Work on AudioServer

The center of this is now an ABuffer class in LibAudio.
ABuffer contains ASample, which has two channels (left/right) in
floating point for mixing purposes, in 44100hz.

This means that the loaders (AWavLoader in this case) needs to do some
manipulation to get things in the right format, but that we don't need
to care after format loading is done.

While we're at it, do some correctness fixes. PCM data is unsigned if
it's 8 bit, but 16 bit is signed. And /dev/audio also wants signed 16
bit audio, so give it what it wants.

On top of this, AudioServer now accepts requests to play a buffer.
The IPC mechanism here is pretty much a 1:1 copy-paste from
LibGUI/WindowServer. It can be generalized more in the future, but for
now I want to get AudioServer working decently first :)

Additionally, add a little "aplay" tool to load and play a WAV file. It
will break with large WAVs (run out of memory, heh...) but it's a start.

Future work needs to make AudioServer block buffer submission from
clients until it has played the buffer they are requesting to play.

8 files changed, 468 insertions, 83 deletions

diff --git a/Servers/AudioServer/ASClientConnection.cpp b/Servers/AudioServer/ASClientConnection.cpp
new file mode 100644
index 0000000000..1bd4a9e255
--- /dev/null
+++ b/Servers/AudioServer/ASClientConnection.cpp
@@ -0,0 +1,176 @@
+#include "ASClientConnection.h"
+#include "ASMixer.h"
+
+#include <LibCore/CEventLoop.h>
+#include <LibAudio/ASAPI.h>
+#include <LibAudio/ABuffer.h>
+#include <SharedBuffer.h>
+
+#include <errno.h>
+#include <unistd.h>
+#include <sys/uio.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <stdio.h>
+
+ASClientConnection::ASClientConnection(int fd, int client_id, ASMixer& mixer)
+    : m_socket(fd)
+    , m_notifier(CNotifier(fd, CNotifier::Read))
+    , m_client_id(client_id)
+    , m_mixer(mixer)
+{
+    m_notifier.on_ready_to_read = [this] { drain_client(); };
+    ASAPI_ServerMessage message;
+    message.type = ASAPI_ServerMessage::Type::Greeting;
+    message.greeting.server_pid = getpid();
+    message.greeting.your_client_id = m_client_id;
+    post_message(message);
+    dbg() << "********** S: Created new ASClientConnection " << fd << client_id << " and said hello";
+}
+
+ASClientConnection::~ASClientConnection()
+{
+    dbg() << "********** S: Destroyed ASClientConnection " << m_socket.fd() << m_client_id;
+}
+
+void ASClientConnection::post_message(const ASAPI_ServerMessage& message, const ByteBuffer& extra_data)
+{
+    if (!extra_data.is_empty())
+        const_cast<ASAPI_ServerMessage&>(message).extra_size = extra_data.size();
+
+    struct iovec iov[2];
+    int iov_count = 1;
+
+    iov[0].iov_base = const_cast<ASAPI_ServerMessage*>(&message);
+    iov[0].iov_len = sizeof(message);
+
+    if (!extra_data.is_empty()) {
+        iov[1].iov_base = const_cast<u8*>(extra_data.data());
+        iov[1].iov_len = extra_data.size();
+        ++iov_count;
+    }
+
+    int nwritten = writev(m_socket.fd(), iov, iov_count);
+    if (nwritten < 0) {
+        switch (errno) {
+        case EPIPE:
+            dbgprintf("WSClientConnection::post_message: Disconnected from peer.\n");
+            delete_later();
+            return;
+            break;
+        case EAGAIN:
+            dbgprintf("WSClientConnection::post_message: Client buffer overflowed.\n");
+            did_misbehave();
+            return;
+            break;
+        default:
+            perror("WSClientConnection::post_message writev");
+            ASSERT_NOT_REACHED();
+        }
+    }
+
+    ASSERT(nwritten == (int)(sizeof(message) + extra_data.size()));
+}
+
+void ASClientConnection::event(CEvent& event)
+{
+    if (event.type() == ASEvent::WM_ClientDisconnected) {
+        int client_id = static_cast<const ASClientDisconnectedNotification&>(event).client_id();
+        dbgprintf("ASClientConnection: Client disconnected: %d\n", client_id);
+        delete this;
+        return;
+    }
+
+    CObject::event(event);
+}
+ 
+void ASClientConnection::drain_client()
+{
