diff --git a/README.md b/README.md
index d0800b4..767e5ca 100644
--- a/README.md
+++ b/README.md
@@ -129,9 +129,9 @@ svr.Get("/stream", [&](const Request &req, Response &res) {
 
   res.set_content_provider(
     data->size(), // Content length
-    [data](uint64_t offset, uint64_t length, DataSink sink) {
+    [data](uint64_t offset, uint64_t length, DataSink &sink) {
       const auto &d = *data;
-      sink(&d[offset], std::min(length, DATA_CHUNK_SIZE));
+      sink.write(&d[offset], std::min(length, DATA_CHUNK_SIZE));
     },
     [data] { delete data; });
 });
@@ -169,11 +169,11 @@ svr.Post("/content_receiver",
 ```cpp
 svr.Get("/chunked", [&](const Request& req, Response& res) {
   res.set_chunked_content_provider(
-    [](uint64_t offset, DataSink sink, Done done) {
-       sink("123", 3);
-       sink("345", 3);
-       sink("789", 3);
-       done();
+    [](uint64_t offset, DataSink &sink) {
+       sink.write("123", 3);
+       sink.write("345", 3);
+       sink.write("789", 3);
+       sink.done();
     }
   );
 });
diff --git a/httplib.h b/httplib.h
index f0e3cfa..2124e68 100644
--- a/httplib.h
+++ b/httplib.h
@@ -195,16 +195,6 @@ using Headers = std::multimap<std::string, std::string, detail::ci>;
 using Params = std::multimap<std::string, std::string>;
 using Match = std::smatch;
 
-using DataSink = std::function<void(const char *data, size_t data_len)>;
-
-using Done = std::function<void()>;
-
-using ContentProvider =
-    std::function<void(size_t offset, size_t length, DataSink sink)>;
-
-using ContentProviderWithCloser =
-    std::function<void(size_t offset, size_t length, DataSink sink, Done done)>;
-
 using Progress = std::function<bool(uint64_t current, uint64_t total)>;
 
 struct Response;
@@ -219,6 +209,20 @@ struct MultipartFormData {
 using MultipartFormDataItems = std::vector<MultipartFormData>;
 using MultipartFormDataMap = std::multimap<std::string, MultipartFormData>;
 
+class DataSink {
+public:
+  DataSink() = default;
+  DataSink(const DataSink &) = delete;
+  DataSink(const DataSink &&) = delete;
+
+  std::function<void(const char *data, size_t data_len)> write;
+  std::function<void()> done;
+  // TODO: std::function<bool()> is_alive;
+};
+
+using ContentProvider =
+    std::function<void(size_t offset, size_t length, DataSink &sink)>;
+
 using ContentReceiver =
     std::function<bool(const char *data, size_t data_length)>;
 
@@ -310,11 +314,12 @@ struct Response {
 
   void set_content_provider(
       size_t length,
-      std::function<void(size_t offset, size_t length, DataSink sink)> provider,
+      std::function<void(size_t offset, size_t length, DataSink &sink)>
+          provider,
       std::function<void()> resource_releaser = [] {});
 
   void set_chunked_content_provider(
-      std::function<void(size_t offset, DataSink sink, Done done)> provider,
+      std::function<void(size_t offset, DataSink &sink)> provider,
       std::function<void()> resource_releaser = [] {});
 
   Response() : status(-1), content_length(0) {}
@@ -327,7 +332,7 @@ struct Response {
 
   // private members...
