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livetrax/libs/pbd/file_manager.cc

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/*
Copyright (C) 2010 Paul Davis
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <cassert>
#include <cstdio>
#ifdef __APPLE__
#include <mach/mach_time.h>
#endif
#include "pbd/compose.h"
#include "pbd/file_manager.h"
#include "pbd/debug.h"
using namespace std;
using namespace PBD;
FileManager* FileDescriptor::_manager;
FileManager::FileManager ()
: _open (0)
{
struct rlimit rl;
int const r = getrlimit (RLIMIT_NOFILE, &rl);
/* XXX: this is a bit arbitrary */
if (r == 0) {
_max_open = rl.rlim_cur - 64;
} else {
_max_open = 256;
}
DEBUG_TRACE (DEBUG::FileManager, string_compose ("FileManager can open up to %1 files.\n", _max_open));
}
void
FileManager::add (FileDescriptor* d)
{
Glib::Mutex::Lock lm (_mutex);
_files.push_back (d);
}
/** @return true on error, otherwise false */
bool
FileManager::allocate (FileDescriptor* d)
{
Glib::Mutex::Lock lm (_mutex);
if (!d->is_open()) {
/* this file needs to be opened */
if (_open == _max_open) {
/* We already have the maximum allowed number of files opened, so we must try to close one.
Find the unallocated, open file with the lowest last_used time.
*/
double lowest_last_used = DBL_MAX;
list<FileDescriptor*>::iterator oldest = _files.end ();
for (list<FileDescriptor*>::iterator i = _files.begin(); i != _files.end(); ++i) {
if ((*i)->is_open() && (*i)->_refcount == 0) {
if ((*i)->_last_used < lowest_last_used) {
lowest_last_used = (*i)->_last_used;
oldest = i;
}
}
}
if (oldest == _files.end()) {
/* no unallocated and open files exist, so there's nothing we can do */
return true;
}
close (*oldest);
DEBUG_TRACE (
DEBUG::FileManager,
string_compose (
"closed file for %1 to release file handle; now have %2 of %3 open\n",
(*oldest)->_path, _open, _max_open
)
);
}
if (d->open ()) {
DEBUG_TRACE (DEBUG::FileManager, string_compose ("open of %1 failed.\n", d->_path));
return true;
}
_open++;
DEBUG_TRACE (DEBUG::FileManager, string_compose ("opened file for %1; now have %2 of %3 open.\n", d->_path, _open, _max_open));
}
#ifdef __APPLE__
d->_last_used = mach_absolute_time();
#else
struct timespec t;
clock_gettime (CLOCK_MONOTONIC, &t);
d->_last_used = t.tv_sec + (double) t.tv_nsec / 10e9;
#endif
d->_refcount++;
return false;
}
/** Tell FileManager that a FileDescriptor is no longer needed for a given handle */
void
FileManager::release (FileDescriptor* d)
{
Glib::Mutex::Lock lm (_mutex);
d->_refcount--;
assert (d->_refcount >= 0);
}
/** Remove a file from our lists. It will be closed if it is currently open. */
void
FileManager::remove (FileDescriptor* d)
{
Glib::Mutex::Lock lm (_mutex);
if (d->is_open ()) {
close (d);
DEBUG_TRACE (
DEBUG::FileManager,
string_compose ("closed file for %1; file is being removed; now have %2 of %3 open\n", d->_path, _open, _max_open)
);
}
_files.remove (d);
}
void
FileManager::close (FileDescriptor* d)
{
/* we must have a lock on our mutex */
d->close ();
d->Closed (); /* EMIT SIGNAL */
_open--;
}
FileDescriptor::FileDescriptor (string const & n, bool w)
: _refcount (0)
, _last_used (0)
, _path (n)
, _writeable (w)
{
}
FileManager*
FileDescriptor::manager ()
{
if (_manager == 0) {
_manager = new FileManager;
}
return _manager;
}
/** Release a previously allocated handle to this file */
void
FileDescriptor::release ()
{
manager()->release (this);
}
/** @param file_name Filename.
* @param writeable true to open writeable, otherwise false.
* @param mode Open mode for the file.
*/
FdFileDescriptor::FdFileDescriptor (string const & file_name, bool writeable, mode_t mode)
: FileDescriptor (file_name, writeable)
, _fd (-1)
, _mode (mode)
{
manager()->add (this);
}
FdFileDescriptor::~FdFileDescriptor ()
{
manager()->remove (this);
}
bool
FdFileDescriptor::is_open () const
{
/* we must have a lock on the FileManager's mutex */
return _fd != -1;
}
bool
FdFileDescriptor::open ()
{
/* we must have a lock on the FileManager's mutex */
_fd = ::open (_path.c_str(), _writeable ? (O_RDWR | O_CREAT) : O_RDONLY, _mode);
return (_fd == -1);
}
void
FdFileDescriptor::close ()
{
/* we must have a lock on the FileManager's mutex */
::close (_fd);
_fd = -1;
}
/** @return fd, or -1 on error */
int
FdFileDescriptor::allocate ()
{
bool const f = manager()->allocate (this);
if (f) {
return -1;
}
/* this is ok thread-wise because allocate () has incremented
the Descriptor's refcount, so the file will not be closed
*/
return _fd;
}
void
FileDescriptor::set_path (const string& p)
{
_path = p;
}
/** @param file_name Filename.
* @param mode Mode to pass to fopen.
*/
StdioFileDescriptor::StdioFileDescriptor (string const & file_name, std::string const & mode)
: FileDescriptor (file_name, false)
, _file (0)
, _mode (mode)
{
manager()->add (this);
}
StdioFileDescriptor::~StdioFileDescriptor ()
{
manager()->remove (this);
}
bool
StdioFileDescriptor::is_open () const
{
/* we must have a lock on the FileManager's mutex */
return _file != 0;
}
bool
StdioFileDescriptor::open ()
{
/* we must have a lock on the FileManager's mutex */
_file = fopen (_path.c_str(), _mode.c_str());
return (_file == 0);
}
void
StdioFileDescriptor::close ()
{
/* we must have a lock on the FileManager's mutex */
fclose (_file);
_file = 0;
}
/** @return FILE*, or 0 on error */
FILE*
StdioFileDescriptor::allocate ()
{
bool const f = manager()->allocate (this);
if (f) {
return 0;
}
/* this is ok thread-wise because allocate () has incremented
the Descriptor's refcount, so the file will not be closed
*/
return _file;
}