includes/libraries/class-wc-eval-math.php
<?php
use Automattic\Jetpack\Constants;
if ( ! defined( 'ABSPATH' ) ) {
exit;
}
if ( ! class_exists( 'WC_Eval_Math', false ) ) {
/**
* Class WC_Eval_Math. Supports basic math only (removed eval function).
*
* Based on EvalMath by Miles Kaufman Copyright (C) 2005 Miles Kaufmann http://www.twmagic.com/.
*/
class WC_Eval_Math {
/**
* Last error.
*
* @var string
*/
public static $last_error = null;
/**
* Variables (and constants).
*
* @var array
*/
public static $v = array( 'e' => 2.71, 'pi' => 3.14 );
/**
* User-defined functions.
*
* @var array
*/
public static $f = array();
/**
* Constants.
*
* @var array
*/
public static $vb = array( 'e', 'pi' );
/**
* Built-in functions.
*
* @var array
*/
public static $fb = array();
/**
* Evaluate maths string.
*
* @param string $expr
* @return mixed
*/
public static function evaluate( $expr ) {
self::$last_error = null;
$expr = trim( $expr );
if ( substr( $expr, -1, 1 ) == ';' ) {
$expr = substr( $expr, 0, strlen( $expr ) -1 ); // strip semicolons at the end
}
// ===============
// is it a variable assignment?
if ( preg_match( '/^\s*([a-z]\w*)\s*=\s*(.+)$/', $expr, $matches ) ) {
if ( in_array( $matches[1], self::$vb ) ) { // make sure we're not assigning to a constant
return self::trigger( "cannot assign to constant '$matches[1]'" );
}
if ( ( $tmp = self::pfx( self::nfx( $matches[2] ) ) ) === false ) {
return false; // get the result and make sure it's good
}
self::$v[ $matches[1] ] = $tmp; // if so, stick it in the variable array
return self::$v[ $matches[1] ]; // and return the resulting value
// ===============
// is it a function assignment?
} elseif ( preg_match( '/^\s*([a-z]\w*)\s*\(\s*([a-z]\w*(?:\s*,\s*[a-z]\w*)*)\s*\)\s*=\s*(.+)$/', $expr, $matches ) ) {
$fnn = $matches[1]; // get the function name
if ( in_array( $matches[1], self::$fb ) ) { // make sure it isn't built in
return self::trigger( "cannot redefine built-in function '$matches[1]()'" );
}
$args = explode( ",", preg_replace( "/\s+/", "", $matches[2] ) ); // get the arguments
if ( ( $stack = self::nfx( $matches[3] ) ) === false ) {
return false; // see if it can be converted to postfix
}
$stack_size = count( $stack );
for ( $i = 0; $i < $stack_size; $i++ ) { // freeze the state of the non-argument variables
$token = $stack[ $i ];
if ( preg_match( '/^[a-z]\w*$/', $token ) and ! in_array( $token, $args ) ) {
if ( array_key_exists( $token, self::$v ) ) {
$stack[ $i ] = self::$v[ $token ];
} else {
return self::trigger( "undefined variable '$token' in function definition" );
}
}
}
self::$f[ $fnn ] = array( 'args' => $args, 'func' => $stack );
return true;
// ===============
} else {
return self::pfx( self::nfx( $expr ) ); // straight up evaluation, woo
}
}
/**
* Convert infix to postfix notation.
*
* @param string $expr
*
* @return array|string
*/
private static function nfx( $expr ) {
$index = 0;
$stack = new WC_Eval_Math_Stack;
$output = array(); // postfix form of expression, to be passed to pfx()
$expr = trim( $expr );
$ops = array( '+', '-', '*', '/', '^', '_' );
$ops_r = array( '+' => 0, '-' => 0, '*' => 0, '/' => 0, '^' => 1 ); // right-associative operator?
$ops_p = array( '+' => 0, '-' => 0, '*' => 1, '/' => 1, '_' => 1, '^' => 2 ); // operator precedence
$expecting_op = false; // we use this in syntax-checking the expression
// and determining when a - is a negation
if ( preg_match( "/[^\w\s+*^\/()\.,-]/", $expr, $matches ) ) { // make sure the characters are all good
return self::trigger( "illegal character '{$matches[0]}'" );
}
while ( 1 ) { // 1 Infinite Loop ;)
$op = substr( $expr, $index, 1 ); // get the first character at the current index
// find out if we're currently at the beginning of a number/variable/function/parenthesis/operand
$ex = preg_match( '/^([A-Za-z]\w*\(?|\d+(?:\.\d*)?|\.\d+|\()/', substr( $expr, $index ), $match );
// ===============
if ( '-' === $op and ! $expecting_op ) { // is it a negation instead of a minus?
