From e4a63cd55c6347dd24938ec8a1ef203409be058e Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Fri, 12 Feb 2016 09:08:32 +0200
Subject: Add path::realize(), which on POSIX calls realpath(3)

---
 butl/path     | 80 +++++++++++++++++++++++++++++++++++------------------------
 butl/path.cxx | 37 ++++++++++++++++++++++++---
 butl/path.ixx | 13 ++++++++++
 3 files changed, 94 insertions(+), 36 deletions(-)

diff --git a/butl/path b/butl/path
index c600e04..1fdc8b6 100644
--- a/butl/path
+++ b/butl/path
@@ -14,6 +14,33 @@
 
 namespace butl
 {
+  class invalid_path_base: std::exception
+  {
+  public:
+    virtual char const*
+    what () const throw ();
+  };
+
+  template <typename C>
+  class invalid_basic_path: public invalid_path_base
+  {
+  public:
+    typedef std::basic_string<C> string_type;
+
+    invalid_basic_path (C const* p): path_ (p) {}
+    invalid_basic_path (string_type const& p): path_ (p) {}
+    ~invalid_basic_path () throw () {}
+
+    string_type const&
+    path () const
+    {
+      return path_;
+    }
+
+  private:
+    string_type path_;
+  };
+
   template <typename C>
   struct path_traits
   {
@@ -123,8 +150,8 @@ namespace butl
       return ln < rn ? -1 : (ln > rn ? 1 : 0);
     }
 
-    // Get/set current working directory. Throw std::system_error
-    // to report the underlying OS errors.
+    // Get/set current working directory. Throw std::system_error to report
+    // the underlying OS errors.
     //
     static string_type
     current ();
@@ -132,6 +159,15 @@ namespace butl
     static void
     current (string_type const&);
 
+    // Make the path real (by calling realpath(3)). Throw invalid_basic_path
+    // if the path is invalid (e.g., some components do not exist) and
+    // std::system_error to report other underlying OS errors.
+    //
+#ifndef _WIN32
+    static void
+    realize (string_type&);
+#endif
+
   private:
 #ifdef _WIN32
     static C
@@ -179,35 +215,6 @@ namespace butl
   typedef basic_path<wchar_t, dir_path_kind<wchar_t>> dir_wpath;
   typedef invalid_basic_path<wchar_t> invalid_wpath;
 
-  //
-  //
-  class invalid_path_base: std::exception
-  {
-  public:
-    virtual char const*
-    what () const throw ();
-  };
-
-  template <typename C>
-  class invalid_basic_path: public invalid_path_base
-  {
-  public:
-    typedef std::basic_string<C> string_type;
-
-    invalid_basic_path (C const* p): path_ (p) {}
-    invalid_basic_path (string_type const& p): path_ (p) {}
-    ~invalid_basic_path () throw () {}
-
-    string_type const&
-    path () const
-    {
-      return path_;
-    }
-
-  private:
-    string_type path_;
-  };
-
   template <typename C>
   class path_data
   {
@@ -477,17 +484,24 @@ namespace butl
     // Normalize the path. This includes collapsing the '.' and '..'
     // directories if possible, collapsing multiple directory
     // separators, and converting all directory separators to the
-    // canonical form. Returns *this.
+    // canonical form. Return *this.
     //
     basic_path&
     normalize ();
 
     // Make the path absolute using the current directory unless
-    // it is already absolute.
+    // it is already absolute. Return *this.
     //
     basic_path&
     complete ();
 
+    // Make the path real, that is, absolute, normalized, and with resolved
+    // symlinks. On POSIX systems this is accomplished with the call to
+    // realpath(3). On Windows -- complete() and normalize(). Return *this.
+    //
+    basic_path&
+    realize ();
+
   public:
     basic_path&
     operator/= (basic_path const&);
diff --git a/butl/path.cxx b/butl/path.cxx
index 5b68749..3e82190 100644
--- a/butl/path.cxx
+++ b/butl/path.cxx
@@ -6,14 +6,15 @@
 
 #ifdef _WIN32
 #  include <stdlib.h> // _MAX_PATH
-#  include <direct.h> // _[w]getcwd, _[w]chdir
+#  include <direct.h> // _[w]getcwd(), _[w]chdir()
 #else
 #  include <errno.h>  // EINVAL
-#  include <stdlib.h> // mbstowcs, wcstombs
+#  include <stdlib.h> // mbstowcs(), wcstombs(), realpath()
 #  include <limits.h> // PATH_MAX
-#  include <unistd.h> // getcwd, chdir
+#  include <unistd.h> // getcwd(), chdir()
 #endif
 
+#include <cassert>
 #include <system_error>
 
 #ifndef _WIN32
@@ -68,6 +69,27 @@ namespace butl
 #endif
   }
 
+#ifndef _WIN32
+  template <>
+  void path_traits<char>::
+  realize (string_type& s)
+  {
+    char r[PATH_MAX];
+    if (realpath (s.c_str (), r) == nullptr)
+    {
+      // @@ If there were a message in invalid_basic_path, we could have said
+      // what exactly is wrong with the path.
+      //
+      if (errno == EACCES || errno == ENOENT || errno == ENOTDIR)
+        throw invalid_basic_path<char> (s);
+      else
+        throw system_error (errno, system_category ());
+    }
+
+    s = r;
+  }
+#endif
+
   //
   // wchar_t
   //
@@ -112,4 +134,13 @@ namespace butl
       throw system_error (errno, system_category ());
 #endif
   }
+
+#ifndef _WIN32
+  template <>
+  void path_traits<wchar_t>::
+  realize (string_type&)
+  {
+    assert (false); // Implement if/when needed.
+  }
+#endif
 }
diff --git a/butl/path.ixx b/butl/path.ixx
index c072075..f933bd3 100644
--- a/butl/path.ixx
+++ b/butl/path.ixx
@@ -177,6 +177,19 @@ namespace butl
   }
 
   template <typename C, typename K>
+  inline basic_path<C, K>& basic_path<C, K>::
+  realize ()
+  {
+#ifdef _WIN32
+    complete ();
+    normalize ();
+#else
+    traits::realize (this->path_);
+#endif
+    return *this;
+  }
+
+  template <typename C, typename K>
   inline typename basic_path<C, K>::dir_type basic_path<C, K>::
   root_directory () const
   {
-- 
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