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|
package app
import (
"encoding/json"
"errors"
"io/fs"
"os"
"sync"
"time"
)
type cacheEntry struct {
DurationSeconds float64 `json:"duration_seconds"`
ModTimeUnix int64 `json:"mod_time_unix"`
Size int64 `json:"size"`
}
type durationCache struct {
path string
entries map[string]cacheEntry
mu sync.Mutex
dirty bool
}
func newDurationCache(path string) *durationCache {
return &durationCache{path: path, entries: make(map[string]cacheEntry)}
}
func loadDurationCache(path string) (*durationCache, error) {
cache := newDurationCache(path)
data, err := os.ReadFile(path)
if err != nil {
if errors.Is(err, fs.ErrNotExist) {
return cache, nil
}
return cache, err
}
if len(data) == 0 {
return cache, nil
}
if err := json.Unmarshal(data, &cache.entries); err != nil {
cache.entries = make(map[string]cacheEntry)
return cache, err
}
return cache, nil
}
func (c *durationCache) Lookup(path string, info os.FileInfo) (time.Duration, bool) {
c.mu.Lock()
defer c.mu.Unlock()
entry, ok := c.entries[path]
if !ok {
return 0, false
}
if entry.ModTimeUnix != info.ModTime().Unix() || entry.Size != info.Size() {
delete(c.entries, path)
c.dirty = true
return 0, false
}
if entry.DurationSeconds <= 0 {
return 0, false
}
return time.Duration(entry.DurationSeconds * float64(time.Second)), true
}
func (c *durationCache) Record(path string, info os.FileInfo, dur time.Duration) error {
if c == nil || dur <= 0 {
return nil
}
c.mu.Lock()
defer c.mu.Unlock()
if c.entries == nil {
c.entries = make(map[string]cacheEntry)
}
c.entries[path] = cacheEntry{
DurationSeconds: dur.Seconds(),
ModTimeUnix: info.ModTime().Unix(),
Size: info.Size(),
}
c.dirty = true
return nil
}
func (c *durationCache) Flush() error {
if c == nil {
return nil
}
c.mu.Lock()
if !c.dirty {
c.mu.Unlock()
return nil
}
snapshot := make(map[string]cacheEntry, len(c.entries))
for k, v := range c.entries {
snapshot[k] = v
}
c.dirty = false
c.mu.Unlock()
data, err := json.MarshalIndent(snapshot, "", " ")
if err != nil {
return err
}
return os.WriteFile(c.path, data, 0o644)
}
|
