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libphutil/src/filesystem/Filesystem.php
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Filesystem.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.
*/
/**
* Simple wrapper class for common filesystem tasks like reading and writing
* files. When things go wrong, this class throws detailed exceptions with
* good information about what didn't work.
*
* Filesystem will resolve relative paths against PWD from the environment.
* When Filesystem is unable to complete an operation, it throws a
* FilesystemException.
*
* @task directory Directories
* @task file Files
* @task path Paths
* @task assert Assertions
* @group filesystem
*/
final class Filesystem {
/* -( Files )-------------------------------------------------------------- */
/**
* Read a file in a manner similar to file_get_contents(), but throw detailed
* exceptions on failure.
*
* @param string File path to read. This file must exist and be readable,
* or an exception will be thrown.
* @return string Contents of the specified file.
*
* @task file
*/
public static function readFile($path) {
$path = self::resolvePath($path);
self::assertExists($path);
self::assertIsFile($path);
self::assertReadable($path);
$data = @file_get_contents($path);
if ($data === false) {
throw new FilesystemException(
$path,
"Failed to read file `{$path}'.");
}
return $data;
}
/**
* Write a file in a manner similar to file_put_contents(), but throw
* detailed exceptions on failure. If the file already exists, it will be
* overwritten.
*
* @param string File path to write. This file must be writable and its
* parent directory must exist.
* @param string Data to write.
*
* @task file
*/
public static function writeFile($path, $data) {
$path = self::resolvePath($path);
$dir = dirname($path);
self::assertExists($dir);
self::assertIsDirectory($dir);
// File either needs to not exist and have a writable parent, or be
// writable itself.
$exists = true;
try {
self::assertNotExists($path);
$exists = false;
} catch (Exception $ex) {
self::assertWritable($path);
}
if (!$exists) {
self::assertWritable($dir);
}
if (@file_put_contents($path, $data) === false) {
throw new FilesystemException(
$path,
"Failed to write file `{$path}'.");
}
}
/**
* Write data to unique file, without overwriting existing files. This is
* useful if you want to write a ".bak" file or something similar, but want
* to make sure you don't overwrite something already on disk.
*
* This function will add a number to the filename if the base name already
* exists, e.g. "example.bak", "example.bak.1", "example.bak.2", etc. (Don't
* rely on this exact behavior, of course.)
*
* @param string Suggested filename, like "example.bak". This name will
* be used if it does not exist, or some similar name will
* be chosen if it does.
* @param string Data to write to the file.
* @return string Path to a newly created and written file which did not
* previously exist, like "example.bak.3".
* @task file
*/
public static function writeUniqueFile($base, $data) {
$full_path = Filesystem::resolvePath($base);
$sequence = 0;
// Try 'file', 'file.1', 'file.2', etc., until something doesn't exist.
while (true) {
$try_path = $full_path;
if ($sequence) {
$try_path .= '.'.$sequence;
}
$handle = @fopen($try_path, 'x');
if ($handle) {
$ok = fwrite($handle, $data);
fclose($handle);
if (!$ok) {
throw new FilesystemException(
$try_path,
"Failed to write file data.");
}
return $try_path;
}
$sequence++;
}
}
/**
* Append to a file without having to deal with file handles, with
* detailed exceptions on failure.
*
* @param string File path to write. This file must be writable or its
* parent directory must exist and be writable.
* @param string Data to write.
*
* @task file
*/
public static function appendFile($path, $data) {
$path = self::resolvePath($path);
// Use self::writeFile() if the file doesn't already exist
try {
self::assertExists($path);
} catch (FilesystemException $ex) {
self::writeFile($path, $data);
return;
}
// File needs to exist or the directory needs to be writable
$dir = dirname($path);
self::assertExists($dir);
self::assertIsDirectory($dir);
self::assertWritable($dir);
if (($fh = fopen($path, 'a')) === false) {
throw new FilesystemException(
$path, "Failed to open file `{$path}'.");
}
$dlen = strlen($data);
if (fwrite($fh, $data) !== $dlen) {
throw new FilesystemException(
$path,
"Failed to write {$dlen} bytes to `{$path}'.");
}
if (!fflush($fh) || !fclose($fh)) {
throw new FilesystemException(
$path,
"Failed closing file `{$path}' after write.");
}
}
/**
* Remove a file or directory.
*
* @param string File to a path or directory to remove.
