分段下载问题

app/controllers/attachments_controller.rb

@@ -21,9 +21,7 @@ class AttachmentsController < ApplicationController
     if type_attachment == "inline"
       send_file absolute_path(local_path(@file)),filename: @file.title, disposition: 'inline',type: 'application/pdf'
     elsif type_attachment == "MP4"
-      response.header["Accept-Ranges"] = "bytes"
-      send_file absolute_path(local_path(@file)),filename: @file.title, disposition: 'inline',
-                type: @file.content_type.presence || 'application/octet-stream', x_sendfile: true
+      send_file_with_range absolute_path(local_path(@file)), disposition: 'inline', type: "video/mp4", range: true
     else
       send_file(absolute_path(local_path(@file)), filename: @file.title,stream:false, type: @file.content_type.presence || 'application/octet-stream')
     end
@@ -206,4 +204,27 @@ class AttachmentsController < ApplicationController
     end
   end
 
+  def send_file_with_range(path, options = {})
+    if File.exist?(path)
+      size = File.size(path)
+      if !request.headers["Range"]
+        status_code = 200 # 200 OK
+        offset = 0
+        length = File.size(path)
+      else
+        status_code = 206 # 206 Partial Content
+        bytes = Rack::Utils.byte_ranges(request.headers, size)[0]
+        offset = bytes.begin
+        length = bytes.end - bytes.begin
+      end
+      response.header["Accept-Ranges"] = "bytes"
+      response.header["Content-Range"] = "bytes #{bytes.begin}-#{bytes.end}/#{size}" if bytes
+      response.header["status"] = status_code
+
+      send_data IO.binread(path, length, offset), options
+    else
+      raise ActionController::MissingFile, "Cannot read file #{path}."
+    end
+  end
+
 end