add other session providers (#5963)

vendor/github.com/syndtr/goleveldb/leveldb/storage.go

@@ -0,0 +1,63 @@
+package leveldb
+
+import (
+	"github.com/syndtr/goleveldb/leveldb/storage"
+	"sync/atomic"
+)
+
+type iStorage struct {
+	storage.Storage
+	read  uint64
+	write uint64
+}
+
+func (c *iStorage) Open(fd storage.FileDesc) (storage.Reader, error) {
+	r, err := c.Storage.Open(fd)
+	return &iStorageReader{r, c}, err
+}
+
+func (c *iStorage) Create(fd storage.FileDesc) (storage.Writer, error) {
+	w, err := c.Storage.Create(fd)
+	return &iStorageWriter{w, c}, err
+}
+
+func (c *iStorage) reads() uint64 {
+	return atomic.LoadUint64(&c.read)
+}
+
+func (c *iStorage) writes() uint64 {
+	return atomic.LoadUint64(&c.write)
+}
+
+// newIStorage returns the given storage wrapped by iStorage.
+func newIStorage(s storage.Storage) *iStorage {
+	return &iStorage{s, 0, 0}
+}
+
+type iStorageReader struct {
+	storage.Reader
+	c *iStorage
+}
+
+func (r *iStorageReader) Read(p []byte) (n int, err error) {
+	n, err = r.Reader.Read(p)
+	atomic.AddUint64(&r.c.read, uint64(n))
+	return n, err
+}
+
+func (r *iStorageReader) ReadAt(p []byte, off int64) (n int, err error) {
+	n, err = r.Reader.ReadAt(p, off)
+	atomic.AddUint64(&r.c.read, uint64(n))
+	return n, err
+}
+
+type iStorageWriter struct {
+	storage.Writer
+	c *iStorage
+}
+
+func (w *iStorageWriter) Write(p []byte) (n int, err error) {
+	n, err = w.Writer.Write(p)
+	atomic.AddUint64(&w.c.write, uint64(n))
+	return n, err
+}