实现基础的206 partial content缓存

internal/utils/writers/writer_bytes_counter.go

@@ -0,0 +1,28 @@
+// Copyright 2022 Liuxiangchao iwind.liu@gmail.com. All rights reserved.
+
+package writers
+
+import "io"
+
+type BytesCounterWriter struct {
+	writer io.Writer
+	count  int64
+}
+
+func NewBytesCounterWriter(rawWriter io.Writer) *BytesCounterWriter {
+	return &BytesCounterWriter{writer: rawWriter}
+}
+
+func (this *BytesCounterWriter) Write(p []byte) (n int, err error) {
+	n, err = this.writer.Write(p)
+	this.count += int64(n)
+	return
+}
+
+func (this *BytesCounterWriter) Close() error {
+	return nil
+}
+
+func (this *BytesCounterWriter) TotalBytes() int64 {
+	return this.count
+}