package artifact import ( "encoding/hex" "errors" "fmt" "io/ioutil" "net/http" "os" "path/filepath" "sync" "gitlab.com/slon/shad-go/distbuild/pkg/build" ) var ( ErrNotFound = errors.New("file not found") ErrWriteLocked = errors.New("file is locked for write") ErrReadLocked = errors.New("file is locked for read") ) type Cache struct { tmpDir string cacheDir string mu sync.Mutex writeLocked map[build.ID]struct{} readLocked map[build.ID]int } func NewCache(root string) (*Cache, error) { tmpDir := filepath.Join(root, "tmp") if err := os.RemoveAll(tmpDir); err != nil { return nil, err } if err := os.MkdirAll(tmpDir, 0777); err != nil { return nil, err } cacheDir := filepath.Join(root, "c") if err := os.MkdirAll(cacheDir, 0777); err != nil { return nil, err } for i := 0; i < 256; i++ { d := hex.EncodeToString([]byte{uint8(i)}) if err := os.MkdirAll(filepath.Join(cacheDir, d), 0777); err != nil { return nil, err } } return &Cache{ tmpDir: tmpDir, cacheDir: cacheDir, writeLocked: make(map[build.ID]struct{}), readLocked: make(map[build.ID]int), }, nil } func (c *Cache) readLock(id build.ID) error { c.mu.Lock() defer c.mu.Unlock() if _, ok := c.writeLocked[id]; ok { return ErrWriteLocked } c.readLocked[id]++ return nil } func (c *Cache) readUnlock(id build.ID) { c.mu.Lock() defer c.mu.Unlock() c.readLocked[id]-- if c.readLocked[id] == 0 { delete(c.readLocked, id) } } func (c *Cache) writeLock(id build.ID) error { c.mu.Lock() defer c.mu.Unlock() if _, ok := c.writeLocked[id]; ok { return ErrWriteLocked } if c.readLocked[id] > 0 { return ErrReadLocked } c.writeLocked[id] = struct{}{} return nil } func (c *Cache) writeUnlock(id build.ID) { c.mu.Lock() defer c.mu.Unlock() delete(c.writeLocked, id) } func (c *Cache) Range(artifactFn func(artifact build.ID) error) error { shards, err := ioutil.ReadDir(c.cacheDir) if err != nil { return err } for _, shard := range shards { dirs, err := ioutil.ReadDir(filepath.Join(c.cacheDir, shard.Name())) if err != nil { return err } for _, d := range dirs { var id build.ID if err := id.UnmarshalText([]byte(d.Name())); err != nil { return fmt.Errorf("invalid artifact name: %w", err) } if err := artifactFn(id); err != nil { return err } } } return nil } func (c *Cache) Remove(artifact build.ID) error { if err := c.writeLock(artifact); err != nil { return err } defer c.writeUnlock(artifact) return os.RemoveAll(filepath.Join(c.cacheDir, artifact.Path())) } func (c *Cache) Create(artifact build.ID) (path string, commit, abort func() error, err error) { if err = c.writeLock(artifact); err != nil { return } path = filepath.Join(c.tmpDir, artifact.String()) if err = os.MkdirAll(path, 0777); err != nil { c.writeUnlock(artifact) return } abort = func() error { defer c.writeUnlock(artifact) return os.RemoveAll(path) } commit = func() error { defer c.writeUnlock(artifact) return os.Rename(path, filepath.Join(c.cacheDir, artifact.Path())) } return } func (c *Cache) Get(artifact build.ID) (path string, unlock func(), err error) { if err = c.readLock(artifact); err != nil { return } path = filepath.Join(c.cacheDir, artifact.Path()) if _, err = os.Stat(path); err != nil { c.readUnlock(artifact) if os.IsNotExist(err) { err = ErrNotFound } return } unlock = func() { c.readUnlock(artifact) } return } func NewHandler(c *Cache) http.Handler { panic("implement me") }