   size_t content_length;
-  ContentProviderWithCloser content_provider;
+  ContentProvider content_provider;
   std::function<void()> content_provider_resource_releaser;
 };
 
@@ -1876,47 +1881,69 @@ inline int write_headers(Stream &strm, const T &info, const Headers &headers) {
   return write_len;
 }
 
-inline ssize_t write_content(Stream &strm,
-                             ContentProviderWithCloser content_provider,
+inline ssize_t write_content(Stream &strm, ContentProvider content_provider,
                              size_t offset, size_t length) {
   size_t begin_offset = offset;
   size_t end_offset = offset + length;
   while (offset < end_offset) {
     ssize_t written_length = 0;
-    content_provider(
-        offset, end_offset - offset,
-        [&](const char *d, size_t l) {
-          offset += l;
-          written_length = strm.write(d, l);
-        },
-        [&](void) { written_length = -1; });
+
+    DataSink data_sink;
+    data_sink.write = [&](const char *d, size_t l) {
+      offset += l;
+      written_length = strm.write(d, l);
+    };
+    data_sink.done = [&](void) { written_length = -1; };
+
+    content_provider(offset, end_offset - offset,
+                     // [&](const char *d, size_t l) {
+                     //   offset += l;
+                     //   written_length = strm.write(d, l);
+                     // },
+                     // [&](void) { written_length = -1; }
+                     data_sink);
     if (written_length < 0) { return written_length; }
   }
   return static_cast<ssize_t>(offset - begin_offset);
 }
 
-inline ssize_t
-write_content_chunked(Stream &strm,
-                      ContentProviderWithCloser content_provider) {
+inline ssize_t write_content_chunked(Stream &strm,
+                                     ContentProvider content_provider) {
   size_t offset = 0;
   auto data_available = true;
   ssize_t total_written_length = 0;
   while (data_available) {
     ssize_t written_length = 0;
+
+    DataSink data_sink;
+    data_sink.write = [&](const char *d, size_t l) {
+      data_available = l > 0;
+      offset += l;
+
+      // Emit chunked response header and footer for each chunk
+      auto chunk = from_i_to_hex(l) + "\r\n" + std::string(d, l) + "\r\n";
+      written_length = strm.write(chunk);
+    };
+    data_sink.done = [&](void) {
+      data_available = false;
+      written_length = strm.write("0\r\n\r\n");
+    };
+
     content_provider(
         offset, 0,
-        [&](const char *d, size_t l) {
-          data_available = l > 0;
-          offset += l;
-
-          // Emit chunked response header and footer for each chunk
-          auto chunk = from_i_to_hex(l) + "\r\n" + std::string(d, l) + "\r\n";
-          written_length = strm.write(chunk);
-        },
-        [&](void) {
-          data_available = false;
-          written_length = strm.write("0\r\n\r\n");
-        });
+        // [&](const char *d, size_t l) {
+        //   data_available = l > 0;
+        //   offset += l;
+        //
+        //   // Emit chunked response header and footer for each chunk
+        //   auto chunk = from_i_to_hex(l) + "\r\n" + std::string(d, l) +
+        //   "\r\n"; written_length = strm.write(chunk);
+        // },
+        // [&](void) {
+        //   data_available = false;
+        //   written_length = strm.write("0\r\n\r\n");
+        // }
+        data_sink);
 
     if (written_length < 0) { return written_length; }
     total_written_length += written_length;
@@ -2652,21 +2679,23 @@ inline void Response::set_content(const std::string &s,
 
 inline void Response::set_content_provider(
     size_t length,
-    std::function<void(size_t offset, size_t length, DataSink sink)> provider,
+    std::function<void(size_t offset, size_t length, DataSink &sink)> provider,
     std::function<void()> resource_releaser) {
   assert(length > 0);
   content_length = length;
-  content_provider = [provider](size_t offset, size_t length, DataSink sink,
-                                Done) { provider(offset, length, sink); };