+    unsigned messages_received = 0;
+    for (;;) {
+        ASAPI_ClientMessage message;
+        // FIXME: Don't go one message at a time, that's so much context switching, oof.
+        ssize_t nread = recv(m_socket.fd(), &message, sizeof(ASAPI_ClientMessage), MSG_DONTWAIT);
+        if (nread == 0 || (nread == -1 && errno == EAGAIN)) {
+            if (!messages_received) {
+                // TODO: is delete_later() sufficient?
+                CEventLoop::current().post_event(*this, make<ASClientDisconnectedNotification>(m_client_id));
+            }
+            break;
+        }
+        if (nread < 0) {
+            perror("recv");
+            ASSERT_NOT_REACHED();
+        }
+        ByteBuffer extra_data;
+        if (message.extra_size) {
+            if (message.extra_size >= 32768) {
+                dbgprintf("message.extra_size is way too large\n");
+                return did_misbehave();
+            }
+            extra_data = ByteBuffer::create_uninitialized(message.extra_size);
+            // FIXME: We should allow this to time out. Maybe use a socket timeout?
+            int extra_nread = read(m_socket.fd(), extra_data.data(), extra_data.size());
+            if (extra_nread != (int)message.extra_size) {
+                dbgprintf("extra_nread(%d) != extra_size(%d)\n", extra_nread, extra_data.size());
+                if (extra_nread < 0)
+                    perror("read");
+                return did_misbehave();
+            }
+        }
+        if (!handle_message(message, move(extra_data)))
+            return;
+        ++messages_received;
+    }
+}
+
+bool ASClientConnection::handle_message(const ASAPI_ClientMessage& message, const ByteBuffer&)
+{
+    switch (message.type) {
+    case ASAPI_ClientMessage::Type::Greeting:
+        m_pid = message.greeting.client_pid;
+        break;
+    case ASAPI_ClientMessage::Type::PlayBuffer: {
+        // ### ensure that the size is that of a Vector<ASample>
+        Vector<ASample> samples;
+
+        {
+            const auto& shared_buf = SharedBuffer::create_from_shared_buffer_id(message.play_buffer.buffer_id);
+            if (!shared_buf) {
+                did_misbehave();
+                return false;
+            }
+
+            if (shared_buf->size() / sizeof(ASample) > 441000) {
+                did_misbehave();
+                return false;
+            }
+            samples.resize(shared_buf->size() / sizeof(ASample));
+            memcpy(samples.data(), shared_buf->data(), shared_buf->size());
+        }
+
+        // we no longer need the buffer, so acknowledge that it's playing
+        // TODO: rate limit playback here somehow
+        ASAPI_ServerMessage reply;
+        reply.type = ASAPI_ServerMessage::Type::PlayingBuffer;
+        reply.playing_buffer.buffer_id = message.play_buffer.buffer_id;
+        post_message(reply);
+
+        m_mixer.queue(*this, adopt(*new ABuffer(samples)));
+        break;
+    }
+    case ASAPI_ClientMessage::Type::Invalid:
+    default:
+        dbgprintf("ASClientConnection: Unexpected message ID %d\n", int(message.type));
+        did_misbehave();
+    }
+
+    return true;
+}
+
+void ASClientConnection::did_misbehave()
+{
+    dbgprintf("ASClientConnection{%p} (id=%d, pid=%d) misbehaved, disconnecting.\n", this, m_client_id, m_pid);
+    delete_later();
+    m_notifier.set_enabled(false);
+}
diff --git a/Servers/AudioServer/ASClientConnection.h b/Servers/AudioServer/ASClientConnection.h
new file mode 100644
index 0000000000..27f9cd3259
--- /dev/null
+++ b/Servers/AudioServer/ASClientConnection.h
@@ -0,0 +1,84 @@
+#pragma once
+
+#include <LibCore/CObject.h>
+#include <LibCore/CEvent.h>
+#include <LibCore/CIODevice.h>
+#include <LibCore/CNotifier.h>
+
+struct ASAPI_ServerMessage;
+struct ASAPI_ClientMessage;
+
+class ASEvent : public CEvent {
+public:
+    enum Type {
+        Invalid = 2000,
+        WM_ClientDisconnected,
+    };
+    ASEvent() {}
+    explicit ASEvent(Type type)
+        : CEvent(type)
+    {
+    }
+};
+
+class ASClientDisconnectedNotification : public ASEvent {