* @return void
*
* @task file
*/
public static function remove($path) {
if (!strlen($path)) {
// Avoid removing PWD.
throw new Exception("No path provided to remove().");
}
$path = self::resolvePath($path);
if (!file_exists($path)) {
return;
}
// PHP's builtin functions for this are such a mess that it's much easier
// to exec out. :/
list($err, $stdout, $stderr) = exec_manual('rm -rf %s', $path);
if ($err) {
throw new FilesystemException(
$path,
"Unable to remove `{$path}'.");
}
}
/**
* Change the permissions of a file or directory.
*
* @param string Path to the file or directory.
* @param int Permission umask. Note that umask is in octal, so you
* should specify it as, e.g., `0777', not `777'.
* @return void
*
* @task file
*/
public static function changePermissions($path, $umask) {
$path = self::resolvePath($path);
self::assertExists($path);
if (!@chmod($path, $umask)) {
$readable_umask = sprintf("%04o", $umask);
throw new FilesystemException(
$path, "Failed to chmod `{$path}' to `{$readable_umask}'.");
}
}
/**
* Get the last modified time of a file
*
* @param string Path to file
* @return Time last modified
*
* @task file
*/
public static function getModifiedTime($path) {
$path = self::resolvePath($path);
self::assertExists($path);
self::assertIsFile($path);
self::assertReadable($path);
$modified_time = @filemtime($path);
if ($modified_time === false) {
throw new FilesystemException(
$path,
'Failed to read modified time for '.$path);
}
return $modified_time;
}
/**
* Read random bytes from /dev/urandom or equivalent. See also
* @{method:readRandomCharacters}.
*
* @param int Number of bytes to read.
* @return string Random bytestring of the provided length.
*
* @task file
*/
public static function readRandomBytes($number_of_bytes) {
$urandom = @fopen('/dev/urandom', 'rb');
if (!$urandom) {
throw new FilesystemException(
'/dev/urandom',
'Failed to open /dev/urandom for reading!');
}
$data = @fread($urandom, $number_of_bytes);
if (strlen($data) != $number_of_bytes) {
throw new FilesystemException(
'/dev/urandom',
'Failed to read random bytes!');
}
@fclose($urandom);
return $data;
}
/**
* Read random alphanumeric characters from /dev/urandom or equivalent. This
* method operates like @{method:readRandomBytes} but produces alphanumeric
* output (a-z, 0-9) so it's appropriate for use in URIs and other contexts
* where it needs to be human readable.
*
* @param int Number of characters to read.
* @return string Random character string of the provided length.
*
* @task file
*/
public static function readRandomCharacters($number_of_characters) {
// NOTE: To produce the character string, we generate a random byte string
// of the same length, select the high 5 bits from each byte, and
// map that to 32 alphanumeric characters. This could be improved (we
// could improve entropy per character with base-62, and some entropy
// sources might be less entropic if we discard the low bits) but for
// reasonable cases where we have a good entropy source and are just
// generating some kind of human-readable secret this should be more than
// sufficient and is vastly simpler than trying to do bit fiddling.
$map = array_merge(range('a', 'z'), range('2', '7'));
$result = '';
$bytes = self::readRandomBytes($number_of_characters);
for ($ii = 0; $ii < $number_of_characters; $ii++) {
$result .= $map[ord($bytes[$ii]) >> 3];
}
return $result;
}
/* -( Directories )-------------------------------------------------------- */
/**
* Create a directory in a manner similar to mkdir(), but throw detailed
* exceptions on failure.
*
* @param string Path to directory. The parent directory must exist and
* be writable.
* @param int Permission umask. Note that umask is in octal, so you
* should specify it as, e.g., `0777', not `777'. By
* default, these permissions are very liberal (0777).
* @param boolean Recursivly create directories. Default to false
* @return string Path to the created directory.
*
* @task directory
*/
public static function createDirectory($path, $umask = 0777,
$recursive = false) {
$path = self::resolvePath($path);
if (is_dir($path)) {
Filesystem::changePermissions($path, $umask);
return $path;
}
$dir = dirname($path);
if ($recursive && !file_exists($dir)) {
// Note: We could do this with the recursive third parameter of mkdir(),
// but then we loose the helpful FilesystemExceptions we normally get.
self::createDirectory($dir, $umask, true);
}
self::assertIsDirectory($dir);
self::assertExists($dir);
self::assertWritable($dir);
self::assertNotExists($path);
if (!mkdir($path, $umask)) {
throw new FilesystemException(
$path,
"Failed to create directory `{$path}'.");
}
// Need to change premissions explicitly because mkdir does something
// slightly different. mkdir(2) man page:
// 'The parameter mode specifies the permissions to use. It is modified by
// the process's umask in the usual way: the permissions of the created
// directory are (mode & ~umask & 0777)."'
