[英]Flatten a Map<Vec<u8>, Vec<u8>> into a Vec<u8> and then return it to a Map<Vec<u8>, Vec<u8>>
I've have data in a HashMap<Vec<u8>, Vec<u8>>
and I want to write that data to a file as a byte buffer (a single Vec<u8>
) and then read it back from the file and reconstruct the HashMap
structure.我在
HashMap<Vec<u8>, Vec<u8>>
中有数据,我想将该数据作为字节缓冲区(单个Vec<u8>
)写入文件,然后从文件中读回重构HashMap
结构。
Is there an established algorithm for flattening and recovering maps like this?有没有一种既定的算法可以像这样展平和恢复地图? I could write metadata into the file to distinguish where the data partitions etc. I can't use structured serialization because of the nature of this project — I am encrypting the data and the file.
我可以将元数据写入文件以区分数据分区的位置等。由于这个项目的性质,我不能使用结构化序列化——我正在加密数据和文件。
You may store this with the following format:您可以使用以下格式存储它:
value1_len | value1_bytes | key1_len | key1_bytes | value2_len | value2_bytes | key2_len | key2_bytes |...
what can be fairly easily done with the standard library ( playground ):使用标准库( 操场)可以很容易地完成什么:
use std::collections::HashMap;
use std::convert::TryInto;
fn serialize(map: &HashMap<Vec<u8>, Vec<u8>>) -> Vec<u8> {
map.iter().fold(Vec::new(), |mut acc, (k, v)| {
acc.extend(&k.len().to_le_bytes());
acc.extend(k.as_slice());
acc.extend(&v.len().to_le_bytes());
acc.extend(v.as_slice());
acc
})
}
fn read_vec(input: &mut &[u8]) -> Vec<u8> {
let (len, rest) = input.split_at(std::mem::size_of::<usize>());
let len = usize::from_le_bytes(len.try_into().unwrap());
let (v, rest) = rest.split_at(len);
*input = rest;
v.to_vec()
}
fn deserialize(bytes: &Vec<u8>) -> HashMap<Vec<u8>, Vec<u8>> {
let mut map = HashMap::new();
let mut left = &bytes[..];
while left.len() > 0 {
let k = read_vec(&mut left);
let v = read_vec(&mut left);
map.insert(k, v);
}
map
}
fn main() {
let mut map = HashMap::new();
map.insert(vec![1, 2, 3], vec![4, 5, 6]);
map.insert(vec![4, 5, 6], vec![1, 2, 3]);
map.insert(vec![1, 5, 3], vec![4, 2, 6]);
let array = serialize(&map);
let recovered_map = deserialize(&array);
assert_eq!(map, recovered_map);
}
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