music-library/hash_cache.go

package main

import (
	"crypto/sha512"
	"encoding/gob"
	"fmt"
	"os"
	"path/filepath"
	"time"

	"git.tordarus.net/tordarus/cmap"
)

var HashCache = cmap.New[[sha512.Size]byte, [sha512.Size]byte]()

func InitCache() {
	path := os.ExpandEnv(FlagCacheFile)

	file, err := os.Open(path)
	if err == nil {
		defer file.Close()
		data := map[[sha512.Size]byte][sha512.Size]byte{}
		gob.NewDecoder(file).Decode(&data)
		HashCache.Do(func(m map[[64]byte][64]byte) {
			for key, value := range data {
				m[key] = value
			}
		})
	}

	go func() {
		ticker := time.NewTicker(FlagUpdateCacheFileInterval)
		defer ticker.Stop()
		for range ticker.C {
			if err := WriteCache(); err != nil {
				fmt.Fprintln(os.Stderr, fmt.Errorf("could not write cache file: %w", err))
			}
		}
	}()
}

func WriteCache() error {
	path := os.ExpandEnv(FlagCacheFile)

	if err := os.MkdirAll(filepath.Dir(path), 0755); err != nil {
		return err
	}

	file, err := os.Create(path)
	if err != nil {
		return err
	}
	defer file.Close()

	data := HashCache.Clone()

	if err := gob.NewEncoder(file).Encode(data); err != nil {
		return err
	}

	fmt.Println("hashsum cache written")

	return nil
}