+  content_provider = [provider](size_t offset, size_t length, DataSink &sink) {
+    provider(offset, length, sink);
+  };
   content_provider_resource_releaser = resource_releaser;
 }
 
 inline void Response::set_chunked_content_provider(
-    std::function<void(size_t offset, DataSink sink, Done done)> provider,
+    std::function<void(size_t offset, DataSink &sink)> provider,
     std::function<void()> resource_releaser) {
   content_length = 0;
-  content_provider = [provider](size_t offset, size_t, DataSink sink,
-                                Done done) { provider(offset, sink, done); };
+  content_provider = [provider](size_t offset, size_t, DataSink &sink) {
+    provider(offset, sink);
+  };
   content_provider_resource_releaser = resource_releaser;
 }
 
@@ -3731,12 +3760,15 @@ inline bool Client::write_request(Stream &strm, const Request &req,
     if (req.content_provider) {
       size_t offset = 0;
       size_t end_offset = req.content_length;
+
+      DataSink data_sink;
+      data_sink.write = [&](const char *d, size_t l) {
+        auto written_length = strm.write(d, l);
+        offset += written_length;
+      };
+
       while (offset < end_offset) {
-        req.content_provider(offset, end_offset - offset,
-                             [&](const char *d, size_t l) {
-                               auto written_length = strm.write(d, l);
-                               offset += written_length;
-                             });
+        req.content_provider(offset, end_offset - offset, data_sink);
       }
     }
   } else {
@@ -3761,12 +3793,15 @@ inline std::shared_ptr<Response> Client::send_with_content_provider(
   if (compress_) {
     if (content_provider) {
       size_t offset = 0;
+
+      DataSink data_sink;
+      data_sink.write = [&](const char *data, size_t data_len) {
+        req.body.append(data, data_len);
+        offset += data_len;
+      };
+
       while (offset < content_length) {
-        content_provider(offset, content_length - offset,
-                         [&](const char *data, size_t data_len) {
-                           req.body.append(data, data_len);
-                           offset += data_len;
-                         });
+        content_provider(offset, content_length - offset, data_sink);
       }
     } else {
       req.body = body;
diff --git a/test/test.cc b/test/test.cc
index 81d4996..a82c31d 100644
--- a/test/test.cc
+++ b/test/test.cc
@@ -697,18 +697,33 @@ protected:
         .Get("/streamed-chunked",
              [&](const Request & /*req*/, Response &res) {
                res.set_chunked_content_provider(
-                   [](uint64_t /*offset*/, DataSink sink, Done done) {
-                     sink("123", 3);
-                     sink("456", 3);
-                     sink("789", 3);
-                     done();
+                   [](uint64_t /*offset*/, DataSink &sink) {
+                     sink.write("123", 3);
+                     sink.write("456", 3);
+                     sink.write("789", 3);
+                     sink.done();
                    });
              })
+        .Get("/streamed-chunked2",
+             [&](const Request & /*req*/, Response &res) {
+               auto i = new int(0);
+               res.set_chunked_content_provider(
+                   [i](uint64_t /*offset*/, DataSink &sink) {
+                     switch (*i) {
+                     case 0: sink.write("123", 3); break;
+                     case 1: sink.write("456", 3); break;
+                     case 2: sink.write("789", 3); break;
+                     case 3: sink.done(); break;
+                     }
+                     (*i)++;
+                   },
+                   [i] { delete i; });
+             })
         .Get("/streamed",
              [&](const Request & /*req*/, Response &res) {
                res.set_content_provider(
-                   6, [](uint64_t offset, uint64_t /*length*/, DataSink sink) {
-                     sink(offset < 3 ? "a" : "b", 1);
+                   6, [](uint64_t offset, uint64_t /*length*/, DataSink &sink) {
