From e283b08481cfec9aa55b3ddbf369d632c7aa7b0f Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Thu, 18 Mar 2021 15:53:49 +0200
Subject: Add fdstat()

---
 libbutl/fdstream.cxx   | 67 ++++++++++++++++++++++++++++++++++++++++++++------
 libbutl/fdstream.mxx   | 12 +++++++--
 libbutl/filesystem.cxx |  7 +++---
 libbutl/filesystem.mxx |  2 ++
 tests/lz4/driver.cxx   |  6 +----
 5 files changed, 76 insertions(+), 18 deletions(-)

diff --git a/libbutl/fdstream.cxx b/libbutl/fdstream.cxx
index 4948052..308d76c 100644
--- a/libbutl/fdstream.cxx
+++ b/libbutl/fdstream.cxx
@@ -12,20 +12,27 @@
 #  include <unistd.h>     // close(), read(), write(), lseek(), dup(), pipe(),
                           // ftruncate(), isatty(), ssize_t, STD*_FILENO
 #  include <sys/uio.h>    // writev(), iovec
-#  include <sys/stat.h>   // stat(), S_I*
+#  include <sys/stat.h>   // stat(), fstat(), S_I*
 #  include <sys/time.h>   // timeval
 #  include <sys/types.h>  // stat, off_t
 #  include <sys/select.h>
 #else
 #  include <libbutl/win32-utility.hxx>
 
-#  include <io.h>       // _close(), _read(), _write(), _setmode(), _sopen(),
-                        // _lseek(), _dup(), _pipe(), _chsize_s,
-                        // _get_osfhandle()
-#  include <share.h>    // _SH_DENYNO
-#  include <stdio.h>    // _fileno(), stdin, stdout, stderr, SEEK_*
-#  include <fcntl.h>    // _O_*
-#  include <sys/stat.h> // S_I*
+#  include <io.h>        // _close(), _read(), _write(), _setmode(), _sopen(),
+                         // _lseek(), _dup(), _pipe(), _chsize_s,
+                         // _get_osfhandle()
+#  include <share.h>     // _SH_DENYNO
+#  include <stdio.h>     // _fileno(), stdin, stdout, stderr, SEEK_*
+#  include <fcntl.h>     // _O_*
+#  include <sys/types.h> // _stat
+#  include <sys/stat.h>  // fstat(), S_I*
+
+#  ifdef _MSC_VER // Unlikely to be fixed in newer versions.
+#    define S_ISREG(m) (((m) & S_IFMT) == S_IFREG)
+#    define S_ISDIR(m) (((m) & S_IFMT) == S_IFDIR)
+#    define S_ISCHR(m) (((m) & S_IFMT) == S_IFCHR)
+#  endif
 
 #  include <wchar.h> // wcsncmp(), wcsstr()
 
@@ -1372,6 +1379,28 @@ namespace butl
       throw_generic_ios_failure (errno);
   }
 
+  entry_stat
+  fdstat (int fd)
+  {
+    struct stat s;
+    if (fstat (fd, &s) != 0)
+      throw_generic_error (errno);
+
+    auto m (s.st_mode);
+    entry_type t (entry_type::unknown);
+
+    // Note: cannot be a symlink.
+    //
+    if (S_ISREG (m))
+      t = entry_type::regular;
+    else if (S_ISDIR (m))
+      t = entry_type::directory;
+    else if (S_ISBLK (m) || S_ISCHR (m) || S_ISFIFO (m) || S_ISSOCK (m))
+      t = entry_type::other;
+
+    return entry_stat {t, static_cast<uint64_t> (s.st_size)};
+  }
+
   bool
   fdterm (int fd)
   {
@@ -1779,6 +1808,28 @@ namespace butl
       throw_generic_ios_failure (e);
   }
 
