From 8481b5c66bc798be2280f0a25092e5d704f87961 Mon Sep 17 00:00:00 2001
From: Daniil Gentili <daniil@daniil.it>
Date: Mon, 1 Apr 2024 17:51:11 +0200
Subject: [PATCH] Finalize

---
 composer.json        |   5 +-
 src/FileId.php       | 102 ++++++++++-----------
 src/Tools.php        | 205 +++++++++++++++++++++++++++++++++++++++++++
 src/UniqueFileId.php |  28 +++---
 src/functions.php    | 203 ------------------------------------------
 5 files changed, 271 insertions(+), 272 deletions(-)
 create mode 100644 src/Tools.php
 delete mode 100644 src/functions.php

diff --git a/composer.json b/composer.json
index bbdeac8..eb2c95c 100644
--- a/composer.json
+++ b/composer.json
@@ -22,10 +22,7 @@
     "autoload": {
         "psr-4": {
             "danog\\Decoder\\": "src/"
-        },
-        "files": [
-            "src/functions.php"
-        ]
+        }
     },
     "autoload-dev": {
         "psr-4": {
diff --git a/src/FileId.php b/src/FileId.php
index dd2d84c..8e127f4 100644
--- a/src/FileId.php
+++ b/src/FileId.php
@@ -111,7 +111,7 @@ final class FileId
     public static function fromBotAPI(string $fileId): self
     {
         $orig = $fileId;
-        $fileId = rleDecode(base64urlDecode($fileId));
+        $fileId = Tools::rleDecode(Tools::base64urlDecode($fileId));
         $version = \ord($fileId[\strlen($fileId) - 1]);
         $subVersion = $version === 4 ? \ord($fileId[\strlen($fileId) - 2]) : 0;
 
@@ -126,16 +126,16 @@ final class FileId
             return $res;
         };
 
-        $typeId = unpackInt($read(4));
-        $dc_id = unpackInt($read(4));
-        $fileReference = $typeId & FILE_REFERENCE_FLAG ? readTLString($fileId) : null;
-        $hasWebLocation = (bool) ($typeId & WEB_LOCATION_FLAG);
-        $typeId &= ~FILE_REFERENCE_FLAG;
-        $typeId &= ~WEB_LOCATION_FLAG;
+        $typeId = Tools::unpackInt($read(4));
+        $dc_id = Tools::unpackInt($read(4));
+        $fileReference = $typeId & Tools::FILE_REFERENCE_FLAG ? Tools::readTLString($fileId) : null;
+        $hasWebLocation = (bool) ($typeId & Tools::WEB_LOCATION_FLAG);
+        $typeId &= ~Tools::FILE_REFERENCE_FLAG;
+        $typeId &= ~Tools::WEB_LOCATION_FLAG;
 
         if ($hasWebLocation) {
-            $url = readTLString($fileId);
-            $access_hash = unpackLong($read(8));
+            $url = Tools::readTLString($fileId);
+            $access_hash = Tools::unpackLong($read(8));
             return new self(
                 $dc_id,
                 FileIdType::from($typeId),
@@ -147,28 +147,28 @@ final class FileId
                 subVersion: $subVersion
             );
         }
-        $id = unpackLong($read(8));
-        $access_hash = unpackLong($read(8));
+        $id = Tools::unpackLong($read(8));
+        $access_hash = Tools::unpackLong($read(8));
 
         $volume_id = null;
         $local_id = null;
         $photoSizeSource = null;
         if ($typeId <= FileIdType::PHOTO->value) {
             if ($subVersion < 32) {
-                $volume_id = unpackLong($read(8));
-                $local_id = unpackInt($read(4));
+                $volume_id = Tools::unpackLong($read(8));
+                $local_id = Tools::unpackInt($read(4));
             }
 
