fix

pkg/finder/reader.go

@@ -0,0 +1,53 @@
+package finder
+
+import (
+	"io"
+	"os"
+)
+
+type TailReader struct {
+	f     *os.File
+	curr  int64
+	isEOF bool
+}
+
+func (t *TailReader) Read(b []byte) (n int, err error) {
+	if t.isEOF {
+		return 0, io.EOF
+	}
+
+	off := t.curr - int64(len(b))
+	if off < 0 {
+		off = 0
+		n, err = t.f.ReadAt(b[0:t.curr], off)
+	} else {
+		t.curr = off
+		n, err = t.f.ReadAt(b, off)
+	}
+
+	if err != nil && err != io.EOF {
+		return n, err
+	}
+
+	invert(b[0:n])
+
+	if off == 0 {
+		t.isEOF = true
+	}
+
+	return
+}
+
+func NewTailReader(f *os.File, offset int64) io.Reader {
+	return &TailReader{
+		f:    f,
+		curr: offset,
+	}
+
+}
+
+func invert(b []byte) {
+	for i, j := 0, len(b)-1; i < j; i, j = i+1, j-1 {
+		b[i], b[j] = b[j], b[i]
+	}
+}