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PhutilDeferredLog.php
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Fri, Feb 7, 20:56

PhutilDeferredLog.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.
*/
/**
* Object that writes to a logfile when it is destroyed. This allows you to add
* more data to the log as execution unfolds, while still ensuring a write in
* normal circumstances (see below for discussion of cases where writes may not
* occur).
*
* Create the object with a logfile and format:
*
* $log = new PhutilDeferredLog('/path/to/access.log', "[%T]\t%u");
*
* Update the log with information as it becomes available:
*
* $log->setData(
* array(
* 'T' => date('c'),
* 'u' => $username,
* ));
*
* The log will be appended when the object's destructor is called, or when you
* invoke @{method:write}. Note that programs can exit without invoking object
* destructors (e.g., in the case of an unhandled exception, memory exhaustion,
* or SIGKILL) so writes are not guaranteed. You can call @{method:write} to
* force an explicit write to disk before the destructor is called.
*
* Log variables will be written with bytes 0x00-0x1F, 0x7F-0xFF, and backslash
* escaped using C-style escaping. Since this range includes tab, you can use
* tabs as field separators to ensure the file format is easily parsable. In
* PHP, you can decode this encoding with @{function:stripcslashes}.
*
* If a variable is included in the log format but a value is never provided
* with @{method:setData}, it will be written as "-".
*
* @task log Logging
* @task internal Internals
* @group filesystem
*/
final class PhutilDeferredLog {
private $file;
private $format;
private $data;
private $didWrite;
/* -( Logging )------------------------------------------------------------ */
/**
* Create a new log entry, which will be written later. The format string
* should use "%x"-style placeholders to represent data which will be added
* later:
*
* $log = new PhutilDeferredLog('/some/file.log', '[%T] %u');
*
* @param string The file the entry should be written to.
* @param string The log entry format.
* @task log
*/
public function __construct($file, $format) {
$this->file = $file;
$this->format = $format;
$this->data = array();
$this->didWrite = false;
}
/**
* Add data to the log. Provide a map of variables to replace in the format
* string. For example, if you use a format string like:
*
* "[%T]\t%u"
*
* ...you might add data like this:
*
* $log->setData(
* array(
* 'T' => date('c'),
* 'u' => $username,
* ));
*
* When the log is written, the "%T" and "%u" variables will be replaced with
* the values you provide.
*
* @param dict Map of variables to values.
* @return this
* @task log
*/
public function setData(array $map) {
$this->data = $map + $this->data;
return $this;
}
/**
* When the log object is destroyed, it writes if it hasn't written yet.
* @task log
*/
public function __destruct() {
$this->write();
}
/**
* Write the log explicitly, if it hasn't been written yet. Normally you do
* not need to call this method; it will be called when the log object is
* destroyed. However, you can explicitly force the write earlier by calling
* this method.
*
* A log object will never write more than once, so it is safe to call this
* method even if the object's destructor later runs.
*
* @return this
* @task log
*/
public function write() {
if ($this->didWrite) {
return $this;
}
$line = $this->format();
$ok = @file_put_contents(
$this->file,
$line,
FILE_APPEND | LOCK_EX);
if ($ok === false) {
throw new Exception(
"Unable to write to logfile '{$this->file}'!");
}
$this->didWrite = true;
return $this;
}
/* -( Internals )---------------------------------------------------------- */
/**
* Format the log string, replacing "%x" variables with values.
*
* @return string Finalized, log string for writing to disk.
* @task internals
*/
private function format() {
$byte = "\1";
$line = $this->format;
$line = addcslashes($line, $byte);
$line = str_replace("%", $byte, $line);
$find = array();
$repl = array();
foreach ($this->data as $key => $value) {
$find[] = $byte.str_replace('%', $byte, $key);
$repl[] = addcslashes($value, "\0..\37\\\177..\377");
}
$line = str_replace($find, $repl, $line);
$line = preg_replace("/{$byte}./", '-', $line);
$line = rtrim($line)."\n";
return $line;
}
}

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