VM

#!/usr/bin/env php
<?php

class VM {
    private $opcodes = array(
        'HALT',
        'ADD', 'SUB', 'MUL', 'DIV',
        'INC', 'DEC',
        'EQ', 'LT', 'GT',
        'JMP', 'JT', 'JF',
        'PUSH', 'POP',
        'LOAD', 'GLOAD',
        'STORE', 'GSTORE',
        'PRINT', 'PRINTLN',
        'CALL', 'ENTER', 'RET',
    );

    private $code = [];

    private $ip = 0;

    function __construct($script = null, $main = 'main') {
        if (null !== $script) {
            $code = $this->load($script);
        } else {
            $code = 'HALT';
        }

        $strings = array(); $string_count = 0;

        # extract strings
        $code = preg_replace_callback(array('#"([^"]+)"#', "#'([^']+)'#"), function($m) use (&$strings, &$string_count) {
            $string_count++;

            $ret = "__S{$string_count}";
            $strings = array_merge($strings, array("{$ret}:", "    {$m[1]}"));

            return $ret;
        }, $code);

        # split code at white spaces, remove // comments
        $this->code = array_merge(array_map('trim',$strings),
                                  array_values(array_filter(preg_split('#[\s+]#', $code))));

        $this->ip = is_numeric($main)
                  ? $main
                  : (($idx = array_search("{$main}:", $this->code)) !== false
                     ? $idx
                     : (array_search("main:", $this->code)) ?: 0);
    }

    function cycle($trace = 0) {
        $stack = [];
        $data = [];
        $traces = [];

        $sp = -1;
        $fp = 0;

        $code_len = count($this->code);
        $opcodes = array_flip($this->opcodes);

        if ($trace) {
            ob_start();
        }

        while ($this->ip < $code_len) {
            $opcode = strtoupper($this->code[$this->ip]); // fetch

            # ommit labels
            if (substr($opcode, -1) == ':') {
                $this->ip++;
                continue;
            }

            if ($trace) {
                $traces[] = sprintf("IP=%04d, SP=%04d: %10s (%2d) stack[%s]\n",
                                    $this->ip, $sp, $opcode, $opcodes[$opcode],
                                    implode(", ", array_slice($stack, 0, $sp+1)));
            }

            $this->ip++;

            switch ($opcode) {
            case 'PUSH':
                $arg = $this->code[$this->ip++];

                $fetch_addr = false;
                if (preg_match('#\(([^\]]+)\)#', $arg, $m)) {
                    $arg = $m[1];
                    $fetch_addr = true;
                }

                # look for a label
                $addr = array_search("{$arg}:", $this->code);
                if (false !== $addr) {
                    $arg = $this->code[$addr+1];

                    # look for a label indirection
                    $addr_indirect = array_search("{$arg}:", $this->code);
                    if (false !== $addr_indirect) {
                        $addr = $addr_indirect;
                        $arg = $this->code[$addr+1];
                    }
                }

                if ($fetch_addr) {
                    $stack[++$sp] = $addr+1;
                } else {
                    $stack[++$sp] = $arg;
                }

                break;

            case 'POP':
                --$sp;

                break;

            case 'PRINT':
                echo $stack[$sp--];
                break;

            case 'PRINTLN':
                echo $stack[$sp--] . PHP_EOL;
                break;

            case 'GSTORE':
                $v = $stack[$sp--];
                $addr = $this->code[$this->ip++];
                $data[$addr] = $v;
                break;

            case 'GLOAD':
                $addr = $this->code[$this->ip++];
                $v = $data[$addr];
                $stack[++$sp] = $v;
                break;

            case 'LOAD':
                $offset = $this->code[$this->ip++];

                $fetch_addr = false;
                if (preg_match('#\(([^\]]+)\)#', $offset, $m)) {
                    $fetch_addr = true;
                    $offset = $m[1];
                }

                $val = $stack[$fp + $offset];

                if ($fetch_addr) {
                    $val = $this->code[$val];
                }

