Add fdtruncate(), fdseek(), file position to [io]fdstream ctors

3 files changed, 126 insertions, 42 deletions

diff --git a/libbutl/fdstream.cxx b/libbutl/fdstream.cxx
index 72439ae..26d5da3 100644
--- a/libbutl/fdstream.cxx
+++ b/libbutl/fdstream.cxx
@@ -11,7 +11,7 @@
 #ifndef _WIN32
 #  include <fcntl.h>     // open(), O_*, fcntl()
 #  include <unistd.h>    // close(), read(), write(), lseek(), dup(), pipe(),
-                         // isatty(), ssize_t, STD*_FILENO
+                         // ftruncate(), isatty(), ssize_t, STD*_FILENO
 #  include <sys/uio.h>   // writev(), iovec
 #  include <sys/stat.h>  // stat(), S_I*
 #  include <sys/types.h> // stat, off_t
@@ -19,9 +19,10 @@
 #  include <libbutl/win32-utility.hxx>
 
 #  include <io.h>       // _close(), _read(), _write(), _setmode(), _sopen(),
-                        // _lseek(), _dup(), _pipe(), _get_osfhandle()
+                        // _lseek(), _dup(), _pipe(), _chsize_s,
+                        // _get_osfhandle()
 #  include <share.h>    // _SH_DENYNO
-#  include <stdio.h>    // _fileno(), stdin, stdout, stderr
+#  include <stdio.h>    // _fileno(), stdin, stdout, stderr, SEEK_*
 #  include <fcntl.h>    // _O_*
 #  include <sys/stat.h> // S_I*
 
@@ -95,15 +96,8 @@ namespace butl
 
   // fdbuf
   //
-  fdbuf::
-  fdbuf (auto_fd&& fd)
-  {
-    if (fd.get () >= 0)
-      open (move (fd));
-  }
-
   void fdbuf::
-  open (auto_fd&& fd)
+  open (auto_fd&& fd, uint64_t pos)
   {
     close ();
 
@@ -118,7 +112,7 @@ namespace butl
 
     setg (buf_, buf_, buf_);
     setp (buf_, buf_ + sizeof (buf_) - 1); // Keep space for overflow's char.
-    off_ = 0; // @@ Strictly speaking, need to query, can be at end.
+    off_ = pos;
     fd_ = move (fd);
   }
 
@@ -457,8 +451,8 @@ namespace butl
   // fdstream_base
   //
   fdstream_base::
-  fdstream_base (auto_fd&& fd, fdstream_mode m)
-      : fdstream_base (mode (move (fd), m)) // Delegate.
+  fdstream_base (auto_fd&& fd, fdstream_mode m, std::uint64_t pos)
+      : fdstream_base (mode (move (fd), m), pos)
   {
   }
 
@@ -635,8 +629,9 @@ namespace butl
     open (fdopen (f, m | fdopen_mode::out));
   }
 
-  // Utility functions
+  // fd*() functions
   //
+
   auto_fd
   fdopen (const char* f, fdopen_mode m, permissions p)
   {
@@ -788,6 +783,33 @@ namespace butl
     return auto_fd (fd);
   }
 
+  uint64_t
+  fdseek (int fd, uint64_t o, fdseek_mode fdm)
+  {
+    int m (-1);
+
+    switch (fdm)
+    {
+    case fdseek_mode::set: m = SEEK_SET; break;
+    case fdseek_mode::cur: m = SEEK_CUR; break;
+    case fdseek_mode::end: m = SEEK_END; break;
+    }
+
+#ifndef _WIN32
+    off_t r (lseek (fd, static_cast<off_t> (o), m));
+    if (r == static_cast<off_t> (-1))
+      throw_generic_ios_failure (errno);
+#else
+    __int64 r (_lseeki64 (fd, static_cast<__int64> (o), m));
+    if (r == -1)
+      throw_generic_ios_failure (errno);
+#endif
+
+    return static_cast<uint64_t> (r);
+  }
+
+  // The rest is platform-specific.
+  //
 #ifndef _WIN32
 
   auto_fd
@@ -927,6 +949,13 @@ namespace butl
     return r;
   }
 
+  void
+  fdtruncate (int fd, uint64_t n)
+  {
+    if (ftruncate (fd, static_cast<off_t> (n)) != 0)
+      throw_generic_ios_failure (errno);
+  }
+
   bool
   fdterm (int fd)
   {
@@ -1128,6 +1157,13 @@ namespace butl
     return {auto_fd (pd[0]), auto_fd (pd[1])};
   }
 
