ProtocolServer: Send the download payload to clients as a shared buffer

The DownloadFinished message from the server now includes a buffer ID
that can be mapped into the client program.

To avoid prematurely destroying the buffer, the server will hang on to
it until the client lets it know that they're all good. That's what the
ProtocolServer::DisownSharedBuffer message is about.

In the future it would be nice if the kernel had a mechanism to allow
passing ownership of a shared buffer along with an IPC message somehow.

Libraries/LibProtocol/Client.cpp

@@ -33,7 +33,8 @@ bool Client::stop_download(i32 download_id)
 void Client::handle(const ProtocolClient::DownloadFinished& message)
 {
     if (on_download_finish)
-        on_download_finish(message.download_id(), message.success());
+        on_download_finish(message.download_id(), message.success(), message.total_size(), message.shared_buffer_id());
+    send_sync<ProtocolServer::DisownSharedBuffer>(message.shared_buffer_id());
 }
 
 void Client::handle(const ProtocolClient::DownloadProgress& message)

Libraries/LibProtocol/Client.h

@@ -18,7 +18,7 @@ public:
     i32 start_download(const String& url);
     bool stop_download(i32 download_id);
 
-    Function<void(i32 download_id, bool success)> on_download_finish;
+    Function<void(i32 download_id, bool success, u32 total_size, i32 shared_buffer_id)> on_download_finish;
     Function<void(i32 download_id, u64 total_size, u64 downloaded_size)> on_download_progress;
 
 private:

Servers/ProtocolServer/Download.cpp

@@ -31,6 +31,12 @@ void Download::stop()
     all_downloads().remove(m_id);
 }
 
+void Download::set_payload(const ByteBuffer& payload)
+{
+    m_payload = payload;
+    m_total_size = payload.size();
+}
+
 void Download::did_finish(bool success)
 {
     if (!m_client) {

Servers/ProtocolServer/Download.h

@@ -17,6 +17,7 @@ public:
 
     size_t total_size() const { return m_total_size; }
     size_t downloaded_size() const { return m_downloaded_size; }
+    const ByteBuffer& payload() const { return m_payload; }
 
     void stop();
 
@@ -25,11 +26,13 @@ protected:
 
     void did_finish(bool success);
     void did_progress(size_t total_size, size_t downloaded_size);
+    void set_payload(const ByteBuffer&);
 
 private:
     i32 m_id;
     URL m_url;
     size_t m_total_size { 0 };
     size_t m_downloaded_size { 0 };
+    ByteBuffer m_payload;
     WeakPtr<PSClientConnection> m_client;
 };

Servers/ProtocolServer/HttpDownload.cpp

@@ -1,4 +1,5 @@
 #include <LibCore/CHttpJob.h>
+#include <LibCore/CHttpResponse.h>
 #include <ProtocolServer/HttpDownload.h>
 
 HttpDownload::HttpDownload(PSClientConnection& client, NonnullRefPtr<CHttpJob>&& job)
@@ -6,6 +7,7 @@ HttpDownload::HttpDownload(PSClientConnection& client, NonnullRefPtr<CHttpJob>&&
     , m_job(job)
 {
     m_job->on_finish = [this](bool success) {
+        set_payload(m_job->response()->payload());
         did_finish(success);
     };
 }

Servers/ProtocolServer/PSClientConnection.cpp

@@ -2,6 +2,7 @@
 #include <ProtocolServer/PSClientConnection.h>
 #include <ProtocolServer/Protocol.h>
 #include <ProtocolServer/ProtocolClientEndpoint.h>
+#include <LibC/SharedBuffer.h>
 
 static HashMap<int, RefPtr<PSClientConnection>> s_connections;
 
