Start work on disk cache for choose files preview caching

tools/disk_cache/api.go

@@ -0,0 +1,82 @@
+package disk_cache
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sync"
+	"time"
+
+	"github.com/kovidgoyal/kitty/tools/utils"
+)
+
+var _ = fmt.Print
+
+type Entry struct {
+	Key      string
+	Size     int64
+	LastUsed time.Time
+}
+
+type Metadata struct {
+	TotalSize     int64
+	SortedEntries []*Entry
+}
+
+type DiskCache struct {
+	Path    string
+	MaxSize int64
+
+	lock_file        *os.File
+	lock_mutex       sync.Mutex
+	entries          Metadata
+	entry_map        map[string]*Entry
+	entries_mod_time time.Time
+}
+
+func NewDiskCache(path string, max_size int64) (dc *DiskCache, err error) {
+	if path, err = filepath.Abs(path); err != nil {
+		return
+	}
+	if err = os.MkdirAll(path, 0o700); err != nil {
+		return
+	}
+	return &DiskCache{Path: path, MaxSize: max_size}, nil
+}
+
+func KeyForPath(path string) (key string, err error) {
+	if path, err = filepath.EvalSymlinks(path); err != nil {
+		return
+	}
+	if path, err = filepath.Abs(path); err != nil {
+		return
+	}
+
+	s, err := os.Stat(path)
+	if err != nil {
+		return
+	}
+	data := fmt.Sprintf("%s\x00%d\x00%d", path, s.Size(), s.ModTime().UnixNano())
+	sum := sha256.Sum256(utils.UnsafeStringToBytes(data))
+	return hex.EncodeToString(sum[:]), nil
+}
+
+func (dc *DiskCache) Get(key string, items ...string) map[string]string {
+	dc.lock()
+	defer dc.unlock()
+	return dc.get(key, items)
+}
+
+func (dc *DiskCache) Remove(key string) (err error) {
+	dc.lock()
+	defer dc.unlock()
+	return dc.remove(key)
+}
+
+func (dc *DiskCache) Add(key string, items map[string][]byte) (err error) {
+	dc.lock()
+	defer dc.unlock()
+	return dc.add(key, items)
+}