+  void
+  fdtruncate (int fd, uint64_t n)
+  {
+    if (errno_t e = _chsize_s (fd, static_cast<__int64> (n)))
+      throw_generic_ios_failure (e);
+  }
+
   bool
   fdterm (int fd)
   {
diff --git a/libbutl/fdstream.ixx b/libbutl/fdstream.ixx
index 50e2018..4323954 100644
--- a/libbutl/fdstream.ixx
+++ b/libbutl/fdstream.ixx
@@ -30,6 +30,13 @@ namespace butl
 
   // fdbuf
   //
+  inline fdbuf::
+  fdbuf (auto_fd&& fd, std::uint64_t pos)
+  {
+    if (fd.get () >= 0)
+      open (std::move (fd), pos);
+  }
+
   inline auto_fd fdbuf::
   release ()
   {
@@ -39,8 +46,8 @@ namespace butl
   // ifdstream
   //
   inline ifdstream::
-  ifdstream (auto_fd&& fd, iostate e)
-      : fdstream_base (std::move (fd)), std::istream (&buf_)
+  ifdstream (auto_fd&& fd, iostate e, std::uint64_t pos)
+      : fdstream_base (std::move (fd), pos), std::istream (&buf_)
   {
     assert (e & badbit);
     exceptions (e);
@@ -53,8 +60,8 @@ namespace butl
   }
 
   inline ifdstream::
-  ifdstream (auto_fd&& fd, fdstream_mode m, iostate e)
-      : fdstream_base (std::move (fd), m),
+  ifdstream (auto_fd&& fd, fdstream_mode m, iostate e, std::uint64_t pos)
+      : fdstream_base (std::move (fd), m, pos),
         std::istream (&buf_),
         skip_ ((m & fdstream_mode::skip) == fdstream_mode::skip)
   {
@@ -141,8 +148,8 @@ namespace butl
   // ofdstream
   //
   inline ofdstream::
-  ofdstream (auto_fd&& fd, iostate e)
-      : fdstream_base (std::move (fd)), std::ostream (&buf_)
+  ofdstream (auto_fd&& fd, iostate e, std::uint64_t pos)
+      : fdstream_base (std::move (fd), pos), std::ostream (&buf_)
   {
     assert (e & badbit);
     exceptions (e);
@@ -155,8 +162,8 @@ namespace butl
   }
 
   inline ofdstream::
-  ofdstream (auto_fd&& fd, fdstream_mode m, iostate e)
-      : fdstream_base (std::move (fd), m), std::ostream (&buf_)
+  ofdstream (auto_fd&& fd, fdstream_mode m, iostate e, std::uint64_t pos)
+      : fdstream_base (std::move (fd), m, pos), std::ostream (&buf_)
   {
     assert (e & badbit);
     exceptions (e);
diff --git a/libbutl/fdstream.mxx b/libbutl/fdstream.mxx
index 440e637..2bb3807 100644
--- a/libbutl/fdstream.mxx
+++ b/libbutl/fdstream.mxx
@@ -106,15 +106,18 @@ LIBBUTL_MODEXPORT namespace butl
   // Notes and limitations:
   //
   // - char only
-  // - input or output but not both
+  // - input or output but not both (can use a union of two streams for that)
   // - no support for put back
+  // - no support for tell[gp]()/seek[gp]() (but see non-standard tellg() and
+  //   tellp() in fdbuf)
   // - non-blocking file descriptor is supported only by showmanyc() function
   //   and only on POSIX
   // - throws ios::failure in case of open()/read()/write()/close() errors
   // - exception mask has at least badbit
   // - after catching an exception caused by badbit the stream is no longer
-  //   used
-  // - not movable, though can be easily supported
+  //   usable
+  // - not movable, though can be easily supported (or not: there is no move
+  //   constructor for istream/ostream in GCC 4.9)
   // - passing to constructor auto_fd with a negative file descriptor is valid
   //   and results in the creation of an unopened object
   //
@@ -122,7 +125,11 @@ LIBBUTL_MODEXPORT namespace butl
   {
   public:
     fdbuf () = default;
-    fdbuf (auto_fd&&);
+
+    // Unless specified, the current read/write position is assumed to
+    // be 0 (note: not queried).
+    //
+    fdbuf (auto_fd&&, std::uint64_t pos = 0);
 
     // Before we invented auto_fd into fdstreams we keept fdbuf opened on
     // faulty close attempt. Now fdbuf is always closed by close() function.
@@ -136,7 +143,7 @@ LIBBUTL_MODEXPORT namespace butl
     release ();
 
     void
-    open (auto_fd&&);
+    open (auto_fd&&, std::uint64_t pos = 0);
 
     bool
     is_open () const {return fd_.get () >= 0;}
@@ -167,7 +174,7 @@ LIBBUTL_MODEXPORT namespace butl
 
