RouterOS\APILengthCoDec::decodeLength()

Complexity

Conditions	7
Paths	7

Size

Total Lines

92

Duplication

Lines	0
Ratio	0 %

Code Coverage

Tests	32
CRAP Score	7

Importance

Changes

0

<?php
    public static function decodeLength(StreamInterface $stream): int
    {
        // if (false === is_resource($stream)) {
        //     throw new \InvalidArgumentException(
        //         sprintf(
        //             'Argument must be a stream resource type. %s given.',
        //             gettype($stream)
        //         )
        //     );
        // }

        // Read first byte
        $firstByte = ord($stream->read(1));

        // If first byte is not set, length is the value of the byte
        if (0 === ($firstByte & 0x80)) {
            return $firstByte;
        }

        // if 10xxxxxx, length is 2 bytes encoded
        if (0x80 === ($firstByte & 0xC0)) {
            // Set 2 most significands bits to 0
            $result = $firstByte & 0x3F;

            // shift left 8 bits to have 2 bytes
            $result <<= 8;

            // read next byte and use it as least significant
            $result |= ord($stream->read(1));
            return $result;
        }

        // if 110xxxxx, length is 3 bytes encoded
        if (0xC0 === ($firstByte & 0xE0)) {
            // Set 3 most significands bits to 0
            $result = $firstByte & 0x1F;

            // shift left 16 bits to have 3 bytes
            $result <<= 16;

            // read next 2 bytes as value and use it as least significant position
            $result |= (ord($stream->read(1)) << 8);
            $result |= ord($stream->read(1));
            return $result;
        }

        // if 1110xxxx, length is 4 bytes encoded
        if (0xE0 === ($firstByte & 0xF0)) {
            // Set 4 most significance bits to 0
            $result = $firstByte & 0x0F;

            // shift left 24 bits to have 4 bytes
            $result <<= 24;

            // read next 3 bytes as value and use it as least significant position
            $result |= (ord($stream->read(1)) << 16);
            $result |= (ord($stream->read(1)) << 8);
            $result |= ord($stream->read(1));
            return $result;
        }

        // if 11110xxx, length is 5 bytes encoded
        if (0xF0 === ($firstByte & 0xF8)) {
            // Not possible on 32 bits systems
            if (PHP_INT_SIZE < 8) {
                // Cannot be done on 32 bits systems
                // PHP5 windows versions of php, even on 64 bits systems was impacted
                // see : https://stackoverflow.com/questions/27865340/php-int-size-returns-4-but-my-operating-system-is-64-bit 
                // How can we test it ?
                // @codeCoverageIgnoreStart
                throw new \OverflowException("Your system is using 32 bits integers, cannot decode this value ($firstByte) on this system");
                // @codeCoverageIgnoreEnd
            }

            // Set 5 most significance bits to 0
            $result = $firstByte & 0x07;

            // shift left 232 bits to have 5 bytes
            $result <<= 32;

            // read next 4 bytes as value and use it as least significant position
            $result |= (ord($stream->read(1)) << 24);
            $result |= (ord($stream->read(1)) << 16);
            $result |= (ord($stream->read(1)) << 8);
            $result |= ord($stream->read(1));
            return $result;
        }

        // Now the only solution is 5 most significance bits are set to 1 (11111xxx)
        // This is a control word, not implemented by Mikrotik for the moment 
        throw new \UnexpectedValueException('Control Word found');
    }
}