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authorKaren Arutyunov <karen@codesynthesis.com>2016-11-03 00:44:53 +0300
committerKaren Arutyunov <karen@codesynthesis.com>2016-11-03 13:47:43 +0300
commit7ce74ce206065c3af0035583330b3c773086f21c (patch)
treefc0fb1d9bd0037299f12a27f1f38ac5056634568 /butl/fdstream
parentcc8a2a1517cc3c55bdeb066a038868fb8c7f04d6 (diff)
Invent auto_fd, make use of it in fdstreams and process
Diffstat (limited to 'butl/fdstream')
-rw-r--r--butl/fdstream121
1 files changed, 75 insertions, 46 deletions
diff --git a/butl/fdstream b/butl/fdstream
index 2d7fae5..9c7274d 100644
--- a/butl/fdstream
+++ b/butl/fdstream
@@ -8,6 +8,7 @@
#include <string>
#include <istream>
#include <ostream>
+#include <utility> // move()
#include <cstdint> // uint16_t
#include <butl/export>
@@ -17,6 +18,45 @@
namespace butl
{
+ // RAII type for file descriptors. Note that failure to close the descriptor
+ // is silently ignored by both the destructor and reset() (thought we could
+ // probably provide the close() function that throws).
+ //
+ // The descriptor can be negative. Such a descriptor is treated as unopened
+ // and is not closed.
+ //
+ struct nullfd_t {constexpr explicit nullfd_t (int) {}};
+ constexpr const nullfd_t nullfd (-1);
+
+ class auto_fd
+ {
+ public:
+ auto_fd (nullfd_t = nullfd): fd_ (-1) {}
+
+ explicit
+ auto_fd (int fd) noexcept: fd_ (fd) {}
+
+ auto_fd (auto_fd&& fd) noexcept: fd_ (fd.release ()) {}
+ auto_fd& operator= (auto_fd&&) noexcept;
+
+ auto_fd (const auto_fd&) = delete;
+ auto_fd& operator= (const auto_fd&) = delete;
+
+ ~auto_fd () noexcept {reset ();}
+
+ int
+ get () const noexcept {return fd_;}
+
+ int
+ release () noexcept;
+
+ void
+ reset (int fd = -1) noexcept;
+
+ private:
+ int fd_;
+ };
+
// An [io]fstream that can be initialized with a file descriptor in addition
// to a file name and that also by default enables exceptions on badbit and
// failbit. So instead of a dance like this:
@@ -41,31 +81,26 @@ namespace butl
// - after catching an exception caused by badbit the stream is no longer
// used
// - not movable, though can be easily supported
- // - passing to constructor -1 file descriptor is valid and results in the
- // creation of an unopened object
+ // - passing to constructor auto_fd with a negative file descriptor is valid
+ // and results in the creation of an unopened object
//
class LIBBUTL_EXPORT fdbuf: public std::basic_streambuf<char>
{
public:
- virtual
- ~fdbuf ();
fdbuf () = default;
- fdbuf (int fd) {if (fd != -1) open (fd);}
-
- fdbuf (const fdbuf&) = delete;
- fdbuf& operator= (const fdbuf&) = delete;
+ fdbuf (auto_fd&&);
void
close ();
void
- open (int fd);
+ open (auto_fd&&);
bool
- is_open () const {return fd_ != -1;}
+ is_open () const {return fd_.get () >= 0;}
int
- fd () const {return fd_;}
+ fd () const {return fd_.get ();}
public:
using int_type = std::basic_streambuf<char>::int_type;
@@ -101,7 +136,7 @@ namespace butl
save ();
private:
- int fd_ = -1;
+ auto_fd fd_;
char buf_[8192];
bool non_blocking_ = false;
};
@@ -164,8 +199,8 @@ namespace butl
{
protected:
fdstream_base () = default;
- fdstream_base (int fd): buf_ (fd) {}
- fdstream_base (int, fdstream_mode);
+ fdstream_base (auto_fd&& fd): buf_ (std::move (fd)) {}
+ fdstream_base (auto_fd&&, fdstream_mode);
public:
int
@@ -191,18 +226,13 @@ namespace butl
// iofdstream constructors and open() functions that take file path as a
// const std::string& or const char* may throw the invalid_path exception.
//
- // Passing -1 as a file descriptor is valid and results in the creation of
- // an unopened object.
+ // Passing auto_fd with a negative file descriptor is valid and results in
+ // the creation of an unopened object.
//
// Also note that open() and close() functions can be successfully called
// for an opened and unopened objects respectively. That is in contrast with
// iofstream that sets failbit in such cases.
//
- // @@ Need to make sure performance is on par with fstream on both
- // Linux and Windows.
- //
- // @@ Do we need to increase default buffer size? Make it customizable?
- // Wonder what it is in libstdc++ and MSVC?
