PhutilCommandString.php
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	<?php

	final class PhutilCommandString extends Phobject {

	private $argv;
	private $escapingMode = false;

	const MODE_DEFAULT = 'default';
	const MODE_LINUX = 'linux';
	const MODE_WINDOWS = 'windows';
	const MODE_POWERSHELL = 'powershell';

	public function __construct(array $argv) {
	$this->argv = $argv;

	$this->escapingMode = self::MODE_DEFAULT;

	// This makes sure we throw immediately if there are errors in the
	// parameters.
	$this->getMaskedString();
	}

	public function __toString() {
	return $this->getMaskedString();
	}

	public function getUnmaskedString() {
	return $this->renderString(true);
	}

	public function getMaskedString() {
	return $this->renderString(false);
	}

	public function setEscapingMode($escaping_mode) {
	$this->escapingMode = $escaping_mode;
	return $this;
	}

	private function renderString($unmasked) {
	return xsprintf(
	'xsprintf_command',
	array(
	'unmasked' => $unmasked,
	'mode' => $this->escapingMode,
	),
	$this->argv);
	}

	public static function escapeArgument($value, $mode) {
	if ($mode === self::MODE_DEFAULT) {
	if (phutil_is_windows()) {
	$mode = self::MODE_WINDOWS;
	} else {
	$mode = self::MODE_LINUX;
	}
	}

	// Be generous about what we accept
	// but normalize to a value that makes sense for a command line
	// premising that CLIs only accept strings since that is how computers work
	if ($value === null) {
	$value = '';
	}

	switch ($mode) {
	case self::MODE_LINUX:
	return self::escapeLinux($value);
	case self::MODE_WINDOWS:
	return self::escapeWindows($value);
	case self::MODE_POWERSHELL:
	return self::escapePowershell($value);
	default:
	throw new Exception(pht('Unknown escaping mode!'));
	}
	}

	private static function escapePowershell($value) {
	// These escape sequences are from http://ss64.com/ps/syntax-esc.html

	// Replace backticks first.
	$value = str_replace('`', '``', $value);

	// Now replace other required notations.
	$value = str_replace("\0", '`0', $value);
	$value = str_replace(chr(7), '`a', $value);
	$value = str_replace(chr(8), '`b', $value);
	$value = str_replace("\f", '`f', $value);
	$value = str_replace("\n", '`n', $value);
	$value = str_replace("\r", '`r', $value);
	$value = str_replace("\t", '`t', $value);
	$value = str_replace("\v", '`v', $value);
	$value = str_replace('#', '`#', $value);
	$value = str_replace("'", '`\'', $value);
	$value = str_replace('"', '`"', $value);

	// The rule on dollar signs is mentioned further down the page, and
	// they only need to be escaped when using double quotes (which we are).
	$value = str_replace('$', '`$', $value);

	return '"'.$value.'"';
	}

	private static function escapeLinux($value) {
	if (strpos($value, "\0") !== false) {
	throw new Exception(
	pht(
	'Command string argument includes a NULL byte. This byte can not '.
	'be safely escaped in command line arguments in Linux '.
	'environments.'));
	}

	// If the argument is nonempty and contains only common printable
	// characters, we do not need to escape it. This makes debugging
	// workflows a little more user-friendly by making command output
	// more readable.
	if (preg_match('(^[a-zA-Z0-9:/@._+-]+\z)', $value)) {
	return $value;
	}

	return escapeshellarg($value);
	}

	private static function escapeWindows($value) {
	if (strpos($value, "\0") !== false) {
	throw new Exception(
	pht(
	'Command string argument includes a NULL byte. This byte can not '.
	'be safely escaped in command line arguments in Windows '.
	'environments.'));
	}

	if (!phutil_is_utf8($value)) {
	throw new Exception(
	pht(
	'Command string argument includes text which is not valid UTF-8. '.
	'This library can not safely escape this sequence in command '.
	'line arguments in Windows environments.'));
	}

	$has_backslash = (strpos($value, '\\') !== false);
	$has_space = (strpos($value, ' ') !== false);
	$has_quote = (strpos($value, '"') !== false);
	$is_empty = (strlen($value) === 0);

	// If a backslash appears before another backslash, a double quote, or
	// the end of the argument, we must escape it. Otherwise, we must leave
	// it unescaped.

	if ($has_backslash) {
	$value_v = preg_split('//', $value, -1, PREG_SPLIT_NO_EMPTY);
	$len = count($value_v);
	for ($ii = 0; $ii < $len; $ii++) {
	if ($value_v[$ii] === '\\') {
	if ($ii + 1 < $len) {
	$next = $value_v[$ii + 1];
	} else {
	$next = null;
	}

	if ($next === '"' \|\| $next === '\\' \|\| $next === null) {
	$value_v[$ii] = '\\\\';
	}
	}
	}
	$value = implode('', $value_v);
	}

	// Then, escape double quotes by prefixing them with backslashes.
	if ($has_quote \|\| $has_space \|\| $has_backslash \|\| $is_empty) {
	$value = addcslashes($value, '"');
	$value = '"'.$value.'"';
	}

	return $value;
	}

	}

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