.

go/pkg/zerotier/sizelimitwriter.go

@@ -0,0 +1,108 @@
+/*
+ * Copyright (c)2019 ZeroTier, Inc.
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file in the project's root directory.
+ *
+ * Change Date: 2023-01-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2.0 of the Apache License.
+ */
+/****/
+
+package zerotier
+
+import (
+	"os"
+	"sync"
+)
+
+type sizeLimitWriter struct {
+	f *os.File
+	l sync.Mutex
+}
+
+func sizeLimitWriterOpen(p string) (*sizeLimitWriter, error) {
+	f, err := os.OpenFile(p, os.O_CREATE|os.O_RDWR, 0644)
+	if err != nil {
+		return nil, err
+	}
+	f.Seek(0, os.SEEK_END)
+	return &sizeLimitWriter{f: f}, nil
+}
+
+// Write implements io.Writer
+func (w *sizeLimitWriter) Write(b []byte) (int, error) {
+	w.l.Lock()
+	defer w.l.Unlock()
+	return w.f.Write(b)
+}
+
+// Close closes the underlying file
+func (w *sizeLimitWriter) Close() error {
+	w.l.Lock()
+	defer w.l.Unlock()
+	return w.f.Close()
+}
+
+func (w *sizeLimitWriter) trim(maxSize int, trimFactor float64, trimAtCR bool) error {
+	w.l.Lock()
+	defer w.l.Unlock()
+
+	flen, err := w.f.Seek(0, os.SEEK_END)
+	if err != nil {
+		return err
+	}
+
+	if flen > int64(maxSize) {
+		var buf [131072]byte
+		trimAt := int64(float64(flen) * trimFactor)
+		if trimAt >= flen { // sanity check
+			return nil
+		}
+
+		if trimAtCR {
+		lookForCR:
+			for {
+				nr, err := w.f.ReadAt(buf[0:1024], trimAt)
+				if err != nil {
+					return err
+				}
+				for i := 0; i < nr; i++ {
+					trimAt++
+					if buf[i] == byte('\n') {
+						break lookForCR
+					}
+				}
+				if trimAt >= flen {
+					return nil
+				}
+			}
+		}
+
+		copyTo := int64(0)
+		for trimAt < flen {
+			nr, _ := w.f.ReadAt(buf[:], trimAt)
+			if nr > 0 {
+				wr, _ := w.f.WriteAt(buf[0:nr], copyTo)
+				if wr > 0 {
+					copyTo += int64(wr)
+				} else {
+					break
+				}
+			} else {
+				break
+			}
+		}
+
+		err = w.f.Truncate(copyTo)
+		if err != nil {
+			return err
+		}
+		_, err = w.f.Seek(0, os.SEEK_END)
+		return err
+	}
+
+	return nil
+}