Trait CursorApi

pub trait CursorApi {
    // Required methods
    fn first(&mut self) -> Option<(&[u8], Option<&[u8]>)>;
    fn last(&mut self) -> Option<(&[u8], Option<&[u8]>)>;
    fn next(&mut self) -> Option<(&[u8], Option<&[u8]>)>;
    fn prev(&mut self) -> Option<(&[u8], Option<&[u8]>)>;
    fn seek<T: AsRef<[u8]>>(
        &mut self,
        seek: T,
    ) -> Option<(&[u8], Option<&[u8]>)>;
}

Read-only Cursor API

Required Methods

fn first(&mut self) -> Option<(&[u8], Option<&[u8]>)>

Moves the cursor to the first item in the bucket and returns its key and value.

If the bucket is empty then None is returned.

use bbolt_rs::*;

fn main() -> Result<()> {
  let mut db = Bolt::open_mem()?;

  db.update(|mut tx| {
    let mut b = tx.create_bucket_if_not_exists("test")?;
    b.put("key1", "value1")?;
    b.put("key2", "value2")?;
    b.put("key3", "value3")?;
    Ok(())
  })?;

  db.view(|tx| {
    let b = tx.bucket("test").unwrap();
    let mut c = b.cursor();
    let first = c.first();
    assert_eq!(Some((b"key1".as_slice(), Some(b"value1".as_slice()))), first);
    Ok(())
  })?;

  Ok(())
}

fn last(&mut self) -> Option<(&[u8], Option<&[u8]>)>

Moves the cursor to the last item in the bucket and returns its key and value.

If the bucket is empty then None is returned.

use bbolt_rs::*;

fn main() -> Result<()> {
  let mut db = Bolt::open_mem()?;

  db.update(|mut tx| {
    let mut b = tx.create_bucket_if_not_exists("test")?;
    b.put("key1", "value1")?;
    b.put("key2", "value2")?;
    b.put("key3", "value3")?;
    Ok(())
  })?;

  db.view(|tx| {
    let b = tx.bucket("test").unwrap();
    let mut c = b.cursor();
    let last = c.last();
    assert_eq!(Some((b"key3".as_slice(), Some(b"value3".as_slice()))), last);
    Ok(())
  })?;

  Ok(())
}

fn next(&mut self) -> Option<(&[u8], Option<&[u8]>)>

Moves the cursor to the next item in the bucket and returns its key and value.

If the cursor is at the end of the bucket then None is returned.

use bbolt_rs::*;

fn main() -> Result<()> {
  let mut db = Bolt::open_mem()?;

  db.update(|mut tx| {
    let mut b = tx.create_bucket_if_not_exists("test")?;
    b.put("key1", "value1")?;
    b.put("key2", "value2")?;
    b.put("key3", "value3")?;
    Ok(())
  })?;

  db.view(|tx| {
    let b = tx.bucket("test").unwrap();
    let mut c = b.cursor();
    c.first();
    let next = c.next();
    assert_eq!(Some((b"key2".as_slice(), Some(b"value2".as_slice()))), next);
    Ok(())
  })?;

  Ok(())
}

fn prev(&mut self) -> Option<(&[u8], Option<&[u8]>)>

Moves the cursor to the previous item in the bucket and returns its key and value. If the cursor is at the beginning of the bucket then None is returned.

use bbolt_rs::*;

fn main() -> Result<()> {
  let mut db = Bolt::open_mem()?;

  db.update(|mut tx| {
    let mut b = tx.create_bucket_if_not_exists("test")?;
    b.put("key1", "value1")?;
    b.put("key2", "value2")?;
    b.put("key3", "value3")?;
    Ok(())
  })?;

  db.view(|tx| {
    let b = tx.bucket("test").unwrap();
    let mut c = b.cursor();
    c.last();
    let prev = c.prev();
    assert_eq!(Some((b"key2".as_slice(), Some(b"value2".as_slice()))), prev);
    Ok(())
  })?;

  Ok(())
}

fn seek<T: AsRef<[u8]>>(&mut self, seek: T) -> Option<(&[u8], Option<&[u8]>)>

Moves the cursor to a given key using a b-tree search and returns it.

If the key does not exist then the next key is used. If no keys follow, None is returned.

use bbolt_rs::*;

fn main() -> Result<()> {
  let mut db = Bolt::open_mem()?;

  db.update(|mut tx| {
    let mut b = tx.create_bucket_if_not_exists("test")?;
    b.put("key1", "value1")?;
    b.put("key2", "value2")?;
    b.put("key3", "value3")?;
    Ok(())
  })?;

  db.view(|tx| {
    let b = tx.bucket("test").unwrap();
    let mut c = b.cursor();
    let seek = c.seek("key2");
    assert_eq!(Some((b"key2".as_slice(), Some(b"value2".as_slice()))), seek);
    Ok(())
  })?;

  Ok(())
}

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors

impl<'tx: 'a, 'a> CursorApi for CursorImpl<'tx, 'a>

impl<'tx: 'a, 'a> CursorApi for CursorRwImpl<'tx, 'a>