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util/bytecounter/bytecounter_reader.go

@@ -0,0 +1,49 @@
+package bytecounter
+
+import (
+	"io"
+	"sync/atomic"
+	"time"
+)
+
+type ByteCounterReader struct {
+	reader io.ReadCloser
+
+	// called & accessed synchronously during Read, no external access
+	cb       func(full int64)
+	cbEvery  time.Duration
+	lastCbAt time.Time
+
+	// set atomically because it may be read by multiple threads
+	bytes int64
+}
+
+func NewByteCounterReader(reader io.ReadCloser) *ByteCounterReader {
+	return &ByteCounterReader{
+		reader: reader,
+	}
+}
+
+func (b *ByteCounterReader) SetCallback(every time.Duration, cb func(full int64)) {
+	b.cbEvery = every
+	b.cb = cb
+}
+
+func (b *ByteCounterReader) Close() error {
+	return b.reader.Close()
+}
+
+func (b *ByteCounterReader) Read(p []byte) (n int, err error) {
+	n, err = b.reader.Read(p)
+	full := atomic.AddInt64(&b.bytes, int64(n))
+	now := time.Now()
+	if b.cb != nil && now.Sub(b.lastCbAt) > b.cbEvery {
+		b.cb(full)
+		b.lastCbAt = now
+	}
+	return n, err
+}
+
+func (b *ByteCounterReader) Bytes() int64 {
+	return atomic.LoadInt64(&b.bytes)
+}