bread-gallery/src/hash_dict.rs

use std::collections::HashMap;
use std::fs::File;
use std::io::Read;
use std::io::Write;
use std::io;
use std::path::PathBuf;

// file-stored hash map used to prevent needless image regenerating
#[derive(Debug)]
pub struct HashDict {
    hashes: HashMap<String, String>,
    path: PathBuf,
    any_change: bool,
}

impl HashDict {
    pub fn load(path: PathBuf) -> Result<HashDict, io::Error>  {
        let mut hd = HashDict {
            hashes: HashMap::new(),
            path,
            any_change: false,
        };

        if !hd.path.exists() {
            return Ok(hd);
        }

        let mut f = File::open(&hd.path)?;
        let mut s = String::new();
        f.read_to_string(&mut s)?;

        let lines: Vec<&str> = s.split("\n").collect();
        for l in lines {
            let halves: Vec<&str> = l.split("\t").collect();
            if halves.len() == 2 {
                hd.hashes.insert(halves[0].to_string(), halves[1].to_string());
            }
        }

        Ok(hd)
    }

    pub fn get(&self, key : &str) -> Option<&String> {
        self.hashes.get(key)
    }

    pub fn put(&mut self, key : String, value: String) {
        self.hashes.insert(key, value);
        self.any_change = true;
    }

    pub fn save(&mut self) {
        if self.any_change || !self.path.exists() {
            let mut f = File::create(&self.path).unwrap();
            let mut buf = String::new();
            for (k, v) in &self.hashes {
                buf.push_str(&format!("{}\t{}\n", k, v));
            }
            f.write(buf.as_ref()).unwrap();

            self.any_change = false;
        }
    }
}