环境
- Time 2022-12-16
- WSL-Ubuntu 22.04
- Rust 1.65.0
前言
说明
参考：https://github.com/pingcap/talent-plan
目标
在上一节的基础上，根据提供的目录，到目录中进行文件的读取。
Cargo.toml
[package]
edition = "2021"
name = "kvs"
version = "1.0.0"[dependencies]
clap = {version = "4", features = ["derive"]}
serde = {version = "1", features = ["derive"]}
serde_json = "1"
log.rs
use std::collections::BTreeMap;
use std::path::Path;use crate::cmd::{Command, Index};use self::{reader::PosBufReader, writer::PosBufWriter};mod reader;
mod writer;pub struct CommandLog {reader: PosBufReader,writer: PosBufWriter,index: Index,
}pub type KvResult = anyhow::Result<Option<String>>;impl CommandLog {pub fn new() -> anyhow::Result<Self> {let path = Path::new("/root/log");let writer = PosBufWriter::new(path)?;let mut index = BTreeMap::default();let mut reader = PosBufReader::new(path)?;reader.load(&mut index)?;Ok(Self {reader,writer,index,})}pub fn get(&mut self, key: &str) -> KvResult {self.reader.read(self.index.get(key))}pub fn set(&mut self, key: String, value: String) -> KvResult {let result = self.reader.read(self.index.get(&key));let command = Command::Set {key: key.to_string(),value,};let json = serde_json::to_string(&command)?;let position = self.writer.write(json.as_bytes())?;self.index.insert(key, position);result}pub fn remove(&mut self, key: String) -> KvResult {let result = self.reader.read(self.index.get(&key));let command = Command::Remove {key: key.to_string(),};let json = serde_json::to_string(&command)?;self.writer.write(json.as_bytes())?;self.index.remove(&key);result}
}
reader.rs
use std::ffi::OsStr;
use std::fs::{File, OpenOptions};
use std::io::{BufReader, Read, Seek, SeekFrom};
use std::path::{Path, PathBuf};use serde_json::Deserializer;use crate::cmd::{Command, CommandPosition, Index};use super::KvResult;pub struct PosBufReader {reader: BufReader<File>,
}impl PosBufReader {pub fn new(path: &Path) -> anyhow::Result<PosBufReader> {let number = *sorted_gen_list(path)?.first().unwrap();let path = path.join(format!("{}.log", number));let file = OpenOptions::new().read(true).open(&path)?;let reader = BufReader::new(file);Ok(Self { reader })}pub fn load(&mut self, map: &mut Index) -> anyhow::Result<()> {let reader = &mut self.reader;let mut old = reader.seek(SeekFrom::Start(0))? as usize;let mut stream = Deserializer::from_reader(reader).into_iter();while let Some(cmd) = stream.next() {let new = stream.byte_offset();match cmd? {Command::Set { key, .. } => {map.insert(key, CommandPosition::new(old, new - old));}Command::Remove { .. } => (),};old = new;}Ok(())}pub fn read(&mut self, position: Option<&CommandPosition>) -> KvResult {let position = match position {Some(position) => position,None => return Ok(None),};self.reader.seek(SeekFrom::Start(position.pos as u64))?;let command = (&mut self.reader).take(position.len as u64);match serde_json::from_reader(command)? {Command::Set { value, .. } => Ok(Some(value)),_ => unreachable!(),}}
}fn sorted_gen_list(path: &Path) -> anyhow::Result<Vec<u64>> {let mut list: Vec<u64> = path.read_dir()?.flat_map(|res| res.map(|entry| entry.path())).filter(|path| path.is_file()).flat_map(file_name_to_number).collect();list.sort_unstable();Ok(list)
}fn file_name_to_number(path: PathBuf) -> Option<u64> {let name = path.file_name().and_then(OsStr::to_str)?;match name.ends_with(".log") {false => None,true => name.trim_end_matches(".log").parse().ok(),}
}
writer.rs
use std::fs::{File, OpenOptions};
use std::io::{BufWriter, Seek, SeekFrom, Write};
use std::path::Path;use crate::cmd::CommandPosition;pub struct PosBufWriter {writer: BufWriter<File>,pos: usize,
}impl PosBufWriter {pub fn new(path: &Path) -> anyhow::Result<Self> {let path = path.join("1.log");let file = OpenOptions::new().append(true).create(true).open(path)?;let mut writer = BufWriter::new(file);let pos = writer.seek(SeekFrom::End(0))? as usize;Ok(Self { writer, pos })}pub fn write(&mut self, buf: &[u8]) -> anyhow::Result<CommandPosition> {let result = CommandPosition::new(self.pos, buf.len());self.writer.write_all(buf)?;self.writer.flush()?;self.pos += result.len;Ok(result)}
}
总结
根据提供的目录，到目录中读取文件，然后将文件中的内容加入到索引中。
