[kernel] Add channel objects

Add the channel object for sending messages between threads. Currently
no good of passing channels to other threads, but global variables in a
single process work. Currently channels are slow and do double copies,
need to refine more.

Tags: ipc

src/kernel/objects/channel.cpp

@@ -0,0 +1,70 @@
+#include "kutil/assert.h"
+
+#include "objects/channel.h"
+
+channel::channel() :
+	m_len(0),
+	m_capacity(0),
+	m_data(nullptr),
+	kobject(kobject::type::channel, j6_signal_channel_can_send)
+{
+}
+
+channel::~channel()
+{
+	kutil::kfree(m_data);
+}
+
+j6_status_t
+channel::enqueue(size_t len, void *data)
+{
+	// TODO: Make this thread safe!
+	if (closed())
+		return j6_status_closed;
+
+	if (!can_send())
+		return j6_err_not_ready;
+
+	if (m_capacity < len) {
+		kutil::kfree(m_data);
+		m_data = kutil::kalloc(len);
+		m_capacity = len;
+		kassert(m_data, "Failed to allocate memory to copy channel message");
+	}
+
+	m_len = len;
+	kutil::memcpy(m_data, data, len);
+	assert_signal(j6_signal_channel_can_recv);
+
+	return j6_status_ok;
+}
+
+j6_status_t
+channel::dequeue(size_t *len, void *data)
+{
+	// TODO: Make this thread safe!
+	if (closed())
+		return j6_status_closed;
+
+	if (!can_receive())
+		return j6_err_not_ready;
+
+	if (!len)
+		return j6_err_invalid_arg;
+
+	if (*len < m_len)
+		return j6_err_insufficient;
+
+	kutil::memcpy(data, m_data, m_len);
+	*len = m_len;
+	assert_signal(j6_signal_channel_can_send);
+
+	return j6_status_ok;
+}
+
+void
+channel::on_no_handles()
+{
+	kobject::on_no_handles();
+	delete this;
+}