stacky.php

#!/usr/bin/php
<?php
    if (empty($argv[1])) {
        die("please specify a file\n");
    }

    function is_str($word) {
        return preg_match('%^".*"$%', $word);
    }

    function is_comment($line) {
        return @$line[0] === ';';
    }

    function is_label($line) {
        return substr($line, -1) === ':';
    }

    function parse_line($line) {
        $words = preg_split('%\s%', $line);
        return $words;
    }

    function eval_expression($exp) {
        global $vars;

        $matches = [];
        $operations = [
            '+' => function ($a, $b) {return $a + $b;},
            '-' => function ($a, $b) {return $a - $b;},
            '*' => function ($a, $b) {return $a * $b;},
            '/' => function ($a, $b) {return $a / $b;},
            '%' => function ($a, $b) {return $a % $b;},
        ];

        $exprgxp = '/(\w+)(['.preg_quote(implode('', array_keys($operations)), '/').'])(\w+)/';
        if (preg_match($exprgxp, $exp, $matches)) {
            list($dummy, $a, $op, $b) = $matches;

            if (array_key_exists($a, $vars)) {
                $a = $vars[$a];
            }

            if (array_key_exists($b, $vars)) {
                $b = $vars[$b];
            }

            $val = $operations[$op]((int)$a, (int)$b);
        } else if (array_key_exists($exp, $vars)) {
            $val = $vars[$exp];
        } else {
            $val = (int)$exp;
        }
        return $val;
    }

    $contents = file_get_contents($argv[1]);
    @list($datasec, $codesec) = explode("CODE\n", $contents);

    $data = array_map('trim', explode("\n", $datasec));
    $code = array_map('trim', explode("\n", $codesec));

    $vars = [];
    $labels = [];
    $stack = [];
    $pcounter = 0;

    // set up vars
    foreach ($data as $dline) {
        if ($dline !== 'DATA' && !is_comment($dline)) {
            @list($name, $value) = parse_line($dline);
            if (!empty($name)) {
                $vars[$name] = (int)$value;
            }
        }
    }

    // set up labels
    foreach ($code as $i => $cline) {
        if (is_label($cline)) {
            $lname = substr($cline, 0, -1);
            $labels[$lname] = $i;
        }
    }

    function execute_line($line) {
        global $pcounter, $vars, $labels, $stack;

        if (is_label($line) || empty($line)) {
            $pcounter += 1;
            return;
        }

        $w = parse_line($line);

        switch(strtolower($w[0])) {
        case 'print':
            if (is_str($w[1])) {
                $val = substr($w[1], 1, -1);
            } else {
                $val = eval_expression($vars[$w[1]]);
            }
            echo "{$val}\n";
            $pcounter += 1;
            break;

        case 'inc':
            $vars[$w[1]] += 1;
            $pcounter += 1;
            break;

        case 'push':
            $stack[] = eval_expression($w[1]);
            $pcounter += 1;
            break;

        case 'pop':
            $times = !empty($w[1]) ? $w[1] : 1;
            for ($i = 0; $i < $times; $i += 1) {
                array_pop($stack);
            }
            $pcounter += 1;
            break;

        case 'jmpeq':
            $sl = sizeof($stack);

            if ($stack[$sl-1] === $stack[$sl-2]) {
                $pcounter = $labels[$w[1]];
            } else if (!empty($w[2])) {
                $pcounter = $labels[$w[2]];
            } else {
                $pcounter += 1;
            }

            break;

        case 'jmp':
            $pcounter = $labels[$w[1]];
            break;

        case 'nop':
        default:
            $pcounter += 1;
            break;
        }
    }

    $codelen = sizeof($code);

    while ($pcounter < $codelen) {
        execute_line($code[$pcounter]);
    }