libcruft-util/posix/fd.cpp

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/*
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* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*
* Copyright 2016-2019 Danny Robson <danny@nerdcruft.net>
*/
#include "fd.hpp"
#include "except.hpp"
#include "cast.hpp"
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
using cruft::posix::fd;
///////////////////////////////////////////////////////////////////////////////
fd::fd (const std::filesystem::path &path, int flags):
fd (path, flags, 0666)
{ ; }
//-----------------------------------------------------------------------------
fd::fd (const std::filesystem::path &path, int flags, mode_t mode):
m_fd (error::try_value (::open (path.string<char> ().c_str (), flags, mode)))
{
// You always want binary mode. Always.
//
// But we want the user to have considered this platform issue regardless
// so we won't forcibly set the flag, but we will abort the program when
// debugging if they've failed to do so.
CHECK_EQ (flags & O_BINARY, O_BINARY);
}
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///////////////////////////////////////////////////////////////////////////////
fd::fd (fd &&rhs) noexcept:
m_fd (-1)
{
std::swap (m_fd, rhs.m_fd);
}
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//-----------------------------------------------------------------------------
fd&
fd::operator= (fd &&rhs) noexcept
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{
close ();
std::swap (m_fd, rhs.m_fd);
return *this;
}
//-----------------------------------------------------------------------------
fd&
fd::operator= (int rhs)
{
reset (rhs);
return *this;
}
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///////////////////////////////////////////////////////////////////////////////
fd::fd (int _fd):
m_fd (_fd)
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{ ; }
///////////////////////////////////////////////////////////////////////////////
fd
fd::dup (void) const
{
return dup (m_fd);
}
//-----------------------------------------------------------------------------
fd
fd::dup (int _fd)
{
return fd {
error::try_value (::dup (_fd))
};
}
///////////////////////////////////////////////////////////////////////////////
fd::~fd ()
{
if (m_fd < 0)
return;
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close ();
}
///////////////////////////////////////////////////////////////////////////////
struct ::stat
fd::stat (void) const
{
struct stat buf;
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error::try_value (fstat (m_fd, &buf));
return buf;
}
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///////////////////////////////////////////////////////////////////////////////
#if defined(PLATFORM_LINUX)
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void
fd::allocate (int mode, off_t offset, off_t len)
{
error::try_call (fallocate, m_fd, mode, offset, len);
}
#endif
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///////////////////////////////////////////////////////////////////////////////
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void
fd::close (void)
{
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error::try_value (::close (m_fd));
m_fd = -1;
}
//-----------------------------------------------------------------------------
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void
fd::reset (void)
{
if (m_fd >= 0) {
close ();
m_fd = -1;
}
}
//-----------------------------------------------------------------------------
void
fd::reset (int rhs)
{
if (m_fd >= 0)
close ();
m_fd = rhs;
}
//-----------------------------------------------------------------------------
int
fd::release (void)
{
int tmp = m_fd;
m_fd = -1;
return tmp;
}
///////////////////////////////////////////////////////////////////////////////
ssize_t
fd::read (void *buffer, std::size_t count)
{
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return error::try_value (
::read (m_fd, buffer, cruft::cast::narrow<unsigned> (count))
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);
}
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//-----------------------------------------------------------------------------
ssize_t
fd::write (const void *buffer, size_t count)
{
return error::try_value (
::write (m_fd, buffer, cruft::cast::narrow<unsigned> (count))
);
}
#if defined(PLATFORM_WIN32)
#include "../win32/windows.hpp"
#endif
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//-----------------------------------------------------------------------------
ssize_t
fd::pwrite (const void *buf, size_t count, size_t offset)
{
#if !defined(PLATFORM_WIN32)
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return error::try_value (
::pwrite (native (), buf, count, offset)
);
#else
// Ideally we'd to use something like WriteFile with an OVERLAPPED
// structure applied to the handle extracted with _get_osfhandle (m_fd).
//
// But this modifies the file cursor, and if we need to seek anyway then
// we may as well just emulate the entire with a query and two seeks.
//
// NOTE: It is thus possible to observe the fd with an 'incorrect' file
// pointer. Do not rely on POSIX behaviour across multiple threads.
auto const initial = lseek (0, SEEK_CUR);
ssize_t written = -1;
try {
(void)lseek (offset, SEEK_SET);
written = write (buf, count);
} catch (...) {
(void)lseek (initial, SEEK_SET);
throw;
}
(void)lseek (initial, SEEK_SET);
return written;
#endif
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}
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///////////////////////////////////////////////////////////////////////////////
off_t
fd::lseek (off_t offset, int whence)
{
return error::try_value (
::lseek (m_fd, offset, whence)
);
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}
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///////////////////////////////////////////////////////////////////////////////
void
fd::truncate (off_t length)
{
error::try_call (
::ftruncate, m_fd, length
);
}
///////////////////////////////////////////////////////////////////////////////
fd::operator int (void) const
{
return m_fd;
}