diff options
Diffstat (limited to 'butl')
| -rw-r--r-- | butl/fdstream | 5 | ||||
| -rw-r--r-- | butl/fdstream.cxx | 126 |
2 files changed, 127 insertions, 4 deletions
diff --git a/butl/fdstream b/butl/fdstream index bb5364b..49b3d4d 100644 --- a/butl/fdstream +++ b/butl/fdstream @@ -86,13 +86,16 @@ namespace butl virtual int sync (); + virtual std::streamsize + xsputn (const char_type*, std::streamsize); + private: bool save (); private: int fd_ = -1; - char buf_[4096]; + char buf_[8192]; }; // File stream mode. diff --git a/butl/fdstream.cxx b/butl/fdstream.cxx index cff9b59..ac5aa79 100644 --- a/butl/fdstream.cxx +++ b/butl/fdstream.cxx @@ -6,7 +6,8 @@ #ifndef _WIN32 # include <fcntl.h> // open(), O_* -# include <unistd.h> // close(), read(), write(), lseek() +# include <unistd.h> // close(), read(), write(), lseek(), ssize_t +# include <sys/uio.h> // writev(), iovec # include <sys/stat.h> // S_I* # include <sys/types.h> // off_t #else @@ -24,6 +25,7 @@ #include <new> // bad_alloc #include <limits> // numeric_limits #include <cassert> +#include <cstring> // memcpy(), memmove() #include <exception> // uncaught_exception() #include <stdexcept> // invalid_argument #include <type_traits> @@ -178,6 +180,124 @@ namespace butl return true; } + streamsize fdbuf:: + xsputn (const char_type* s, streamsize sn) + { + // To avoid futher 'signed/unsigned comparison' compiler warnings. + // + size_t n (static_cast<size_t> (sn)); + + // Buffer the data if there is enough space. + // + size_t an (epptr () - pptr ()); // Amount of free space in the buffer. + if (n <= an) + { + memcpy (pptr (), s, n); + pbump (n); + return n; + } + + size_t bn (pptr () - pbase ()); // Buffered data size. + +#ifndef _WIN32 + + ssize_t r; + if (bn > 0) + { + // Write both buffered and new data with a single system call. + // + iovec iov[2] = {{pbase (), bn}, {const_cast<char*> (s), n}}; + r = writev (fd_, iov, 2); + } + else + r = write (fd_, s, n); + + if (r == -1) + throw_ios_failure (errno); + + size_t m (static_cast<size_t> (r)); + + // If the buffered data wasn't fully written then move the unwritten part + // to the beginning of the buffer. + // + if (m < bn) + { + memmove (pbase (), pbase () + m, bn - m); + pbump (-m); // Note that pbump() accepts negatives. + return 0; + } + + setp (buf_, buf_ + sizeof (buf_) - 1); + return m - bn; + +#else + + // On Windows there is no writev() available so sometimes we will make two + // system calls. Fill and flush the buffer, then try to fit the data tail + // into the empty buffer. If the data tail is too long then just write it + // to the file and keep the buffer empty. + // + // We will end up with two _write() calls if the total data size to be + // written exceeds double the buffer size. In this case the buffer filling + // is redundant so let's pretend there is no free space in the buffer, and + // so buffered and new data will be written separatelly. + // + if (bn + n > 2 * (bn + an)) + an = 0; + else + { + memcpy (pptr (), s, an); + pbump (an); + } + + // Flush the buffer. + // + size_t wn (bn + an); + int r (wn > 0 ? _write (fd_, buf_, wn) : 0); + + if (r == -1) + throw_ios_failure (errno); + + size_t m (static_cast<size_t> (r)); + + // If the buffered data wasn't fully written then move the unwritten part + // to the beginning of the buffer. + // + if (m < wn) + { + memmove (pbase (), pbase () + m, wn - m); + pbump (-m); // Note that pbump() accepts negatives. + return m < bn ? 0 : m - bn; + } + + setp (buf_, buf_ + sizeof (buf_) - 1); + + // Now 'an' holds the size of the data portion written as a part of the + // buffer flush. + // + s += an; + n -= an; + + // Buffer the data tail if it fits the buffer. + // + if (n <= static_cast<size_t> (epptr () - pbase ())) + { + memcpy (pbase (), s, n); + pbump (n); + return sn; + } + + // The data tail doesn't fit the buffer so write it to the file. + // + r = _write (fd_, s, n); + + if (r == -1) + throw_ios_failure (errno); + + return an + r; +#endif + } + // fdstream_base // fdstream_base:: @@ -477,9 +597,9 @@ namespace butl if (mode (fdopen_mode::at_end)) { #ifndef _WIN32 - bool r (lseek(fd, 0, SEEK_END) != static_cast<off_t>(-1)); + bool r (lseek (fd, 0, SEEK_END) != static_cast<off_t> (-1)); #else - bool r (_lseek(fd, 0, SEEK_END) != -1); + bool r (_lseek (fd, 0, SEEK_END) != -1); #endif // Note that in the case of an error we don't delete the newly created |