add download test fake file

server/web/api/download.go

@@ -0,0 +1,52 @@
+package api
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"strconv"
+	"time"
+
+	"github.com/gin-gonic/gin"
+)
+
+type fileReader struct {
+	pos  int64
+	size int64
+	io.ReadSeeker
+}
+
+func newFR(size int64) *fileReader {
+	return &fileReader{
+		pos:  0,
+		size: size,
+	}
+}
+
+func (f *fileReader) Read(p []byte) (n int, err error) {
+	f.pos = f.pos + int64(len(p))
+	return len(p), nil
+}
+
+func (f *fileReader) Seek(offset int64, whence int) (int64, error) {
+	switch whence {
+	case 0:
+		f.pos = offset
+	case 1:
+		f.pos += offset
+	case 2:
+		f.pos = f.size + offset
+	}
+	return f.pos, nil
+}
+
+func download(c *gin.Context) {
+	szStr := c.Param("size")
+	sz, err := strconv.Atoi(szStr)
+	if err != nil {
+		c.Error(err)
+		return
+	}
+
+	http.ServeContent(c.Writer, c.Request, fmt.Sprintln(szStr)+"mb.bin", time.Now(), newFR(int64(sz*1024*1024)))
+}