             /** @psalm-suppress MixedArgument */
             $photosize_source = PhotoSizeSourceType::from($subVersion >= 4 ? \unpack('V', $read(4))[1] : 0);
             switch ($photosize_source) {
                 case PhotoSizeSourceType::LEGACY:
-                    $photoSizeSource = new PhotoSizeSourceLegacy(unpackLong($read(8)));
+                    $photoSizeSource = new PhotoSizeSourceLegacy(Tools::unpackLong($read(8)));
                     break;
                 case PhotoSizeSourceType::FULL_LEGACY:
-                    $volume_id = unpackLong($read(8));
-                    $photoSizeSource = new PhotoSizeSourceLegacy(unpackLong($read(8)));
-                    $local_id = unpackInt($read(4));
+                    $volume_id = Tools::unpackLong($read(8));
+                    $photoSizeSource = new PhotoSizeSourceLegacy(Tools::unpackLong($read(8)));
+                    $local_id = Tools::unpackInt($read(4));
                     break;
                 case PhotoSizeSourceType::THUMBNAIL:
                     /** @var array{file_type: int, thumbnail_type: string} */
@@ -184,14 +184,14 @@ final class FileId
                         ? PhotoSizeSourceDialogPhotoSmall::class
                         : PhotoSizeSourceDialogPhotoBig::class;
                     $photoSizeSource = new $clazz(
-                        unpackLong($read(8)),
-                        unpackLong($read(8)),
+                        Tools::unpackLong($read(8)),
+                        Tools::unpackLong($read(8)),
                     );
                     break;
                 case PhotoSizeSourceType::STICKERSET_THUMBNAIL:
                     $photoSizeSource = new PhotoSizeSourceStickersetThumbnail(
-                        unpackLong($read(8)),
-                        unpackLong($read(8))
+                        Tools::unpackLong($read(8)),
+                        Tools::unpackLong($read(8))
                     );
                     break;
                 case PhotoSizeSourceType::DIALOGPHOTO_BIG_LEGACY:
@@ -200,27 +200,27 @@ final class FileId
                         ? PhotoSizeSourceDialogPhotoSmall::class
                         : PhotoSizeSourceDialogPhotoBig::class;
                     $photoSizeSource = new $clazz(
-                        unpackLong($read(8)),
-                        unpackLong($read(8))
+                        Tools::unpackLong($read(8)),
+                        Tools::unpackLong($read(8))
                     );
 
-                    $volume_id = unpackLong($read(8));
-                    $local_id = unpackInt($read(4));
+                    $volume_id = Tools::unpackLong($read(8));
+                    $local_id = Tools::unpackInt($read(4));
                     break;
                 case PhotoSizeSourceType::STICKERSET_THUMBNAIL_LEGACY:
                     $photoSizeSource = new PhotoSizeSourceStickersetThumbnail(
-                        unpackLong($read(8)),
-                        unpackLong($read(8)),
+                        Tools::unpackLong($read(8)),
+                        Tools::unpackLong($read(8)),
                     );
 
-                    $volume_id = unpackLong($read(8));
-                    $local_id = unpackInt($read(4));
+                    $volume_id = Tools::unpackLong($read(8));
+                    $local_id = Tools::unpackInt($read(4));
                     break;
                 case PhotoSizeSourceType::STICKERSET_THUMBNAIL_VERSION:
                     $photoSizeSource = new PhotoSizeSourceStickersetThumbnailVersion(
-                        unpackLong($read(8)),
-                        unpackLong($read(8)),
-                        unpackInt($read(4))
+                        Tools::unpackLong($read(8)),
+                        Tools::unpackLong($read(8)),
+                        Tools::unpackInt($read(4))
                     );
                     break;
             }
@@ -253,25 +253,25 @@ final class FileId
     {
         $type = $this->type->value;
         if ($this->fileReference !== null) {
-            $type |= FILE_REFERENCE_FLAG;
+            $type |= Tools::FILE_REFERENCE_FLAG;
         }
         if ($this->url !== null) {
-            $type |= WEB_LOCATION_FLAG;
+            $type |= Tools::WEB_LOCATION_FLAG;
         }
 
         $fileId = \pack('VV', $type, $this->dcId);
         if ($this->fileReference !== null) {
-            $fileId .= packTLString($this->fileReference);
+            $fileId .= Tools::packTLString($this->fileReference);
         }
         if ($this->url !== null) {
-            $fileId .= packTLString($this->url);
-            $fileId .= packLong($this->accessHash);
-            return base64urlEncode(rleEncode($fileId));
+            $fileId .= Tools::packTLString($this->url);
+            $fileId .= Tools::packLong($this->accessHash);
+            return Tools::base64urlEncode(Tools::rleEncode($fileId));
         }
 
