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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
//! A Rust wrapper for mozStorage.
//!
//! mozStorage wraps the SQLite C API with support for XPCOM data structures,
//! asynchronous statement execution, cleanup on shutdown, and connection
//! cloning that propagates attached databases, pragmas, functions, and
//! temporary entities. It also collects timing and memory usage stats for
//! telemetry, and supports detailed statement logging. Additionally, mozStorage
//! makes it possible to use the same connection handle from JS and native
//! (C++ and Rust) code.
//!
//! Most mozStorage objects, like connections, statements, result rows,
//! and variants, are thread-safe. Each connection manages a background
//! thread that can be used to execute statements asynchronously, without
//! blocking the main thread.
//!
//! This crate provides a thin wrapper to make mozStorage easier to use
//! from Rust. It only wraps the synchronous API, so you can either manage
//! the entire connection from a background thread, or use the `moz_task`
//! crate to dispatch tasks to the connection's async thread. Executing
//! synchronous statements on the main thread is not supported, and will
//! assert in debug builds.
#![allow(non_snake_case)]
use std::{borrow::Cow, convert::TryFrom, error, fmt, ops::Deref, result};
use nserror::{nsresult, NS_ERROR_NO_INTERFACE, NS_ERROR_UNEXPECTED};
use nsstring::nsCString;
use storage_variant::VariantType;
use xpcom::{
getter_addrefs,
interfaces::{
mozIStorageAsyncConnection, mozIStorageConnection, mozIStorageStatement, nsIEventTarget,
nsIThread,
},
RefPtr, XpCom,
};
const SQLITE_OK: i32 = 0;
pub type Result<T> = result::Result<T, Error>;
/// `Conn` wraps a `mozIStorageConnection`.
#[derive(Clone)]
pub struct Conn {
handle: RefPtr<mozIStorageConnection>,
}
// This is safe as long as our `mozIStorageConnection` is an instance of
// `mozilla::storage::Connection`, which is atomically reference counted.
unsafe impl Send for Conn {}
unsafe impl Sync for Conn {}
impl Conn {
/// Wraps a `mozIStorageConnection` in a `Conn`.
#[inline]
pub fn wrap(connection: RefPtr<mozIStorageConnection>) -> Conn {
Conn { handle: connection }
}
/// Returns the wrapped `mozIStorageConnection`.
#[inline]
pub fn connection(&self) -> &mozIStorageConnection {
&self.handle
}
/// Returns the maximum number of bound parameters for statements executed
/// on this connection.
pub fn variable_limit(&self) -> Result<usize> {
let mut limit = 0i32;
let rv = unsafe { self.handle.GetVariableLimit(&mut limit) };
if rv.failed() {
return Err(Error::Limit);
}
usize::try_from(limit).map_err(|_| Error::Limit)
}
/// Returns the async thread for this connection. This can be used
/// with `moz_task` to run synchronous statements on the storage
/// thread, without blocking the main thread.
pub fn thread(&self) -> Result<RefPtr<nsIThread>> {
let target = self.handle.get_interface::<nsIEventTarget>();
target
.and_then(|t| t.query_interface::<nsIThread>())
.ok_or(Error::NoThread)
}
/// Prepares a SQL statement. `query` should only contain one SQL statement.
/// If `query` contains multiple statements, only the first will be prepared,
/// and the rest will be ignored.
pub fn prepare<Q: AsRef<str>>(&self, query: Q) -> Result<Statement> {
let statement = self.call_and_wrap_error(DatabaseOp::Prepare, || {
getter_addrefs(|p| unsafe {
self.handle
.CreateStatement(&*nsCString::from(query.as_ref()), p)
})
})?;
Ok(Statement {
conn: self,
handle: statement,
})
}
/// Executes a SQL statement. `query` may contain one or more
/// semicolon-separated SQL statements.
pub fn exec<Q: AsRef<str>>(&self, query: Q) -> Result<()> {
self.call_and_wrap_error(DatabaseOp::Exec, || {
unsafe {
self.handle
.ExecuteSimpleSQL(&*nsCString::from(query.as_ref()))
}
.to_result()
})
}
/// Opens a transaction with the default transaction behavior for this
/// connection. The transaction should be committed when done. Uncommitted
/// `Transaction`s will automatically roll back when they go out of scope.
pub fn transaction(&mut self) -> Result<Transaction> {
let behavior = self.get_default_transaction_behavior();
Transaction::new(self, behavior)
}
/// Indicates if a transaction is currently open on this connection.