     // Return the (logical) position of the next byte to be read.
     //
-    uint64_t
+    std::uint64_t
     tellg () const {return off_ - (egptr () - gptr ());}
 
   private:
@@ -188,7 +195,7 @@ LIBBUTL_MODEXPORT namespace butl
 
     // Return the (logical) position of the next byte to be written.
     //
-    uint64_t
+    std::uint64_t
     tellp () const {return off_ + (pptr () - buf_);}
 
   private:
@@ -197,7 +204,7 @@ LIBBUTL_MODEXPORT namespace butl
 
   private:
     auto_fd fd_;
-    uint64_t off_;
+    std::uint64_t off_;
     char buf_[8192];
     bool non_blocking_ = false;
   };
@@ -251,7 +258,7 @@ LIBBUTL_MODEXPORT namespace butl
     binary     = 0x40, // Set binary translation mode.
     at_end     = 0x80, // Seek to the end of stream immediately after open.
 
-    none = 0           // Usefull when build the mode incrementally.
+    none = 0           // Usefull when building the mode incrementally.
   };
 
   inline fdopen_mode operator& (fdopen_mode, fdopen_mode);
@@ -263,8 +270,9 @@ LIBBUTL_MODEXPORT namespace butl
   {
   protected:
     fdstream_base () = default;
-    fdstream_base (auto_fd&& fd): buf_ (std::move (fd)) {}
-    fdstream_base (auto_fd&&, fdstream_mode);
+    fdstream_base (auto_fd&& fd, std::uint64_t pos)
+      : buf_ (std::move (fd), pos) {}
+    fdstream_base (auto_fd&&, fdstream_mode, std::uint64_t);
 
   public:
     int
@@ -368,8 +376,14 @@ LIBBUTL_MODEXPORT namespace butl
     ifdstream (iostate e = badbit | failbit);
 
     explicit
-    ifdstream (auto_fd&&, iostate e = badbit | failbit);
-    ifdstream (auto_fd&&, fdstream_mode m, iostate e = badbit | failbit);
+    ifdstream (auto_fd&&,
+               iostate e = badbit | failbit,
+               std::uint64_t pos = 0);
+
+    ifdstream (auto_fd&&,
+               fdstream_mode m,
+               iostate e = badbit | failbit,
+               std::uint64_t pos = 0);
 
     explicit
     ifdstream (const char*,
@@ -419,12 +433,16 @@ LIBBUTL_MODEXPORT namespace butl
     open (const path&, fdopen_mode);
 
     void
-    open (auto_fd&& fd) {buf_.open (std::move (fd)); clear ();}
+    open (auto_fd&& fd, std::uint64_t pos = 0)
+    {
+      buf_.open (std::move (fd), pos);
+      clear ();
+    }
 
     void
-    open (auto_fd&& fd, fdstream_mode m)
+    open (auto_fd&& fd, fdstream_mode m, std::uint64_t pos = 0)
     {
-      open (std::move (fd));
+      open (std::move (fd), pos);
       skip_ = (m & fdstream_mode::skip) == fdstream_mode::skip;
     }
 
@@ -464,8 +482,14 @@ LIBBUTL_MODEXPORT namespace butl
     ofdstream (iostate e = badbit | failbit);
 
     explicit
-    ofdstream (auto_fd&&, iostate e = badbit | failbit);
-    ofdstream (auto_fd&&, fdstream_mode m, iostate e = badbit | failbit);
+    ofdstream (auto_fd&&,
+               iostate e = badbit | failbit,
+               std::uint64_t pos = 0);
+
+    ofdstream (auto_fd&&,
+               fdstream_mode m,
+               iostate e = badbit | failbit,
+               std::uint64_t pos = 0);
 
     explicit
     ofdstream (const char*,
@@ -515,7 +539,11 @@ LIBBUTL_MODEXPORT namespace butl
     open (const path&, fdopen_mode);
 
     void
-    open (auto_fd&& fd) {buf_.open (std::move (fd)); clear ();}
+    open (auto_fd&& fd, std::uint64_t pos = 0)
+    {
+      buf_.open (std::move (fd), pos);
+      clear ();
+    }
 
     void close () {if (is_open ()) flush (); buf_.close ();}
     auto_fd release ();
@@ -709,6 +737,19 @@ LIBBUTL_MODEXPORT namespace butl
   LIBBUTL_SYMEXPORT fdpipe
   fdopen_pipe (fdopen_mode = fdopen_mode::none);
 
+  // Seeking.
+  //
+  enum class fdseek_mode {set, cur, end};
+
+  LIBBUTL_SYMEXPORT std::uint64_t
+  fdseek (int, std::uint64_t, fdseek_mode);
+
+  // Truncate or expand the file to the specified size. Throw ios::failure on
+  // the underlying OS error.
+  //
+  LIBBUTL_SYMEXPORT void
+  fdtruncate (int, std::uint64_t);
+
   // Test whether a file descriptor refers to a terminal. Throw ios::failure on
   // the underlying OS error.
   //