storeengine / includes / classes / eval-math / eval-math.php

eval-math.php in StoreEngine — Complete eCommerce Solution with Memberships, Licensing, Affiliates & More 2.2.0, at includes/classes/eval-math/eval-math.php

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1	<?php
2
3	namespace StoreEngine\Classes\EvalMath;
4
5	if ( ! defined( 'ABSPATH' ) ) {
6	exit;
7	}
8
9	/**
10	* Class EvalMath. Supports basic math only (removed eval function).
11	*
12	* Based on EvalMath by Miles Kaufmann Copyright (C) 2005 Miles Kaufmann http://www.twmagic.com/.
13	*/
14	class EvalMath {
15
16	/**
17	* Last error.
18	*
19	* @var string
20	*/
21	public static $last_error = null;
22
23	/**
24	* Variables (and constants).
25	*
26	* @var array
27	*/
28	public static $v = array(
29	'e' => 2.71,
30	'pi' => 3.14,
31	);
32
33	/**
34	* User-defined functions.
35	*
36	* @var array
37	*/
38	public static $f = array();
39
40	/**
41	* Constants.
42	*
43	* @var array
44	*/
45	public static $vb = array( 'e', 'pi' );
46
47	/**
48	* Built-in functions.
49	*
50	* @var array
51	*/
52	public static $fb = array();
53
54	/**
55	* Evaluate maths string.
56	*
57	* @param string $expr
58	* @return mixed
59	*/
60	public static function evaluate( $expr ) {
61	self::$last_error = null;
62	$expr = trim( $expr );
63	if ( substr( $expr, -1, 1 ) == ';' ) {
64	$expr = substr( $expr, 0, strlen( $expr ) - 1 ); // strip semicolons at the end
65	}
66	// ===============
67	// is it a variable assignment?
68	if ( preg_match( '/^\s([a-z]\w)\s=\s(.+)$/', $expr, $matches ) ) {
69	if ( in_array( $matches[1], self::$vb ) ) { // make sure we're not assigning to a constant
70	return self::trigger( "cannot assign to constant '$matches[1]'" );
71	}
72	if ( ( $tmp = self::pfx( self::nfx( $matches[2] ) ) ) === false ) {
73	return false; // get the result and make sure it's good
74	}
75	self::$v[ $matches[1] ] = $tmp; // if so, stick it in the variable array
76	return self::$v[ $matches[1] ]; // and return the resulting value
77	// ===============
78	// is it a function assignment?
79	} elseif ( preg_match( '/^\s([a-z]\w)\s$\s([a-z]\w(?:\s,\s[a-z]\w))\s$\s=\s(.+)$/', $expr, $matches ) ) {
80	$fnn = $matches[1]; // get the function name
81	if ( in_array( $matches[1], self::$fb ) ) { // make sure it isn't built in
82	return self::trigger( "cannot redefine built-in function '$matches[1]()'" );
83	}
84	$args = explode( ',', preg_replace( '/\s+/', '', $matches[2] ) ); // get the arguments
85	if ( ( $stack = self::nfx( $matches[3] ) ) === false ) {
86	return false; // see if it can be converted to postfix
87	}
88	$stack_size = count( $stack );
89	for ( $i = 0; $i < $stack_size; $i++ ) { // freeze the state of the non-argument variables
90	$token = $stack[ $i ];
91	if ( preg_match( '/^[a-z]\w*$/', $token ) and ! in_array( $token, $args ) ) {
92	if ( array_key_exists( $token, self::$v ) ) {
93	$stack[ $i ] = self::$v[ $token ];
94	} else {
95	return self::trigger( "undefined variable '$token' in function definition" );
96	}
97	}
98	}
99	self::$f[ $fnn ] = array(
100	'args' => $args,
101	'func' => $stack,
102	);
103	return true;
104	// ===============
105	} else {
106	return self::pfx( self::nfx( $expr ) ); // straight up evaluation, woo
107	}
108	}
109
110	/**
111	* Convert infix to postfix notation.
112	*
113	* @param string $expr
114	*
115	* @return array\|string
116	*/
117	private static function nfx( $expr ) {
118	$index = 0;
119	$stack = new EvalMathStack();
120	$output = array(); // postfix form of expression, to be passed to pfx()
121	$expr = trim( $expr );
122
123	$ops = array( '+', '-', '*', '/', '^', '_' );
124	$ops_r = array(
125	'+' => 0,
126	'-' => 0,
127	'*' => 0,
128	'/' => 0,
129	'^' => 1,
130	); // right-associative operator?