/// Attempting to open a new transaction when one is already in progress
/// will fail with a "cannot start a transaction within a transaction"
/// error.
///
/// Note that this is `true` even if the transaction was started by another
/// caller, like `Sqlite.jsm` or `mozStorageTransaction` from C++. See the
/// explanation above `mozIStorageConnection.transactionInProgress` for why
/// this matters.
pub fn transaction_in_progress(&self) -> Result<bool> {
let mut in_progress = false;
unsafe { self.handle.GetTransactionInProgress(&mut in_progress) }.to_result()?;
Ok(in_progress)
}
/// Opens a transaction with the requested behavior.
pub fn transaction_with_behavior(
&mut self,
behavior: TransactionBehavior,
) -> Result<Transaction> {
Transaction::new(self, behavior)
}
fn get_default_transaction_behavior(&self) -> TransactionBehavior {
let mut typ = 0i32;
let rv = unsafe { self.handle.GetDefaultTransactionType(&mut typ) };
if rv.failed() {
return TransactionBehavior::Deferred;
}
match typ {
mozIStorageAsyncConnection::TRANSACTION_IMMEDIATE => TransactionBehavior::Immediate,
mozIStorageAsyncConnection::TRANSACTION_EXCLUSIVE => TransactionBehavior::Exclusive,
_ => TransactionBehavior::Deferred,
}
}
/// Invokes a storage operation and returns the last SQLite error if the
/// operation fails. This lets `Conn::{prepare, exec}` and
/// `Statement::{step, execute}` return more detailed errors, as the
/// `nsresult` codes that mozStorage uses are often too generic. For
/// example, `NS_ERROR_FAILURE` might be anything from a SQL syntax error
/// to an invalid column name in a trigger.
///
/// Note that the last error may not be accurate if the underlying
/// `mozIStorageConnection` is used concurrently from multiple threads.
/// Multithreaded callers that share a connection should serialize their
/// uses.
fn call_and_wrap_error<T>(
&self,
op: DatabaseOp,
func: impl FnOnce() -> result::Result<T, nsresult>,
) -> Result<T> {
func().or_else(|rv| -> Result<T> {
let mut code = 0i32;
unsafe { self.handle.GetLastError(&mut code) }.to_result()?;
Err(if code != SQLITE_OK {
let mut message = nsCString::new();
unsafe { self.handle.GetLastErrorString(&mut *message) }.to_result()?;
Error::Database {
rv,
op,
code,
message,
}
} else {
rv.into()
})
})
}
}
pub enum TransactionBehavior {
Deferred,
Immediate,
Exclusive,
}
pub struct Transaction<'c> {
conn: &'c mut Conn,
active: bool,
}
impl<'c> Transaction<'c> {
/// Opens a transaction on `conn` with the given `behavior`.
fn new(conn: &'c mut Conn, behavior: TransactionBehavior) -> Result<Transaction<'c>> {
conn.exec(match behavior {
TransactionBehavior::Deferred => "BEGIN DEFERRED",
TransactionBehavior::Immediate => "BEGIN IMMEDIATE",
TransactionBehavior::Exclusive => "BEGIN EXCLUSIVE",
})?;
Ok(Transaction { conn, active: true })
}
/// Commits the transaction.
pub fn commit(mut self) -> Result<()> {
if self.active {
self.conn.exec("COMMIT")?;
self.active = false;
}
Ok(())
}
/// Rolls the transaction back.
pub fn rollback(mut self) -> Result<()> {
self.abort()
}
fn abort(&mut self) -> Result<()> {
if self.active {
self.conn.exec("ROLLBACK")?;
self.active = false;
}
Ok(())
}
}
impl<'c> Deref for Transaction<'c> {
type Target = Conn;
fn deref(&self) -> &Conn {
self.conn
}
}
impl<'c> Drop for Transaction<'c> {
fn drop(&mut self) {
let _ = self.abort();
}
}
pub struct Statement<'c> {
conn: &'c Conn,
handle: RefPtr<mozIStorageStatement>,
}
impl<'c> Statement<'c> {
/// Binds a parameter at the given `index` to the prepared statement.
