wpiutil: Add C++ libuv wrappers (#1166)

- Provide an EventLoopRunner to run uv::Loop on a separate thread.

- Add raw_ostream wrapper for uv::Buffer.

wpiutil/src/main/native/cpp/uv/Pipe.cpp

@@ -0,0 +1,115 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2018 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#include "wpi/uv/Pipe.h"
+
+#include <cstdlib>
+
+#include "wpi/SmallString.h"
+
+namespace wpi {
+namespace uv {
+
+std::shared_ptr<Pipe> Pipe::Create(Loop& loop, bool ipc) {
+  auto h = std::make_shared<Pipe>(private_init{});
+  int err = uv_pipe_init(loop.GetRaw(), h->GetRaw(), ipc ? 1 : 0);
+  if (err < 0) {
+    loop.ReportError(err);
+    return nullptr;
+  }
+  h->Keep();
+  return h;
+}
+
+std::shared_ptr<Pipe> Pipe::Accept() {
+  auto client = Create(GetLoopRef());
+  if (!client) return nullptr;
+  if (!Accept(client)) {
+    client->Release();
+    return nullptr;
+  }
+  return client;
+}
+
+Pipe* Pipe::DoAccept() { return Accept().get(); }
+
+void Pipe::Bind(const Twine& name) {
+  SmallString<128> nameBuf;
+  Invoke(&uv_pipe_bind, GetRaw(),
+         name.toNullTerminatedStringRef(nameBuf).data());
+}
+
+void Pipe::Connect(const Twine& name,
+                   const std::shared_ptr<PipeConnectReq>& req) {
+  SmallString<128> nameBuf;
+  uv_pipe_connect(req->GetRaw(), GetRaw(),
+                  name.toNullTerminatedStringRef(nameBuf).data(),
+                  [](uv_connect_t* req, int status) {
+                    auto& h = *static_cast<PipeConnectReq*>(req->data);
+                    if (status < 0)
+                      h.ReportError(status);
+                    else
+                      h.connected();
+                    h.Release();  // this is always a one-shot
+                  });
+  req->Keep();
+}
+
+void Pipe::Connect(const Twine& name, std::function<void()> callback) {
+  auto req = std::make_shared<PipeConnectReq>();
+  req->connected.connect(callback);
+  Connect(name, req);
+}
+
+std::string Pipe::GetSock() {
+  // Per libuv docs, the returned buffer is NOT null terminated.
+  // common case should be small
+  char buf[128];
+  size_t size = 128;
+  int r = uv_pipe_getsockname(GetRaw(), buf, &size);
+  if (r == 0) {
+    return std::string{buf, size};
+  } else if (r == UV_ENOBUFS) {
+    // need to allocate a big enough buffer
+    char* buf2 = static_cast<char*>(std::malloc(size));
+    r = uv_pipe_getsockname(GetRaw(), buf2, &size);
+    if (r == 0) {
+      std::string out{buf2, size};
+      std::free(buf2);
+      return out;
+    }
+    std::free(buf2);
+  }
+  ReportError(r);
+  return std::string{};
+}
+
+std::string Pipe::GetPeer() {
+  // Per libuv docs, the returned buffer is NOT null terminated.
+  // common case should be small
+  char buf[128];
+  size_t size = 128;
+  int r = uv_pipe_getpeername(GetRaw(), buf, &size);
+  if (r == 0) {
+    return std::string{buf, size};
+  } else if (r == UV_ENOBUFS) {
+    // need to allocate a big enough buffer
+    char* buf2 = static_cast<char*>(std::malloc(size));
+    r = uv_pipe_getpeername(GetRaw(), buf2, &size);
+    if (r == 0) {
+      std::string out{buf2, size};
+      std::free(buf2);
+      return out;
+    }
+    std::free(buf2);
+  }
+  ReportError(r);
+  return std::string{};
+}
+
+}  // namespace uv
+}  // namespace wpi