use crate::DbHash;
use codec::{Decode, Encode};
use sp_blockchain;
use sp_database::{Database, Transaction};
use std::hash::Hash;
pub fn read_children<
K: Eq + Hash + Clone + Encode + Decode,
V: Eq + Hash + Clone + Encode + Decode,
>(
db: &dyn Database<DbHash>,
column: u32,
prefix: &[u8],
parent_hash: K,
) -> sp_blockchain::Result<Vec<V>> {
let mut buf = prefix.to_vec();
parent_hash.using_encoded(|s| buf.extend(s));
let raw_val_opt = db.get(column, &buf[..]);
let raw_val = match raw_val_opt {
Some(val) => val,
None => return Ok(Vec::new()),
};
let children: Vec<V> = match Decode::decode(&mut &raw_val[..]) {
Ok(children) => children,
Err(_) => return Err(sp_blockchain::Error::Backend("Error decoding children".into())),
};
Ok(children)
}
pub fn write_children<
K: Eq + Hash + Clone + Encode + Decode,
V: Eq + Hash + Clone + Encode + Decode,
>(
tx: &mut Transaction<DbHash>,
column: u32,
prefix: &[u8],
parent_hash: K,
children_hashes: V,
) {
let mut key = prefix.to_vec();
parent_hash.using_encoded(|s| key.extend(s));
tx.set_from_vec(column, &key[..], children_hashes.encode());
}
pub fn remove_children<K: Eq + Hash + Clone + Encode + Decode>(
tx: &mut Transaction<DbHash>,
column: u32,
prefix: &[u8],
parent_hash: K,
) {
let mut key = prefix.to_vec();
parent_hash.using_encoded(|s| key.extend(s));
tx.remove(column, &key);
}
#[cfg(test)]
mod tests {
use super::*;
use std::sync::Arc;
#[test]
fn children_write_read_remove() {
const PREFIX: &[u8] = b"children";
let db = Arc::new(sp_database::MemDb::default());
let mut tx = Transaction::new();
let mut children1 = Vec::new();
children1.push(1_3);
children1.push(1_5);
write_children(&mut tx, 0, PREFIX, 1_1, children1);
let mut children2 = Vec::new();
children2.push(1_4);
children2.push(1_6);
write_children(&mut tx, 0, PREFIX, 1_2, children2);
db.commit(tx.clone()).unwrap();
let r1: Vec<u32> = read_children(&*db, 0, PREFIX, 1_1).expect("(1) Getting r1 failed");
let r2: Vec<u32> = read_children(&*db, 0, PREFIX, 1_2).expect("(1) Getting r2 failed");
assert_eq!(r1, vec![1_3, 1_5]);
assert_eq!(r2, vec![1_4, 1_6]);
remove_children(&mut tx, 0, PREFIX, 1_2);
db.commit(tx).unwrap();
let r1: Vec<u32> = read_children(&*db, 0, PREFIX, 1_1).expect("(2) Getting r1 failed");
let r2: Vec<u32> = read_children(&*db, 0, PREFIX, 1_2).expect("(2) Getting r2 failed");
assert_eq!(r1, vec![1_3, 1_5]);
assert_eq!(r2.len(), 0);
}
}