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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289
//! Types and traits related to serializing values for the database
use std::error::Error;
use std::fmt;
use std::io::{self, Write};
use std::result;
use crate::backend::{Backend, HasBindCollector};
use crate::query_builder::bind_collector::RawBytesBindCollector;
use crate::query_builder::BindCollector;
#[doc(inline)]
#[cfg(feature = "postgres_backend")]
pub use crate::pg::serialize::WriteTuple;
/// A specialized result type representing the result of serializing
/// a value for the database.
pub type Result = result::Result<IsNull, Box<dyn Error + Send + Sync>>;
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
/// Tiny enum to make the return type of `ToSql` more descriptive
pub enum IsNull {
/// No data was written, as this type is null
Yes,
/// The value is not null
///
/// This does not necessarily mean that any data was written to the buffer.
/// For example, an empty string has no data to be sent over the wire, but
/// also is not null.
No,
}
/// Wraps a buffer to be written by `ToSql` with additional backend specific
/// utilities.
pub struct Output<'a, 'b, DB>
where
DB: Backend,
DB::MetadataLookup: 'a,
{
out: <crate::backend::BindCollector<'a, DB> as BindCollector<'a, DB>>::Buffer,
metadata_lookup: Option<&'b mut DB::MetadataLookup>,
}
impl<'a, 'b, DB: Backend> Output<'a, 'b, DB> {
/// Construct a new `Output`
pub fn new(
out: <crate::backend::BindCollector<'a, DB> as BindCollector<'a, DB>>::Buffer,
metadata_lookup: &'b mut DB::MetadataLookup,
) -> Self {
Output {
out,
metadata_lookup: Some(metadata_lookup),
}
}
/// Consume the current `Output` structure to access the inner buffer type
///
/// This function is only useful for people implementing their own Backend.
pub fn into_inner(
self,
) -> <crate::backend::BindCollector<'a, DB> as BindCollector<'a, DB>>::Buffer {
self.out
}
/// Returns the backend's mechanism for dynamically looking up type
/// metadata at runtime, if relevant for the given backend.
pub fn metadata_lookup(&mut self) -> &mut DB::MetadataLookup {
*self.metadata_lookup.as_mut().expect("Lookup is there")
}
/// Set the inner buffer to a specific value
///
/// Checkout the documentation of the type of `BindCollector::Buffer`
/// for your specific backend for supported types.
pub fn set_value<V>(&mut self, value: V)
where
V: Into<<crate::backend::BindCollector<'a, DB> as BindCollector<'a, DB>>::Buffer>,
{
self.out = value.into();
}
}
#[cfg(test)]
impl<'a, DB: Backend> Output<'a, 'static, DB> {
/// Returns a `Output` suitable for testing `ToSql` implementations.
/// Unsafe to use for testing types which perform dynamic metadata lookup.
pub fn test(
buffer: <crate::backend::BindCollector<'a, DB> as BindCollector<'a, DB>>::Buffer,
) -> Self {
Self {
out: buffer,
metadata_lookup: None,
}
}
}
impl<'a, 'b, DB: Backend<BindCollector = RawBytesBindCollector<DB>>> Write for Output<'a, 'b, DB> {
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
self.out.0.write(buf)
}
fn flush(&mut self) -> io::Result<()> {
self.out.0.flush()
}
fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
self.out.0.write_all(buf)
}
fn write_fmt(&mut self, fmt: fmt::Arguments<'_>) -> io::Result<()> {
self.out.0.write_fmt(fmt)
}
}
impl<'a, 'b, DB: Backend<BindCollector = RawBytesBindCollector<DB>>> Output<'a, 'b, DB> {
/// Call this method whenever you pass an instance of `Output<DB>` by value.
///
/// Effectively copies `self`, with a narrower lifetime. When passing a
/// reference or a mutable reference, this is normally done by rust
/// implicitly. This is why you can pass `&mut Foo` to multiple functions,
/// even though mutable references are not `Copy`. However, this is only
/// done implicitly for references. For structs with lifetimes it must be
/// done explicitly. This method matches the semantics of what Rust would do
/// implicitly if you were passing a mutable reference
pub fn reborrow<'c>(&'c mut self) -> Output<'c, 'c, DB>
where
'a: 'c,
{
Output {
out: RawBytesBindCollector::<DB>::reborrow_buffer(&mut self.out),
metadata_lookup: match &mut self.metadata_lookup {
None => None,
Some(m) => Some(&mut **m),
},
}
}
}
impl<'a, 'b, DB> fmt::Debug for Output<'a, 'b, DB>
where
<<DB as HasBindCollector<'a>>::BindCollector as BindCollector<'a, DB>>::Buffer: fmt::Debug,
DB: Backend,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
self.out.fmt(f)
}
}
/// Serializes a single value to be sent to the database.
///
/// The output is sent as a bind parameter, and the data must be written in the
/// expected format for the given backend.
