//! Types and traits for encoding values to the database.

use crate::database::Database;

use crate::types::HasSqlType;

use std::mem;

/// 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<DB>

where

DB: Database + ?Sized,

{

/// Writes the value of `self` into `buf` in the expected format for the database.

fn encode(&self, buf: &mut Vec<u8>);

fn encode_nullable(&self, buf: &mut Vec<u8>) -> IsNull {

self.encode(buf);

IsNull::No

}

fn size_hint(&self) -> usize {

mem::size_of_val(self)

}

}

impl<T: ?Sized, DB> Encode<DB> for &'_ T

where

DB: Database + HasSqlType<T>,

T: Encode<DB>,

{

fn encode(&self, buf: &mut Vec<u8>) {

(*self).encode(buf)

}

fn encode_nullable(&self, buf: &mut Vec<u8>) -> IsNull {

(*self).encode_nullable(buf)

}

fn size_hint(&self) -> usize {

(*self).size_hint()

}

}

impl<T, DB> Encode<DB> for Option<T>

where

DB: Database + HasSqlType<T>,

T: Encode<DB>,

{

fn encode(&self, buf: &mut Vec<u8>) {

// Forward to [encode_nullable] and ignore the result

let _ = self.encode_nullable(buf);

}

fn encode_nullable(&self, buf: &mut Vec<u8>) -> IsNull {

if let Some(self_) = self {

self_.encode(buf);

IsNull::No

} else {

IsNull::Yes

}

}

fn size_hint(&self) -> usize {

if self.is_some() {

(*self).size_hint()

} else {

0

}

}

}