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Diffstat (limited to 'src/params.rs')
| -rw-r--r-- | src/params.rs | 358 |
1 files changed, 358 insertions, 0 deletions
diff --git a/src/params.rs b/src/params.rs new file mode 100644 index 0000000..54aa571 --- /dev/null +++ b/src/params.rs @@ -0,0 +1,358 @@ +use crate::{Result, Statement, ToSql}; + +mod sealed { + /// This trait exists just to ensure that the only impls of `trait Params` + /// that are allowed are ones in this crate. + pub trait Sealed {} +} +use sealed::Sealed; + +/// Trait used for [sets of parameter][params] passed into SQL +/// statements/queries. +/// +/// [params]: https://www.sqlite.org/c3ref/bind_blob.html +/// +/// Note: Currently, this trait can only be implemented inside this crate. +/// Additionally, it's methods (which are `doc(hidden)`) should currently not be +/// considered part of the stable API, although it's possible they will +/// stabilize in the future. +/// +/// # Passing parameters to SQLite +/// +/// Many functions in this library let you pass parameters to SQLite. Doing this +/// lets you avoid any risk of SQL injection, and is simpler than escaping +/// things manually. Aside from deprecated functions and a few helpers, this is +/// indicated by the function taking a generic argument that implements `Params` +/// (this trait). +/// +/// ## Positional parameters +/// +/// For cases where you want to pass a list of parameters where the number of +/// parameters is known at compile time, this can be done in one of the +/// following ways: +/// +/// - Using the [`rusqlite::params!`](crate::params!) macro, e.g. +/// `thing.query(rusqlite::params![1, "foo", bar])`. This is mostly useful for +/// heterogeneous lists of parameters, or lists where the number of parameters +/// exceeds 32. +/// +/// - For small heterogeneous lists of parameters, they can either be passed as: +/// +/// - an array, as in `thing.query([1i32, 2, 3, 4])` or `thing.query(["foo", +/// "bar", "baz"])`. +/// +/// - a reference to an array of references, as in `thing.query(&["foo", +/// "bar", "baz"])` or `thing.query(&[&1i32, &2, &3])`. +/// +/// (Note: in this case we don't implement this for slices for coherence +/// reasons, so it really is only for the "reference to array" types — +/// hence why the number of parameters must be <= 32 or you need to +/// reach for `rusqlite::params!`) +/// +/// Unfortunately, in the current design it's not possible to allow this for +/// references to arrays of non-references (e.g. `&[1i32, 2, 3]`). Code like +/// this should instead either use `params!`, an array literal, a `&[&dyn +/// ToSql]` or if none of those work, [`ParamsFromIter`]. +/// +/// - As a slice of `ToSql` trait object references, e.g. `&[&dyn ToSql]`. This +/// is mostly useful for passing parameter lists around as arguments without +/// having every function take a generic `P: Params`. +/// +/// ### Example (positional) +/// +/// ```rust,no_run +/// # use rusqlite::{Connection, Result, params}; +/// fn update_rows(conn: &Connection) -> Result<()> { +/// let mut stmt = conn.prepare("INSERT INTO test (a, b) VALUES (?, ?)")?; +/// +/// // Using `rusqlite::params!`: +/// stmt.execute(params![1i32, "blah"])?; +/// +/// // array literal — non-references +/// stmt.execute([2i32, 3i32])?; +/// +/// // array literal — references +/// stmt.execute(["foo", "bar"])?; +/// +/// // Slice literal, references: +/// stmt.execute(&[&2i32, &3i32])?; +/// +/// // Note: The types behind the references don't have to be `Sized` +/// stmt.execute(&["foo", "bar"])?; +/// +/// // However, this doesn't work (see above): +/// // stmt.execute(&[1i32, 2i32])?; +/// Ok(()) +/// } +/// ``` +/// +/// ## Named parameters +/// +/// SQLite lets you name parameters using a number of conventions (":foo", +/// "@foo", "$foo"). You can pass named parameters in to SQLite using rusqlite +/// in a few ways: +/// +/// - Using the [`rusqlite::named_params!`](crate::named_params!) macro, as in +/// `stmt.execute(named_params!