redis_rocksdb 0.3.9

rust implement structure kv(key/value) embedded database, storage by rocksdb
Documentation 
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use std::ptr;

pub(crate) fn make_field_key(key: &[u8], field: &[u8]) -> Vec<u8> {
	let mut new_key = Vec::with_capacity(key.len() + field.len() + 3);
	unsafe {
		//这里使用性能更高的 copy_nonoverlapping
		let mut p = new_key.as_mut_ptr();
		ptr::copy_nonoverlapping(key.as_ptr(), p, key.len());
		p = p.offset(key.len() as isize);
		*p = ':' as u8;
		*(p.offset(1)) = '_' as u8;
		*(p.offset(2)) = '_' as u8;
		p = p.offset(3);
		ptr::copy_nonoverlapping(field.as_ptr(), p, field.len());
		new_key.set_len(new_key.capacity());
	}
	return new_key;
}

#[inline]
pub(crate) fn make_head_key(key: &[u8]) -> Vec<u8> {
	return make_field_key(key, &[]);
}

pub(crate) fn get_field_from_key<'a>(key: &[u8], field_key: &'a [u8]) -> &'a [u8] {
	&field_key[key.len() + 3..]
}