+public:
+    explicit ASClientDisconnectedNotification(int client_id)
+        : ASEvent(WM_ClientDisconnected)
+        , m_client_id(client_id)
+    {
+    }
+
+    int client_id() const { return m_client_id; }
+
+private:
+    int m_client_id { 0 };
+};
+
+class ASMixer;
+
+class ASClientConnection : public CObject
+{
+public:
+    ASClientConnection(int fd, int client_id, ASMixer& mixer);
+    ~ASClientConnection();
+
+    void post_message(const ASAPI_ServerMessage&, const ByteBuffer& = {});
+    bool handle_message(const ASAPI_ClientMessage&, const ByteBuffer& = {});
+
+    void drain_client();
+
+    void did_misbehave();
+
+    const char* class_name() const override { return "ASClientConnection"; }
+
+protected:
+    void event(CEvent& event) override;
+private:
+    // TODO: A way to create some kind of CIODevice with an open FD would be nice.
+    class ASOpenedSocket : public CIODevice
+    {
+    public:
+        const char* class_name() const override { return "ASOpenedSocket"; }
+        ASOpenedSocket(int fd)
+        {
+            set_fd(fd);
+            set_mode(CIODevice::OpenMode::ReadWrite);
+        }
+
+        bool open(CIODevice::OpenMode) override
+        {
+            ASSERT_NOT_REACHED();
+            return true;
+        };
+
+        int fd() const { return CIODevice::fd(); }
+    };
+
+    ASOpenedSocket m_socket;
+    CNotifier m_notifier;
+    int m_client_id;
+    int m_pid;
+    ASMixer& m_mixer;
+};
+
diff --git a/Servers/AudioServer/ASEventLoop.cpp b/Servers/AudioServer/ASEventLoop.cpp
new file mode 100644
index 0000000000..d68916efd6
--- /dev/null
+++ b/Servers/AudioServer/ASEventLoop.cpp
@@ -0,0 +1,37 @@
+#include "ASEventLoop.h"
+#include "ASClientConnection.h"
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+ASEventLoop::ASEventLoop()
+{
+    unlink("/tmp/asportal");
+
+    sockaddr_un address;
+    address.sun_family = AF_LOCAL;
+    strcpy(address.sun_path, "/tmp/asportal");
+    int rc = bind(m_server_sock.fd(), (const sockaddr*)&address, sizeof(address));
+    ASSERT(rc == 0);
+    rc = listen(m_server_sock.fd(), 5);
+    ASSERT(rc == 0);
+
+    m_server_notifier = make<CNotifier>(m_server_sock.fd(), CNotifier::Read);
+    m_server_notifier->on_ready_to_read = [this] { drain_server(); };
+}
+
+void ASEventLoop::drain_server()
+{
+    sockaddr_un address;
+    socklen_t address_size = sizeof(address);
+    int client_fd = accept(m_server_sock.fd(), (sockaddr*)&address, &address_size);
+    if (client_fd < 0) {
+        dbgprintf("AudioServer: accept() failed: %s\n", strerror(errno));
+    } else {
+        dbgprintf("AudioServer: accept()ed client %d\n", client_fd);
+        static int s_next_client_id = 0;
+        new ASClientConnection(client_fd, s_next_client_id++, m_mixer);
+    }
+}
+
diff --git a/Servers/AudioServer/ASEventLoop.h b/Servers/AudioServer/ASEventLoop.h
new file mode 100644
index 0000000000..c6a5ed259f
--- /dev/null
+++ b/Servers/AudioServer/ASEventLoop.h
@@ -0,0 +1,20 @@
+#pragma once
+
+#include <LibCore/CEventLoop.h>
+#include <LibCore/CLocalSocket.h>
+#include <LibCore/CNotifier.h>
+#include "ASMixer.h"
+
+class ASEventLoop
+{
+public:
+    ASEventLoop();
+    int exec() { return m_event_loop.exec(); }
+private:
+    CEventLoop m_event_loop;
+    CLocalSocket m_server_sock;
+    OwnPtr<CNotifier> m_server_notifier;
+    ASMixer m_mixer;
+
+    void drain_server();
+};
diff --git a/Servers/AudioServer/ASMixer.cpp b/Servers/AudioServer/ASMixer.cpp
new file mode 100644
index 0000000000..15a00dcb4d
--- /dev/null
+++ b/Servers/AudioServer/ASMixer.cpp
@@ -0,0 +1,112 @@
+#include <AK/BufferStream.h>
+#include <LibCore/CThread.h>
+
+#include <limits>
+#include "ASMixer.h"
+
+ASMixer::ASMixer()
+    : m_device("/dev/audio")
+{
+    if (!m_device.open(CIODevice::WriteOnly)) {
+        dbgprintf("Can't open audio device: %s\n", m_device.error_string());
+        return;
+    }
+
+    CThread sound_thread([](void* context) -> int {
+        ASMixer* mixer = (ASMixer*)context;
+        mixer->mix();
+        return 0;
+    }, this);