         \assert($this->id !== null);
-        $fileId .= packLong($this->id);
-        $fileId .= packLong($this->accessHash);
+        $fileId .= Tools::packLong($this->id);
+        $fileId .= Tools::packLong($this->accessHash);
 
         if ($this->photoSizeSource !== null) {
             $photoSize = $this->photoSizeSource;
@@ -281,11 +281,11 @@ final class FileId
                     if ($this->volumeId === null) {
                         $writeExtra = true;
                         $fileId .= \pack('V', PhotoSizeSourceType::LEGACY->value);
-                        $fileId .= packLong($photoSize->secret);
+                        $fileId .= Tools::packLong($photoSize->secret);
                     } else {
                         $fileId .= \pack('V', PhotoSizeSourceType::FULL_LEGACY->value);
-                        $fileId .= packLong($this->volumeId);
-                        $fileId .= packLong($photoSize->secret);
+                        $fileId .= Tools::packLong($this->volumeId);
+                        $fileId .= Tools::packLong($photoSize->secret);
                         $fileId .= \pack('l', $this->localId);
                     }
                     break;
@@ -307,22 +307,22 @@ final class FileId
                             : PhotoSizeSourceType::DIALOGPHOTO_BIG->value
                         )
                     );
-                    $fileId .= packLong($photoSize->dialogId);
-                    $fileId .= packLong($photoSize->dialogAccessHash);
+                    $fileId .= Tools::packLong($photoSize->dialogId);
+                    $fileId .= Tools::packLong($photoSize->dialogAccessHash);
                     break;
                 case $photoSize instanceof PhotoSizeSourceStickersetThumbnail:
                     $writeExtra = $this->volumeId !== null;
-                    $fileId .= packLong($photoSize->stickerSetId);
-                    $fileId .= packLong($photoSize->stickerSetAccessHash);
+                    $fileId .= Tools::packLong($photoSize->stickerSetId);
+                    $fileId .= Tools::packLong($photoSize->stickerSetAccessHash);
                     break;
                 case $photoSize instanceof PhotoSizeSourceStickersetThumbnailVersion:
-                    $fileId .= packLong($photoSize->stickerSetId);
-                    $fileId .= packLong($photoSize->stickerSetAccessHash);
+                    $fileId .= Tools::packLong($photoSize->stickerSetId);
+                    $fileId .= Tools::packLong($photoSize->stickerSetAccessHash);
                     $fileId .= \pack('l', $photoSize->stickerSetVersion);
                     break;
             }
             if ($writeExtra && $this->volumeId !== null && $this->localId !== null) {
-                $fileId .= packLong($this->volumeId);
+                $fileId .= Tools::packLong($this->volumeId);
                 $fileId .= \pack('l', $this->localId);
             }
         }
@@ -332,7 +332,7 @@ final class FileId
         }
         $fileId .= \chr($this->version);
 
-        return base64urlEncode(rleEncode($fileId));
+        return Tools::base64urlEncode(Tools::rleEncode($fileId));
     }
 
