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use std::ops::{Deref, DerefMut};
use std::{marker, mem, ptr};
use crate::mdb::error::mdb_result;
use crate::mdb::ffi;
use crate::*;
pub struct RoCursor<'txn> {
cursor: *mut ffi::MDB_cursor,
_marker: marker::PhantomData<&'txn ()>,
}
impl<'txn> RoCursor<'txn> {
pub(crate) fn new(txn: &'txn RoTxn, dbi: ffi::MDB_dbi) -> Result<RoCursor<'txn>> {
let mut cursor: *mut ffi::MDB_cursor = ptr::null_mut();
unsafe { mdb_result(ffi::mdb_cursor_open(txn.txn, dbi, &mut cursor))? }
Ok(RoCursor {
cursor,
_marker: marker::PhantomData,
})
}
pub fn current(&mut self) -> Result<Option<(&'txn [u8], &'txn [u8])>> {
let mut key_val = mem::MaybeUninit::uninit();
let mut data_val = mem::MaybeUninit::uninit();
// Move the cursor on the first database key
let result = unsafe {
mdb_result(ffi::mdb_cursor_get(
self.cursor,
key_val.as_mut_ptr(),
data_val.as_mut_ptr(),
ffi::cursor_op::MDB_GET_CURRENT,
))
};
match result {
Ok(()) => {
let key = unsafe { crate::from_val(key_val.assume_init()) };
let data = unsafe { crate::from_val(data_val.assume_init()) };
Ok(Some((key, data)))
}
Err(e) if e.not_found() => Ok(None),
Err(e) => Err(e.into()),
}
}
pub fn move_on_first(&mut self) -> Result<Option<(&'txn [u8], &'txn [u8])>> {
let mut key_val = mem::MaybeUninit::uninit();
let mut data_val = mem::MaybeUninit::uninit();
// Move the cursor on the first database key
let result = unsafe {
mdb_result(ffi::mdb_cursor_get(
self.cursor,
key_val.as_mut_ptr(),
data_val.as_mut_ptr(),
ffi::cursor_op::MDB_FIRST,
))
};
match result {
Ok(()) => {
let key = unsafe { crate::from_val(key_val.assume_init()) };
let data = unsafe { crate::from_val(data_val.assume_init()) };
Ok(Some((key, data)))
}
Err(e) if e.not_found() => Ok(None),
Err(e) => Err(e.into()),
}
}
pub fn move_on_last(&mut self) -> Result<Option<(&'txn [u8], &'txn [u8])>> {
let mut key_val = mem::MaybeUninit::uninit();
let mut data_val = mem::MaybeUninit::uninit();
// Move the cursor on the first database key
let result = unsafe {
mdb_result(ffi::mdb_cursor_get(
self.cursor,
key_val.as_mut_ptr(),
data_val.as_mut_ptr(),
ffi::cursor_op::MDB_LAST,
))
};
match result {
Ok(()) => {
let key = unsafe { crate::from_val(key_val.assume_init()) };
let data = unsafe { crate::from_val(data_val.assume_init()) };
Ok(Some((key, data)))
}
Err(e) if e.not_found() => Ok(None),
Err(e) => Err(e.into()),
}
}
pub fn move_on_key_greater_than_or_equal_to(
&mut self,
key: &[u8],
) -> Result<Option<(&'txn [u8], &'txn [u8])>> {
let mut key_val = unsafe { crate::into_val(&key) };
let mut data_val = mem::MaybeUninit::uninit();
// Move the cursor to the specified key
let result = unsafe {
mdb_result(ffi::mdb_cursor_get(
self.cursor,
&mut key_val,
data_val.as_mut_ptr(),
ffi::cursor_op::MDB_SET_RANGE,
))
};
match result {
Ok(()) => {
let key = unsafe { crate::from_val(key_val) };
let data = unsafe { crate::from_val(data_val.assume_init()) };
Ok(Some((key, data)))
}
Err(e) if e.not_found() => Ok(None),
Err(e) => Err(e.into()),
}
}
pub fn move_on_prev(&mut self) -> Result<Option<(&'txn [u8], &'txn [u8])>> {
let mut key_val = mem::MaybeUninit::uninit();
let mut data_val = mem::MaybeUninit::uninit();
// Move the cursor to the previous non-dup key
let result = unsafe {
mdb_result(ffi::mdb_cursor_get(
self.cursor,
key_val.as_mut_ptr(),
data_val.as_mut_ptr(),
ffi::cursor_op::MDB_PREV,
))
};
match result {
Ok(()) => {
let key = unsafe { crate::from_val(key_val.assume_init()) };
let data = unsafe { crate::from_val(data_val.assume_init()) };
Ok(Some((key, data)))
}
Err(e) if e.not_found() => Ok(None),
Err(e) => Err(e.into()),
}
}
pub fn move_on_next(&mut self) -> Result<Option<(&'txn [u8], &'txn [u8])>> {
let mut key_val = mem::MaybeUninit::uninit();
let mut data_val = mem::MaybeUninit::uninit();
// Move the cursor to the next non-dup key
let result = unsafe {
mdb_result(ffi::mdb_cursor_get(
self.cursor,
key_val.as_mut_ptr(),
data_val.as_mut_ptr(),
ffi::cursor_op::MDB_NEXT,
))
};
match result {
Ok(()) => {
let key = unsafe { crate::from_val(key_val.assume_init()) };
let data = unsafe { crate::from_val(data_val.assume_init()) };
Ok(Some((key, data)))
}
Err(e) if e.not_found() => Ok(None),
Err(e) => Err(e.into()),
}
}
}
impl Drop for RoCursor<'_> {
fn drop(&mut self) {
unsafe { ffi::mdb_cursor_close(self.cursor) }
}
}
pub struct RwCursor<'txn> {
cursor: RoCursor<'txn>,
}
impl<'txn> RwCursor<'txn> {
pub(crate) fn new(txn: &'txn RwTxn, dbi: ffi::MDB_dbi) -> Result<RwCursor<'txn>> {
Ok(RwCursor {
cursor: RoCursor::new(txn, dbi)?,
})
}
/// Delete the entry the cursor is currently pointing to.