$stack->push( '_' ); // put a negation on the stack
$index++;
} elseif ( '_' === $op ) { // we have to explicitly deny this, because it's legal on the stack
return self::trigger( "illegal character '_'" ); // but not in the input expression
// ===============
} elseif ( ( in_array( $op, $ops ) or $ex ) and $expecting_op ) { // are we putting an operator on the stack?
if ( $ex ) { // are we expecting an operator but have a number/variable/function/opening parenthesis?
$op = '*';
$index--; // it's an implicit multiplication
}
// heart of the algorithm:
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 ] ) ) {
$output[] = $stack->pop(); // pop stuff off the stack into the output
}
// many thanks: https://en.wikipedia.org/wiki/Reverse_Polish_notation#The_algorithm_in_detail
$stack->push( $op ); // finally put OUR operator onto the stack
$index++;
$expecting_op = false;
// ===============
} elseif ( ')' === $op && $expecting_op ) { // ready to close a parenthesis?
while ( ( $o2 = $stack->pop() ) != '(' ) { // pop off the stack back to the last (
if ( is_null( $o2 ) ) {
return self::trigger( "unexpected ')'" );
} else {
$output[] = $o2;
}
}
if ( preg_match( "/^([A-Za-z]\w*)\($/", $stack->last( 2 ), $matches ) ) { // did we just close a function?
$fnn = $matches[1]; // get the function name
$arg_count = $stack->pop(); // see how many arguments there were (cleverly stored on the stack, thank you)
$output[] = $stack->pop(); // pop the function and push onto the output
if ( in_array( $fnn, self::$fb ) ) { // check the argument count
if ( $arg_count > 1 ) {
return self::trigger( "too many arguments ($arg_count given, 1 expected)" );
}
} elseif ( array_key_exists( $fnn, self::$f ) ) {
if ( count( self::$f[ $fnn ]['args'] ) != $arg_count ) {
return self::trigger( "wrong number of arguments ($arg_count given, " . count( self::$f[ $fnn ]['args'] ) . " expected)" );
}
} else { // did we somehow push a non-function on the stack? this should never happen
return self::trigger( "internal error" );
}
}
$index++;
// ===============
} elseif ( ',' === $op and $expecting_op ) { // did we just finish a function argument?
while ( ( $o2 = $stack->pop() ) != '(' ) {
if ( is_null( $o2 ) ) {
return self::trigger( "unexpected ','" ); // oops, never had a (
} else {
$output[] = $o2; // pop the argument expression stuff and push onto the output
}
}
// make sure there was a function
if ( ! preg_match( "/^([A-Za-z]\w*)\($/", $stack->last( 2 ), $matches ) ) {
return self::trigger( "unexpected ','" );
}
$stack->push( $stack->pop() + 1 ); // increment the argument count
$stack->push( '(' ); // put the ( back on, we'll need to pop back to it again
$index++;
$expecting_op = false;
// ===============
} elseif ( '(' === $op and ! $expecting_op ) {
$stack->push( '(' ); // that was easy
$index++;
// ===============
} elseif ( $ex and ! $expecting_op ) { // do we now have a function/variable/number?
$expecting_op = true;
$val = $match[1];
if ( preg_match( "/^([A-Za-z]\w*)\($/", $val, $matches ) ) { // may be func, or variable w/ implicit multiplication against parentheses...
if ( in_array( $matches[1], self::$fb ) or array_key_exists( $matches[1], self::$f ) ) { // it's a func
$stack->push( $val );
$stack->push( 1 );
$stack->push( '(' );
$expecting_op = false;
} else { // it's a var w/ implicit multiplication
$val = $matches[1];
$output[] = $val;
}
} else { // it's a plain old var or num
$output[] = $val;
}
$index += strlen( $val );
// ===============
} elseif ( ')' === $op ) { // miscellaneous error checking
return self::trigger( "unexpected ')'" );
} elseif ( in_array( $op, $ops ) and ! $expecting_op ) {
return self::trigger( "unexpected operator '$op'" );
} else { // I don't even want to know what you did to get here
return self::trigger( "an unexpected error occurred" );
}
if ( strlen( $expr ) == $index ) {
if ( in_array( $op, $ops ) ) { // did we end with an operator? bad.
return self::trigger( "operator '$op' lacks operand" );
} else {
break;
}
}
while ( substr( $expr, $index, 1 ) == ' ' ) { // step the index past whitespace (pretty much turns whitespace
$index++; // into implicit multiplication if no operator is there)
}
}
while ( ! is_null( $op = $stack->pop() ) ) { // pop everything off the stack and push onto output
if ( '(' === $op ) {
return self::trigger( "expecting ')'" ); // if there are (s on the stack, ()s were unbalanced
}
$output[] = $op;
}
return $output;
}
/**
* Evaluate postfix notation.
