修复http文件下载指定目录时mmap导致崩溃的bug (#4213)

在`HttpBody.cpp`中，`getSharedMmap`函数直接尝试对所有路径进行mmap操作，没有进行文件类型检查

server/FFmpegSource.cpp

@@ -341,10 +341,14 @@ void FFmpegSource::onGetMediaSource(const MediaSource::Ptr &src) {
         setDelegate(listener);
         muxer->setDelegate(shared_from_this());
         if (_enable_hls) {
-            src->setupRecord(Recorder::type_hls, true, "", 0);
+            src->getOwnerPoller()->async([=]() mutable {
+                 src->setupRecord(Recorder::type_hls, true, "", 0);
+            });
         }
         if (_enable_mp4) {
-            src->setupRecord(Recorder::type_mp4, true, "", 0);
+            src->getOwnerPoller()->async([=]() mutable {
+                src->setupRecord(Recorder::type_mp4, true, "", 0);
+            });
         }
     }
 }

src/Http/HttpBody.cpp

@@ -194,6 +194,13 @@ static std::shared_ptr<char> getSharedMmap(const string &file_path, int64_t &fil
 }
 
 HttpFileBody::HttpFileBody(const string &file_path, bool use_mmap) {
+
+    // 判断是否为目录，避免对目录进行mmap操作，导致程序崩溃。
+    if (File::is_dir(file_path)) {
+        _read_to = -1;
+        return;
+    }
+
     if (use_mmap ) {
         _map_addr = getSharedMmap(file_path, _read_to);       
     }