/// `value` is any type that can be converted into a `Variant`.
pub fn bind_by_index<V: VariantType>(&mut self, index: u32, value: V) -> Result<()> {
let variant = value.into_variant();
unsafe { self.handle.BindByIndex(index as u32, variant.coerce()) }
.to_result()
.map_err(|rv| Error::BindByIndex {
rv,
data_type: V::type_name(),
index,
})
}
/// Binds a parameter with the given `name` to the prepared statement.
pub fn bind_by_name<N: AsRef<str>, V: VariantType>(&mut self, name: N, value: V) -> Result<()> {
let name = name.as_ref();
let variant = value.into_variant();
unsafe {
self.handle
.BindByName(&*nsCString::from(name), variant.coerce())
}
.to_result()
.map_err(|rv| Error::BindByName {
rv,
data_type: V::type_name(),
name: name.into(),
})
}
/// Executes the statement and returns the next row of data.
pub fn step<'s>(&'s mut self) -> Result<Option<Step<'c, 's>>> {
let has_more = self.conn.call_and_wrap_error(DatabaseOp::Step, || {
let mut has_more = false;
unsafe { self.handle.ExecuteStep(&mut has_more) }.to_result()?;
Ok(has_more)
})?;
Ok(if has_more { Some(Step(self)) } else { None })
}
/// Executes the statement once, discards any data, and resets the
/// statement.
pub fn execute(&mut self) -> Result<()> {
self.conn.call_and_wrap_error(DatabaseOp::Execute, || {
unsafe { self.handle.Execute() }.to_result()
})
}
/// Resets the prepared statement so that it's ready to be executed
/// again, and clears any bound parameters.
pub fn reset(&mut self) -> Result<()> {
unsafe { self.handle.Reset() }.to_result()?;
Ok(())
}
fn get_column_index(&self, name: &str) -> Result<u32> {
let mut index = 0u32;
let rv = unsafe {
self.handle
.GetColumnIndex(&*nsCString::from(name), &mut index)
};
if rv.succeeded() {
Ok(index)
} else {
Err(Error::InvalidColumn {
rv,
name: name.into(),
})
}
}
fn get_column_value<T: VariantType>(&self, index: u32) -> result::Result<T, nsresult> {
let variant = getter_addrefs(|p| unsafe { self.handle.GetVariant(index, p) })?;
let value = T::from_variant(variant.coerce())?;
Ok(value)
}
}
impl<'c> Drop for Statement<'c> {
fn drop(&mut self) {
unsafe { self.handle.Finalize() };
}
}
/// A step is the next row in the result set for a statement.
pub struct Step<'c, 's>(&'s mut Statement<'c>);
impl<'c, 's> Step<'c, 's> {
/// Returns the value of the column at `index` for the current row.
pub fn get_by_index<T: VariantType>(&self, index: u32) -> Result<T> {
self.0
.get_column_value(index)
.map_err(|rv| Error::GetByIndex {
rv,
data_type: T::type_name(),
index,
})
}
/// A convenience wrapper that returns the default value for the column
/// at `index` if `NULL`.
pub fn get_by_index_or_default<T: VariantType + Default>(&self, index: u32) -> T {
self.get_by_index(index).unwrap_or_default()
}
/// Returns the value of the column specified by `name` for the current row.
pub fn get_by_name<N: AsRef<str>, T: VariantType>(&self, name: N) -> Result<T> {
let name = name.as_ref();
let index = self.0.get_column_index(name)?;
self.0
.get_column_value(index)
.map_err(|rv| Error::GetByName {
rv,
data_type: T::type_name(),
name: name.into(),
})
}
/// Returns the default value for the column with the given `name`, or the
/// default if the column is `NULL`.
