diff options
Diffstat (limited to 'butl/fdstream')
| -rw-r--r-- | butl/fdstream | 121 |
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; |