Filesystem::changePermissions($path, $umask);
return $path;
}
/**
* Create a temporary directory and return the path to it. You are
* responsible for removing it (e.g., with Filesystem::remove())
* when you are done with it.
*
* @param string Optional directory prefix.
* @param int Permissions to create the directory with. By default,
* these permissions are very restrictive (0700).
* @return string Path to newly created temporary directory.
*
* @task directory
*/
public static function createTemporaryDirectory($prefix = '', $umask = 0700) {
$prefix = preg_replace('/[^A-Z0-9._-]+/i', '', $prefix);
$tmp = sys_get_temp_dir();
if (!$tmp) {
throw new FilesystemException(
$tmp, 'Unable to determine system temporary directory.');
}
$base = $tmp.DIRECTORY_SEPARATOR.$prefix;
$tries = 3;
do {
$dir = $base.substr(base_convert(md5(mt_rand()), 16, 36), 0, 16);
try {
self::createDirectory($dir, $umask);
break;
} catch (FilesystemException $ex) {
// Ignore.
}
} while (--$tries);
if (!$tries) {
$df = disk_free_space($tmp);
if ($df !== false && $df < 1024 * 1024) {
throw new FilesystemException(
$dir, "Failed to create a temporary directory: the disk is full.");
}
throw new FilesystemException(
$dir, "Failed to create a temporary directory.");
}
return $dir;
}
/**
* List files in a directory.
*
* @param string Path, absolute or relative to PWD.
* @param bool If false, exclude files beginning with a ".".
*
* @return array List of files and directories in the specified
* directory, excluding `.' and `..'.
*
* @task directory
*/
public static function listDirectory($path, $include_hidden = true) {
$path = self::resolvePath($path);
self::assertExists($path);
self::assertIsDirectory($path);
self::assertReadable($path);
$list = @scandir($path);
if ($list === false) {
throw new FilesystemException(
$path,
"Unable to list contents of directory `{$path}'.");
}
foreach ($list as $k => $v) {
if ($v == '.' || $v == '..' || (!$include_hidden && $v[0] == '.')) {
unset($list[$k]);
}
}
return array_values($list);
}
/**
* Return all directories between a path and "/". Iterating over them walks
* from the path to the root.
*
* @param string Path, absolute or relative to PWD.
* @return list List of parent paths, including the provided path.
* @task directory
*/
public static function walkToRoot($path) {
$path = self::resolvePath($path);
if (is_link($path)) {
$path = realpath($path);
}
$walk = array();
$parts = explode('/', $path);
foreach ($parts as $k => $part) {
if (!strlen($part)) {
unset($parts[$k]);
}
}
do {
$walk[] = '/'.implode('/', $parts);
if (empty($parts)) {
break;
}
array_pop($parts);
} while (true);
return $walk;
}
/* -( Paths )-------------------------------------------------------------- */
/**
* Canonicalize a path by resolving it relative to some directory (by
* default PWD), following parent symlinks and removing artifacts. If the
* path is itself a symlink it is left unresolved.
*
* @param string Path, absolute or relative to PWD.
* @return string Canonical, absolute path.
*
* @task path
*/
public static function resolvePath($path, $relative_to = null) {
if (strncmp($path, '/', 1)) {
if (!$relative_to) {
$relative_to = $_SERVER['PWD'];
}
$path = $relative_to.'/'.$path;
}
if (is_link($path)) {
$parent_realpath = realpath(dirname($path));
if ($parent_realpath !== false) {
return $parent_realpath.'/'.basename($path);
}
}
$realpath = realpath($path);
if ($realpath !== false) {
return $realpath;
}
// This won't work if the file doesn't exist or is on an unreadable mount
// or something crazy like that. Try to resolve a parent so we at least
// cover the nonexistent file case.
$parts = explode('/', trim($path, '/'));
while (end($parts) !== false) {
array_pop($parts);
$attempt = '/'.implode('/', $parts);
$realpath = realpath($attempt);
if ($realpath !== false) {
$path = $realpath.substr($path, strlen($attempt));
break;
}
}
return $path;
}
/**
* Test whether a path is descendant from some root path after resolving all
* symlinks and removing artifacts. Both paths must exists for the relation
* to obtain. A path is always a descendant of itself as long as it exists.
