解码存储在数据库中的数据

Question

我正在尝试对数据进行编码，然后将其存储在leveldb中，然后对其进行读取和解码，但是当我尝试进行解码并且确实不知道如何解决此错误时出现错误InvalidTagEncoding（usize）] >：如果反序列化器尝试反序列化不在预期范围内的枚举的标签，则返回此参数]

[dependencies]
serde = { version = "1.0.101", features = ["derive"] }
bincode = "1.2.0"
leveldb = "0.8.4"

main.rs

extern crate bincode;

use leveldb::database::Database;
use leveldb::kv::KV;
use leveldb::options::{Options, ReadOptions, WriteOptions};
use std::path::Path;

fn main() {
    // Encode data
    let encoded: Vec<u8> = bincode::serialize(&String::from("This is some data")).unwrap();

    // Open database
    let mut options = Options::new();
    options.create_if_missing = true;
    let path = Path::new("./db");
    let database = match Database::open(&path, options) {
        Ok(db) => db,
        Err(e) => panic!("failed to open database: {:?}", e),
    };

    // Write encoded data into database
    let write_opts = WriteOptions::new();
    match database.put(write_opts, 1, &encoded) {
        Ok(_) => (),
        Err(e) => panic!("failed to write to database: {:?}", e),
    };

    // Read encoded data from the database
    let read_opts = ReadOptions::new();
    let res = database.get(read_opts, 1);
    match res {
        Ok(data) => {
            println!("the bytecode is {:?}", data);
            match data {
                Some(inner) => {
                    let decoded: Option<String> = bincode::deserialize(&inner[..]).unwrap(); // ERROR
                    println!("{:?}", decoded);
                },
                None => println!("None 2"),
            }
        }
        Err(e) => panic!("failed reading data: {:?}", e),
    }
}
输出

the bytecode is Some([17, 0, 0, 0, 0, 0, 0, 0, 84, 104, 105, 115, 32, 105, 115, 32, 115, 111, 109, 101, 32, 100, 97, 116, 97])
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: InvalidTagEncoding(17)', src/libcore/result.rs:999:5
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace.
我正在尝试对数据进行编码，然后将其存储在leveldb中，然后读取它并对其进行解码，但是当我尝试进行解码并且确实不知道如何解决此错误时，我得到了一个错误InvalidTagEncoding（...

Answer 1

如注释中的trentcl所指出，您正在编码String，但尝试将其解码为Option<String>。更改：

let decoded: Option<String> = bincode::deserialize(&inner[..]).unwrap(); // ERROR