pub fn get_by_name_or_default<N: AsRef<str>, T: VariantType + Default>(&self, name: N) -> T {
self.get_by_name(name).unwrap_or_default()
}
}
/// A database operation, included for better context in error messages.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum DatabaseOp {
Exec,
Prepare,
Step,
Execute,
}
impl DatabaseOp {
/// Returns a description of the operation to include in an error message.
pub fn what(&self) -> &'static str {
match self {
DatabaseOp::Exec => "execute SQL string",
DatabaseOp::Prepare => "prepare statement",
DatabaseOp::Step => "step statement",
DatabaseOp::Execute => "execute statement",
}
}
}
/// Storage errors.
#[derive(Debug)]
pub enum Error {
/// A connection doesn't have a usable async thread. The connection might be
/// closed, or the thread manager may have shut down.
NoThread,
/// Failed to get a limit for a database connection.
Limit,
/// A database operation failed. The error includes a SQLite result code,
/// and an explanation string.
Database {
rv: nsresult,
op: DatabaseOp,
code: i32,
message: nsCString,
},
/// A parameter with the given data type couldn't be bound at this index,
/// likely because the index is out of range.
BindByIndex {
rv: nsresult,
data_type: Cow<'static, str>,
index: u32,
},
/// A parameter with the given type couldn't be bound to this name, likely
/// because the statement doesn't have a matching `:`-prefixed parameter
/// with the name.
BindByName {
rv: nsresult,
data_type: Cow<'static, str>,
name: String,
},
/// A column with this name doesn't exist.
InvalidColumn { rv: nsresult, name: String },
/// A value of the given type couldn't be accessed at this index. This is
/// the error returned when a type conversion fails; for example, requesting
/// an `nsString` instead of an `Option<nsString>` when the column is `NULL`.
GetByIndex {
rv: nsresult,
data_type: Cow<'static, str>,
index: u32,
},
/// A value of the given type couldn't be accessed for the column with
/// this name.
GetByName {
rv: nsresult,
data_type: Cow<'static, str>,
name: String,
},
/// A storage operation failed for other reasons.
Other(nsresult),
}
impl error::Error for Error {
fn source(&self) -> Option<&(dyn error::Error + 'static)> {
None
}
}
impl From<nsresult> for Error {
fn from(rv: nsresult) -> Error {
Error::Other(rv)
}
}
impl From<Error> for nsresult {
fn from(err: Error) -> nsresult {
match err {
Error::NoThread => NS_ERROR_NO_INTERFACE,
Error::Limit => NS_ERROR_UNEXPECTED,
Error::Database { rv, .. }
| Error::BindByIndex { rv, .. }
| Error::BindByName { rv, .. }
| Error::InvalidColumn { rv, .. }
| Error::GetByIndex { rv, .. }
| Error::GetByName { rv, .. }
| Error::Other(rv) => rv,
}
}
}
impl fmt::Display for Error {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self {
Error::NoThread => f.write_str("Async thread unavailable for storage connection"),
Error::Limit => f.write_str("Failed to get limit for storage connection"),
Error::Database {
op, code, message, ..
} => {
if message.is_empty() {
write!(f, "Failed to {} with code {}", op.what(), code)
} else {
write!(
f,
"Failed to {} with code {} ({})",
op.what(),
code,
message
)
}
}
Error::BindByIndex {
data_type, index, ..
} => write!(f, "Can't bind {} at {}", data_type, index),
Error::BindByName {
data_type, name, ..
} => write!(f, "Can't bind {} to named parameter {}", data_type, name),
Error::InvalidColumn { name, .. } => write!(f, "Column {} doesn't exist", name),
Error::GetByIndex {
data_type, index, ..
} => write!(f, "Can't get {} at {}", data_type, index),
Error::GetByName {
data_type, name, ..
} => write!(f, "Can't get {} for column {}", data_type, name),
Error::Other(rv) => write!(f, "Storage operation failed with {}", rv.error_name()),
}
}
}