bencoded.php

<?php

/**
 * Really simple, concise and fairly efficient bencode/bdecode functions
 * for manipulating BitTorrent metadata within PHP.
 * Lookout for a C PHP extension coming to a server near you!
 * by Samuel Cochran <sj26@sj26.com>
 */

function bdecode($stream) {
        if (feof($stream)) {
                throw new Exception('Unexpected end of stream while reading.');
        }
        $c = fgetc($stream);
        if ($c == 'd') {
                $v = array();
                while (($k = bdecode($stream)) !== NULL) {
                        if (!is_string($k)) 
                                throw new Exception('Dictionary keys must be strings.');
                        $v[$k] = bdecode($stream);
                }
        } else if ($c == 'l') {
                $v = array();
                while (($e = bdecode($stream)) !== NULL) {
                        $v[] = $e;
                }
        } else if ($c == 'i') {
                $v = 0;
                while (($c = fgetc($stream)) !== FALSE) {
                        if (is_numeric($c)) {
                                $v = $v * 10 + intval($c);
                        } else if ($c == 'e') {
                                break;
                        } else {
                                throw new Exception('Unexpected character while reading integer: '.$c);
                        }
                }
                if (feof($stream)) {
                        throw new Exception('Unexpected end of stream while reading string length.');
                }
        } else if ($c == 'e') {
                $v = NULL;
        } else if (is_numeric($c)) {
                $l = intval($c);
                while (($c = fgetc($stream)) !== FALSE) {
                        if (is_numeric($c)) {
                                $l = $l * 10 + intval($c);
                        } else if ($c == ':') {
                                break;
                        } else {
                                throw new Exception('Unexpected character while reading string length: '.$c);
                        }
                }
                if (feof($stream)) {
                        throw new Exception('Unexpected end of stream while reading string length.');
                }
                $v = '';
                while (strlen($v) < $l) {
                        if (($s = fread($stream, $l - strlen($v))) === FALSE) {
                                throw new Exception('Unexpected end of stream while reading string.');
                        } else {
                                $v .= $s;
                        }
                }
        }
        return $v;
}

function bencode($value) {
        if (is_null($value)) {
                $s = '0:';
        } else if (is_int($value) || is_double($value)) {
                $s = 'i' . (int)($value) . 'e';
        } else if (is_string($value)) {
                $s = strlen($value).':'.$value;
        } else if (is_array($value)) {
                $l = true;
                foreach(array_keys($value) as $key) {
                        if (!is_int($key)) {
                                $l = false;
                                break;
                        }
                }
                if ($l) {
                        $s = 'l';
                        ksort($value, SORT_NUMERIC);
                        foreach($value as $v) {
                                $s .= bencode($v);
                        }
                        $s .= 'e';
                } else {
                        $s = 'd';
                        ksort($value, SORT_STRING);
                        foreach($value as $k => $v) {
                                $s .= bencode(strval($k));
                                $s .= bencode($v);
                        }
                        $s .= 'e';
                }
        } else {
                throw new Exception('Cannot encode value, unsupported type: '.$value);
        }
        return $s;
}