RouterOS\APILengthCoDec::encodeLength()

Complexity

Conditions	8
Paths	8

Size

Total Lines

68

Duplication

Lines	0
Ratio	0 %

Code Coverage

Tests	15
CRAP Score	8

Importance

Changes

0

<?php
    public static function encodeLength(int $length): string
    {
        // Encode the length :
        // - if length <= 0x7F (binary : 01111111 => 7 bits set to 1)
        //      - encode length with one byte
        //      - set the byte to length value, as length maximal value is 7 bits set to 1, the most significant bit is always 0
        //      - end
        // - length <= 0x3FFF (binary : 00111111 11111111 => 14 bits set to 1)
        //      - encode length with two bytes
        //      - set length value to 0x8000 (=> 10000000 00000000)
        //      - add length : as length maximumal value is 14 bits to 1, this does not modify the 2 most significance bits (10)
        //      - end
        //      => minimal encoded value is 10000000 10000000
        // - length <= 0x1FFFFF (binary : 00011111 11111111 11111111 => 21 bits set to 1)
        //      - encode length with three bytes
        //      - set length value to 0xC00000 (binary : 11000000 00000000 00000000)
        //      - add length : as length maximal vlaue is 21 bits to 1, this does not modify the 3 most significance bits (110)
        //      - end
        //      => minimal encoded value is 11000000 01000000 00000000
        // - length <= 0x0FFFFFFF (binary : 00001111 11111111 11111111 11111111 => 28 bits set to 1)
        //      - encode length with four bytes
        //      - set length value to 0xE0000000 (binary : 11100000 00000000 00000000 00000000)
        //      - add length : as length maximal vlaue is 28 bits to 1, this does not modify the 4 most significance bits (1110)
        //      - end
        //      => minimal encoded value is 11100000 00100000 00000000 00000000
        // - length <= 0x7FFFFFFFFF (binary : 00000111 11111111 11111111 11111111 11111111 => 35 bits set to 1)
        //      - encode length with five bytes
        //      - set length value to 0xF000000000 (binary : 11110000 00000000 00000000 00000000 00000000)
        //      - add length : as length maximal vlaue is 35 bits to 1, this does not modify the 5 most significance bits (11110)
        //      - end
        // - length > 0x7FFFFFFFFF : not supported

        if ($length < 0) {
            throw new \DomainException("Length of word can not be negative ($length)");
        }

        if ($length <= 0x7F) {
            return BinaryStringHelper::IntegerToNBOBinaryString($length);
        }

        if ($length <= 0x3FFF) {
            return BinaryStringHelper::IntegerToNBOBinaryString(0x8000 + $length);
        }

        if ($length <= 0x1FFFFF) {
            return BinaryStringHelper::IntegerToNBOBinaryString(0xC00000 + $length);
        }

        if ($length <= 0x0FFFFFFF) {
            return BinaryStringHelper::IntegerToNBOBinaryString(0xE0000000 + $length);
        } // cannot compare with 0x7FFFFFFFFF 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

            // @codeCoverageIgnoreStart
            throw new \OverflowException("Your system is using 32 bits integers, cannot encode length of $length bytes on this system");
            // @codeCoverageIgnoreEnd
        }

        if ($length <= 0x7FFFFFFFFF) {
            return BinaryStringHelper::IntegerToNBOBinaryString(0xF000000000 + $length);
        }

        throw new \DomainException("Length of word too huge ($length)");
    }