///
/// Returns `true` if the entry was successfully deleted.
///
/// # Safety
///
/// It is _[undefined behavior]_ to keep a reference of a value from this database
/// while modifying it.
///
/// > [Values returned from the database are valid only until a subsequent update operation,
/// or the end of the transaction.](http://www.lmdb.tech/doc/group__mdb.html#structMDB__val).
///
/// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
pub unsafe fn del_current(&mut self) -> Result<bool> {
// Delete the current entry
let result = mdb_result(ffi::mdb_cursor_del(self.cursor.cursor, 0));
match result {
Ok(()) => Ok(true),
Err(e) if e.not_found() => Ok(false),
Err(e) => Err(e.into()),
}
}
/// Write a new value to the current entry.
///
/// The given key **must** be equal to the one this cursor is pointing otherwise the database
/// can be put into an inconsistent state.
///
/// Returns `true` if the entry was successfully written.
///
/// > This is intended to be used when the new data is the same size as the old.
/// > Otherwise it will simply perform a delete of the old record followed by an insert.
///
/// # Safety
///
/// It is _[undefined behavior]_ to keep a reference of a value from this database while
/// modifying it, so you can't use the key/value that comes from the cursor to feed
/// this function.
///
/// In other words: Tranform the key and value that you borrow from this database into an owned
/// version of them i.e. `&str` into `String`.
///
/// > [Values returned from the database are valid only until a subsequent update operation,
/// or the end of the transaction.](http://www.lmdb.tech/doc/group__mdb.html#structMDB__val).
///
/// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
pub unsafe fn put_current(&mut self, key: &[u8], data: &[u8]) -> Result<bool> {
let mut key_val = crate::into_val(&key);
let mut data_val = crate::into_val(&data);
// Modify the pointed data
let result = mdb_result(ffi::mdb_cursor_put(
self.cursor.cursor,
&mut key_val,
&mut data_val,
ffi::MDB_CURRENT,
));
match result {
Ok(()) => Ok(true),
Err(e) if e.not_found() => Ok(false),
Err(e) => Err(e.into()),
}
}
/// Append the given key/value pair to the end of the database.
///
/// If a key is inserted that is less than any previous key a `KeyExist` error
/// is returned and the key is not inserted into the database.
///
/// # Safety
///
/// It is _[undefined behavior]_ to keep a reference of a value from this database while
/// modifying it, so you can't use the key/value that comes from the cursor to feed
/// this function.
///
/// In other words: Tranform the key and value that you borrow from this database into an owned
/// version of them i.e. `&str` into `String`.
///
/// > [Values returned from the database are valid only until a subsequent update operation,
/// or the end of the transaction.](http://www.lmdb.tech/doc/group__mdb.html#structMDB__val).
///
/// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
pub unsafe fn append(&mut self, key: &[u8], data: &[u8]) -> Result<()> {
let mut key_val = crate::into_val(&key);
let mut data_val = crate::into_val(&data);
// Modify the pointed data
let result = mdb_result(ffi::mdb_cursor_put(
self.cursor.cursor,
&mut key_val,
&mut data_val,
ffi::MDB_APPEND,
));
result.map_err(Into::into)
}
}
impl<'txn> Deref for RwCursor<'txn> {
type Target = RoCursor<'txn>;
fn deref(&self) -> &Self::Target {
&self.cursor
}
}
impl DerefMut for RwCursor<'_> {
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.cursor
}
}