+}
+
+void ASMixer::queue(ASClientConnection&, const ABuffer& buffer)
+{
+    ASSERT(buffer.size_in_bytes());
+    CLocker lock(m_lock);
+    m_pending_mixing.append(ASMixerBuffer(buffer));
+}
+
+void ASMixer::mix()
+{
+    Vector<ASMixerBuffer> active_mix_buffers;
+
+    for (;;) {
+        {
+            CLocker lock(m_lock);
+            for (const auto& buf : m_pending_mixing)
+                active_mix_buffers.append(buf);
+            m_pending_mixing.clear();
+        }
+
+        // ### use a wakeup of some kind rather than this garbage
+        if (active_mix_buffers.size() == 0) {
+            // nothing to mix yet
+            usleep(10000);
+            continue;
+        }
+
+        int max_size = 0;
+
+        for (auto& buffer : active_mix_buffers) {
+            if (buffer.done)
+                continue;
+            ASSERT(buffer.buffer->size_in_bytes()); // zero sized buffer? how?
+            max_size = max(max_size, buffer.buffer->size_in_bytes() - buffer.pos);
+        }
+
+        // ### clear up 'done' buffers more aggressively
+        if (max_size == 0) {
+            active_mix_buffers.clear();
+            continue;
+        }
+
+        max_size = min(1023, max_size);
+
+        Vector<ASample> mixed_buffer;
+        mixed_buffer.resize(max_size);
+
+        // Mix the buffers together into the output
+        for (auto& buffer : active_mix_buffers) {
+            if (buffer.done)
+                continue;
+            auto& samples = buffer.buffer->samples();
+
+            for (int i = 0; i < max_size && buffer.pos < samples.size(); ++buffer.pos, ++i) {
+                auto& mixed_sample = mixed_buffer[i];
+                mixed_sample += samples[buffer.pos];
+            }
+
+            // clear it later
+            if (buffer.pos == samples.size())
+                buffer.done = true;
+        }
+
+        // output the mixed stuff to the device
+        // max_size is 0 indexed, so add 1.
+        const int output_buffer_byte_size = (max_size + 1) * 2 * 2;
+        ASSERT(output_buffer_byte_size == 4096);
+        ByteBuffer buffer(ByteBuffer::create_uninitialized(output_buffer_byte_size));
+        BufferStream stream(buffer);
+
+        for (int i = 0; i < mixed_buffer.size(); ++i) {
+            auto& mixed_sample = mixed_buffer[i];
+            mixed_sample.clamp();
+
+            i16 out_sample;
+            out_sample = mixed_sample.left * std::numeric_limits<i16>::max();
+            stream << out_sample;
+
+            ASSERT(!stream.at_end()); // we should have enough space for both channels in one buffer!
+            out_sample = mixed_sample.right * std::numeric_limits<i16>::max();
+            stream << out_sample;
+
+            ASSERT(!stream.at_end());
+        }
+
+        if (stream.offset() != 0) {
+            buffer.trim(stream.offset());
+            m_device.write(buffer);
+            mixed_buffer.resize(0);
+        }
+    }
+}
diff --git a/Servers/AudioServer/ASMixer.h b/Servers/AudioServer/ASMixer.h
new file mode 100644
index 0000000000..2cf45fd13f
--- /dev/null
+++ b/Servers/AudioServer/ASMixer.h
@@ -0,0 +1,33 @@
+#pragma once
+
+#include <AK/RefCounted.h>
+#include <AK/ByteBuffer.h>
+#include <LibCore/CFile.h>
+#include <LibCore/CLock.h>
+#include <LibAudio/ABuffer.h>
+#include <AK/NonnullRefPtrVector.h>
+
+class ASClientConnection;
+
+class ASMixer : public RefCounted<ASMixer> {
+public:
+    ASMixer();
+
+    void queue(ASClientConnection&, const ABuffer&);
+
+private:
+    struct ASMixerBuffer {
+        ASMixerBuffer(const NonnullRefPtr<ABuffer>& buf)
+            : buffer(buf)
+        {}
+        NonnullRefPtr<ABuffer> buffer;
+        int pos { 0 };
+        bool done { false };
+    };
+
+    Vector<ASMixerBuffer> m_pending_mixing;
+    CFile m_device;
+    CLock m_lock;
+
+    void mix();
+};
diff --git a/Servers/AudioServer/Makefile b/Servers/AudioServer/Makefile
index 74b7b9c22d..e813207d10 100644
--- a/Servers/AudioServer/Makefile
+++ b/Servers/AudioServer/Makefile
@@ -1,7 +1,10 @@
 include ../../Makefile.common
 
