redis_rocksdb 0.3.9

use std::mem;
use std::mem::size_of;

use crate::datas::{BytesMeta, Metas, VecBytes};
use crate::{read_int_ptr, write_int_ptr, BytesType, LenType};

/// 数据直接使用kv存入数据库中，所以leaf节点只有key的内容
pub type LeafData = VecBytes<KeyValueMetas>;

pub struct KeyValue {}

impl KeyValue {
	pub fn to_vec(key: &[u8], value: &[u8]) -> Vec<u8> {
		let mut bytes = Vec::with_capacity(key.len() + value.len() + size_of::<BytesType>());
		unsafe {
			bytes.set_len(size_of::<BytesType>());
			write_int_ptr(bytes.as_mut_ptr(), key.len() as BytesType);
		}
		bytes.extend_from_slice(key);
		bytes.extend_from_slice(value);
		bytes
	}
	pub fn to_kv(data: &[u8]) -> (&[u8], &[u8]) {
		let l = read_int_ptr::<BytesType>(data.as_ptr());
		let key = &data[size_of::<BytesType>()..size_of::<BytesType>() + l as usize];
		let value = &data[size_of::<BytesType>() + l as usize..];
		(key, value)
	}
}

#[derive(Debug, Clone)]
pub struct KeyValueMetas {
	//这个数据是一个引用
	data: Vec<BytesMeta>,
}

impl Drop for KeyValueMetas {
	fn drop(&mut self) {
		let data = mem::replace(&mut self.data, vec![]);
		mem::forget(data);
	}
}

impl Metas for KeyValueMetas {
	fn new(data: &[u8], offset: isize, len: LenType, cap: i64) -> Self {
		unsafe { Self { data: Vec::from_raw_parts(data.as_ptr().offset(offset) as *mut _, len as usize, cap as usize) } }
	}
	fn insert(&mut self, index: usize, key_meta: BytesMeta) {
		self.data.insert(index, key_meta);
	}

	fn search(&self, data: &[u8], offset: isize, key: &[u8]) -> Result<usize, usize> {
		unsafe {
			self.data.binary_search_by(|a| {
				let mut start = offset + a.to_isize();
				let bytes_ = read_int_ptr::<BytesType>(data.as_ptr().offset(start));
				start += size_of::<BytesType>() as isize;
				let o_key = &data[start as usize..start as usize + bytes_ as usize];
				return key.cmp(o_key);
			})
		}
	}
}