@@ -48,7 +49,15 @@ OwnPtr<ProtocolServer::StopDownloadResponse> PSClientConnection::handle(const Pr
 
 void PSClientConnection::did_finish_download(Badge<Download>, Download& download, bool success)
 {
-    post_message(ProtocolClient::DownloadFinished(download.id(), success));
+    RefPtr<SharedBuffer> buffer;
+    if (success && !download.payload().is_null()) {
+        buffer = SharedBuffer::create_with_size(download.payload().size());
+        memcpy(buffer->data(), download.payload().data(), download.payload().size());
+        buffer->seal();
+        buffer->share_with(client_pid());
+        m_shared_buffers.set(buffer->shared_buffer_id(), buffer);
+    }
+    post_message(ProtocolClient::DownloadFinished(download.id(), success, download.total_size(), buffer ? buffer->shared_buffer_id() : -1));
 }
 
 void PSClientConnection::did_progress_download(Badge<Download>, Download& download)
@@ -61,3 +70,9 @@ OwnPtr<ProtocolServer::GreetResponse> PSClientConnection::handle(const ProtocolS
     set_client_pid(message.client_pid());
     return make<ProtocolServer::GreetResponse>(getpid(), client_id());
 }
+
+OwnPtr<ProtocolServer::DisownSharedBufferResponse> PSClientConnection::handle(const ProtocolServer::DisownSharedBuffer& message)
+{
+    m_shared_buffers.remove(message.shared_buffer_id());
+    return make<ProtocolServer::DisownSharedBufferResponse>();
+}

Servers/ProtocolServer/PSClientConnection.h

@@ -5,6 +5,7 @@
 #include <ProtocolServer/ProtocolServerEndpoint.h>
 
 class Download;
+class SharedBuffer;
 
 class PSClientConnection final : public IPC::Server::ConnectionNG<ProtocolServerEndpoint>
     , public ProtocolServerEndpoint {
@@ -23,4 +24,7 @@ private:
     virtual OwnPtr<ProtocolServer::IsSupportedProtocolResponse> handle(const ProtocolServer::IsSupportedProtocol&) override;
     virtual OwnPtr<ProtocolServer::StartDownloadResponse> handle(const ProtocolServer::StartDownload&) override;
     virtual OwnPtr<ProtocolServer::StopDownloadResponse> handle(const ProtocolServer::StopDownload&) override;
+    virtual OwnPtr<ProtocolServer::DisownSharedBufferResponse> handle(const ProtocolServer::DisownSharedBuffer&) override;
+
+    HashMap<i32, RefPtr<SharedBuffer>> m_shared_buffers;
 };

Servers/ProtocolServer/ProtocolClient.ipc

@@ -2,5 +2,5 @@ endpoint ProtocolClient = 13
 {
     // Download notifications
     DownloadProgress(i32 download_id, u32 total_size, u32 downloaded_size) =|
-    DownloadFinished(i32 download_id, bool success) =|
+    DownloadFinished(i32 download_id, bool success, u32 total_size, i32 shared_buffer_id) =|
 }

Servers/ProtocolServer/ProtocolServer.ipc

@@ -3,6 +3,9 @@ endpoint ProtocolServer = 9
     // Basic protocol
     Greet(i32 client_pid) => (i32 server_pid, i32 client_id)
 
+    // FIXME: It would be nice if the kernel provided a way to avoid this
+    DisownSharedBuffer(i32 shared_buffer_id) => ()
+
     // Test if a specific protocol is supported, e.g "http"
     IsSupportedProtocol(String protocol) => (bool supported)
 

Userland/pro.cpp

@@ -1,5 +1,6 @@
 #include <LibCore/CEventLoop.h>
 #include <LibProtocol/Client.h>
+#include <LibC/SharedBuffer.h>
 #include <stdio.h>
 
 int main(int argc, char** argv)
@@ -13,8 +14,14 @@ int main(int argc, char** argv)
     printf("supports HTTP? %u\n", protocol_client->is_supported_protocol("http"));
     printf(" supports FTP? %u\n", protocol_client->is_supported_protocol("ftp"));
 
-    protocol_client->on_download_finish = [&](i32 download_id, bool success) {
-        printf("download %d finished, success=%u\n", download_id, success);
+    protocol_client->on_download_finish = [&](i32 download_id, bool success, u32 total_size, i32 shared_buffer_id) {
+        printf("download %d finished, success=%u, shared_buffer_id=%d\n", download_id, success, shared_buffer_id);
+        if (success) {
+            ASSERT(shared_buffer_id != -1);
+            auto shared_buffer = SharedBuffer::create_from_shared_buffer_id(shared_buffer_id);
+            auto payload_bytes = ByteBuffer::wrap(shared_buffer->data(), total_size);
+            write(STDOUT_FILENO, payload_bytes.data(), payload_bytes.size());
+        }
         loop.quit(0);
     };