<?php

abstract class ParagonIE_Sodium_Core_Base64_Common
{
    public static function encode($src)
    {
        return self::doEncode($src, true);
    }
    public static function encodeUnpadded($src)
    {
        return self::doEncode($src, false);
    }
    protected static function doEncode($src, $pad = true)
    {
        $dest = '';
        $srcLen = ParagonIE_Sodium_Core_Util::strlen($src);
        for ($i = 0; $i + 3 <= $srcLen; $i += 3) {
            $chunk = unpack('C*', ParagonIE_Sodium_Core_Util::substr($src, $i, 3));
            $b0 = $chunk[1];
            $b1 = $chunk[2];
            $b2 = $chunk[3];
            $dest .= self::encode6Bits($b0 >> 2) . self::encode6Bits(($b0 << 4 | $b1 >> 4) & 63) . self::encode6Bits(($b1 << 2 | $b2 >> 6) & 63) . self::encode6Bits($b2 & 63);
        }
        if ($i < $srcLen) {
            $chunk = unpack('C*', ParagonIE_Sodium_Core_Util::substr($src, $i, $srcLen - $i));
            $b0 = $chunk[1];
            if ($i + 1 < $srcLen) {
                $b1 = $chunk[2];
                $dest .= self::encode6Bits($b0 >> 2) . self::encode6Bits(($b0 << 4 | $b1 >> 4) & 63) . self::encode6Bits($b1 << 2 & 63);
                if ($pad) {
                    $dest .= '=';
                }
            } else {
                $dest .= self::encode6Bits($b0 >> 2) . self::encode6Bits($b0 << 4 & 63);
                if ($pad) {
                    $dest .= '==';
                }
            }
        }
        return $dest;
    }
    public static function decode($src, $strictPadding = false)
    {
        $srcLen = ParagonIE_Sodium_Core_Util::strlen($src);
        if ($srcLen === 0) {
            return '';
        }
        if ($strictPadding) {
            if (($srcLen & 3) === 0) {
                if ($src[$srcLen - 1] === '=') {
                    $srcLen--;
                    if ($src[$srcLen - 1] === '=') {
                        $srcLen--;
                    }
                }
            }
            if (($srcLen & 3) === 1) {
                throw new RangeException('Incorrect padding');
            }
            if ($src[$srcLen - 1] === '=') {
                throw new RangeException('Incorrect padding');
            }
        } else {
            $src = rtrim($src, '=');
            $srcLen = ParagonIE_Sodium_Core_Util::strlen($src);
        }
        $err = 0;
        $dest = '';
        for ($i = 0; $i + 4 <= $srcLen; $i += 4) {
            $chunk = unpack('C*', ParagonIE_Sodium_Core_Util::substr($src, $i, 4));
            $c0 = self::decode6Bits($chunk[1]);
            $c1 = self::decode6Bits($chunk[2]);
            $c2 = self::decode6Bits($chunk[3]);
            $c3 = self::decode6Bits($chunk[4]);
            $dest .= pack('CCC', ($c0 << 2 | $c1 >> 4) & 0xff, ($c1 << 4 | $c2 >> 2) & 0xff, ($c2 << 6 | $c3) & 0xff);
            $err |= ($c0 | $c1 | $c2 | $c3) >> 8;
        }
        if ($i < $srcLen) {
            $chunk = unpack('C*', ParagonIE_Sodium_Core_Util::substr($src, $i, $srcLen - $i));
            $c0 = self::decode6Bits($chunk[1]);
            if ($i + 2 < $srcLen) {
                $c1 = self::decode6Bits($chunk[2]);
                $c2 = self::decode6Bits($chunk[3]);
                $dest .= pack('CC', ($c0 << 2 | $c1 >> 4) & 0xff, ($c1 << 4 | $c2 >> 2) & 0xff);
                $err |= ($c0 | $c1 | $c2) >> 8;
            } elseif ($i + 1 < $srcLen) {
                $c1 = self::decode6Bits($chunk[2]);
                $dest .= pack('C', ($c0 << 2 | $c1 >> 4) & 0xff);
                $err |= ($c0 | $c1) >> 8;
            } elseif ($i < $srcLen && $strictPadding) {
                $err |= 1;
            }
        }
        $check = $err === 0;
        if (!$check) {
            throw new RangeException('Base64::decode() only expects characters in the correct base64 alphabet');
        }
        return $dest;
    }
    protected static abstract function decode6Bits($src);
    protected static abstract function encode6Bits($src);
}