131	$ops_p = array(
132	'+' => 0,
133	'-' => 0,
134	'*' => 1,
135	'/' => 1,
136	'_' => 1,
137	'^' => 2,
138	); // operator precedence
139
140	$expecting_op = false; // we use this in syntax-checking the expression
141	// and determining when a - is a negation
142	if ( preg_match( '/[^\w\s+*^\/()\.,-]/', $expr, $matches ) ) { // make sure the characters are all good
143	return self::trigger( "illegal character '{$matches[0]}'" );
144	}
145
146	while ( 1 ) { // 1 Infinite Loop ;)
147	$op = substr( $expr, $index, 1 ); // get the first character at the current index
148	// find out if we're currently at the beginning of a number/variable/function/parenthesis/operand
149	$ex = preg_match( '/^([A-Za-z]\w\(?\|\d+(?:\.\d)?\|\.\d+\|\()/', substr( $expr, $index ), $match );
150	// ===============
151	if ( '-' === $op and ! $expecting_op ) { // is it a negation instead of a minus?
152	$stack->push( '_' ); // put a negation on the stack
153	$index++;
154	} elseif ( '_' === $op ) { // we have to explicitly deny this, because it's legal on the stack
155	return self::trigger( "illegal character '_'" ); // but not in the input expression
156	// ===============
157	} elseif ( ( in_array( $op, $ops ) or $ex ) and $expecting_op ) { // are we putting an operator on the stack?
158	if ( $ex ) { // are we expecting an operator but have a number/variable/function/opening parenthesis?
159	$op = '*';
160	$index--; // it's an implicit multiplication
161	}
162	// heart of the algorithm:
163	while ( $stack->count > 0 and ( $o2 = $stack->last() ) and in_array( $o2, $ops ) and ( $ops_r[ $op ] ? $ops_p[ $op ] < $ops_p[ $o2 ] : $ops_p[ $op ] <= $ops_p[ $o2 ] ) ) {
164	$output[] = $stack->pop(); // pop stuff off the stack into the output
165	}
166	// many thanks: https://en.wikipedia.org/wiki/Reverse_Polish_notation#The_algorithm_in_detail
167	$stack->push( $op ); // finally put OUR operator onto the stack
168	$index++;
169	$expecting_op = false;
170	// ===============
171	} elseif ( ')' === $op && $expecting_op ) { // ready to close a parenthesis?
172	while ( ( $o2 = $stack->pop() ) != '(' ) { // pop off the stack back to the last (
173	if ( is_null( $o2 ) ) {
174	return self::trigger( "unexpected ')'" );
175	} else {
176	$output[] = $o2;
177	}
178	}
179	if ( preg_match( '/^([A-Za-z]\w*)\($/', $stack->last( 2 ), $matches ) ) { // did we just close a function?
180	$fnn = $matches[1]; // get the function name
181	$arg_count = $stack->pop(); // see how many arguments there were (cleverly stored on the stack, thank you)
182	$output[] = $stack->pop(); // pop the function and push onto the output
183	if ( in_array( $fnn, self::$fb ) ) { // check the argument count
184	if ( $arg_count > 1 ) {
185	return self::trigger( "too many arguments ($arg_count given, 1 expected)" );
186	}
187	} elseif ( array_key_exists( $fnn, self::$f ) ) {
188	if ( count( self::$f[ $fnn ]['args'] ) != $arg_count ) {
189	return self::trigger( "wrong number of arguments ($arg_count given, " . count( self::$f[ $fnn ]['args'] ) . ' expected)' );
190	}
191	} else { // did we somehow push a non-function on the stack? this should never happen
192	return self::trigger( 'internal error' );
193	}
194	}
195	$index++;
196	// ===============
197	} elseif ( ',' === $op and $expecting_op ) { // did we just finish a function argument?
198	while ( ( $o2 = $stack->pop() ) != '(' ) {
199	if ( is_null( $o2 ) ) {
200	return self::trigger( "unexpected ','" ); // oops, never had a (
201	} else {
202	$output[] = $o2; // pop the argument expression stuff and push onto the output
203	}
204	}
205	// make sure there was a function
206	if ( ! preg_match( '/^([A-Za-z]\w*)\($/', $stack->last( 2 ), $matches ) ) {
207	return self::trigger( "unexpected ','" );
208	}
209	$stack->push( $stack->pop() + 1 ); // increment the argument count
210	$stack->push( '(' ); // put the ( back on, we'll need to pop back to it again
211	$index++;
212	$expecting_op = false;
213	// ===============
214	} elseif ( '(' === $op and ! $expecting_op ) {
215	$stack->push( '(' ); // that was easy
216	$index++;
217	// ===============
218	} elseif ( $ex and ! $expecting_op ) { // do we now have a function/variable/number?
219	$expecting_op = true;
220	$val = $match[1];
221	if ( preg_match( '/^([A-Za-z]\w*)\($/', $val, $matches ) ) { // may be func, or variable w/ implicit multiplication against parentheses...