{ ":name": "foo", ":age": 99 })`. Similar to +/// the `params` macro, this is most useful for heterogeneous lists of +/// parameters, or lists where the number of parameters exceeds 32. +/// +/// - As a slice of `&[(&str, &dyn ToSql)]`. This is what essentially all of +/// these boil down to in the end, conceptually at least. In theory you can +/// pass this as `stmt`. +/// +/// - As array references, similar to the positional params. This looks like +/// `thing.query(&[(":foo", &1i32), (":bar", &2i32)])` or +/// `thing.query(&[(":foo", "abc"), (":bar", "def")])`. +/// +/// Note: Unbound named parameters will be left to the value they previously +/// were bound with, falling back to `NULL` for parameters which have never been +/// bound. +/// +/// ### Example (named) +/// +/// ```rust,no_run +/// # use rusqlite::{Connection, Result, named_params}; +/// fn insert(conn: &Connection) -> Result<()> { +/// let mut stmt = conn.prepare("INSERT INTO test (key, value) VALUES (:key, :value)")?; +/// // Using `rusqlite::params!`: +/// stmt.execute(named_params! { ":key": "one", ":val": 2 })?; +/// // Alternatively: +/// stmt.execute(&[(":key", "three"), (":val", "four")])?; +/// // Or: +/// stmt.execute(&[(":key", &100), (":val", &200)])?; +/// Ok(()) +/// } +/// ``` +/// +/// ## No parameters +/// +/// You can just use an empty array literal for no params. The +/// `rusqlite::NO_PARAMS` constant which was so common in previous versions of +/// this library is no longer needed (and is now deprecated). +/// +/// ### Example (no parameters) +/// +/// ```rust,no_run +/// # use rusqlite::{Connection, Result, params}; +/// fn delete_all_users(conn: &Connection) -> Result<()> { +/// // Just use an empty array (e.g. `[]`) for no params. +/// conn.execute("DELETE FROM users", [])?; +/// Ok(()) +/// } +/// ``` +/// +/// ## Dynamic parameter list +/// +/// If you have a number of parameters which is unknown at compile time (for +/// example, building a dynamic query at runtime), you have two choices: +/// +/// - Use a `&[&dyn ToSql]`, which is nice if you have one otherwise might be +/// annoying. +/// - Use the [`ParamsFromIter`] type. This essentially lets you wrap an +/// iterator some `T: ToSql` with something that implements `Params`. +/// +/// A lot of the considerations here are similar either way, so you should see +/// the [`ParamsFromIter`] documentation for more info / examples. +pub trait Params: Sealed { + // XXX not public api, might not need to expose. + // + // Binds the parameters to the statement. It is unlikely calling this + // explicitly will do what you want. Please use `Statement::query` or + // similar directly. + // + // For now, just hide the function in the docs... + #[doc(hidden)] + fn __bind_in(self, stmt: &mut Statement<'_>) -> Result<()>; +} + +// Explicitly impl for empty array. Critically, for `conn.execute([])` to be +// unambiguous, this must be the *only* implementation for an empty array. This +// avoids `NO_PARAMS` being a necessary part of the API. +impl Sealed for [&(dyn ToSql + Send + Sync); 0] {} +impl Params for [&(dyn ToSql + Send + Sync); 0] { + #[inline] + fn __bind_in(self, stmt: &mut Statement<'_>) -> Result<()> { + // Note: Can't just return `Ok(())` — `Statement::bind_parameters` + // checks that the right number of params were passed too. + // TODO: we should have tests for `Error::InvalidParameterCount`... + stmt.bind_parameters(&[] as &[&dyn ToSql]) + } +} + +impl Sealed for &[&dyn ToSql] {} +impl Params for &[&dyn ToSql] { + #[inline] + fn __bind_in(self, stmt: &mut Statement<'_>) -> Result<()> { + stmt.bind_parameters(self) + } +} + +impl Sealed for &[(&str, &dyn ToSql)] {} +impl Params for &[(&str, &dyn ToSql)] { + #[inline] + fn __bind_in(self, stmt: &mut Statement<'_>) -> Result<()> { + stmt.bind_parameters_named(self) + } +} + +macro_rules! impl_for_array_ref { + ($($N:literal)+) => {$( + // These are already generic, and there's a shedload of them, so lets + // avoid the compile time hit from making them all inline for now. + impl<T: ToSql + ?Sized> Sealed for &[&T; $N] {} + impl<T: ToSql + ?Sized> Params for &[&T; $N] { + fn __bind_in(self, stmt: &mut Statement<'_>) -> Result<()> { + stmt.bind_parameters(self) + } + } + impl<T: ToSql + ?Sized> Sealed for &[(&str, &T); $N] {} + impl<T: ToSql + ?Sized> Params for &[(&str, &T); $N] { + fn __bind_in(self, stmt: &mut Statement<'_>) -> Result<()> { + stmt.bind_parameters_named(self) + } + } + impl<T: ToSql> Sealed for [T; $N] {} + impl<T: ToSql> Params for [T; $N] { + #[inline] + fn __bind_in(self, stmt: &mut Statement<'_>) -> Result<()> { + stmt.bind_parameters(&self) + } + } + )+}; +} + +// Following libstd/libcore's (old) lead, implement this for arrays up to `[_; +// 32]`. Note `[_; 0]` is intentionally omitted for coherence reasons, see the +// note above the impl of `[&dyn ToSql; 0]` for more information. +impl_for_array_ref!