cs: implement TakeScreenShot command

libraries/libstratosphere/source/cs/cs_command_impl.cpp

@@ -18,9 +18,65 @@
 
 namespace ams::cs {
 
+    namespace {
+
+        void SendEmptyData(const CommandDataTakeScreenShot &params, size_t remaining_size) {
+            /* Clear the data buffer. */
+            std::memset(params.buffer, 0, params.buffer_size);
+
+            /* Send data until the end. */
+            while (remaining_size > 0) {
+                /* Send as much as we can. */
+                const auto cur_size = std::min(remaining_size, params.buffer_size);
+                params.send_data(params.buffer, cur_size);
+
+                /* Advance. */
+                remaining_size -= cur_size;
+            }
+        }
+
+    }
+
     Result DoGetFirmwareVersionCommand(settings::system::FirmwareVersion *out) {
         settings::system::GetFirmwareVersion(out);
         return ResultSuccess();
     }
 
+    Result DoTakeScreenShotCommand(const CommandDataTakeScreenShot &params) {
+        /* Initialize screenshot control. */
+        R_TRY(capsrv::InitializeScreenShotControl());
+
+        /* Finalize screenshot control when we're done. */
+        ON_SCOPE_EXIT { capsrv::FinalizeScreenShotControl(); };
+
+        /* Open screenshot read stream. */
+        size_t data_size;
+        s32 width, height;
+        R_TRY(capsrv::OpenRawScreenShotReadStreamForDevelop(std::addressof(data_size), std::addressof(width), std::addressof(height), params.layer_stack, TimeSpan::FromSeconds(10)));
+
+        /* Close the screenshot stream when we're done. */
+        ON_SCOPE_EXIT { capsrv::CloseRawScreenShotReadStreamForDevelop(); };
+
+        /* Send the header. */
+        params.send_header(static_cast<s32>(data_size), width, height);
+
+        /* Read and send data. */
+        size_t total_read_size = 0;
+        auto data_guard = SCOPE_GUARD { SendEmptyData(params, data_size - total_read_size); };
+        while (total_read_size < data_size) {
+            /* Read data from the stream. */
+            size_t read_size;
+            R_TRY(capsrv::ReadRawScreenShotReadStreamForDevelop(std::addressof(read_size), params.buffer, params.buffer_size, total_read_size));
+
+            /* Send the data that was read. */
+            params.send_data(params.buffer, read_size);
+
+            /* Advance. */
+            total_read_size += read_size;
+        }
+        data_guard.Cancel();
+
+        return ResultSuccess();
+    }
+
 }