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Read-only and read-write Database and Transaction #49

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Read-only and read-write Database and Transaction #49

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128 changes: 72 additions & 56 deletions src/core.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -385,19 +385,43 @@ bitflags! {
}
}

/// `Access` designates a type as specifying access (e.g., read-only vs
/// read-write).
///
/// The purpose of the `Access` trait is to allow the `Transaction` and
/// `Database` types to be generic with regard to read-only vs read-write
/// access.
///
pub trait Access {}

/// `ReadOnly` is a marker type for specifying read-only access to something.
#[derive(Debug)]
pub struct ReadOnly;

impl Access for ReadOnly {}

/// `ReadWrite` is a marker type for specifying read-write access to something.
#[derive(Debug)]
pub struct ReadWrite;

impl Access for ReadWrite {}

/// Database
#[derive(Debug)]
pub struct Database<'a> {
pub struct Database<'a, A: Access> {
handle: ffi::MDB_dbi,
txn: &'a NativeTransaction<'a>,
_access: std::marker::PhantomData<A>,
}

// FIXME: provide different interfaces for read-only/read-write databases
pub type ReadOnlyDatabase<'a> = Database<'a, ReadOnly>;
pub type ReadWriteDatabase<'a> = Database<'a, ReadWrite>;

// FIXME: provide different interfaces for simple KV and storage with duplicates

impl<'a> Database<'a> {
fn new_with_handle(handle: ffi::MDB_dbi, txn: &'a NativeTransaction<'a>) -> Database<'a> {
Database { handle: handle, txn: txn }
impl<'a, A: Access> Database<'a, A> {
fn new_with_handle(handle: ffi::MDB_dbi, txn: &'a NativeTransaction<'a>) -> Database<'a, A> {
Database { handle: handle, txn: txn, _access: std::marker::PhantomData, }
}

/// Retrieves current db's statistics.
Expand All @@ -409,7 +433,9 @@ impl<'a> Database<'a> {
pub fn get<V: FromMdbValue + 'a>(&'a self, key: &ToMdbValue) -> MdbResult<V> {
self.txn.get(self.handle, key)
}
}

impl<'a> Database<'a, ReadWrite> {
/// Sets value for key. In case of DbAllowDups it will add a new item
pub fn set(&self, key: &ToMdbValue, value: &ToMdbValue) -> MdbResult<()> {
self.txn.set(self.handle, key, value)
Expand Down Expand Up @@ -443,12 +469,16 @@ impl<'a> Database<'a> {
pub fn del_item(&self, key: &ToMdbValue, data: &ToMdbValue) -> MdbResult<()> {
self.txn.del_item(self.handle, key, data)
}
}

impl<'a, A: Access> Database<'a, A> {
/// Returns a new cursor
pub fn new_cursor(&'a self) -> MdbResult<Cursor<'a>> {
self.txn.new_cursor(self.handle)
}
}

impl<'a> Database<'a, ReadWrite> {
/// Deletes current db, also moves it out
pub fn del_db(self) -> MdbResult<()> {
self.txn.del_db(self)
Expand All @@ -458,7 +488,9 @@ impl<'a> Database<'a> {
pub fn clear(&self) -> MdbResult<()> {
self.txn.clear_db(self.handle)
}
}

impl<'a, A: Access> Database<'a, A> {
/// Returns an iterator for all values in database
pub fn iter(&'a self) -> MdbResult<CursorIterator<'a, CursorIter>> {
self.txn.new_cursor(self.handle)
Expand Down Expand Up @@ -826,7 +858,7 @@ impl Environment {
/// Creates a new read-write transaction
///
/// Use `get_reader` to get much faster lock-free alternative
pub fn new_transaction(&self) -> MdbResult<Transaction> {
pub fn new_transaction(&self) -> MdbResult<ReadWriteTransaction> {
if self.is_readonly {
return Err(MdbError::StateError("Error: creating read-write transaction in read-only environment".to_owned()))
}
Expand All @@ -835,9 +867,9 @@ impl Environment {
}

/// Creates a readonly transaction
pub fn get_reader(&self) -> MdbResult<ReadonlyTransaction> {
pub fn get_reader(&self) -> MdbResult<ReadOnlyTransaction> {
self.create_transaction(None, ffi::MDB_RDONLY)
.and_then(|txn| Ok(ReadonlyTransaction::new_with_native(txn)))
.and_then(|txn| Ok(ReadOnlyTransaction::new_with_native(txn)))
}

fn _open_db(&self, db_name: & str, flags: DbFlags, force_creation: bool) -> MdbResult<ffi::MDB_dbi> {
Expand Down Expand Up @@ -1137,7 +1169,7 @@ impl<'a> NativeTransaction<'a> {
}

