SpiceAgent: Add a new spice agent service :^)

A SPICE agent communicates with the host OS to provide nifty features
like clipboard sharing :^)

This patch implements only plain-text clipboard sharing.

See: github.com/freedesktop/spice-protocol/blob/master/spice/vd_agent.h

Userland/Services/SpiceAgent/SpiceAgent.cpp

@@ -0,0 +1,202 @@
+/*
+ * Copyright (c) 2021, Kyle Pereira <kyle@xylepereira.me>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "SpiceAgent.h"
+#include "ClipboardServerConnection.h"
+#include <AK/String.h>
+#include <LibC/memory.h>
+#include <LibC/unistd.h>
+
+SpiceAgent::SpiceAgent(int fd, ClipboardServerConnection& connection)
+    : m_fd(fd)
+    , m_clipboard_connection(connection)
+{
+    m_notifier = Core::Notifier::construct(fd, Core::Notifier::Read);
+    m_notifier->on_ready_to_read = [this] {
+        on_message_received();
+    };
+    m_clipboard_connection.on_data_changed = [this] {
+        if (m_just_set_clip) {
+            m_just_set_clip = false;
+            return;
+        }
+        auto grab_buffer = ClipboardGrab::make_buffer({ ClipboardType::Text });
+        send_message(grab_buffer);
+    };
+    auto buffer = AnnounceCapabilities::make_buffer(true, { Capability::ClipboardByDemand });
+    send_message(buffer);
+}
+
+void SpiceAgent::on_message_received()
+{
+    ChunkHeader header {};
+    read_n(&header, sizeof(header));
+    auto buffer = ByteBuffer::create_uninitialized(header.size);
+    read_n(buffer.data(), buffer.size());
+    auto* message = reinterpret_cast<Message*>(buffer.data());
+    switch (message->type) {
+    case (u32)MessageType::AnnounceCapabilities: {
+        auto* capabilities_message = reinterpret_cast<AnnounceCapabilities*>(message->data);
+        if (capabilities_message->request) {
+            auto capabilities_buffer = AnnounceCapabilities::make_buffer(false, { Capability::ClipboardByDemand });
+            send_message(capabilities_buffer);
+        }
+        break;
+    }
+    case (u32)MessageType::ClipboardRequest: {
+        auto clip_data = m_clipboard_connection.get_clipboard_data().data();
+        ByteBuffer byte_buffer = ByteBuffer::copy(clip_data.data<void>(), clip_data.size());
+        auto clipboard_buffer = Clipboard::make_buffer(ClipboardType::Text, byte_buffer);
+        send_message(clipboard_buffer);
+        break;
+    }
+    case (u32)MessageType::ClipboardGrab: {
+        auto request_buffer = ClipboardRequest::make_buffer(ClipboardType::Text);
+        send_message(request_buffer);
+        break;
+    }
+    case (u32)MessageType::Clipboard: {
+        auto* clipboard_message = reinterpret_cast<Clipboard*>(message->data);
+        auto data_buffer = ByteBuffer::create_uninitialized(message->size - sizeof(u32));
+
+        const auto total_bytes = message->size - sizeof(Clipboard);
+        auto bytes_copied = header.size - sizeof(Message) - sizeof(Clipboard);
+        memcpy(data_buffer.data(), clipboard_message->data, bytes_copied);
+
+        while (bytes_copied < total_bytes) {
+            ChunkHeader next_header;
+            read_n(&next_header, sizeof(ChunkHeader));
+            read_n(data_buffer.data() + bytes_copied, next_header.size);
+            bytes_copied += next_header.size;
+        }
+
+        m_just_set_clip = true;
+        auto anon_buffer = Core::AnonymousBuffer::create_with_size(data_buffer.size());
+        memcpy(anon_buffer.data<void>(), data_buffer.data(), data_buffer.size());
+        m_clipboard_connection.async_set_clipboard_data(anon_buffer, "text/plain", {});
+        break;
+    }
+    default:
+        dbgln("Unhandled message type {}", message->type);
+    }
+}
+