*
* @param string Child path, absolute or relative to PWD.
* @param string Root path, absolute or relative to PWD.
* @return bool True if resolved child path is in fact a descendant of
* resolved root path and both exist.
* @task path
*/
public static function isDescendant($path, $root) {
try {
self::assertExists($path);
self::assertExists($root);
} catch (FilesystemException $e) {
return false;
}
$fs = new FileList(array($root));
return $fs->contains($path);
}
/**
* Convert a canonical path to its most human-readable format. It is
* guaranteed that you can use resolvePath() to restore a path to its
* canonical format.
*
* @param string Path, absolute or relative to PWD.
* @param string Optionally, working directory to make files readable
* relative to.
* @return string Human-readable path.
*
* @task path
*/
public static function readablePath($path, $pwd = null) {
if ($pwd === null) {
$pwd = $_SERVER['PWD'];
}
foreach (array($pwd, self::resolvePath($pwd)) as $parent) {
$parent = rtrim($parent, '/').'/';
$len = strlen($parent);
if (!strncmp($parent, $path, $len)) {
$path = substr($path, $len);
return $path;
}
}
return $path;
}
/**
* Determine whether or not a path exists in the filesystem. This differs from
* file_exists() in that it returns true for symlinks. This method does not
* attempt to resolve paths before testing them.
*
* @param string Test for the existence of this path.
* @return bool True if the path exists in the filesystem.
* @task path
*/
public static function pathExists($path) {
return file_exists($path) || is_link($path);
}
/**
* Determine if two paths are equivalent by resolving symlinks. This is
* different from resolving both paths and comparing them because
* resolvePath() only resolves symlinks in parent directories, not the
* path itself.
*
* @param string First path to test for equivalence.
* @param string Second path to test for equivalence.
* @return bool True if both paths are equivalent, i.e. reference the same
* entity in the filesystem.
* @task path
*/
public static function pathsAreEquivalent($u, $v) {
$u = Filesystem::resolvePath($u);
$v = Filesystem::resolvePath($v);
$real_u = realpath($u);
$real_v = realpath($v);
if ($real_u) {
$u = $real_u;
}
if ($real_v) {
$v = $real_v;
}
return ($u == $v);
}
/* -( Assert )------------------------------------------------------------- */
/**
* Assert that something (e.g., a file, directory, or symlink) is an
* absolute path to the specified location.
*
* @param string Assert that this path is absolute.
* @return void
*
* @task assert
*/
public static function assertAbsolute($path) {
if (empty($path) || $path[0] != '/') {
throw new FilesystemException(
$path,
"Filesystem entity `{$path}' is not absolute.");
}
}
/**
* Assert that something (e.g., a file, directory, or symlink) exists at a
* specified location.
*
* @param string Assert that this path exists.
* @return void
*
* @task assert
*/
public static function assertExists($path) {
if (!self::pathExists($path)) {
throw new FilesystemException(
$path,
"Filesystem entity `{$path}' does not exist.");
}
}
/**
* Assert that nothing exists at a specified location.
*
* @param string Assert that this path does not exist.
* @return void
*
* @task assert
*/
public static function assertNotExists($path) {
if (file_exists($path) || is_link($path)) {
throw new FilesystemException(
$path,
"Path `{$path}' already exists!");
}
}
/**
* Assert that a path represents a file, strictly (i.e., not a directory).
*
* @param string Assert that this path is a file.
* @return void
*
* @task assert
*/
public static function assertIsFile($path) {
if (!is_file($path)) {
throw new FilesystemException(
$path,
"Requested path `{$path}' is not a file.");
}
}
/**
* Assert that a path represents a directory, strictly (i.e., not a file).
*
* @param string Assert that this path is a directory.
* @return void
*
* @task assert
*/
public static function assertIsDirectory($path) {
if (!is_dir($path)) {
throw new FilesystemException(
$path,
"Requested path `{$path}' is not a directory.");
}
}
/**
* Assert that a file or directory exists and is writable.
*
* @param string Assert that this path is writable.
* @return void
*
* @task assert
*/
public static function assertWritable($path) {
if (!is_writable($path)) {
throw new FilesystemException(
$path,
"Requested path `{$path}' is not writable.");
}
}
/**
* Assert that a file or directory exists and is readable.
*
* @param string Assert that this path is readable.
* @return void
*
* @task assert
*/
public static function assertReadable($path) {
if (!is_readable($path)) {
throw new FilesystemException(
$path,
"Path `{$path}' is not readable.");
}
}
}
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