+  entry_stat
+  fdstat (int fd)
+  {
+    // Since symlinks have been taken care of, we can just _fstat().
+    //
+    struct __stat64 s;
+    if (_fstat64 (fd, &s) != 0)
+      throw_generic_error (errno);
+
+    auto m (s.st_mode);
+    entry_type t (entry_type::unknown);
+
+    if (S_ISREG (m))
+      t = entry_type::regular;
+    else if (S_ISDIR (m))
+      t = entry_type::directory;
+    else if (S_ISCHR (m))
+      t = entry_type::other;
+
+    return entry_stat {t, static_cast<uint64_t> (s.st_size)};
+  }
+
   bool
   fdterm (int fd)
   {
diff --git a/libbutl/fdstream.mxx b/libbutl/fdstream.mxx
index c863d2c..9818732 100644
--- a/libbutl/fdstream.mxx
+++ b/libbutl/fdstream.mxx
@@ -30,7 +30,7 @@ import std.core;
 import std.io;
 #endif
 import butl.path;
-import butl.filesystem; // permissions
+import butl.filesystem; // permissions, entry_stat
 import butl.small_vector;
 #else
 #include <libbutl/path.mxx>
@@ -862,9 +862,17 @@ LIBBUTL_MODEXPORT namespace butl
   LIBBUTL_SYMEXPORT void
   fdtruncate (int, std::uint64_t);
 
-  // Test whether a file descriptor refers to a terminal. Throw ios::failure on
+  // Return filesystem entry stat from file descriptor. Throw ios::failure on
   // the underlying OS error.
   //
+  // See also path_entry() in filesystem.
+  //
+  LIBBUTL_SYMEXPORT entry_stat
+  fdstat (int);
+
+  // Test whether a file descriptor refers to a terminal. Throw ios::failure
+  // on the underlying OS error.
+  //
   LIBBUTL_SYMEXPORT bool
   fdterm (int);
 
diff --git a/libbutl/filesystem.cxx b/libbutl/filesystem.cxx
index 2147c6f..787747d 100644
--- a/libbutl/filesystem.cxx
+++ b/libbutl/filesystem.cxx
@@ -24,13 +24,14 @@
 #  include <sys/types.h> // _stat
 #  include <sys/stat.h>  // _stat(), S_I*
 
-#  include <cwchar>  // mbsrtowcs(), wcsrtombs(), mbstate_t
-#  include <cstring> // strncmp()
-
 #  ifdef _MSC_VER // Unlikely to be fixed in newer versions.
 #    define S_ISREG(m) (((m) & S_IFMT) == S_IFREG)
 #    define S_ISDIR(m) (((m) & S_IFMT) == S_IFDIR)
+#    define S_ISCHR(m) (((m) & S_IFMT) == S_IFCHR)
 #  endif
+
+#  include <cwchar>  // mbsrtowcs(), wcsrtombs(), mbstate_t
+#  include <cstring> // strncmp()
 #endif
 
 #include <cassert>
diff --git a/libbutl/filesystem.mxx b/libbutl/filesystem.mxx
index 7506439..eb03ab2 100644
--- a/libbutl/filesystem.mxx
+++ b/libbutl/filesystem.mxx
@@ -125,6 +125,8 @@ LIBBUTL_MODEXPORT namespace butl
   // std::system_error, unless ignore_error is true (in which case erroneous
   // entries are treated as non-existent).
   //
+  // See also fdstat() in fdstream.
+  //
   LIBBUTL_SYMEXPORT std::pair<bool, entry_stat>
   path_entry (const char*,
               bool follow_symlinks = false,
diff --git a/tests/lz4/driver.cxx b/tests/lz4/driver.cxx
index e3da5e6..e2fd537 100644
--- a/tests/lz4/driver.cxx
+++ b/tests/lz4/driver.cxx
@@ -24,14 +24,10 @@ try
 
   if (argv[1][1] == 'c')
   {
-    // @@ TODO: would be nice to get it from fd.
-    //
-    entry_stat st (path_entry (argv[2], true /* follow_symlinks */).second);
-
     lz4::compress (ofs, ifs,
                    1 /* compression_level */,
                    4 /* block_size_id (64KB) */,
-                   st.size);
+                   fdstat (ifs.fd ()).size);
   }
   else
   {
-- 
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