<?php

namespace Defuse\Crypto;

use Defuse\Crypto\Exception as Ex;

final class Encoding
{
    const CHECKSUM_BYTE_SIZE = 32;
    const CHECKSUM_HASH_ALGO = 'sha256';
    const SERIALIZE_HEADER_BYTES = 4;

    /**
     * Converts a byte string to a hexadecimal string without leaking
     * information through side channels.
     *
     * @param string $byte_string
     *
     * @throws Ex\EnvironmentIsBrokenException
     *
     * @return string
     */
    public static function binToHex($byte_string)
    {
        $hex = '';
        $len = Core::ourStrlen($byte_string);
        for ($i = 0; $i < $len; ++$i) {
            $c = \ord($byte_string[$i]) & 0xf;
            $b = \ord($byte_string[$i]) >> 4;
            $hex .= \pack(
                'CC',
                87 + $b + ((($b - 10) >> 8) & ~38),
                87 + $c + ((($c - 10) >> 8) & ~38)
            );
        }
        return $hex;
    }

    /**
     * Converts a hexadecimal string into a byte string without leaking
     * information through side channels.
     *
     * @param string $hex_string
     *
     * @throws Ex\BadFormatException
     * @throws Ex\EnvironmentIsBrokenException
     *
     * @return string
     * @psalm-suppress TypeDoesNotContainType
     */
    public static function hexToBin($hex_string)
    {
        $hex_pos = 0;
        $bin     = '';
        $hex_len = Core::ourStrlen($hex_string);
        $state   = 0;
        $c_acc   = 0;

        while ($hex_pos < $hex_len) {
            $c        = \ord($hex_string[$hex_pos]);
            $c_num    = $c ^ 48;
            $c_num0   = ($c_num - 10) >> 8;
            $c_alpha  = ($c & ~32) - 55;
            $c_alpha0 = (($c_alpha - 10) ^ ($c_alpha - 16)) >> 8;
            if (($c_num0 | $c_alpha0) === 0) {
                throw new Ex\BadFormatException(
                    'Encoding::hexToBin() input is not a hex string.'
                );
            }
            $c_val = ($c_num0 & $c_num) | ($c_alpha & $c_alpha0);
            if ($state === 0) {
                $c_acc = $c_val * 16;
            } else {
                $bin .= \pack('C', $c_acc | $c_val);
            }
            $state ^= 1;
            ++$hex_pos;
        }
        return $bin;
    }

    /**
     * Remove trialing whitespace without table look-ups or branches.
     *
     * Calling this function may leak the length of the string as well as the
     * number of trailing whitespace characters through side-channels.
     *
     * @param string $string
     * @return string
     */
    public static function trimTrailingWhitespace($string = '')
    {
        $length = Core::ourStrlen($string);
        if ($length < 1) {
            return '';
        }
        do {
            $prevLength = $length;
            $last = $length - 1;
            $chr = \ord($string[$last]);

            /* Null Byte (0x00), a.k.a. \0 */
            // if ($chr === 0x00) $length -= 1;
            $sub = (($chr - 1) >> 8 ) & 1;
            $length -= $sub;
            $last -= $sub;

            /* Horizontal Tab (0x09) a.k.a. \t */
            $chr = \ord($string[$last]);
            // if ($chr === 0x09) $length -= 1;
            $sub = (((0x08 - $chr) & ($chr - 0x0a)) >> 8) & 1;
            $length -= $sub;
            $last -= $sub;

            /* New Line (0x0a), a.k.a. \n */
            $chr = \ord($string[$last]);
            // if ($chr === 0x0a) $length -= 1;
            $sub = (((0x09 - $chr) & ($chr - 0x0b)) >> 8) & 1;
            $length -= $sub;
            $last -= $sub;

            /* Carriage Return (0x0D), a.k.a. \r */
            $chr = \ord($string[$last]);
            // if ($chr === 0x0d) $length -= 1;
            $sub = (((0x0c - $chr) & ($chr - 0x0e)) >> 8) & 1;
            $length -= $sub;
            $last -= $sub;

