friendica/src/Util/ReversedFileReader.php
2021-09-27 12:14:19 +02:00

170 lines
3.5 KiB
PHP

<?php
/**
* @copyright Copyright (C) 2021, Friendica
*
* @license GNU AGPL version 3 or any later version
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*
*/
namespace Friendica\Util;
/**
* An iterator which returns lines from file in reversed order
*
* original code https://stackoverflow.com/a/10494801
*/
class ReversedFileReader implements \Iterator
{
const BUFFER_SIZE = 4096;
const SEPARATOR = "\n";
/** @var resource */
private $fh = null;
/** @var int */
private $filesize = -1;
/** @var int */
private $pos = -1;
/** @var array */
private $buffer = null;
/** @var int */
private $key = -1;
/** @var string */
private $value = null;
/**
* Open $filename for read and reset iterator
*
* @param string $filename File to open
* @return $this
*/
public function open(string $filename)
{
$this->fh = fopen($filename, 'r');
if (!$this->fh) {
// this should use a custom exception.
throw \Exception("Unable to open $filename");
}
$this->filesize = filesize($filename);
$this->pos = -1;
$this->buffer = null;
$this->key = -1;
$this->value = null;
return $this;
}
/**
* Read $size bytes behind last position
*
* @return string
*/
private function _read($size)
{
$this->pos -= $size;
fseek($this->fh, $this->pos);
return fread($this->fh, $size);
}
/**
* Read next line from end of file
* Return null if no lines are left to read
*
* @return ?string
*/
private function _readline()
{
$buffer = & $this->buffer;
while (true) {
if ($this->pos == 0) {
return array_pop($buffer);
}
if (is_null($buffer)) {
return null;
}
if (count($buffer) > 1) {
return array_pop($buffer);
}
$buffer = explode(self::SEPARATOR, $this->_read(self::BUFFER_SIZE) . $buffer[0]);
}
}
/**
* Fetch next line from end and set it as current iterator value.
*
* @see Iterator::next()
* @return void
*/
public function next()
{
++$this->key;
$this->value = $this->_readline();
}
/**
* Rewind iterator to the first line at the end of file
*
* @see Iterator::rewind()
* @return void
*/
public function rewind()
{
if ($this->filesize > 0) {
$this->pos = $this->filesize;
$this->value = null;
$this->key = -1;
$this->buffer = explode(self::SEPARATOR, $this->_read($this->filesize % self::BUFFER_SIZE ?: self::BUFFER_SIZE));
$this->next();
}
}
/**
* Return current line number, starting from zero at the end of file
*
* @see Iterator::key()
* @return int
*/
public function key()
{
return $this->key;
}
/**
* Return current line
*
* @see Iterator::current()
* @return string
*/
public function current()
{
return $this->value;
}
/**
* Checks if current iterator value is valid, that is, we readed all lines in files
*
* @see Iterator::valid()
* @return bool
*/
public function valid()
{
return ! is_null($this->value);
}
}