+                     sink.write(offset < 3 ? "a" : "b", 1);
                    });
              })
         .Get("/streamed-with-range",
@@ -716,23 +731,23 @@ protected:
                auto data = new std::string("abcdefg");
                res.set_content_provider(
                    data->size(),
-                   [data](uint64_t offset, uint64_t length, DataSink sink) {
+                   [data](uint64_t offset, uint64_t length, DataSink &sink) {
                      size_t DATA_CHUNK_SIZE = 4;
                      const auto &d = *data;
                      auto out_len =
                          std::min(static_cast<size_t>(length), DATA_CHUNK_SIZE);
-                     sink(&d[static_cast<size_t>(offset)], out_len);
+                     sink.write(&d[static_cast<size_t>(offset)], out_len);
                    },
                    [data] { delete data; });
              })
         .Get("/streamed-cancel",
              [&](const Request & /*req*/, Response &res) {
-               res.set_content_provider(
-                   size_t(-1),
-                   [](uint64_t /*offset*/, uint64_t /*length*/, DataSink sink) {
-                     std::string data = "data_chunk";
-                     sink(data.data(), data.size());
-                   });
+               res.set_content_provider(size_t(-1), [](uint64_t /*offset*/,
+                                                       uint64_t /*length*/,
+                                                       DataSink &sink) {
+                 std::string data = "data_chunk";
+                 sink.write(data.data(), data.size());
+               });
              })
         .Get("/with-range",
              [&](const Request & /*req*/, Response &res) {
@@ -1508,6 +1523,13 @@ TEST_F(ServerTest, GetStreamedChunked) {
   EXPECT_EQ(std::string("123456789"), res->body);
 }
 
+TEST_F(ServerTest, GetStreamedChunked2) {
+  auto res = cli_.Get("/streamed-chunked2");
+  ASSERT_TRUE(res != nullptr);
+  EXPECT_EQ(200, res->status);
+  EXPECT_EQ(std::string("123456789"), res->body);
+}
+
 TEST_F(ServerTest, LargeChunkedPost) {
   Request req;
   req.method = "POST";
@@ -1567,8 +1589,8 @@ TEST_F(ServerTest, Put) {
 TEST_F(ServerTest, PutWithContentProvider) {
   auto res = cli_.Put(
       "/put", 3,
-      [](size_t /*offset*/, size_t /*length*/, DataSink sink) {
-        sink("PUT", 3);
+      [](size_t /*offset*/, size_t /*length*/, DataSink &sink) {
+        sink.write("PUT", 3);
       },
       "text/plain");
 
@@ -1582,8 +1604,8 @@ TEST_F(ServerTest, PutWithContentProviderWithGzip) {
   cli_.set_compress(true);
   auto res = cli_.Put(
       "/put", 3,
-      [](size_t /*offset*/, size_t /*length*/, DataSink sink) {
-        sink("PUT", 3);
+      [](size_t /*offset*/, size_t /*length*/, DataSink &sink) {
+        sink.write("PUT", 3);
       },
       "text/plain");
 
@@ -1689,7 +1711,8 @@ TEST_F(ServerTest, PatchContentReceiver) {
 }
 
 TEST_F(ServerTest, PostQueryStringAndBody) {
-  auto res = cli_.Post("/query-string-and-body?key=value", "content", "text/plain");
+  auto res =
+      cli_.Post("/query-string-and-body?key=value", "content", "text/plain");
   ASSERT_TRUE(res != nullptr);
   ASSERT_EQ(200, res->status);
 }
@@ -2139,8 +2162,7 @@ TEST(SSLClientServerTest, ClientCertPresent) {
   thread t = thread([&]() { ASSERT_TRUE(svr.listen(HOST, PORT)); });
   msleep(1);
 
-  httplib::SSLClient cli(HOST, PORT, CLIENT_CERT_FILE,
-                         CLIENT_PRIVATE_KEY_FILE);
+  httplib::SSLClient cli(HOST, PORT, CLIENT_CERT_FILE, CLIENT_PRIVATE_KEY_FILE);
   auto res = cli.Get("/test");
   cli.set_timeout_sec(30);
   ASSERT_TRUE(res != nullptr);
@@ -2181,8 +2203,7 @@ TEST(SSLClientServerTest, TrustDirOptional) {
   thread t = thread([&]() { ASSERT_TRUE(svr.listen(HOST, PORT)); });
   msleep(1);
 
-  httplib::SSLClient cli(HOST, PORT, CLIENT_CERT_FILE,
-                         CLIENT_PRIVATE_KEY_FILE);
+  httplib::SSLClient cli(HOST, PORT, CLIENT_CERT_FILE, CLIENT_PRIVATE_KEY_FILE);
   auto res = cli.Get("/test");
   cli.set_timeout_sec(30);
   ASSERT_TRUE(res != nullptr);