                $stack[++$sp] = $val;

                break;

            case 'JMP':
                $lbl = $this->code[$this->ip++];
                $addr = array_search("{$lbl}:", $this->code);
                if (false === $addr) throw new Exception("Jump to undefined label {$lbl}");
                $this->ip = $addr;
                break;

            case 'JT':
                $lbl = $this->code[$this->ip++];
                $addr = array_search("{$lbl}:", $this->code);
                if (false === $addr) throw new Exception("Jump to undefined label {$lbl}");
                if ($stack[$sp--]) $this->ip = $addr;
                break;

            case 'JF':
                $lbl = $this->code[$this->ip++];
                $addr = array_search("{$lbl}:", $this->code);
                if (false === $addr) throw new Exception("Jump to undefined label {$lbl}");
                if (!$stack[$sp--]) $this->ip = $addr;
                break;

            case 'ADD':
                $b = $stack[$sp--];
                $a = $stack[$sp--];
                $stack[++$sp] = $a + $b;
                break;

            case 'SUB':
                $b = $stack[$sp--];
                $a = $stack[$sp--];
                $stack[++$sp] = $a - $b;
                break;

            case 'INC':
                $stack[$sp]++;
                break;

            case 'DEC':
                $stack[$sp]--;
                break;

            case 'MUL':
                $b = $stack[$sp--];
                $a = $stack[$sp--];
                $stack[++$sp] = $a * $b;
                break;

            case 'DIV':
                $b = $stack[$sp--];
                $a = $stack[$sp--];
                $stack[++$sp] = $a / $b;
                break;

            case 'GT':
                $b = $stack[$sp--];
                $a = $stack[$sp--];
                $stack[++$sp] = intval($a > $b);
                break;

            case 'LT':
                $b = $stack[$sp--];
                $a = $stack[$sp--];
                $stack[++$sp] = intval($a < $b);
                break;

            case 'EQ':
                $b = $stack[$sp--];
                $a = $stack[$sp--];
                $stack[++$sp] = intval($a == $b);
                break;

            case 'CALL':
                $lbl = $this->code[$this->ip++];           // target addr of function
                $addr = array_search("{$lbl}:", $this->code);
                $argc = $this->code[$this->ip++];           // number of args
                if (false === $addr) {
                    if (function_exists($lbl)) {
                        $args = array_slice(array_reverse($stack), 0, $argc);
                        $ret = call_user_func_array($lbl, $args);
                        $sp -= $argc;                         // pop args
                        $stack[++$sp] = $ret;
                        break;
                    } else {
                        throw new Exception("Call to undefined function {$lbl}");
                    }
                }
                $stack[++$sp] = $argc;          // save number of args
                $stack[++$sp] = $fp;            // save frame pointer
                $stack[++$sp] = $this->ip;      // push return address
                $fp = $sp;
                $this->ip = $addr;

                break;

            case 'RET':
                $rval = $stack[$sp--];          // pop return value
                $sp = $fp;                      // jump over locals to fp
                $this->ip = $stack[$sp--];      // pop return address, jump to it
                $fp = $stack[$sp--];      // restore fp
                $argc = $stack[$sp--];          // how many args to throw away
                $sp -= $argc;                         // pop args
                $stack[++$sp] = $rval;          // leave result on stack

                break;

            case 'HALT';

                break 2; # break loop not switch

            default:
                throw new Exception("invalid opcode {$opcode} @ ip=(" . ($this->ip - 1) . ")");
            } // switch

            #sleep(1);
        } // while

        if ($trace) {
            echo 'OUTPUT:' . PHP_EOL . ob_get_clean() . PHP_EOL;

            echo json_encode(array(
                'STACK', array_slice($stack, 0, $sp+1),
                'SP', $sp,
                'DATA', $data
            )) . PHP_EOL;

            echo implode("", $traces);

            echo implode("\n", $this->code) . PHP_EOL;

        }

        return 0;
    } // fn cpu

    function load($script) {
        static $seen = array();

        if (isset($seen[$script])) return;
        $seen[$script] = 1;

        $dirname = dirname($script);
        $basename = basename($script);

        $code = file_get_contents($script);

        # get rid of comments
        $code = preg_replace(array("#//[^\n]+$#m", "#/\*.*?\*/#ms"), array(""), $code);

        $code = preg_replace_callback("#include ['\"]?([\w\.]+)['\"]?$#m", function($m) use ($dirname) {
            return $this->load("$dirname/$m[1]");
        }, $code);

        return $code;
    } // fn load

}

$vm = new VM(isset($_SERVER['argv'][1]) && file_exists($_SERVER['argv'][1]) ? $_SERVER['argv'][1] : NULL,
             isset($_SERVER['argv'][2]) ? $_SERVER['argv'][2] : 'main');

try {
    return $vm->cycle(isset($_SERVER['argv'][3]) && $_SERVER['argv'][3]);
} catch (Exception $ex) {
    print $ex->getMessage() . " (" . $ex->getLine() . ")" . PHP_EOL;
    throw $ex;
}