[wpinet] Move network portions of wpiutil into new wpinet library (#4077)

wpinet/src/main/native/cpp/hostname.cpp

@@ -0,0 +1,58 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include "wpinet/hostname.h"
+
+#include <cstdlib>
+#include <string>
+#include <string_view>
+
+#include <wpi/SmallVector.h>
+
+#include "uv.h"
+
+namespace wpi {
+
+std::string GetHostname() {
+  std::string rv;
+  char name[256];
+  size_t size = sizeof(name);
+
+  int err = uv_os_gethostname(name, &size);
+  if (err == 0) {
+    rv.assign(name, size);
+  } else if (err == UV_ENOBUFS) {
+    char* name2 = static_cast<char*>(std::malloc(size));
+    err = uv_os_gethostname(name2, &size);
+    if (err == 0) {
+      rv.assign(name2, size);
+    }
+    std::free(name2);
+  }
+
+  return rv;
+}
+
+std::string_view GetHostname(SmallVectorImpl<char>& name) {
+  // Use a tmp array to not require the SmallVector to be too large.
+  char tmpName[256];
+  size_t size = sizeof(tmpName);
+
+  name.clear();
+
+  int err = uv_os_gethostname(tmpName, &size);
+  if (err == 0) {
+    name.append(tmpName, tmpName + size);
+  } else if (err == UV_ENOBUFS) {
+    name.resize(size);
+    err = uv_os_gethostname(name.data(), &size);
+    if (err != 0) {
+      size = 0;
+    }
+  }
+
+  return {name.data(), size};
+}
+
+}  // namespace wpi