实现基础的206 partial content缓存

internal/utils/readers/reader_bytes_counter.go

@@ -0,0 +1,26 @@
+// Copyright 2022 Liuxiangchao iwind.liu@gmail.com. All rights reserved.
+
+package readers
+
+import "io"
+
+type BytesCounterReader struct {
+	rawReader io.Reader
+	count     int64
+}
+
+func NewBytesCounterReader(rawReader io.Reader) *BytesCounterReader {
+	return &BytesCounterReader{
+		rawReader: rawReader,
+	}
+}
+
+func (this *BytesCounterReader) Read(p []byte) (n int, err error) {
+	n, err = this.rawReader.Read(p)
+	this.count += int64(n)
+	return
+}
+
+func (this *BytesCounterReader) TotalBytes() int64 {
+	return this.count
+}