cros-disks/process.h

// Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CROS_DISKS_PROCESS_H_
#define CROS_DISKS_PROCESS_H_

#include <string>
#include <vector>

#include <base/files/scoped_file.h>
#include <base/macros.h>

#include <gtest/gtest_prod.h>

namespace cros_disks {

// A base class for executing a process.
//
// TODO(crbug.com/1003654) This base class is not feature complete yet.
class Process {
 public:
  // Invalid process ID assigned to a process that has not started.
  static const pid_t kInvalidProcessId;

  static const int kInvalidFD;

  virtual ~Process();

  // Adds an argument to the end of the argument list. Any argument added by
  // this method does not affect the process that has been started by Start().
  void AddArgument(const std::string& argument);

  // Starts the process without waiting for it to terminate.
  bool Start();

  // Waits for the process to finish and returns its exit status.
  int Wait();

  // Checks if the process finished.
  bool IsFinished();

  // Starts a process, captures its output and waits for it to finish. Returns
  // the same exit status as Wait().
  //
  // Precondition: output is non-null
  int Run(std::vector<std::string>* output);

  pid_t pid() const { return pid_; }

  const std::vector<std::string>& arguments() const { return arguments_; }

 protected:
  Process();

  // Returns the array of arguments used to start the process, or NULL if
  // no arguments is added using AddArgument(). This method calls
  // BuildArgumentsArray() to build |arguments_array_| only once (i.e.
  // when |arguments_array_| is null). Once |arguments_array_| is built,
  // subsequent calls to AddArgument() do not change the return value of
  // this method. The returned array of arguments is managed by the base
  // class.
  char* const* GetArguments();

  virtual pid_t StartImpl(base::ScopedFD* in_fd,
                          base::ScopedFD* out_fd,
                          base::ScopedFD* err_fd) = 0;

  // Once either WaitImpl() or WaitNonBlockingImpl() has returned a nonnegative
  // exit status, none of these methods is called again.

  // Waits for the process to finish and returns its nonnegative exit status.
  virtual int WaitImpl() = 0;

  // Checks if the process has finished and returns its nonnegative exit status,
  // or -1 if the process is still running.
  virtual int WaitNonBlockingImpl() = 0;

 private:
  // Waits for process to finish collecting process' stdout and stderr
  // output and fills interleaved version of it.
  void Communicate(std::vector<std::string>* output);

  // Builds |arguments_array_| and |arguments_buffer_| from |arguments_|.
  // Existing values of |arguments_array_| and |arguments_buffer_| are
  // overridden. Return false if |arguments_| is empty.
  bool BuildArgumentsArray();

  bool finished() const { return status_ >= 0; }

  // Process arguments.
  std::vector<std::string> arguments_;
  std::vector<char*> arguments_array_;
  std::vector<char> arguments_buffer_;

  // Process ID (default to kInvalidProcessId when the process has not started).
  pid_t pid_ = kInvalidProcessId;

  base::ScopedFD in_fd_;
  base::ScopedFD out_fd_;
  base::ScopedFD err_fd_;

  // Exit status. A nonnegative value indicates that the process has finished.
  int status_ = -1;

  FRIEND_TEST(ProcessTest, GetArguments);
  FRIEND_TEST(ProcessTest, GetArgumentsWithNoArgumentsAdded);

  DISALLOW_COPY_AND_ASSIGN(Process);
};

}  // namespace cros_disks

#endif  // CROS_DISKS_PROCESS_H_