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198 lines
8.4 KiB
198 lines
8.4 KiB
<?php
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namespace RouterOS;
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use DomainException;
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use RouterOS\Interfaces\StreamInterface;
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use RouterOS\Helpers\BinaryStringHelper;
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/**
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* class APILengthCoDec
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*
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* Coder / Decoder for length field in mikrotik API communication protocol
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*
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* @package RouterOS
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* @since 0.9
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*/
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class APILengthCoDec
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{
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/**
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* Encode string to length of string
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*
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* @param int|float $length
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*
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* @return string
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*/
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public static function encodeLength($length): string
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{
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// Encode the length :
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// - if length <= 0x7F (binary : 01111111 => 7 bits set to 1)
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// - encode length with one byte
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// - set the byte to length value, as length maximal value is 7 bits set to 1, the most significant bit is always 0
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// - end
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// - length <= 0x3FFF (binary : 00111111 11111111 => 14 bits set to 1)
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// - encode length with two bytes
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// - set length value to 0x8000 (=> 10000000 00000000)
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// - add length : as length maximumal value is 14 bits to 1, this does not modify the 2 most significance bits (10)
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// - end
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// => minimal encoded value is 10000000 10000000
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// - length <= 0x1FFFFF (binary : 00011111 11111111 11111111 => 21 bits set to 1)
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// - encode length with three bytes
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// - set length value to 0xC00000 (binary : 11000000 00000000 00000000)
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// - add length : as length maximal vlaue is 21 bits to 1, this does not modify the 3 most significance bits (110)
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// - end
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// => minimal encoded value is 11000000 01000000 00000000
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// - length <= 0x0FFFFFFF (binary : 00001111 11111111 11111111 11111111 => 28 bits set to 1)
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// - encode length with four bytes
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// - set length value to 0xE0000000 (binary : 11100000 00000000 00000000 00000000)
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// - add length : as length maximal vlaue is 28 bits to 1, this does not modify the 4 most significance bits (1110)
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// - end
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// => minimal encoded value is 11100000 00100000 00000000 00000000
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// - length <= 0x7FFFFFFFFF (binary : 00000111 11111111 11111111 11111111 11111111 => 35 bits set to 1)
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// - encode length with five bytes
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// - set length value to 0xF000000000 (binary : 11110000 00000000 00000000 00000000 00000000)
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// - add length : as length maximal vlaue is 35 bits to 1, this does not modify the 5 most significance bits (11110)
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// - end
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// - length > 0x7FFFFFFFFF : not supported
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if ($length < 0) {
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throw new DomainException("Length of word could not to be negative ($length)");
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}
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if ($length <= 0x7F) {
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return BinaryStringHelper::IntegerToNBOBinaryString($length);
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}
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if ($length <= 0x3FFF) {
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return BinaryStringHelper::IntegerToNBOBinaryString(0x8000 + $length);
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}
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if ($length <= 0x1FFFFF) {
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return BinaryStringHelper::IntegerToNBOBinaryString(0xC00000 + $length);
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}
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if ($length <= 0x0FFFFFFF) {
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return BinaryStringHelper::IntegerToNBOBinaryString(0xE0000000 + $length);
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}
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// https://wiki.mikrotik.com/wiki/Manual:API#API_words
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// If len >= 0x10000000 then 0xF0 and len as four bytes
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return BinaryStringHelper::IntegerToNBOBinaryString(0xF000000000 + $length);
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}
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// Decode length of data when reading :
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// The 5 firsts bits of the first byte specify how the length is encoded.
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// The position of the first 0 value bit, starting from the most significant postion.
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// - 0xxxxxxx => The 7 remaining bits of the first byte is the length :
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// => min value of length is 0x00
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// => max value of length is 0x7F (127 bytes)
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// - 10xxxxxx => The 6 remaining bits of the first byte plus the next byte represent the lenght
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// NOTE : the next byte MUST be at least 0x80 !!