+void SpiceAgent::read_n(void* dest, size_t n)
+{
+    size_t bytes_read = 0;
+    while (bytes_read < n) {
+        int nread = read(m_fd, (u8*)dest + bytes_read, n - bytes_read);
+        if (nread > 0) {
+            bytes_read += nread;
+        } else if (errno == EAGAIN) {
+            continue;
+        } else {
+            dbgln("Failed to read: {}", errno);
+            return;
+        }
+    }
+}
+
+void SpiceAgent::send_message(ByteBuffer const& buffer)
+{
+    size_t bytes_written = 0;
+    while (bytes_written < buffer.size()) {
+        int result = write(m_fd, buffer.data() + bytes_written, buffer.size() - bytes_written);
+        if (result < 0) {
+            dbgln("Failed to write: {}", errno);
+            return;
+        }
+        bytes_written += result;
+    }
+}
+
+SpiceAgent::Message* SpiceAgent::initialize_headers(u8* data, size_t additional_data_size, MessageType type)
+{
+    new (data) ChunkHeader {
+        (u32)Port::Client,
+        (u32)(sizeof(Message) + additional_data_size)
+    };
+
+    auto* message = new (data + sizeof(ChunkHeader)) Message {
+        AGENT_PROTOCOL,
+        (u32)type,
+        0,
+        (u32)additional_data_size
+    };
+    return message;
+}
+
+ByteBuffer SpiceAgent::AnnounceCapabilities::make_buffer(bool request, const Vector<Capability>& capabilities)
+{
+    size_t required_size = sizeof(ChunkHeader) + sizeof(Message) + sizeof(AnnounceCapabilities);
+    auto buffer = ByteBuffer::create_uninitialized(required_size);
+    u8* data = buffer.data();
+
+    auto* message = initialize_headers(data, sizeof(AnnounceCapabilities), MessageType::AnnounceCapabilities);
+
+    auto* announce_message = new (message->data) AnnounceCapabilities {
+        request,
+        {}
+    };
+
+    for (auto& cap : capabilities) {
+        announce_message->caps[0] |= (1 << (u32)cap);
+    }
+
+    return buffer;
+}
+
+ByteBuffer SpiceAgent::ClipboardGrab::make_buffer(const Vector<ClipboardType>& types)
+{
+    VERIFY(types.size() > 0);
+    size_t variable_data_size = sizeof(u32) * types.size();
+    size_t required_size = sizeof(ChunkHeader) + sizeof(Message) + variable_data_size;
+    auto buffer = ByteBuffer::create_uninitialized(required_size);
+    u8* data = buffer.data();
+
+    auto* message = initialize_headers(data, variable_data_size, MessageType::ClipboardGrab);
+
+    auto* grab_message = new (message->data) ClipboardGrab {};
+
+    for (auto i = 0u; i < types.size(); i++) {
+        grab_message->types[i] = (u32)types[i];
+    }
+
+    return buffer;
+}
+
+ByteBuffer SpiceAgent::Clipboard::make_buffer(ClipboardType type, ReadonlyBytes contents)
+{
+    size_t data_size = sizeof(Clipboard) + contents.size();
+    size_t required_size = sizeof(ChunkHeader) + sizeof(Message) + data_size;
+    auto buffer = ByteBuffer::create_uninitialized(required_size);
+    u8* data = buffer.data();
+
+    auto* message = initialize_headers(data, data_size, MessageType::Clipboard);
+
+    auto* clipboard_message = new (message->data) Clipboard {
+        .type = (u32)type
+    };
+
+    memcpy(clipboard_message->data, contents.data(), contents.size());
+
+    return buffer;
+}
+
+ByteBuffer SpiceAgent::ClipboardRequest::make_buffer(ClipboardType type)
+{
+    size_t data_size = sizeof(ClipboardRequest);
+    size_t required_size = sizeof(ChunkHeader) + sizeof(Message) + data_size;
+    auto buffer = ByteBuffer::create_uninitialized(required_size);
+    u8* data = buffer.data();
+
+    auto* message = initialize_headers(data, data_size, MessageType::ClipboardRequest);
+    new (message->data) ClipboardRequest {
+        .type = (u32)type
+    };
+
+    return buffer;
+}