split big chunk of data to write to printer

printer.go

@@ -17,7 +17,9 @@ import (
 
 	"github.com/kenshaw/escpos"
 )
-import "errors"
+import (
+	"errors"
+)
 
 //export PrintImg
 func PrintImg(printer *C.char, imagePath *C.char) *C.char {
@@ -87,10 +89,17 @@ func PrintImg(printer *C.char, imagePath *C.char) *C.char {
 	prt.SetSmooth(1)
 	prt.SetAlign("left")
 
-	err := printImg(prt, goImagePath)
+	imgBytes, err := imgData(goImagePath)
 	if err != nil {
 		return NewErr(err)
 	}
+	err = WriteChunk(w, prt, imgBytes)
+	if err != nil {
+		return NewErr(err)
+	}
+	time.Sleep(500 * time.Millisecond)
+	w.Flush()
+
 	prt.WriteRaw([]byte{0x1B, 0x64, 0x03})
 	prt.Cut()
 	prt.End()
@@ -104,3 +113,24 @@ func Print(printer, imagePath string) string {
 	r := C.GoString(result)
 	return r
 }
+
+// WriteChunk breaks the large byte array into smaller chunks
+func WriteChunk(w *bufio.ReadWriter, prt *escpos.Escpos, data []byte) error {
+	chunkSize := 1024 // 1 KB chunks work best for network printers
+	for i := 0; i < len(data); i += chunkSize {
+		end := min(i+chunkSize, len(data))
+
+		_, err := prt.WriteRaw(data[i:end])
+		if err != nil {
+			log.Println("Error writing image chunk:", err)
+			return err
+		}
+		if err := w.Flush(); err != nil {
+			log.Println("Error flushing buffer:", err)
+			return err
+		}
+		// Give the printer's network chip a microsecond to breathe
+		time.Sleep(5 * time.Millisecond)
+	}
+	return nil
+}