( + 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 29 30 31 32 +); + +/// Adapter type which allows any iterator over [`ToSql`] values to implement +/// [`Params`]. +/// +/// This struct is created by the [`params_from_iter`] function. +/// +/// This can be useful if you have something like an `&[String]` (of unknown +/// length), and you want to use them with an API that wants something +/// implementing `Params`. This way, you can avoid having to allocate storage +/// for something like a `&[&dyn ToSql]`. +/// +/// This essentially is only ever actually needed when dynamically generating +/// SQL — static SQL (by definition) has the number of parameters known +/// statically. As dynamically generating SQL is itself pretty advanced, this +/// API is itself for advanced use cases (See "Realistic use case" in the +/// examples). +/// +/// # Example +/// +/// ## Basic usage +/// +/// ```rust,no_run +/// use rusqlite::{params_from_iter, Connection, Result}; +/// use std::collections::BTreeSet; +/// +/// fn query(conn: &Connection, ids: &BTreeSet<String>) -> Result<()> { +/// assert_eq!(ids.len(), 3, "Unrealistic sample code"); +/// +/// let mut stmt = conn.prepare("SELECT * FROM users WHERE id IN (?, ?, ?)")?; +/// let _rows = stmt.query(params_from_iter(ids.iter()))?; +/// +/// // use _rows... +/// Ok(()) +/// } +/// ``` +/// +/// ## Realistic use case +/// +/// Here's how you'd use `ParamsFromIter` to call [`Statement::exists`] with a +/// dynamic number of parameters. +/// +/// ```rust,no_run +/// use rusqlite::{Connection, Result}; +/// +/// pub fn any_active_users(conn: &Connection, usernames: &[String]) -> Result<bool> { +/// if usernames.is_empty() { +/// return Ok(false); +/// } +/// +/// // Note: `repeat_vars` never returns anything attacker-controlled, so +/// // it's fine to use it in a dynamically-built SQL string. +/// let vars = repeat_vars(usernames.len()); +/// +/// let sql = format!( +/// // In practice this would probably be better as an `EXISTS` query. +/// "SELECT 1 FROM user WHERE is_active AND name IN ({}) LIMIT 1", +/// vars, +/// ); +/// let mut stmt = conn.prepare(&sql)?; +/// stmt.exists(rusqlite::params_from_iter(usernames)) +/// } +/// +/// // Helper function to return a comma-separated sequence of `?`. +/// // - `repeat_vars(0) => panic!(...)` +/// // - `repeat_vars(1) => "?"` +/// // - `repeat_vars(2) => "?,?"` +/// // - `repeat_vars(3) => "?,?,?"` +/// // - ... +/// fn repeat_vars(count: usize) -> String { +/// assert_ne!(count, 0); +/// let mut s = "?,".repeat(count); +/// // Remove trailing comma +/// s.pop(); +/// s +/// } +/// ``` +/// +/// That is fairly complex, and even so would need even more work to be fully +/// production-ready: +/// +/// - production code should ensure `usernames` isn't so large that it will +/// surpass [`conn.limit(Limit::SQLITE_LIMIT_VARIABLE_NUMBER)`][limits]), +/// chunking if too large. (Note that the limits api requires rusqlite to have +/// the "limits" feature). +/// +/// - `repeat_vars` can be implemented in a way that avoids needing to allocate +/// a String. +/// +/// - Etc... +/// +/// [limits]: crate::Connection::limit +/// +/// This complexity reflects the fact that `ParamsFromIter` is mainly intended +/// for advanced use cases — most of the time you should know how many +/// parameters you have statically (and if you don't, you're either doing +/// something tricky, or should take a moment to think about the design). +#[derive(Clone, Debug)] +pub struct ParamsFromIter<I>(I); + +/// Constructor function for a [`ParamsFromIter`]. See its documentation for +/// more. +#[inline] +pub fn params_from_iter<I>(iter: I) -> ParamsFromIter<I> +where + I: IntoIterator, + I::Item: ToSql, +{ + ParamsFromIter(iter) +} + +impl<I> Sealed for ParamsFromIter<I> +where + I: IntoIterator, + I::Item: ToSql, +{ +} + +impl<I> Params for ParamsFromIter<I> +where + I: IntoIterator, + I::Item: ToSql, +{ + #[inline] + fn __bind_in(self, stmt: &mut Statement<'_>) -> Result<()> { + stmt.bind_parameters(self.0) + } +} |