// Note that ifdstream destructor will close an open file descriptor but
// will ignore any errors. To detect such errors, call close() explicitly.
@@ -219,8 +249,8 @@ namespace butl
// {
// // In case of exception, skip and close input after output.
// //
- // ifdstream is (pr.in_ofd, fdstream_mode::skip);
- // ofdstream os (pr.out_fd);
+ // ifdstream is (move (pr.in_ofd), fdstream_mode::skip);
+ // ofdstream os (move (pr.out_fd));
//
// // Write.
//
@@ -268,17 +298,14 @@ namespace butl
class LIBBUTL_EXPORT ifdstream: public fdstream_base, public std::istream
{
public:
- // Create an unopened object with iostate = badbit | failbit (we cannot
- // have the iostate as an argument since it clashes with int fd) To create
- // an unopened object with non-default exception mask one can do:
- //
- // ifdstream (-1, ...);
+ // Create an unopened object.
//
- ifdstream ();
+ explicit
+ ifdstream (iostate e = badbit | failbit);
explicit
- ifdstream (int fd, iostate e = badbit | failbit);
- ifdstream (int fd, fdstream_mode m, iostate e = badbit | failbit);
+ ifdstream (auto_fd&&, iostate e = badbit | failbit);
+ ifdstream (auto_fd&&, fdstream_mode m, iostate e = badbit | failbit);
explicit
ifdstream (const char*,
@@ -328,7 +355,7 @@ namespace butl
open (const path&, fdopen_mode);
void
- open (int fd) {buf_.open (fd); clear ();}
+ open (auto_fd&& fd) {buf_.open (std::move (fd)); clear ();}
void close ();
bool is_open () const {return buf_.is_open ();}
@@ -348,17 +375,14 @@ namespace butl
class LIBBUTL_EXPORT ofdstream: public fdstream_base, public std::ostream
{
public:
- // Create an unopened object with iostate = badbit | failbit (we cannot
- // have the iostate as an argument since it clashes with int fd). To create
- // an unopened object with non-default exception mask one can do:
- //
- // ofdstream (-1, ...);
+ // Create an unopened object.
//
- ofdstream ();
+ explicit
+ ofdstream (iostate e = badbit | failbit);
explicit
- ofdstream (int fd, iostate e = badbit | failbit);
- ofdstream (int fd, fdstream_mode m, iostate e = badbit | failbit);
+ ofdstream (auto_fd&&, iostate e = badbit | failbit);
+ ofdstream (auto_fd&&, fdstream_mode m, iostate e = badbit | failbit);
explicit
ofdstream (const char*,
@@ -408,7 +432,7 @@ namespace butl
open (const path&, fdopen_mode);
void
- open (int fd) {buf_.open (fd); clear ();}
+ open (auto_fd&& fd) {buf_.open (std::move (fd)); clear ();}
void close () {if (is_open ()) flush (); buf_.close ();}
bool is_open () const {return buf_.is_open ();}
@@ -432,8 +456,8 @@ namespace butl
LIBBUTL_EXPORT ifdstream&
getline (ifdstream&, std::string&, char delim = '\n');
- // Open a file returning the file descriptor on success and throwing
- // ios:failure otherwise.
+ // Open a file returning an auto_fd that holds its file descriptor on
+ // success and throwing ios::failure otherwise.
//
// The mode argument should have at least one of the in or out flags set.
// The append and truncate flags are meaningless in the absense of the out
@@ -448,21 +472,21 @@ namespace butl
// process' umask, so effective permissions are permissions & ~umask. On
// Windows permissions other than ru and wu are unlikelly to have effect.
//
- LIBBUTL_EXPORT int
+ LIBBUTL_EXPORT auto_fd
fdopen (const char*,
fdopen_mode,
permissions = permissions::ru | permissions::wu |
permissions::rg | permissions::wg |
permissions::ro | permissions::wo);
- LIBBUTL_EXPORT int
+ LIBBUTL_EXPORT auto_fd
fdopen (const std::string&,
fdopen_mode,
permissions = permissions::ru | permissions::wu |
permissions::rg | permissions::wg |
permissions::ro | permissions::wo);
- LIBBUTL_EXPORT int
+ LIBBUTL_EXPORT auto_fd
fdopen (const path&,
fdopen_mode,
permissions = permissions::ru | permissions::wu |
@@ -510,6 +534,11 @@ namespace butl
// closed. One difference, however, would be if you were to both write to
// and read from the descriptor.
//
+ // @@ You may have noticed that this interface doesn't match fdopen() (it
+ // does not throw and return int instead of auto_fd). The reason for this
+ // is process and its need to translate everything to process_error).
+ // Once we solve that we can clean this up as well.
+ //
#ifndef _WIN32
LIBBUTL_EXPORT int
fdnull () noexcept;