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// => min value of length is 0x80
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// => max value of length is 0x3FFF (16,383 bytes, near 16 KB)
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// - 110xxxxx => The 5 remaining bits of th first byte and the two next bytes represent the length
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// => max value of length is 0x1FFFFF (2,097,151 bytes, near 2 MB)
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// - 1110xxxx => The 4 remaining bits of the first byte and the three next bytes represent the length
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// => max value of length is 0xFFFFFFF (268,435,455 bytes, near 270 MB)
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// - 11110xxx => The 3 remaining bits of the first byte and the four next bytes represent the length
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// => max value of length is 0x7FFFFFFF (2,147,483,647 byes, 2GB)
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// - 11111xxx => This byte is not a length-encoded word but a control byte.
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// => Extracted from Mikrotik API doc :
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// it is a reserved control byte.
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// After receiving unknown control byte API client cannot proceed, because it cannot know how to interpret following bytes
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// Currently control bytes are not used
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public static function decodeLength(StreamInterface $stream): int
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{
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// if (false === is_resource($stream)) {
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// throw new \InvalidArgumentException(
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// sprintf(
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// 'Argument must be a stream resource type. %s given.',
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// gettype($stream)
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// )
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// );
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// }
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// Read first byte
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$firstByte = ord($stream->read(1));
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// If first byte is not set, length is the value of the byte
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if (0 === ($firstByte & 0x80)) {
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return $firstByte;
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}
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// if 10xxxxxx, length is 2 bytes encoded
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if (0x80 === ($firstByte & 0xC0)) {
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// Set 2 most significands bits to 0
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$result = $firstByte & 0x3F;
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// shift left 8 bits to have 2 bytes
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$result <<= 8;
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// read next byte and use it as least significant
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$result |= ord($stream->read(1));
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return $result;
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}
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// if 110xxxxx, length is 3 bytes encoded
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if (0xC0 === ($firstByte & 0xE0)) {
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// Set 3 most significands bits to 0
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$result = $firstByte & 0x1F;
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// shift left 16 bits to have 3 bytes
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$result <<= 16;
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// read next 2 bytes as value and use it as least significant position
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$result |= (ord($stream->read(1)) << 8);
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$result |= ord($stream->read(1));
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return $result;
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}
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// if 1110xxxx, length is 4 bytes encoded
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if (0xE0 === ($firstByte & 0xF0)) {
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// Set 4 most significance bits to 0
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$result = $firstByte & 0x0F;
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// shift left 24 bits to have 4 bytes
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$result <<= 24;
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// read next 3 bytes as value and use it as least significant position
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$result |= (ord($stream->read(1)) << 16);
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$result |= (ord($stream->read(1)) << 8);
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$result |= ord($stream->read(1));
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return $result;
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}
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// if 11110xxx, length is 5 bytes encoded
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if (0xF0 === ($firstByte & 0xF8)) {
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// Not possible on 32 bits systems
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if (PHP_INT_SIZE < 8) {
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// Cannot be done on 32 bits systems
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// PHP5 windows versions of php, even on 64 bits systems was impacted
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// see : https://stackoverflow.com/questions/27865340/php-int-size-returns-4-but-my-operating-system-is-64-bit
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// How can we test it ?
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// @codeCoverageIgnoreStart
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throw new \OverflowException("Your system is using 32 bits integers, cannot decode this value ($firstByte) on this system");
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// @codeCoverageIgnoreEnd
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}
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// Set 5 most significance bits to 0
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$result = $firstByte & 0x07;
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// shift left 232 bits to have 5 bytes
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$result <<= 32;
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// read next 4 bytes as value and use it as least significant position
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$result |= (ord($stream->read(1)) << 24);
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$result |= (ord($stream->read(1)) << 16);
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$result |= (ord($stream->read(1)) << 8);
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$result |= ord($stream->read(1));
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return $result;
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}
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// Now the only solution is 5 most significance bits are set to 1 (11111xxx)
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// This is a control word, not implemented by Mikrotik for the moment
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throw new \UnexpectedValueException('Control Word found');
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}
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}
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