From 6cd172c32ebe79692e19433f49716e58c57c8677 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Wed, 27 Apr 2016 18:47:01 +0200
Subject: Rework process internals, add current_id()

---
 NEWS             |  4 ++++
 butl/process     | 22 +++++++++++++++-------
 butl/process.cxx | 32 ++++++++++++++++++++++----------
 butl/process.ixx | 12 ++++++------
 4 files changed, 47 insertions(+), 23 deletions(-)

diff --git a/NEWS b/NEWS
index d406f23..dfcbd6c 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,7 @@
+Version 0.4.0
+
+  * Add process::current_id().
+
 Version 0.3.0
 
   * Add SHA256 hash calculator based on code from the FreeBSD project. That
diff --git a/butl/process b/butl/process
index ef8c057..c485835 100644
--- a/butl/process
+++ b/butl/process
@@ -10,6 +10,7 @@
 #endif
 
 #include <cassert>
+#include <cstdint> // uint32_t
 #include <system_error>
 
 namespace butl
@@ -26,8 +27,9 @@ namespace butl
     bool child_;
   };
 
-  struct process
+  class process
   {
+  public:
     // Start another process using the specified command line. The default
     // values to the in, out and err arguments indicate that the child
     // process should inherit the parent process stdin, stdout, and stderr,
@@ -81,7 +83,7 @@ namespace butl
     bool
     try_wait (bool&);
 
-    ~process () {if (id != 0) wait ();}
+    ~process () {if (handle != 0) wait ();}
 
     // Moveable-only type.
     //
@@ -91,20 +93,26 @@ namespace butl
     process (const process&) = delete;
     process& operator= (const process&) = delete;
 
-    // Create an empty or "already terminated" process. That is, id is 0
+    // Create an empty or "already terminated" process. That is, handle is 0
     // and exit status is 0.
     //
     process ();
 
   public:
 #ifndef _WIN32
-    typedef pid_t id_type;
-    typedef int status_type;
+    using handle_type = pid_t;
+    using id_type = pid_t;
+    using status_type = int;
 #else
-    typedef void* id_type; // Win32 HANDLE.
+    using handle_type = void*;      // Win32 HANDLE
+    using id_type = std::uint32_t;  // Win32 DWORD
 #endif
 
-    id_type id;
+    static id_type
+    current_id ();
+
+  public:
+    handle_type handle;
     status_type status;
 
     int out_fd; // Write to this fd to send to the new process' stdin.
diff --git a/butl/process.cxx b/butl/process.cxx
index 4203735..f00f03a 100644
--- a/butl/process.cxx
+++ b/butl/process.cxx
@@ -5,7 +5,7 @@
 #include <butl/process>
 
 #ifndef _WIN32
-#  include <unistd.h>    // execvp, fork, dup2, pipe, chdir, *_FILENO
+#  include <unistd.h>    // execvp, fork, dup2, pipe, chdir, *_FILENO, getpid
 #  include <sys/wait.h>  // waitpid
 #else
 #  ifndef WIN32_LEAN_AND_MEAN
@@ -36,12 +36,12 @@ namespace butl
         (err == -1 && pipe (in_efd) == -1))
       throw process_error (errno, false);
 
-    id = fork ();
+    handle = fork ();
 
-    if (id == -1)
+    if (handle == -1)
       throw process_error (errno, false);
 
-    if (id == 0)
+    if (handle == 0)
     {
       // Child. If requested, close the write end of the pipe and duplicate
       // the read end to stdin. Then close the original read end descriptor.
@@ -109,10 +109,10 @@ namespace butl
   bool process::
   wait ()
   {
-    if (id != 0)
+    if (handle != 0)
     {
-      int r (waitpid (id, &status, 0));
-      id = 0; // We have tried.
+      int r (waitpid (handle, &status, 0));
+      handle = 0; // We have tried.
 
       if (r == -1)
         throw process_error (errno, false);
@@ -124,14 +124,14 @@ namespace butl
   bool process::
   try_wait (bool& s)
   {
-    if (id != 0)
+    if (handle != 0)
     {
-      int r (waitpid (id, &status, WNOHANG));
+      int r (waitpid (handle, &status, WNOHANG));
 
       if (r == 0) // Not exited yet.
         return false;
 
-      id = 0; // We have tried.
+      handle = 0; // We have tried.
 
       if (r == -1)
         throw process_error (errno, false);
@@ -141,8 +141,20 @@ namespace butl
     return true;
   }
 
+  process::id_type process::
+  current_id ()
+  {
+    return getpid ();
+  }
+
 #else // _WIN32
 
+  process::id_type process::
+  current_id ()
+  {
+    return GetCurrentProcessId ();
+  }
+
   static void
   print_error (char const* name)
   {
diff --git a/butl/process.ixx b/butl/process.ixx
index e840372..3b7ed7d 100644
--- a/butl/process.ixx
+++ b/butl/process.ixx
@@ -6,7 +6,7 @@ namespace butl
 {
   inline process::
   process ()
-      : id (0),
+      : handle (0),
         status (0), // This is a bit of an assumption.
         out_fd (-1),
         in_ofd (-1),
@@ -24,13 +24,13 @@ namespace butl
 
   inline process::
   process (process&& p)
-      : id (p.id),
+      : handle (p.handle),
         status (p.status),
         out_fd (p.out_fd),
         in_ofd (p.in_ofd),
         in_efd (p.in_efd)
   {
-    p.id = 0;
+    p.handle = 0;
   }
 
   inline process& process::
@@ -38,16 +38,16 @@ namespace butl
   {
     if (this != &p)
     {
-      if (id != 0)
+      if (handle != 0)
         wait ();
 
-      id = p.id;
+      handle = p.handle;
       status = p.status;
       out_fd = p.out_fd;
       in_ofd = p.in_ofd;
       in_efd = p.in_efd;
 
-      p.id = 0;
+      p.handle = 0;
     }
 
     return *this;
-- 
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