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libphutil/src/filesystem/linesofalarge/file/LinesOfALargeFile.php
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LinesOfALargeFile.php
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<?php
/*
* Copyright 2012 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* Read the lines of a file, one at a time. This allows you to process large
* files without holding them in memory. In most cases, it is more efficient
* (and certainly simpler) to read the entire file and `explode()` it. For more
* information, see @{class:LinesOfALarge}. See also
* @{class:LinesOfALargeExecFuture}, for a similar abstraction that works on
* executed commands.
*
* foreach (new LinesOfALargeFile('/some/large/logfile.log') as $line) {
* // ...
* }
*
* If the file can not be read, a @{class:FilesystemException} is thrown.
*
* @task construct Construction
* @task internals Internals
* @group filesystem
*/
final class LinesOfALargeFile extends LinesOfALarge {
private $fileName;
private $handle;
/* -( Construction )------------------------------------------------------- */
/**
* To construct, pass the path to a file.
*
* @param string File path to read.
* @return void
* @task construct
*/
public function __construct($file_name) {
$this->fileName = Filesystem::resolvePath((string)$file_name);
}
/* -( Internals )---------------------------------------------------------- */
/**
* Closes the file handle.
*
* @return void
* @task internals
*/
public function __destruct() {
$this->closeHandle();
}
/**
* Close the file handle, if it is open.
*
* @return $this
* @task internals
*/
private function closeHandle() {
if ($this->handle) {
fclose($this->handle);
$this->handle = null;
}
return $this;
}
/**
* Closes the file handle if it is open, and reopens it.
*
* @return void
* @task internals
*/
protected function willRewind() {
$this->closeHandle();
$this->handle = @fopen($this->fileName, 'r');
if (!$this->handle) {
throw new FilesystemException(
$this->fileName,
"Failed to open file!");
}
}
/**
* Read the file chunk-by-chunk.
*
* @return string Next chunk of the file.
* @task internals
*/
public function readMore() {
// NOTE: At least on OSX in reasonably normal test cases, increasing the
// size of this read has no impact on performance.
$more = @fread($this->handle, 2048);
if ($more === false) {
throw new FilesystemException(
$this->fileName,
"Failed to read file!");
}
return $more;
}
}
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