222	if ( in_array( $matches[1], self::$fb ) or array_key_exists( $matches[1], self::$f ) ) { // it's a func
223	$stack->push( $val );
224	$stack->push( 1 );
225	$stack->push( '(' );
226	$expecting_op = false;
227	} else { // it's a var w/ implicit multiplication
228	$val = $matches[1];
229	$output[] = $val;
230	}
231	} else { // it's a plain old var or num
232	$output[] = $val;
233	}
234	$index += strlen( $val );
235	// ===============
236	} elseif ( ')' === $op ) { // miscellaneous error checking
237	return self::trigger( "unexpected ')'" );
238	} elseif ( in_array( $op, $ops ) and ! $expecting_op ) {
239	return self::trigger( "unexpected operator '$op'" );
240	} else { // I don't even want to know what you did to get here
241	return self::trigger( 'an unexpected error occurred' );
242	}
243	if ( strlen( $expr ) == $index ) {
244	if ( in_array( $op, $ops ) ) { // did we end with an operator? bad.
245	return self::trigger( "operator '$op' lacks operand" );
246	} else {
247	break;
248	}
249	}
250	while ( substr( $expr, $index, 1 ) == ' ' ) { // step the index past whitespace (pretty much turns whitespace
251	$index++; // into implicit multiplication if no operator is there)
252	}
253	}
254	while ( ! is_null( $op = $stack->pop() ) ) { // pop everything off the stack and push onto output
255	if ( '(' === $op ) {
256	return self::trigger( "expecting ')'" ); // if there are (s on the stack, ()s were unbalanced
257	}
258	$output[] = $op;
259	}
260	return $output;
261	}
262
263	/**
264	* Evaluate postfix notation.
265	*
266	* @param mixed $tokens
267	* @param array $vars
268	*
269	* @return mixed
270	*/
271	private static function pfx( $tokens, $vars = array() ) {
272	if ( false == $tokens ) {
273	return false;
274	}
275	$stack = new EvalMathStack();
276
277	foreach ( $tokens as $token ) { // nice and easy
278	// if the token is a binary operator, pop two values off the stack, do the operation, and push the result back on
279	if ( in_array( $token, array( '+', '-', '*', '/', '^' ) ) ) {
280	if ( is_null( $op2 = $stack->pop() ) ) {
281	return self::trigger( 'internal error' );
282	}
283	if ( is_null( $op1 = $stack->pop() ) ) {
284	return self::trigger( 'internal error' );
285	}
286	switch ( $token ) {
287	case '+':
288	$stack->push( $op1 + $op2 );
289	break;
290	case '-':
291	$stack->push( $op1 - $op2 );
292	break;
293	case '*':
294	$stack->push( $op1 * $op2 );
295	break;
296	case '/':
297	if ( 0 == $op2 ) {
298	return self::trigger( 'division by zero' );
299	}
300	$stack->push( $op1 / $op2 );
301	break;
302	case '^':
303	$stack->push( pow( $op1, $op2 ) );
304	break;
305	}
306	// if the token is a unary operator, pop one value off the stack, do the operation, and push it back on
307	} elseif ( '_' === $token ) {
308	$stack->push( -1 * $stack->pop() );
309	// if the token is a function, pop arguments off the stack, hand them to the function, and push the result back on
310	} elseif ( ! preg_match( '/^([a-z]\w*)\($/', $token, $matches ) ) {
311	if ( is_numeric( $token ) ) {
312	$stack->push( $token );
313	} elseif ( array_key_exists( $token, self::$v ) ) {
314	$stack->push( self::$v[ $token ] );
315	} elseif ( array_key_exists( $token, $vars ) ) {
316	$stack->push( $vars[ $token ] );
317	} else {
318	return self::trigger( "undefined variable '$token'" );
319	}
320	}
321	}
322	// when we're out of tokens, the stack should have a single element, the final result
323	if ( 1 != $stack->count ) {
324	return self::trigger( 'internal error' );
325	}
326	return $stack->pop();
327	}
328
329	/**
330	* Trigger an error, but nicely, if need be.
331	*
332	* @param string $msg
333	*
334	* @return bool
335	*/
336	private static function trigger( string $msg ): bool {
337	self::$last_error = $msg;
338	if ( ! defined( 'DOING_AJAX' ) && ( defined('WP_DEBUG') && WP_DEBUG ) ) {
339	echo "\nError found in:";
340	self::debugPrintCallingFunction();
341	trigger_error( $msg, E_USER_WARNING ); // phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_trigger_error, WordPress.Security.EscapeOutput.OutputNotEscaped -- debug output.
342	}
343	return false;
344	}
345
346	/**
347	* Prints the file name, function name, and
348	* line number which called your function
349	* (not this function, then one that called
350	* it to begin with)
351	*/
352	private static function debugPrintCallingFunction() {
353	$file = 'n/a';
354	$func = 'n/a';
355	$line = 'n/a';
356	$debugTrace = debug_backtrace(); // phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_debug_backtrace -- debug output.
357
358	if ( isset( $debugTrace[1] ) ) {
359	$file = $debugTrace[1]['file'] ?: 'n/a';
360	$line = $debugTrace[1]['line'] ?: 'n/a';
361	}
362
363	if ( isset( $debugTrace[2] ) ) {
364	$func = $debugTrace[2]['function'] ?: 'n/a';
365	}
366
367	echo "\n$file, $func, $line\n"; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
368	}
369	}
370