/// Deletes provided database completely
fn del_db(&self, db: Database) -> MdbResult<()> {
fn del_db(&self, db: Database<ReadWrite>) -> MdbResult<()> {
assert_state_eq!(txn, self.state, TransactionState::Normal);
unsafe {
self.env.drop_db_from_cache(db.handle);
Expand Down Expand Up @@ -1181,65 +1213,33 @@ impl<'a> Drop for NativeTransaction<'a> {
}

#[derive(Debug)]
pub struct Transaction<'a> {
pub struct Transaction<'a, A: Access> {
inner: NativeTransaction<'a>,
_access: std::marker::PhantomData<A>,
}

impl<'a> Transaction<'a> {
fn new_with_native(txn: NativeTransaction<'a>) -> Transaction<'a> {
pub type ReadOnlyTransaction<'a> = Transaction<'a, ReadOnly>;
pub type ReadWriteTransaction<'a> = Transaction<'a, ReadWrite>;

impl<'a, A: Access> Transaction<'a, A> {
fn new_with_native(txn: NativeTransaction<'a>) -> Self {
Transaction {
inner: txn
inner: txn,
_access: std::marker::PhantomData,
}
}

pub fn new_child(&self) -> MdbResult<Transaction> {
self.inner.new_child(0)
.and_then(|txn| Ok(Transaction::new_with_native(txn)))
}

pub fn new_ro_child(&self) -> MdbResult<ReadonlyTransaction> {
pub fn new_ro_child(&self) -> MdbResult<ReadOnlyTransaction> {
self.inner.new_child(ffi::MDB_RDONLY)
.and_then(|txn| Ok(ReadonlyTransaction::new_with_native(txn)))
}

/// Commits transaction, moves it out
pub fn commit(self) -> MdbResult<()> {
//self.inner.commit()
let mut t = self;
t.inner.commit()
}

/// Aborts transaction, moves it out
pub fn abort(self) {
let mut t = self;
t.inner.abort();
.and_then(|txn| Ok(ReadOnlyTransaction::new_with_native(txn)))
}

pub fn bind(&self, db_handle: &DbHandle) -> Database {
pub fn bind(&self, db_handle: &DbHandle) -> Database<A> {
Database::new_with_handle(db_handle.handle, &self.inner)
}
}


#[derive(Debug)]
pub struct ReadonlyTransaction<'a> {
inner: NativeTransaction<'a>,
}


impl<'a> ReadonlyTransaction<'a> {
fn new_with_native(txn: NativeTransaction<'a>) -> ReadonlyTransaction<'a> {
ReadonlyTransaction {
inner: txn,
}
}

pub fn new_ro_child(&self) -> MdbResult<ReadonlyTransaction> {
self.inner.new_child(ffi::MDB_RDONLY)
.and_then(|txn| Ok(ReadonlyTransaction::new_with_native(txn)))

}

impl<'a> Transaction<'a, ReadOnly> {
/// Aborts transaction. But readonly transaction could be
/// reused later by calling `renew`
pub fn abort(&mut self) {
Expand All @@ -1257,9 +1257,25 @@ impl<'a> ReadonlyTransaction<'a> {
pub fn renew(&mut self) -> MdbResult<()> {
self.inner.renew()
}
}

impl<'a> Transaction<'a, ReadWrite> {
pub fn new_child(&self) -> MdbResult<Transaction<ReadWrite>> {
self.inner.new_child(0)
.and_then(|txn| Ok(Transaction::new_with_native(txn)))
}

pub fn bind(&self, db_handle: &DbHandle) -> Database {
Database::new_with_handle(db_handle.handle, &self.inner)
/// Commits transaction, moves it out
pub fn commit(self) -> MdbResult<()> {
//self.inner.commit()
let mut t = self;
t.inner.commit()
}

/// Aborts transaction, moves it out
pub fn abort(self) {
let mut t = self;
t.inner.abort();
}
}

Expand Down
4 changes: 2 additions & 2 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,8 +11,8 @@ extern crate liblmdb_sys as ffi;
pub use libc::c_int;
pub use ffi::{mdb_filehandle_t, MDB_stat, MDB_envinfo, MDB_val};
pub use core::{EnvBuilder, Environment, EnvFlags, EnvCreateFlags};
pub use core::{Database, DbFlags, DbHandle};
pub use core::{Transaction, ReadonlyTransaction, MdbError, MdbValue};
pub use core::{Database, ReadOnlyDatabase, ReadWriteDatabase, DbFlags, DbHandle};
pub use core::{Transaction, ReadOnlyTransaction, ReadWriteTransaction, MdbError, MdbValue};
pub use core::{Cursor, CursorValue, CursorIter, CursorKeyRangeIter};
pub use traits::{FromMdbValue, ToMdbValue};

Expand Down