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/Process.cpp

@@ -0,0 +1,78 @@
+/*----------------------------------------------------------------------------*/
+/* 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/Process.h"
+
+#include "wpi/SmallString.h"
+#include "wpi/uv/Loop.h"
+#include "wpi/uv/Pipe.h"
+
+namespace wpi {
+namespace uv {
+
+ProcessOptions& ProcessOptions::StdioIgnore(size_t index) {
+  if (index >= m_stdio.size()) m_stdio.resize(index + 1);
+  m_stdio[index].flags = UV_IGNORE;
+  m_stdio[index].data.fd = 0;
+  return *this;
+}
+
+ProcessOptions& ProcessOptions::StdioInherit(size_t index, int fd) {
+  if (index >= m_stdio.size()) m_stdio.resize(index + 1);
+  m_stdio[index].flags = UV_INHERIT_FD;
+  m_stdio[index].data.fd = fd;
+  return *this;
+}
+
+ProcessOptions& ProcessOptions::StdioInherit(size_t index, Pipe& pipe) {
+  if (index >= m_stdio.size()) m_stdio.resize(index + 1);
+  m_stdio[index].flags = UV_INHERIT_STREAM;
+  m_stdio[index].data.stream = pipe.GetRawStream();
+  return *this;
+}
+
+ProcessOptions& ProcessOptions::StdioCreatePipe(size_t index, Pipe& pipe,
+                                                unsigned int flags) {
+  if (index >= m_stdio.size()) m_stdio.resize(index + 1);
+  m_stdio[index].flags = static_cast<uv_stdio_flags>(UV_CREATE_PIPE | flags);
+  m_stdio[index].data.stream = pipe.GetRawStream();
+  return *this;
+}
+
+std::shared_ptr<Process> Process::Spawn(Loop& loop, const Twine& file,
+                                        char** args,
+                                        const ProcessOptions& options) {
+  // convert ProcessOptions to libuv structure
+  SmallString<128> fileBuf;
+  uv_process_options_t coptions;
+  coptions.exit_cb = [](uv_process_t* handle, int64_t status, int signal) {
+    auto& h = *static_cast<Process*>(handle->data);
+    h.exited(status, signal);
+  };
+  coptions.file = file.toNullTerminatedStringRef(fileBuf).data();
+  coptions.args = args;
+  coptions.env = options.m_env;
+  coptions.cwd = options.m_cwd.empty() ? nullptr : options.m_cwd.c_str();
+  coptions.flags = options.m_flags;
+  coptions.stdio_count = options.m_stdio.size();
+  coptions.stdio = const_cast<uv_stdio_container_t*>(
+      static_cast<const uv_stdio_container_t*>(options.m_stdio.data()));
+  coptions.uid = options.m_uid;
+  coptions.gid = options.m_gid;
+
+  auto h = std::make_shared<Process>(private_init{});
+  int err = uv_spawn(loop.GetRaw(), h->GetRaw(), &coptions);
+  if (err < 0) {
+    loop.ReportError(err);
+    return nullptr;
+  }
+  h->Keep();
+  return h;
+}
+
+}  // namespace uv
+}  // namespace wpi