Inline small file data in xl.meta file (#11758)

cmd/bitrot.go

@@ -17,6 +17,7 @@
 package cmd
 
 import (
+	"bytes"
 	"crypto/sha256"
 	"errors"
 	"hash"
@@ -143,3 +144,54 @@ func bitrotShardFileSize(size int64, shardSize int64, algo BitrotAlgorithm) int6
 	}
 	return ceilFrac(size, shardSize)*int64(algo.New().Size()) + size
 }
+
+// bitrotVerify a single stream of data.
+func bitrotVerify(r io.Reader, wantSize, partSize int64, algo BitrotAlgorithm, want []byte, shardSize int64) error {
+	if algo != HighwayHash256S {
+		h := algo.New()
+		if n, err := io.Copy(h, r); err != nil || n != wantSize {
+			// Premature failure in reading the object, file is corrupt.
+			return errFileCorrupt
+		}
+		if !bytes.Equal(h.Sum(nil), want) {
+			return errFileCorrupt
+		}
+		return nil
+	}
+
+	h := algo.New()
+	hashBuf := make([]byte, h.Size())
+	buf := make([]byte, shardSize)
+	left := wantSize
+
+	// Calculate the size of the bitrot file and compare
+	// it with the actual file size.
+	if left != bitrotShardFileSize(partSize, shardSize, algo) {
+		return errFileCorrupt
+	}
+
+	for left > 0 {
+		// Read expected hash...
+		h.Reset()
+		n, err := io.ReadFull(r, hashBuf)
+		if err != nil {
+			// Read's failed for object with right size, file is corrupt.
+			return err
+		}
+		// Subtract hash length..
+		left -= int64(n)
+		if left < shardSize {
+			shardSize = left
+		}
+		read, err := io.CopyBuffer(h, io.LimitReader(r, shardSize), buf)
+		if err != nil {
+			// Read's failed for object with right size, at different offsets.
+			return err
+		}
+		left -= read
+		if !bytes.Equal(h.Sum(nil), hashBuf) {
+			return errFileCorrupt
+		}
+	}
+	return nil
+}