 AUDIOSERVER_OBJS = \
-    main.o
+    main.o \
+    ASMixer.o \
+    ASClientConnection.o \
+    ASEventLoop.o
 
 APP = AudioServer
 OBJS = $(AUDIOSERVER_OBJS)
@@ -11,7 +14,7 @@ DEFINES += -DUSERLAND
 all: $(APP)
 
 $(APP): $(OBJS)
-	$(LD) -o $(APP) $(LDFLAGS) $(OBJS) -lc -lcore -laudio
+	$(LD) -o $(APP) $(LDFLAGS) $(OBJS) -lc -lcore
 
 .cpp.o:
 	@echo "CXX $<"; $(CXX) $(CXXFLAGS) -o $@ -c $<
diff --git a/Servers/AudioServer/main.cpp b/Servers/AudioServer/main.cpp
index 915aad33f5..ac7ef5297b 100644
--- a/Servers/AudioServer/main.cpp
+++ b/Servers/AudioServer/main.cpp
@@ -1,86 +1,6 @@
 #include <LibCore/CFile.h>
-#include <LibCore/CEventLoop.h>
-#include <LibCore/CLocalSocket.h>
-#include <LibCore/CNotifier.h>
-#include <LibAudio/AWavLoader.h>
-#include <LibAudio/AWavFile.h>
 
-#include <sys/types.h>
-#include <sys/socket.h>
-#include <unistd.h>
-
-class ASEventLoop
-{
-public:
-    ASEventLoop();
-    int exec() { return m_event_loop.exec(); }
-private:
-    CEventLoop m_event_loop;
-    CLocalSocket m_server_sock;
-    OwnPtr<CNotifier> m_server_notifier;
-
-    void drain_server();
-};
-
-void read_and_play_wav()
-{
-    CFile audio("/dev/audio");
-    if (!audio.open(CIODevice::WriteOnly)) {
-        dbgprintf("Can't open audio device: %s\n", audio.error_string());
-        return;
-    }
-
-    AWavLoader loader;
-    const auto& file = loader.load_wav("/home/anon/tmp.wav");
-    if (!file) {
-        dbgprintf("Can't parse WAV: %s\n", loader.error_string());
-        return;
-    }
-
-    dbgprintf("Read WAV of format %d with num_channels %d sample rate %d, bits per sample %d\n", (u8)file->format(), file->channel_count(), file->sample_rate_per_second(), file->bits_per_sample());
-
-    auto contents = file->sample_data();
-    const int chunk_size = 4096;
-    int i = 0;
-    while (i < contents.size()) {
-        const auto chunk = contents.slice(i, chunk_size);
-        audio.write(chunk);
-        i += chunk_size;
-    }
-}
-
-ASEventLoop::ASEventLoop()
-{
-    read_and_play_wav();
-
-    unlink("/tmp/asportal");
-
-    sockaddr_un address;
-    address.sun_family = AF_LOCAL;
-    strcpy(address.sun_path, "/tmp/asportal");
-    int rc = bind(m_server_sock.fd(), (const sockaddr*)&address, sizeof(address));
-    ASSERT(rc == 0);
-    rc = listen(m_server_sock.fd(), 5);
-    ASSERT(rc == 0);
-
-    m_server_notifier = make<CNotifier>(m_server_sock.fd(), CNotifier::Read);
-    m_server_notifier->on_ready_to_read = [this] { drain_server(); };
-}
-
-void ASEventLoop::drain_server()
-{
-    sockaddr_un address;
-    socklen_t address_size = sizeof(address);
-    int client_fd = accept(m_server_sock.fd(), (sockaddr*)&address, &address_size);
-    if (client_fd < 0) {
-        dbgprintf("WindowServer: accept() failed: %s\n", strerror(errno));
-    } else {
-        dbgprintf("AudioServer: accept()ed client %d\n", client_fd);
-        String s("hello, client!\n");
-        write(client_fd, s.characters(), s.length());
-        close(client_fd);
-    }
-}
+#include "ASEventLoop.h"
 
 int main(int, char**)
 {