     /**
diff --git a/src/Tools.php b/src/Tools.php
new file mode 100644
index 0000000..fdc555e
--- /dev/null
+++ b/src/Tools.php
@@ -0,0 +1,205 @@
+<?php declare(strict_types=1);
+
+namespace danog\Decoder;
+
+\define('BIG_ENDIAN', \pack('L', 1) === \pack('N', 1));
+
+final class Tools
+{
+    public const WEB_LOCATION_FLAG =  1 << 24;
+    public const FILE_REFERENCE_FLAG = 1 << 25;
+
+    /**
+     * Unpack long properly, returns an actual number in any case.
+     *
+     * @internal
+     *
+     * @param string $field Field to unpack
+     */
+    public static function unpackLong(string $field): int
+    {
+        /** @psalm-suppress MixedReturnStatement */
+        return \unpack('q', BIG_ENDIAN ? \strrev($field) : $field)[1];
+    }
+    /**
+     * Unpack integer.
+     * @internal
+     *
+     * @param string $field Field to unpack
+     */
+    public static function unpackInt(string $field): int
+    {
+        /** @psalm-suppress MixedReturnStatement */
+        return \unpack('l', $field)[1];
+    }
+    /**
+     * Pack string long.
+     *
+     * @internal
+     *
+     */
+    public static function packLong(int $field): string
+    {
+        $res = \pack('q', $field);
+        return BIG_ENDIAN ? \strrev($res) : $res;
+    }
+    /**
+     * Base64URL decode.
+     *
+     * @param string $data Data to decode
+     *
+     * @internal
+     *
+     */
+    public static function base64urlDecode(string $data): string
+    {
+        return \base64_decode(\str_pad(\strtr($data, '-_', '+/'), \strlen($data) % 4, '=', STR_PAD_RIGHT));
+    }
+
+    /**
+     * Base64URL encode.
+     *
+     * @param string $data Data to encode
+     *
+     * @internal
+     *
+     */
+    public static function base64urlEncode(string $data): string
+    {
+        return \rtrim(\strtr(\base64_encode($data), '+/', '-_'), '=');
+    }
+
+    /**
+     * Null-byte RLE decode.
+     *
+     * @param string $string Data to decode
+     *
+     * @internal
+     *
+     */
+    public static function rleDecode(string $string): string
+    {
+        $new = '';
+        $last = '';
+        $null = "\0";
+        foreach (\str_split($string) as $cur) {
+            if ($last === $null) {
+                $new .= \str_repeat($last, \ord($cur));
+                $last = '';
+            } else {
+                $new .= $last;
+                $last = $cur;
+            }
+        }
+        $string = $new.$last;
+
+        return $string;
+    }
+
+    /**
+     * Null-byte RLE encode.
+     *
+     * @param string $string Data to encode
+     *
+     * @internal
+     *
+     */
+    public static function rleEncode(string $string): string
+    {
+        $new = '';
+        $count = 0;
+        $null = "\0";
+        foreach (\str_split($string) as $cur) {
+            if ($cur === $null) {
+                ++$count;
+            } else {
+                if ($count > 0) {
+                    $new .= $null.\chr($count);
+                    $count = 0;
+                }
+                $new .= $cur;
+            }
+        }
+        if ($count > 0) {
+            $new .= $null.\chr($count);
+        }
+
+        return $new;
+    }
+
+    /**
+     * Positive modulo
+     * Works just like the % (modulus) operator, only returns always a postive number.
+     *
+     * @param int $a A
+     * @param int $b B
+     *
+     * @internal
+     *
+     * @return int Modulo
+     */
+    public static function posmod(int $a, int $b): int
+    {
+        $resto = $a % $b;
+
+        return $resto < 0 ? $resto + \abs($b) : $resto;
+    }
+
+    /**
+     * Read TL string.
+     *
+     * @param resource $stream Byte stream
+     *
+     * @internal
+     *
+     */
+    public static function readTLString(mixed $stream): string
+    {
+        $l = \ord(\stream_get_contents($stream, 1));
+        if ($l > 254) {
+            throw new \InvalidArgumentException("Length too big!");
+        }
+        if ($l === 254) {
+            /** @var int */
+            $long_len = \unpack('V', \stream_get_contents($stream, 3).\chr(0))[1];
+            $x = \stream_get_contents($stream, $long_len);
+            $resto = self::posmod(-$long_len, 4);
+            if ($resto > 0) {
+                \fseek($stream, $resto, SEEK_CUR);
+            }
+        } else {
+            $x = $l ? \stream_get_contents($stream, $l) : '';
+            $resto = self::posmod(-($l + 1), 4);
+            if ($resto > 0) {
+                \fseek($stream, $resto, SEEK_CUR);
+            }
+        }
+        \assert($x !== false);
+        return $x;
+    }
+
+    /**
+     * Pack TL string.
+     *
+     * @param string $string String
+     *
+     * @internal
+     */
+    public static function packTLString(string $string): string
+    {
+        $l = \strlen($string);
+        $concat = '';
+        if ($l <= 253) {
+            $concat .= \chr($l);
+            $concat .= $string;
+            $concat .= \pack('@'.self::posmod(-$l - 1, 4));
+        } else {
+            $concat .= \chr(254);
+            $concat .= \substr(\pack('V', $l), 0, 3);
+            $concat .= $string;
+            $concat .= \pack('@'.self::posmod(-$l, 4));
+        }
+        return $concat;
+    }
+
+}
diff --git a/src/UniqueFileId.php b/src/UniqueFileId.php
index 086071c..f85ddb9 100644
--- a/src/UniqueFileId.php
+++ b/src/UniqueFileId.php
@@ -93,26 +93,26 @@ final class UniqueFileId
     {
         $fileId = \pack('V', $this->type->value);
         if ($this->url !== null) {
-            $fileId .= packTLString($this->url);
+            $fileId .= Tools::packTLString($this->url);
         } elseif ($this->type === UniqueFileIdType::PHOTO) {
             if ($this->volumeId !== null) {
-                $fileId .= packLong($this->volumeId);
+                $fileId .= Tools::packLong($this->volumeId);
                 $fileId .= \pack('l', $this->localId);
             } elseif ($this->stickerSetId !== null) {
                 \assert($this->subType !== null);
                 $fileId .= \chr($this->subType);
-                $fileId .= packLong($this->stickerSetId);
+                $fileId .= Tools::packLong($this->stickerSetId);
                 $fileId .= \pack('l', $this->stickerSetVersion);
             } else {
                 \assert($this->subType !== null && $this->id !== null);
-                $fileId .= packLong($this->id);
+                $fileId .= Tools::packLong($this->id);
                 $fileId .= \chr($this->subType);
             }
         } elseif ($this->id !== null) {
-            $fileId .= packLong($this->id);
+            $fileId .= Tools::packLong($this->id);
         }
 
