160 lines
4.2 KiB
C++
160 lines
4.2 KiB
C++
/*
|
|
* 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 2015 Danny Robson <danny@nerdcruft.net>
|
|
*/
|
|
|
|
#include "paged.hpp"
|
|
|
|
#include "../cast.hpp"
|
|
#include "../maths.hpp"
|
|
#include "../pointer.hpp"
|
|
#include "../posix/except.hpp"
|
|
#include "../memory/system.hpp"
|
|
|
|
#include <sys/mman.h>
|
|
|
|
using cruft::buffer::paged;
|
|
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
paged::paged (size_t bytes, size_t _window):
|
|
m_window (round_up (_window, pagesize ()))
|
|
{
|
|
// reserve the address region with no access permissions
|
|
m_begin = reinterpret_cast<char*> (
|
|
mmap (nullptr, bytes, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0)
|
|
);
|
|
|
|
if (m_begin == MAP_FAILED)
|
|
posix::error::throw_code ();
|
|
|
|
// remap the initial window with read/write permissions
|
|
m_cursor = m_begin + round_up (min (m_window, bytes), pagesize ());
|
|
if (MAP_FAILED == mmap (m_begin,
|
|
m_cursor - m_begin,
|
|
PROT_READ | PROT_WRITE,
|
|
MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0))
|
|
posix::error::throw_code ();
|
|
|
|
// record the nominal end address
|
|
m_end = m_begin + round_up (bytes, pagesize ());
|
|
}
|
|
|
|
|
|
//-----------------------------------------------------------------------------
|
|
paged::~paged ()
|
|
{
|
|
// ignore errors in production; we don't want to double throw.
|
|
auto res = munmap (m_begin, m_end - m_begin);
|
|
(void)res;
|
|
CHECK_ZERO (res);
|
|
}
|
|
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
char*
|
|
paged::begin (void)&
|
|
{
|
|
return m_begin;
|
|
}
|
|
|
|
|
|
//-----------------------------------------------------------------------------
|
|
char*
|
|
paged::end (void)&
|
|
{
|
|
return m_end;
|
|
}
|
|
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
void
|
|
paged::access (char *cursor)
|
|
{
|
|
if (cursor < m_cursor)
|
|
release (cursor);
|
|
else
|
|
commit (cursor);
|
|
}
|
|
|
|
|
|
//-----------------------------------------------------------------------------
|
|
void
|
|
paged::commit (char *cursor)
|
|
{
|
|
// bail if it's already mapped
|
|
if (cursor <= m_cursor)
|
|
return;
|
|
|
|
if (cursor > m_end || cursor < m_begin)
|
|
throw std::out_of_range ("invalid commit cursor");
|
|
|
|
// bump the request up to page aligned and tack on a little to amortize
|
|
// syscall overheads
|
|
cursor = align (cursor, pagesize ()) + m_window;
|
|
cursor = min (cursor, m_end);
|
|
|
|
if (MAP_FAILED == mmap (m_cursor,
|
|
cursor - m_cursor,
|
|
PROT_READ | PROT_WRITE,
|
|
MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,
|
|
-1, 0))
|
|
posix::error::throw_code ();
|
|
|
|
m_cursor = cursor;
|
|
}
|
|
|
|
|
|
//-----------------------------------------------------------------------------
|
|
void
|
|
paged::release (char *desired)
|
|
{
|
|
if (desired > m_end || desired < m_begin)
|
|
throw std::out_of_range ("invalid release cursor");
|
|
|
|
align (desired, pagesize ());
|
|
|
|
// bail if the region is alread unmapped, or if it's not sufficiently
|
|
// behind the current cursor.
|
|
if (desired >= m_cursor || cruft::cast::sign<size_t> (m_cursor - desired) < m_window)
|
|
return;
|
|
|
|
desired += m_window;
|
|
|
|
if (MAP_FAILED == mmap (desired,
|
|
m_end - desired,
|
|
PROT_NONE,
|
|
MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,
|
|
-1, 0))
|
|
posix::error::throw_code ();
|
|
|
|
m_cursor = desired;
|
|
}
|
|
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
size_t
|
|
paged::size (void) const
|
|
{
|
|
return m_cursor - m_begin;
|
|
}
|
|
|
|
|
|
//-----------------------------------------------------------------------------
|
|
size_t
|
|
paged::capacity (void) const
|
|
{
|
|
return m_end - m_begin;
|
|
}
|
|
|
|
|
|
//-----------------------------------------------------------------------------
|
|
size_t
|
|
paged::window (void) const
|
|
{
|
|
return m_window;
|
|
}
|