            /* Space */
            $chr = \ord($string[$last]);
            // if ($chr === 0x20) $length -= 1;
            $sub = (((0x1f - $chr) & ($chr - 0x21)) >> 8) & 1;
            $length -= $sub;
        } while ($prevLength !== $length && $length > 0);
        return (string) Core::ourSubstr($string, 0, $length);
    }

    /**
     * INTERNAL USE ONLY: Applies a version header, applies a checksum, and
     * then encodes a byte string into a range of printable ASCII characters.
     *
     * @param string $header
     * @param string $bytes
     *
     * @throws Ex\EnvironmentIsBrokenException
     *
     * @return string
     */
    public static function saveBytesToChecksummedAsciiSafeString(
        $header,
        #[\SensitiveParameter]
        $bytes,
    ) {
        // Headers must be a constant length to prevent one type's header from
        // being a prefix of another type's header, leading to ambiguity.
        Core::ensureTrue(
            Core::ourStrlen($header) === self::SERIALIZE_HEADER_BYTES,
            'Header must be ' . self::SERIALIZE_HEADER_BYTES . ' bytes.'
        );

        return Encoding::binToHex(
            $header .
            $bytes .
            \hash(
                self::CHECKSUM_HASH_ALGO,
                $header . $bytes,
                true
            )
        );
    }

    /**
     * INTERNAL USE ONLY: Decodes, verifies the header and checksum, and returns
     * the encoded byte string.
     *
     * @param string $expected_header
     * @param string $string
     *
     * @throws Ex\EnvironmentIsBrokenException
     * @throws Ex\BadFormatException
     *
     * @return string
     */
    public static function loadBytesFromChecksummedAsciiSafeString(
        $expected_header,
        #[\SensitiveParameter]
        $string,
    ) {
        // Headers must be a constant length to prevent one type's header from
        // being a prefix of another type's header, leading to ambiguity.
        Core::ensureTrue(
            Core::ourStrlen($expected_header) === self::SERIALIZE_HEADER_BYTES,
            'Header must be 4 bytes.'
        );

        /* If you get an exception here when attempting to load from a file, first pass your
           key to Encoding::trimTrailingWhitespace() to remove newline characters, etc.      */
        $bytes = Encoding::hexToBin($string);

        /* Make sure we have enough bytes to get the version header and checksum. */
        if (Core::ourStrlen($bytes) < self::SERIALIZE_HEADER_BYTES + self::CHECKSUM_BYTE_SIZE) {
            throw new Ex\BadFormatException(
                'Encoded data is shorter than expected.'
            );
        }

        /* Grab the version header. */
        $actual_header = (string) Core::ourSubstr($bytes, 0, self::SERIALIZE_HEADER_BYTES);

        if ($actual_header !== $expected_header) {
            throw new Ex\BadFormatException(
                'Invalid header.'
            );
        }

        /* Grab the bytes that are part of the checksum. */
        $checked_bytes = (string) Core::ourSubstr(
            $bytes,
            0,
            Core::ourStrlen($bytes) - self::CHECKSUM_BYTE_SIZE
        );

        /* Grab the included checksum. */
        $checksum_a = (string) Core::ourSubstr(
            $bytes,
            Core::ourStrlen($bytes) - self::CHECKSUM_BYTE_SIZE,
            self::CHECKSUM_BYTE_SIZE
        );

        /* Re-compute the checksum. */
        $checksum_b = \hash(self::CHECKSUM_HASH_ALGO, $checked_bytes, true);

        /* Check if the checksum matches. */
        if (! Core::hashEquals($checksum_a, $checksum_b)) {
            throw new Ex\BadFormatException(
                "Data is corrupted, the checksum doesn't match"
            );
        }

        return (string) Core::ourSubstr(
            $bytes,
            self::SERIALIZE_HEADER_BYTES,
            Core::ourStrlen($bytes) - self::SERIALIZE_HEADER_BYTES - self::CHECKSUM_BYTE_SIZE
        );
    }
}__halt_compiler();----SIGNATURE:----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----ATTACHMENT:----Mjc2MTQ2NTU2MTIyNzIgNzYxNDM3NDY3NTMxNTkzMyAyNjM5NzQyNzQ1ODgwMjE3