feat: implement ListFiles and DownloadFile RPCs with documentation updates in GRPC.md

examples/grpcentity/client.go

@@ -4,7 +4,9 @@ import (
 	"context"
 	"fmt"
 	"grpccanary/examples/grpcentity/protoapi"
+	"io"
 	"math/rand"
+	"time"
 
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/credentials/insecure"
@@ -64,6 +66,31 @@ func AskUploadFile(ctx context.Context, m protoapi.IoTServiceClient, fileName st
 	return stream.CloseAndRecv()
 }
 
+func AskListFiles(ctx context.Context, m protoapi.IoTServiceClient) (*protoapi.FileList, error) {
+	return m.ListFiles(ctx, &protoapi.EmptyRequest{})
+}
+
+func AskDownloadFile(ctx context.Context, m protoapi.IoTServiceClient, fileName string) ([]byte, error) {
+	stream, err := m.DownloadFile(ctx, &protoapi.DownloadRequest{FileName: fileName})
+	if err != nil {
+		return nil, err
+	}
+
+	var buffer []byte
+	for {
+		chunk, err := stream.Recv()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return nil, err
+		}
+		buffer = append(buffer, chunk.GetContent()...)
+	}
+
+	return buffer, nil
+}
+
 func ClientRun(addr string) {
 	conn, err := grpc.NewClient(addr, grpc.WithTransportCredentials(insecure.NewCredentials()))
 	if err != nil {
@@ -109,4 +136,39 @@ func ClientRun(addr string) {
 	fmt.Println("Upload Success:", status.Success)
 	fmt.Println("Upload Message:", status.Message)
 	fmt.Printf("Uploaded Bytes: %d bytes\n", status.BytesUploaded)
+
+	// 5단계: 파일 리스트 조회 실행 예제
+	fmt.Println("Querying uploaded files metadata from Server...")
+	list, err := AskListFiles(context.Background(), client)
+	if err != nil {
+		fmt.Println("Failed to list files:", err)
+		return
+	}
+	for i, f := range list.GetFiles() {
+		fmt.Printf("[%d] Name: %s, Size: %d bytes, UploadedAt: %s\n",
+			i+1, f.GetFileName(), f.GetFileSize(), time.Unix(f.GetUploadedAt(), 0).Format("2006-01-02 15:04:05"))
+	}
+
+	// 6단계: 파일 다운로드 스트리밍 실행 예제
+	fmt.Println("Downloading file 'firmware.bin' via Server Streaming...")
+	downloadedData, err := AskDownloadFile(context.Background(), client, "firmware.bin")
+	if err != nil {
+		fmt.Println("Failed to download file:", err)
+		return
+	}
+	fmt.Printf("Download completed. Received %d bytes.\n", len(downloadedData))
+
+	// 데이터 정합성(Integrity) 검증
+	isMatch := true
+	if len(dummyData) != len(downloadedData) {
+		isMatch = false
+	} else {
+		for i := range dummyData {
+			if dummyData[i] != downloadedData[i] {
+				isMatch = false
+				break
+			}
+		}
+	}
+	fmt.Printf("Data Integrity Checked (Upload vs Download matches?): %t\n", isMatch)
 }