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package main
import (
"os"
"encoding/json"
"./drive"
)
const MinCacheFileSize = 5 * 1024 * 1024
type Md5Comparer struct {}
func (self Md5Comparer) Changed(local *drive.LocalFile, remote *drive.RemoteFile) bool {
return remote.Md5() != md5sum(local.AbsPath())
}
type CachedFileInfo struct {
Size int64 `json:"size"`
Modified int64 `json:"modified"`
Md5 string `json:"md5"`
}
func NewCachedMd5Comparer(path string) CachedMd5Comparer {
cache := map[string]*CachedFileInfo{}
f, err := os.Open(path)
if err == nil {
json.NewDecoder(f).Decode(&cache)
}
f.Close()
return CachedMd5Comparer{path, cache}
}
type CachedMd5Comparer struct {
path string
cache map[string]*CachedFileInfo
}
func (self CachedMd5Comparer) Changed(local *drive.LocalFile, remote *drive.RemoteFile) bool {
return remote.Md5() != self.md5(local)
}
func (self CachedMd5Comparer) md5(local *drive.LocalFile) string {
// See if file exist in cache
cached, found := self.cache[local.AbsPath()]
// If found and modification time and size has not changed, return cached md5
if found && local.Modified().UnixNano() == cached.Modified && local.Size() == cached.Size {
return cached.Md5
}
// Calculate new md5 sum
md5 := md5sum(local.AbsPath())
// Cache file info if file meets size criteria
if local.Size() > MinCacheFileSize {
self.cacheAdd(local, md5)
self.persist()
}
return md5
}
func (self CachedMd5Comparer) cacheAdd(lf *drive.LocalFile, md5 string) {
self.cache[lf.AbsPath()] = &CachedFileInfo{
Size: lf.Size(),
Modified: lf.Modified().UnixNano(),
Md5: md5,
}
}
func (self CachedMd5Comparer) persist() {
writeJson(self.path, self.cache)
}
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