Add a utility for spawning subprocesses

include/gz/utils/Subprocess.hh

@@ -0,0 +1,165 @@
+/*
+ * Copyright (C) 2023 Open Source Robotics Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GZ_UTILS__SUBPROCESS_HH_
+#define GZ_UTILS__SUBPROCESS_HH_
+
+#include "detail/subprocess.h"
+#include <string>
+#include <vector>
+
+#include <gz/utils/detail/subprocess.h>
+
+// This header contains a wrapper to the cross-platform subprocess library.
+// It can be used to spawn processes to interact with, primarily for testing.
+
+namespace gz
+{
+namespace utils
+{
+
+class Subprocess
+{
+  public: Subprocess(const std::vector<std::string> &_commandLine,
+                     const std::vector<std::string> &_environment = {}):
+    commandLine(_commandLine),
+    environment(_environment)
+  {
+    this->Create();
+  }
+
+  private: void Create()
+  {
+    if (this->process)
+        return;
+
+    this->process = new subprocess_s;
+
+    std::vector<const char*> commandLineCstr;
+    for (const auto &val : this->commandLine)
+    {
+      commandLineCstr.push_back(val.c_str());
+    }
+    commandLineCstr.push_back(nullptr);
+
+    std::vector<const char*> environmentCstr;
+    for (const auto &val : this->environment)
+    {
+      environmentCstr.push_back(val.c_str());
+    }
+    environmentCstr.push_back(nullptr);
+
+    int ret = -1;
+    if (this->environment.size())
+    {
+      ret = subprocess_create_ex(commandLineCstr.data(),
+                                 0, environmentCstr.data(), this->process);
+    }
+    else
+    {
+      ret = subprocess_create(commandLineCstr.data(), 0, this->process);
+    }
+
+    if (0 != ret)
+    {
+      std::cerr << "failed to create subprocess" << std::endl;
+      delete this->process;
+      this->process = nullptr;
+    }
+  }
+
+  public: ~Subprocess()
+  {
+    if (this->process)
+      subprocess_destroy(this->process);
+    delete this->process;
+  }
+
+  public: std::string Stdout()
+  {
+    std::string result{""};
+    if (this->process)
+    {
+      auto p_stdout = subprocess_stdout(this->process);
+      char buffer[128];
+      while (!feof(p_stdout))
+      {
+        if (fgets(buffer, 128, p_stdout) != NULL)
+          result += buffer;
+      }
+    }
+    return result;
+  }
+
+  public: std::string Stderr()
+  {
+    std::string result{""};
+    if (this->process)
+    {
+      auto p_stdout = subprocess_stderr(this->process);
+      char buffer[128];
+      while (!feof(p_stdout))
+      {
+        if (fgets(buffer, 128, p_stdout) != NULL)
+          result += buffer;
+      }
+    }
+    return result;
+
+  }
+
+  public: bool Alive()
+  {
+    if (this->process)
+      return subprocess_alive(this->process);
+    else
+      return false;
+  }
+
+  public: bool Terminate()
+  {
+    if (this->process)
+      return subprocess_terminate(this->process) != 0;
+    else
+      return false;
+  }
+
+  public: int Join()
+  {
+    int return_code = -1;
+    if (this->process)
+    {
+      auto ret = subprocess_join(this->process, &return_code);
+      if (ret != 0)
+      {
+        std::cerr << "Failed to join subprocess" << std::endl;
+      }
+    }
+
+    return return_code;
+  }
+
+  protected: std::vector<std::string> commandLine;
+
+  protected: std::vector<std::string> environment;
+
+  protected: subprocess_s * process {nullptr};
+};
+}  // namespace utils
+}  // namespace gz
+
+#endif  // GZ_UTILS__SUBPROCESS_HH_