        pub fn take_inner(self) -> Box<dyn std::error::Error + Send + Sync + 'static> {
            self.inner
        }

        /// Extract the raw OS error code (if this error came from the OS)
        ///
        /// This method is identical to `std::io::Error::raw_os_error()`, except
        /// that it works in `no_std` contexts. If this method returns `None`, the
        /// error value can still be formatted via the `Diplay` implementation.
        #[inline]
        pub fn raw_os_error(&self) -> Option<i32> {
            #[cfg(feature = "std")]
            {
                if let Some(e) = self.inner.downcast_ref::<std::io::Error>() {
                    return e.raw_os_error();
                }
            }
            match self.code() {
                Some(code) if u32::from(code) < Self::INTERNAL_START => Some(u32::from(code) as i32),
                _ => None,
            }
        }

        /// Retrieve the error code, if any.
        ///
        /// If this `Error` was constructed via `From<NonZeroU32>`, then this method
        /// will return this `NonZeroU32` code (for `no_std` this is always the
        /// case). Otherwise, this method will return `None`.
        #[inline]
        pub fn code(&self) -> Option<NonZeroU32> {
            #[cfg(feature = "std")]
            {
                self.inner.downcast_ref::<ErrorCode>().map(|c| c.0)
            }
            #[cfg(not(feature = "std"))]
            {
                Some(self.code)
            }
        }
    }

    impl fmt::Debug for Error {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            #[cfg(feature = "std")]
            {
                write!(f, "Error {{ inner: {:?} }}", self.inner)
            }
            #[cfg(all(feature = "getrandom", not(feature = "std")))]
            {
                getrandom::Error::from(self.code).fmt(f)
            }
            #[cfg(not(feature = "getrandom"))]
            {
                write!(f, "Error {{ code: {} }}", self.code)
            }
        }
    }

    impl fmt::Display for Error {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            #[cfg(feature = "std")]
            {
                write!(f, "{}", self.inner)
            }
            #[cfg(all(feature = "getrandom", not(feature = "std")))]
            {
                getrandom::Error::from(self.code).fmt(f)
            }
            #[cfg(not(feature = "getrandom"))]
            {
                write!(f, "error code {}", self.code)
            }
        }
    }

    impl From<NonZeroU32> for Error {
        #[inline]
        fn from(code: NonZeroU32) -> Self {
            #[cfg(feature = "std")]
            {
                Error {
                    inner: Box::new(ErrorCode(code)),
                }
            }
            #[cfg(not(feature = "std"))]
            {
                Error { code }
            }
        }
    }

    #[cfg(feature = "getrandom")]
    impl From<getrandom::Error> for Error {
        #[inline]
        fn from(error: getrandom::Error) -> Self {
            #[cfg(feature = "std")]
            {
                Error {
                    inner: Box::new(error),
                }
            }
            #[cfg(not(feature = "std"))]
            {
                Error { code: error.code() }
            }
        }
    }

    #[cfg(feature = "std")]
    impl std::error::Error for Error {
        #[inline]
        fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
            self.inner.source()
        }
    }

    #[cfg(feature = "std")]
    impl From<Error> for std::io::Error {
        #[inline]
        fn from(error: Error) -> Self {
            if let Some(code) = error.raw_os_error() {
                std::io::Error::from_raw_os_error(code)
            } else {
                std::io::Error::new(std::io::ErrorKind::Other, error)
            }
        }
    }

    #[cfg(feature = "std")]
    #[derive(Debug, Copy, Clone)]
    struct ErrorCode(NonZeroU32);

    #[cfg(feature = "std")]
    impl fmt::Display for ErrorCode {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            write!(f, "error code {}", self.0)
        }
    }

    #[cfg(feature = "std")]
    impl std::error::Error for ErrorCode {}

    #[cfg(test)]
    mod test {
        #[cfg(feature = "getrandom")]
        #[test]
        fn test_error_codes() {
            // Make sure the values are the same as in `getrandom`.
            assert_eq!(super::Error::CUSTOM_START, getrandom::Error::CUSTOM_START);
            assert_eq!(super::Error::INTERNAL_START, getrandom::Error::INTERNAL_START);
        }
    }