cdbc 0.1.23

Rust Coroutine Database Driver Connectivity
Documentation 
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//! Provides [`Encode`] for encoding values for the database.

use std::mem;

use crate::database::{Database, HasArguments};

/// The return type of [Encode::encode].
pub enum IsNull {
    /// The value is null; no data was written.
    Yes,

    /// The value is not null.
    ///
    /// This does not mean that data was written.
    No,
}

/// Encode a single value to be sent to the database.
pub trait Encode<'q, DB: Database> {
    /// Writes the value of `self` into `buf` in the expected format for the database.
    #[must_use]
    fn encode(self, buf: &mut <DB as HasArguments<'q>>::ArgumentBuffer) -> IsNull
        where
            Self: Sized,
    {
        self.encode_by_ref(buf)
    }

    /// Writes the value of `self` into `buf` without moving `self`.
    ///
    /// Where possible, make use of `encode` instead as it can take advantage of re-using
    /// memory.
    #[must_use]
    fn encode_by_ref(&self, buf: &mut <DB as HasArguments<'q>>::ArgumentBuffer) -> IsNull;

    fn produces(&self) -> Option<DB::TypeInfo> {
        // `produces` is inherently a hook to allow database drivers to produce value-dependent
        // type information; if the driver doesn't need this, it can leave this as `None`
        None
    }

    #[inline]
    fn size_hint(&self) -> usize {
        mem::size_of_val(self)
    }
}

impl<'q, T, DB: Database> Encode<'q, DB> for &'_ T
    where
        T: Encode<'q, DB>,
{
    #[inline]
    fn encode(self, buf: &mut <DB as HasArguments<'q>>::ArgumentBuffer) -> IsNull {
        <T as Encode<DB>>::encode_by_ref(self, buf)
    }

    #[inline]
    fn encode_by_ref(&self, buf: &mut <DB as HasArguments<'q>>::ArgumentBuffer) -> IsNull {
        <&T as Encode<DB>>::encode(self, buf)
    }

    #[inline]
    fn produces(&self) -> Option<DB::TypeInfo> {
        (**self).produces()
    }

    #[inline]
    fn size_hint(&self) -> usize {
        (**self).size_hint()
    }
}

// #[macro_export]
// #[allow(unused_macros)]
// macro_rules! impl_encode_for_option {
//     ($DB:ident) => {
//         impl<'q, T> cdbc::encode::Encode<'q, $DB> for Option<T>
//         where
//             T: cdbc::encode::Encode<'q, $DB> + cdbc::types::Type<$DB> + 'q,
//         {
//             #[inline]
//             fn produces(&self) -> Option<<$DB as cdbc::database::Database>::TypeInfo> {
//                 if let Some(v) = self {
//                     v.produces()
//                 } else {
//                     T::type_info().into()
//                 }
//             }
//
//             #[inline]
//             fn encode(
//                 self,
//                 buf: &mut <$DB as cdbc::database::HasArguments<'q>>::ArgumentBuffer,
//             ) -> cdbc::encode::IsNull {
//                 if let Some(v) = self {
//                     v.encode(buf)
//                 } else {
//                     cdbc::encode::IsNull::Yes
//                 }
//             }
//
//             #[inline]
//             fn encode_by_ref(
//                 &self,
//                 buf: &mut <$DB as cdbc::database::HasArguments<'q>>::ArgumentBuffer,
//             ) -> cdbc::encode::IsNull {
//                 if let Some(v) = self {
//                     v.encode_by_ref(buf)
//                 } else {
//                     cdbc::encode::IsNull::Yes
//                 }
//             }
//
//             #[inline]
//             fn size_hint(&self) -> usize {
//                 self.as_ref().map_or(0, cdbc::encode::Encode::size_hint)
//             }
//         }
//     };
// }

impl<'q, DB: Database, T> Encode<'q, DB> for Option<T>
    where
        T: crate::encode::Encode<'q, DB> + crate::types::Type<DB> + 'q,{
    #[inline]
    fn produces(&self) -> Option<<DB as crate::database::Database>::TypeInfo> {
        if let Some(v) = self {
            v.produces()
        } else {
            T::type_info().into()
        }
    }

    #[inline]
    fn encode(
        self,
        buf: &mut <DB as crate::database::HasArguments<'q>>::ArgumentBuffer,
    ) -> crate::encode::IsNull {
        if let Some(v) = self {
            v.encode(buf)
        } else {
            crate::encode::IsNull::Yes
        }
    }

    #[inline]
    fn encode_by_ref(&self, buf: &mut <DB as HasArguments<'q>>::ArgumentBuffer) -> IsNull {
        if let Some(v) = self {
            v.encode_by_ref(buf)
        } else {
            crate::encode::IsNull::Yes
        }
    }
    #[inline]
    fn size_hint(&self) -> usize {
        self.as_ref().map_or(0, crate::encode::Encode::size_hint)
    }
}