如何解决结构体的保存/加载工作或失败取决于成员向量长度
我使用 serde 和 bincode 使用自定义加载/保存方法定义了以下结构:
use std::{
fs::File,io::{Read,Seek,SeekFrom,Write},};
use serde::{Deserialize,Serialize};
#[derive(Clone,Debug,Serialize,Deserialize)]
pub struct Histogram {
pub bars: Vec<f64>,}
#[derive(Clone,Deserialize)]
pub struct Histograms {
pub num_bars: usize,pub num_histograms: usize,pub vec: Vec<Histogram>,}
fn main() {
println!("Hello,world!");
}
impl Histogram {
pub fn new(num_bars: usize) -> Histogram {
Histogram {
bars: vec![0.0; num_bars],}
}
}
impl Histograms {
pub fn new(num_histograms: usize,num_bars: usize) -> Histograms {
let histograms = Histograms {
vec: vec![Histogram::new(num_bars); num_histograms],num_histograms,num_bars,};
histograms
}
pub fn save(&self,filename: &str) {
let mut file = File::create(format!("{}{}","path",filename)).unwrap();
let bin = bincode::serialize(&self).unwrap();
Write::write_all(&mut file,&bin).unwrap();
}
pub fn load(filename: &str) -> Histograms {
let mut file = File::open(format!("{}{}",filename)).unwrap();
let mut vec: Vec<u8> = vec![0; file.seek(SeekFrom::End(0)).unwrap() as usize];
file.seek(SeekFrom::Start(0)).unwrap();
file.read(&mut vec).unwrap();
let result: Histograms = bincode::deserialize(&vec).unwrap();
result
}
}
现在奇怪的是,下面的测试告诉我,如果 vec(直方图的成员)的长度很小,则保存/加载工作正常,但它失败了(我没有收到任何错误,只是结果直方图实例是错误的)具有较大的值,例如 10000000。确切地说,我从它不再正确的地方得到了 5263431 的值。
mod tests {
use core::panic;
use super::*;
#[test]
fn save_load_test() {
let histogramms = Histograms::new(10000000,50);
histogramms.save("debug_test");
let histogramms1 = Histograms::load("debug_test");
assert_eq!(histogramms.vec.len(),histogramms1.vec.len());
let mut Failed = false;
for i in 0..histogramms.vec.len() {
if histogramms.vec[i].bars.len() != histogramms1.vec[i].bars.len() {
Failed = true;
println!("first i that Failed: {}",i);
println!(
"histogramms.vec.bars.len: {} histogramms1.vec.bars.len: {}",histogramms.vec[i].bars.len(),histogramms1.vec[i].bars.len()
);
break;
}
}
if Failed {
panic!()
}
}
}
知道出了什么问题吗?
解决方法
Read::read()
函数从源中提取一些 字节,但不能保证读取所有字节。您得到的唯一保证是,如果还有剩余字节,您将获得 一些 字节(至少如果您的缓冲区的长度不为零)。
解决此问题的最简单方法是改用 std::fs::read()
函数:
pub fn load(filename: &str) -> Histograms {
let vec = std::fs::read(format!("{}{}","path",filename)).unwrap();
bincode::deserialize(&vec).unwrap()
}
更好的解决方法是直接从文件中反序列化,而不是先将整个文件读入内存:
pub fn save(&self,filename: &str) {
let mut w = BufWriter::new(File::create(format!("{}{}",filename)).unwrap());
bincode::serialize_into(&mut w,&self).unwrap();
w.flush().unwrap();
}
pub fn load(filename: &str) -> Histograms {
let file = File::open(format!("{}{}",filename)).unwrap();
bincode::deserialize_from(BufReader::new(file)).unwrap()
}
(当然,您应该为实际代码添加适当的错误处理。)
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