From 374db6aebec2a008538c7708305b9be01000c013 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Sat, 22 Jul 2017 14:15:35 +0200
Subject: Add touch_file() filesystem function

---
 libbutl/filesystem.cxx | 29 +++++++++++++++++++++++++++++
 libbutl/filesystem.hxx |  8 ++++++++
 2 files changed, 37 insertions(+)

diff --git a/libbutl/filesystem.cxx b/libbutl/filesystem.cxx
index 70597b9..7ba5275 100644
--- a/libbutl/filesystem.cxx
+++ b/libbutl/filesystem.cxx
@@ -6,6 +6,7 @@
 
 #ifndef _WIN32
 #  include <stdio.h>     // rename()
+#  include <utime.h>     // utime()
 #  include <dirent.h>    // struct dirent, *dir()
 #  include <unistd.h>    // symlink(), link(), stat(), rmdir(), unlink()
 #  include <sys/time.h>  // utimes()
@@ -18,6 +19,7 @@
 #  include <direct.h>    // _mkdir(), _rmdir()
 #  include <sys/types.h> // _stat
 #  include <sys/stat.h>  // _stat(), S_I*
+#  include <sys/utime.h> // _utime()
 
 #  ifdef _MSC_VER // Unlikely to be fixed in newer versions.
 #    define S_ISREG(m) (((m) & S_IFMT) == S_IFREG)
@@ -153,6 +155,33 @@ namespace butl
   }
 #endif
 
+  bool
+  touch_file (const path& p, bool create)
+  {
+    if (file_exists (p))
+    {
+#ifndef _WIN32
+      if (utime  (p.string ().c_str (), nullptr) == -1)
+#else
+      if (_utime (p.string ().c_str (), nullptr) == -1)
+#endif
+        throw_generic_error (errno);
+
+      return false;
+    }
+
+    if (create && !entry_exists (p))
+    {
+      // Assuming the file access and modification times are set to the
+      // current time automatically.
+      //
+      fdopen (p, fdopen_mode::out | fdopen_mode::create);
+      return true;
+    }
+
+    throw_generic_error (ENOENT); // Does not exist or not a file.
+  }
+
   mkdir_status
 #ifndef _WIN32
   try_mkdir (const dir_path& p, mode_t m)
diff --git a/libbutl/filesystem.hxx b/libbutl/filesystem.hxx
index 9bf6f0c..ef1b22b 100644
--- a/libbutl/filesystem.hxx
+++ b/libbutl/filesystem.hxx
@@ -104,6 +104,14 @@ namespace butl
   bool
   file_empty (const path&);
 
+  // Set the file access and modification times to the current time. If the
+  // file does not exist and create is true, create it and fail otherwise.
+  // Return true if the file was created and false otherwise. Errors are
+  // reported by throwing std::system_error.
+  //
+  LIBBUTL_SYMEXPORT bool
+  touch_file (const path&, bool create = true);
+
   // Try to create a directory unless it already exists. If you expect
   // the directory to exist and performance is important, then you
   // should first call dir_exists() above since that's what this
-- 
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