///
/// When possible, implementations of this trait should prefer using an existing
/// implementation, rather than writing to `out` directly. (For example, if you
/// are implementing this for an enum, which is represented as an integer in the
/// database, you should use `i32::to_sql(x, out)` instead of writing to `out`
/// yourself.)
///
/// Any types which implement this trait should also
/// [`#[derive(AsExpression)]`](derive@crate::expression::AsExpression).
///
/// ### Backend specific details
///
/// - For PostgreSQL, the bytes will be sent using the binary protocol, not text.
/// - For SQLite, all implementations should be written in terms of an existing
/// `ToSql` implementation.
/// - For MySQL, the expected bytes will depend on the return value of
/// `type_metadata` for the given SQL type. See [`MysqlType`] for details.
/// - For third party backends, consult that backend's documentation.
///
/// [`MysqlType`]: ../mysql/enum.MysqlType.html
///
/// ### Examples
///
/// Most implementations of this trait will be defined in terms of an existing
/// implementation.
///
/// ```rust
/// # use diesel::backend::Backend;
/// # use diesel::expression::AsExpression;
/// # use diesel::sql_types::*;
/// # use diesel::serialize::{self, ToSql, Output};
/// # use std::io::Write;
/// #
/// #[repr(i32)]
/// #[derive(Debug, Clone, Copy, AsExpression)]
/// #[diesel(sql_type = Integer)]
/// pub enum MyEnum {
/// A = 1,
/// B = 2,
/// }
///
/// impl<DB> ToSql<Integer, DB> for MyEnum
/// where
/// DB: Backend,
/// i32: ToSql<Integer, DB>,
/// {
/// fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, DB>) -> serialize::Result {
/// match self {
/// MyEnum::A => 1.to_sql(out),
/// MyEnum::B => 2.to_sql(out),
/// }
/// }
/// }
/// ```
///
/// Using temporary values as part of the `ToSql` implemenation requires additional
/// work.
///
/// Backends using [`RawBytesBindCollector`] as [`BindCollector`] copy the serialized values as part
/// of `Write` implementation. This includes the `Mysql` and the `Pg` backend provided by diesel.
/// This means existing `ToSql` implemenations can be used even with
/// temporary values. For these it is required to call
/// [`Output::reborrow`] to shorten the lifetime of the `Output` type correspondenly.
///
/// ```
/// # use diesel::backend::Backend;
/// # use diesel::expression::AsExpression;
/// # use diesel::sql_types::*;
/// # use diesel::serialize::{self, ToSql, Output};
/// # use std::io::Write;
/// #
/// #[repr(i32)]
/// #[derive(Debug, Clone, Copy, AsExpression)]
/// #[diesel(sql_type = Integer)]
/// pub enum MyEnum {
/// A = 1,
/// B = 2,
/// }
///
/// # #[cfg(feature = "postgres")]
/// impl ToSql<Integer, diesel::pg::Pg> for MyEnum
/// where
/// i32: ToSql<Integer, diesel::pg::Pg>,
/// {
/// fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, diesel::pg::Pg>) -> serialize::Result {
/// let v = *self as i32;
/// <i32 as ToSql<Integer, diesel::pg::Pg>>::to_sql(&v, &mut out.reborrow())
/// }
/// }
/// ````
///
/// For any other backend the [`Output::set_value`] method provides a way to
/// set the output value directly. Checkout the documentation of the corresponding
/// `BindCollector::Buffer` type for provided `From<T>` implementations for a list
/// of accepted types. For the `Sqlite` backend see `SqliteBindValue`.
///
/// ```
/// # use diesel::backend::Backend;
/// # use diesel::expression::AsExpression;
/// # use diesel::sql_types::*;
/// # use diesel::serialize::{self, ToSql, Output, IsNull};
/// # use std::io::Write;
/// #
/// #[repr(i32)]
/// #[derive(Debug, Clone, Copy, AsExpression)]
/// #[diesel(sql_type = Integer)]
/// pub enum MyEnum {
/// A = 1,
/// B = 2,
/// }
///
/// # #[cfg(feature = "sqlite")]
/// impl ToSql<Integer, diesel::sqlite::Sqlite> for MyEnum
/// where
/// i32: ToSql<Integer, diesel::sqlite::Sqlite>,
/// {
/// fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, diesel::sqlite::Sqlite>) -> serialize::Result {
/// out.set_value(*self as i32);
/// Ok(IsNull::No)
/// }
/// }
/// ````
pub trait ToSql<A, DB: Backend>: fmt::Debug {
/// See the trait documentation.
fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, DB>) -> Result;
}
impl<'a, A, T, DB> ToSql<A, DB> for &'a T
where
DB: Backend,
T: ToSql<A, DB> + ?Sized,
{
fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, DB>) -> Result {
(*self).to_sql(out)
}
}