Extract process-management functionality into a new lib/process

Note that procmon does *not* go here, since procmon needs to
integrate with the event loop.

src/lib/process/subprocess.h

@@ -0,0 +1,129 @@
+/* Copyright (c) 2003-2004, Roger Dingledine
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2018, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#ifndef TOR_SUBPROCESS_H
+#define TOR_SUBPROCESS_H
+
+#include "lib/cc/torint.h"
+#include "lib/testsupport/testsupport.h"
+#include <stddef.h>
+#ifdef _WIN32
+#include <windows.h>
+#endif
+
+struct smartlist_t;
+
+void tor_disable_spawning_background_processes(void);
+
+typedef struct process_handle_t process_handle_t;
+struct process_environment_t;
+int tor_spawn_background(const char *const filename, const char **argv,
+                         struct process_environment_t *env,
+                         process_handle_t **process_handle_out);
+
+#define SPAWN_ERROR_MESSAGE "ERR: Failed to spawn background process - code "
+
+/** Status of an I/O stream. */
+enum stream_status {
+  IO_STREAM_OKAY,
+  IO_STREAM_EAGAIN,
+  IO_STREAM_TERM,
+  IO_STREAM_CLOSED
+};
+
+const char *stream_status_to_string(enum stream_status stream_status);
+
+enum stream_status get_string_from_pipe(int fd, char *buf, size_t count);
+
+/* Values of process_handle_t.status. */
+#define PROCESS_STATUS_NOTRUNNING 0
+#define PROCESS_STATUS_RUNNING 1
+#define PROCESS_STATUS_ERROR -1
+
+#ifdef SUBPROCESS_PRIVATE
+struct waitpid_callback_t;
+
+/** Structure to represent the state of a process with which Tor is
+ * communicating. The contents of this structure are private to util.c */
+struct process_handle_t {
+  /** One of the PROCESS_STATUS_* values */
+  int status;
+#ifdef _WIN32
+  HANDLE stdin_pipe;
+  HANDLE stdout_pipe;
+  HANDLE stderr_pipe;
+  PROCESS_INFORMATION pid;
+#else /* !(defined(_WIN32)) */
+  int stdin_pipe;
+  int stdout_pipe;
+  int stderr_pipe;
+  pid_t pid;
+  /** If the process has not given us a SIGCHLD yet, this has the
+   * waitpid_callback_t that gets invoked once it has. Otherwise this
+   * contains NULL. */
+  struct waitpid_callback_t *waitpid_cb;
+  /** The exit status reported by waitpid. */
+  int waitpid_exit_status;
+#endif /* defined(_WIN32) */
+};
+#endif /* defined(SUBPROCESS_PRIVATE) */
+
+/* Return values of tor_get_exit_code() */
+#define PROCESS_EXIT_RUNNING 1
+#define PROCESS_EXIT_EXITED 0
+#define PROCESS_EXIT_ERROR -1
+int tor_get_exit_code(process_handle_t *process_handle,
+                      int block, int *exit_code);
+int tor_split_lines(struct smartlist_t *sl, char *buf, int len);
+#ifdef _WIN32
+ssize_t tor_read_all_handle(HANDLE h, char *buf, size_t count,
+                            const process_handle_t *process);
+#else
+ssize_t tor_read_all_handle(int fd, char *buf, size_t count,
+                            const process_handle_t *process,
+                            int *eof);
+#endif /* defined(_WIN32) */
+ssize_t tor_read_all_from_process_stdout(
+    const process_handle_t *process_handle, char *buf, size_t count);
+ssize_t tor_read_all_from_process_stderr(
+    const process_handle_t *process_handle, char *buf, size_t count);
+char *tor_join_win_cmdline(const char *argv[]);
+
+int tor_process_get_pid(process_handle_t *process_handle);
+#ifdef _WIN32
+HANDLE tor_process_get_stdout_pipe(process_handle_t *process_handle);
+#else
+int tor_process_get_stdout_pipe(process_handle_t *process_handle);
+#endif
+
+#ifdef _WIN32
+MOCK_DECL(struct smartlist_t *, tor_get_lines_from_handle,(HANDLE *handle,
+                           enum stream_status *stream_status));
+#else
+MOCK_DECL(struct smartlist_t *, tor_get_lines_from_handle,(int fd,
+                                       enum stream_status *stream_status));
+#endif /* defined(_WIN32) */
+
+int tor_terminate_process(process_handle_t *process_handle);
+
+MOCK_DECL(void, tor_process_handle_destroy,(process_handle_t *process_handle,
+                                            int also_terminate_process));
+
+#ifdef SUBPROCESS_PRIVATE
+/* Prototypes for private functions only used by util.c (and unit tests) */
+
+#ifndef _WIN32
+STATIC int format_helper_exit_status(unsigned char child_state,
+                              int saved_errno, char *hex_errno);
+
+/* Space for hex values of child state, a slash, saved_errno (with
+   leading minus) and newline (no null) */
+#define HEX_ERRNO_SIZE (sizeof(char) * 2 + 1 + \
+                        1 + sizeof(int) * 2 + 1)
+#endif /* !defined(_WIN32) */
+
+#endif /* defined(SUBPROCESS_PRIVATE) */
+
+#endif