*
* @param mixed $tokens
* @param array $vars
*
* @return mixed
*/
private static function pfx( $tokens, $vars = array() ) {
if ( false == $tokens ) {
return false;
}
$stack = new WC_Eval_Math_Stack;
foreach ( $tokens as $token ) { // nice and easy
// if the token is a binary operator, pop two values off the stack, do the operation, and push the result back on
if ( in_array( $token, array( '+', '-', '*', '/', '^' ) ) ) {
if ( is_null( $op2 = $stack->pop() ) ) {
return self::trigger( "internal error" );
}
if ( is_null( $op1 = $stack->pop() ) ) {
return self::trigger( "internal error" );
}
switch ( $token ) {
case '+':
$stack->push( $op1 + $op2 );
break;
case '-':
$stack->push( $op1 - $op2 );
break;
case '*':
$stack->push( $op1 * $op2 );
break;
case '/':
if ( 0 == $op2 ) {
return self::trigger( 'division by zero' );
}
$stack->push( $op1 / $op2 );
break;
case '^':
$stack->push( pow( $op1, $op2 ) );
break;
}
// if the token is a unary operator, pop one value off the stack, do the operation, and push it back on
} elseif ( '_' === $token ) {
$stack->push( -1 * $stack->pop() );
// if the token is a function, pop arguments off the stack, hand them to the function, and push the result back on
} elseif ( ! preg_match( "/^([a-z]\w*)\($/", $token, $matches ) ) {
if ( is_numeric( $token ) ) {
$stack->push( $token );
} elseif ( array_key_exists( $token, self::$v ) ) {
$stack->push( self::$v[ $token ] );
} elseif ( array_key_exists( $token, $vars ) ) {
$stack->push( $vars[ $token ] );
} else {
return self::trigger( "undefined variable '$token'" );
}
}
}
// when we're out of tokens, the stack should have a single element, the final result
if ( 1 != $stack->count ) {
return self::trigger( "internal error" );
}
return $stack->pop();
}
/**
* Trigger an error, but nicely, if need be.
*
* @param string $msg
*
* @return bool
*/
private static function trigger( $msg ) {
self::$last_error = $msg;
if ( ! Constants::is_true( 'DOING_AJAX' ) && Constants::is_true( 'WP_DEBUG' ) ) {
echo "\nError found in:";
self::debugPrintCallingFunction();
trigger_error( $msg, E_USER_WARNING );
}
return false;
}
/**
* Prints the file name, function name, and
* line number which called your function
* (not this function, then one that called
* it to begin with)
*/
private static function debugPrintCallingFunction() {
$file = 'n/a';
$func = 'n/a';
$line = 'n/a';
$debugTrace = debug_backtrace();
if ( isset( $debugTrace[1] ) ) {
$file = $debugTrace[1]['file'] ? $debugTrace[1]['file'] : 'n/a';
$line = $debugTrace[1]['line'] ? $debugTrace[1]['line'] : 'n/a';
}
if ( isset( $debugTrace[2] ) ) {
$func = $debugTrace[2]['function'] ? $debugTrace[2]['function'] : 'n/a';
}
echo "\n$file, $func, $line\n";
}
}
/**
* Class WC_Eval_Math_Stack.
*/
class WC_Eval_Math_Stack {
/**
* Stack array.
*
* @var array
*/
public $stack = array();
/**
* Stack counter.
*
* @var integer
*/
public $count = 0;
/**
* Push value into stack.
*
* @param mixed $val
*/
public function push( $val ) {
$this->stack[ $this->count ] = $val;
$this->count++;
}
/**
* Pop value from stack.
*
* @return mixed
*/
public function pop() {
if ( $this->count > 0 ) {
$this->count--;
return $this->stack[ $this->count ];
}
return null;
}
/**
* Get last value from stack.
*
* @param int $n
*
* @return mixed
*/
public function last( $n=1 ) {
$key = $this->count - $n;
return array_key_exists( $key, $this->stack ) ? $this->stack[ $key ] : null;
}
}
}