Add a basic IPC setup with Channel Object.

Pass a process a channel endpoint on startup that it will use to
get it's initial capabilities.

zion/object/channel.cpp

@@ -0,0 +1,61 @@
+#include "object/channel.h"
+
+#include "include/zerrors.h"
+
+Pair<RefPtr<Channel>, RefPtr<Channel>> Channel::CreateChannelPair() {
+  auto c1 = MakeRefCounted<Channel>();
+  auto c2 = MakeRefCounted<Channel>();
+  c1->SetPeer(c2);
+  c2->SetPeer(c1);
+  return {c1, c2};
+}
+
+uint64_t Channel::Write(const ZMessage& msg) {
+  return peer_->EnqueueMessage(msg);
+}
+
+uint64_t Channel::Read(ZMessage& msg) {
+  if (pending_messages_.size() == 0) {
+    dbgln("Unimplemented add blocking.");
+    return ZE_UNIMPLEMENTED;
+  }
+  Message next_msg = pending_messages_.PeekFront();
+  if (next_msg.num_bytes > msg.num_bytes) {
+    return ZE_BUFF_SIZE;
+  }
+
+  msg.type = next_msg.type;
+  msg.num_bytes = next_msg.num_bytes;
+  msg.num_caps = 0;
+
+  for (uint64_t i = 0; i < msg.num_bytes; i++) {
+    msg.bytes[i] = next_msg.bytes[i];
+  }
+
+  pending_messages_.PopFront();
+
+  return Z_OK;
+}
+
+uint64_t Channel::EnqueueMessage(const ZMessage& msg) {
+  if (msg.num_caps > 0) {
+    dbgln("Unimplemented passing caps on channel");
+    return ZE_UNIMPLEMENTED;
+  }
+
+  if (msg.num_bytes > 0x1000) {
+    dbgln("Large message size unimplemented: %x", msg.num_bytes);
+    return ZE_INVALID;
+  }
+
+  Message message{
+      .type = msg.type,
+      .num_bytes = msg.num_bytes,
+      .bytes = new uint8_t[msg.num_bytes],
+  };
+  for (uint64_t i = 0; i < msg.num_bytes; i++) {
+    message.bytes[i] = msg.bytes[i];
+  }
+  pending_messages_.PushBack(message);
+  return Z_OK;
+}