ParagonIE_Sodium_Core_Base64_UrlSafe::decode( string $src, bool $strictPadding = false ): string

102    public static function decode($src, $strictPadding = false)103    {104        // Remove padding105        $srcLen = ParagonIE_Sodium_Core_Util::strlen($src);106        if ($srcLen === 0) {107            return '';108        }109 110        if ($strictPadding) {111            if (($srcLen & 3) === 0) {112                if ($src[$srcLen - 1] === '=') {113                    $srcLen--;114                    if ($src[$srcLen - 1] === '=') {115                        $srcLen--;116                    }117                }118            }119            if (($srcLen & 3) === 1) {120                throw new RangeException(121                    'Incorrect padding'122                );123            }124            if ($src[$srcLen - 1] === '=') {125                throw new RangeException(126                    'Incorrect padding'127                );128            }129        } else {130            $src = rtrim($src, '=');131            $srcLen =  ParagonIE_Sodium_Core_Util::strlen($src);132        }133 134        $err = 0;135        $dest = '';136        // Main loop (no padding):137        for ($i = 0; $i + 4 <= $srcLen; $i += 4) {138            /** @var array<int, int> $chunk */139            $chunk = unpack('C*', ParagonIE_Sodium_Core_Util::substr($src, $i, 4));140            $c0 = self::decode6Bits($chunk[1]);141            $c1 = self::decode6Bits($chunk[2]);142            $c2 = self::decode6Bits($chunk[3]);143            $c3 = self::decode6Bits($chunk[4]);144 145            $dest .= pack(146                'CCC',147                ((($c0 << 2) | ($c1 >> 4)) & 0xff),148                ((($c1 << 4) | ($c2 >> 2)) & 0xff),149                ((($c2 << 6) | $c3) & 0xff)150            );151            $err |= ($c0 | $c1 | $c2 | $c3) >> 8;152        }153        // The last chunk, which may have padding:154        if ($i < $srcLen) {155            /** @var array<int, int> $chunk */156            $chunk = unpack('C*', ParagonIE_Sodium_Core_Util::substr($src, $i, $srcLen - $i));157            $c0 = self::decode6Bits($chunk[1]);158 159            if ($i + 2 < $srcLen) {160                $c1 = self::decode6Bits($chunk[2]);161                $c2 = self::decode6Bits($chunk[3]);162                $dest .= pack(163                    'CC',164                    ((($c0 << 2) | ($c1 >> 4)) & 0xff),165                    ((($c1 << 4) | ($c2 >> 2)) & 0xff)166                );167                $err |= ($c0 | $c1 | $c2) >> 8;168            } elseif ($i + 1 < $srcLen) {169                $c1 = self::decode6Bits($chunk[2]);170                $dest .= pack(171                    'C',172                    ((($c0 << 2) | ($c1 >> 4)) & 0xff)173                );174                $err |= ($c0 | $c1) >> 8;175            } elseif ($i < $srcLen && $strictPadding) {176                $err |= 1;177            }178        }179        /** @var bool $check */180        $check = ($err === 0);181        if (!$check) {