-        return base64urlEncode(rleEncode($fileId));
+        return Tools::base64urlEncode(Tools::rleEncode($fileId));
     }
 
     /**
@@ -124,7 +124,7 @@ final class UniqueFileId
     public static function fromUniqueBotAPI(string $fileId): self
     {
         $orig = $fileId;
-        $fileId = rleDecode(base64urlDecode($fileId));
+        $fileId = Tools::rleDecode(Tools::base64urlDecode($fileId));
 
         /** @var int */
         $typeId = \unpack('V', $fileId)[1];
@@ -144,26 +144,26 @@ final class UniqueFileId
             \fwrite($res, $fileId);
             \fseek($res, 0);
             $fileId = $res;
-            $url = readTLString($fileId);
+            $url = Tools::readTLString($fileId);
 
             $l = \fstat($fileId)['size'] - \ftell($fileId);
             \trigger_error("Unique file ID $orig has $l bytes of leftover data");
         } elseif (\strlen($fileId) === 12) {
             // Legacy photos
-            $volume_id = unpackLong(\substr($fileId, 0, 8));
-            $local_id = unpackInt(\substr($fileId, 8));
+            $volume_id = Tools::unpackLong(\substr($fileId, 0, 8));
+            $local_id = Tools::unpackInt(\substr($fileId, 8));
         } elseif (\strlen($fileId) === 9) {
             // Dialog photos/thumbnails
-            $id = unpackLong($fileId);
+            $id = Tools::unpackLong($fileId);
             $subType = \ord($fileId[8]);
         } elseif (\strlen($fileId) === 13) {
             // Stickerset ID/version
             $subType = \ord($fileId[0]);
-            $sticker_set_id = unpackLong(\substr($fileId, 1, 8));
-            $sticker_set_version = unpackInt(\substr($fileId, 9));
+            $sticker_set_id = Tools::unpackLong(\substr($fileId, 1, 8));
+            $sticker_set_version = Tools::unpackInt(\substr($fileId, 9));
         } elseif (\strlen($fileId) === 8) {
             // Any other document
-            $id = unpackLong($fileId);
+            $id = Tools::unpackLong($fileId);
         } else {
             $l = \strlen($fileId);
             \trigger_error("Unique file ID $orig has $l bytes of leftover data");
diff --git a/src/functions.php b/src/functions.php
deleted file mode 100644
index 6faecf8..0000000
--- a/src/functions.php
+++ /dev/null
@@ -1,203 +0,0 @@
-<?php declare(strict_types=1);
-
-namespace danog\Decoder;
-
-const WEB_LOCATION_FLAG =  1 << 24;
-const FILE_REFERENCE_FLAG = 1 << 25;
-
-$BIG_ENDIAN = \pack('L', 1) === \pack('N', 1);
-
-/**
- * Unpack long properly, returns an actual number in any case.
- *
- * @internal
- *
- * @param string $field Field to unpack
- */
-function unpackLong(string $field): int
-{
-    global $BIG_ENDIAN; // Evil
-    /** @psalm-suppress MixedReturnStatement */
-    return \unpack('q', $BIG_ENDIAN ? \strrev($field) : $field)[1];
-}
-/**
- * Unpack integer.
- * @internal
- *
- * @param string $field Field to unpack
- */
-function unpackInt(string $field): int
-{
-    /** @psalm-suppress MixedReturnStatement */
-    return \unpack('l', $field)[1];
-}
-/**
- * Pack string long.
- *
- * @internal
- *
- */
-function packLong(int $field): string
-{
-    global $BIG_ENDIAN; // Evil
-    $res = \pack('q', $field);
-    return $BIG_ENDIAN ? \strrev($res) : $res;
-}
-/**
