mox!

moxio/limitatreader.go

@@ -0,0 +1,20 @@
+package moxio
+
+import (
+	"io"
+)
+
+// LimitAtReader is a reader at that returns ErrLimit if reads would extend
+// beyond Limit.
+type LimitAtReader struct {
+	R     io.ReaderAt
+	Limit int64
+}
+
+// ReadAt passes the read on to R, but returns an error if the read data would extend beyond Limit.
+func (r *LimitAtReader) ReadAt(buf []byte, offset int64) (int, error) {
+	if offset+int64(len(buf)) > r.Limit {
+		return 0, ErrLimit
+	}
+	return r.R.ReadAt(buf, offset)
+}