- * Base64URL decode.
- *
- * @param string $data Data to decode
- *
- * @internal
- *
- */
-function base64urlDecode(string $data): string
-{
-    return \base64_decode(\str_pad(\strtr($data, '-_', '+/'), \strlen($data) % 4, '=', STR_PAD_RIGHT));
-}
-
-/**
- * Base64URL encode.
- *
- * @param string $data Data to encode
- *
- * @internal
- *
- */
-function base64urlEncode(string $data): string
-{
-    return \rtrim(\strtr(\base64_encode($data), '+/', '-_'), '=');
-}
-
-/**
- * Null-byte RLE decode.
- *
- * @param string $string Data to decode
- *
- * @internal
- *
- */
-function rleDecode(string $string): string
-{
-    $new = '';
-    $last = '';
-    $null = "\0";
-    foreach (\str_split($string) as $cur) {
-        if ($last === $null) {
-            $new .= \str_repeat($last, \ord($cur));
-            $last = '';
-        } else {
-            $new .= $last;
-            $last = $cur;
-        }
-    }
-    $string = $new.$last;
-
-    return $string;
-}
-
-/**
- * Null-byte RLE encode.
- *
- * @param string $string Data to encode
- *
- * @internal
- *
- */
-function rleEncode(string $string): string
-{
-    $new = '';
-    $count = 0;
-    $null = "\0";
-    foreach (\str_split($string) as $cur) {
-        if ($cur === $null) {
-            ++$count;
-        } else {
-            if ($count > 0) {
-                $new .= $null.\chr($count);
-                $count = 0;
-            }
-            $new .= $cur;
-        }
-    }
-    if ($count > 0) {
-        $new .= $null.\chr($count);
-    }
-
-    return $new;
-}
-
-/**
- * Positive modulo
- * Works just like the % (modulus) operator, only returns always a postive number.
- *
- * @param int $a A
- * @param int $b B
- *
- * @internal
- *
- * @return int Modulo
- */
-function posmod(int $a, int $b): int
-{
-    $resto = $a % $b;
-
-    return $resto < 0 ? $resto + \abs($b) : $resto;
-}
-
-/**
- * Read TL string.
- *
- * @param resource $stream Byte stream
- *
- * @internal
- *
- */
-function readTLString(mixed $stream): string
-{
-    $l = \ord(\stream_get_contents($stream, 1));
-    if ($l > 254) {
-        throw new \InvalidArgumentException("Length too big!");
-    }
-    if ($l === 254) {
-        /** @var int */
-        $long_len = \unpack('V', \stream_get_contents($stream, 3).\chr(0))[1];
-        $x = \stream_get_contents($stream, $long_len);
-        $resto = posmod(-$long_len, 4);
-        if ($resto > 0) {
-            \fseek($stream, $resto, SEEK_CUR);
-        }
-    } else {
-        $x = $l ? \stream_get_contents($stream, $l) : '';
-        $resto = posmod(-($l + 1), 4);
-        if ($resto > 0) {
-            \fseek($stream, $resto, SEEK_CUR);
-        }
-    }
-    \assert($x !== false);
-    return $x;
-}
-
-/**
- * Pack TL string.
- *
- * @param string $string String
- *
- * @internal
- */
-function packTLString(string $string): string
-{
-    $l = \strlen($string);
-    $concat = '';
-    if ($l <= 253) {
-        $concat .= \chr($l);
-        $concat .= $string;
-        $concat .= \pack('@'.posmod(-$l - 1, 4));
-    } else {
-        $concat .= \chr(254);
-        $concat .= \substr(\pack('V', $l), 0, 3);
-        $concat .= $string;
-        $concat .= \pack('@'.posmod(-$l, 4));
-    }
-    return $concat;
-}