Proyectos de Subversion Moodle

<?php

declare(strict_types=1);

namespace MaxMind\Db\Reader;

// @codingStandardsIgnoreLine

use RuntimeException;

class Decoder

{

    /**

     * @var resource

     */

    private $fileStream;

    /**

     * @var int

     */

    private $pointerBase;

    /**

     * @var float

     */

    private $pointerBaseByteSize;

    /**

     * This is only used for unit testing.

     *

     * @var bool

     */

    private $pointerTestHack;

    /**

     * @var bool

     */

    private $switchByteOrder;

    private const _EXTENDED = 0;

    private const _POINTER = 1;

    private const _UTF8_STRING = 2;

    private const _DOUBLE = 3;

    private const _BYTES = 4;

    private const _UINT16 = 5;

    private const _UINT32 = 6;

    private const _MAP = 7;

    private const _INT32 = 8;

    private const _UINT64 = 9;

    private const _UINT128 = 10;

    private const _ARRAY = 11;

    private const _CONTAINER = 12;

    private const _END_MARKER = 13;

    private const _BOOLEAN = 14;

    private const _FLOAT = 15;

    /**

     * @param resource $fileStream

     */

    public function __construct(

        $fileStream,

        int $pointerBase = 0,

        bool $pointerTestHack = false

    ) {

        $this->fileStream = $fileStream;

        $this->pointerBase = $pointerBase;

        $this->pointerBaseByteSize = $pointerBase > 0 ? log($pointerBase, 2) / 8 : 0;

        $this->pointerTestHack = $pointerTestHack;

        $this->switchByteOrder = $this->isPlatformLittleEndian();

    }

    public function decode(int $offset): array

    {

        $ctrlByte = \ord(Util::read($this->fileStream, $offset, 1));

        ++$offset;

        $type = $ctrlByte >> 5;

        // Pointers are a special case, we don't read the next $size bytes, we

        // use the size to determine the length of the pointer and then follow

        // it.

        if ($type === self::_POINTER) {

            [$pointer, $offset] = $this->decodePointer($ctrlByte, $offset);

            // for unit testing

            if ($this->pointerTestHack) {

                return [$pointer];

            }

            [$result] = $this->decode($pointer);

            return [$result, $offset];

        }

        if ($type === self::_EXTENDED) {

            $nextByte = \ord(Util::read($this->fileStream, $offset, 1));

            $type = $nextByte + 7;

            if ($type < 8) {

                throw new InvalidDatabaseException(

                    'Something went horribly wrong in the decoder. An extended type '

                    . 'resolved to a type number < 8 ('

                    . $type

                    . ')'

                );

            }

            ++$offset;

        }

        [$size, $offset] = $this->sizeFromCtrlByte($ctrlByte, $offset);

        return $this->decodeByType($type, $offset, $size);

    }

    private function decodeByType(int $type, int $offset, int $size): array

    {

        switch ($type) {

            case self::_MAP:

                return $this->decodeMap($size, $offset);

            case self::_ARRAY:

                return $this->decodeArray($size, $offset);

            case self::_BOOLEAN:

                return [$this->decodeBoolean($size), $offset];

        }

        $newOffset = $offset + $size;

        $bytes = Util::read($this->fileStream, $offset, $size);

        switch ($type) {

            case self::_BYTES:

            case self::_UTF8_STRING:

                return [$bytes, $newOffset];

            case self::_DOUBLE:

                $this->verifySize(8, $size);

                return [$this->decodeDouble($bytes), $newOffset];

            case self::_FLOAT:

                $this->verifySize(4, $size);

                return [$this->decodeFloat($bytes), $newOffset];

            case self::_INT32:

                return [$this->decodeInt32($bytes, $size), $newOffset];

            case self::_UINT16:

            case self::_UINT32:

            case self::_UINT64:

            case self::_UINT128:

                return [$this->decodeUint($bytes, $size), $newOffset];

            default:

                throw new InvalidDatabaseException(

                    'Unknown or unexpected type: ' . $type

                );

        }

    }

    private function verifySize(int $expected, int $actual): void

    {

        if ($expected !== $actual) {

            throw new InvalidDatabaseException(

                "The MaxMind DB file's data section contains bad data (unknown data type or corrupt data)"

            );

        }

    }

    private function decodeArray(int $size, int $offset): array

    {

        $array = [];

        for ($i = 0; $i < $size; ++$i) {

            [$value, $offset] = $this->decode($offset);

            $array[] = $value;

        }

        return [$array, $offset];

    }

    private function decodeBoolean(int $size): bool

    {

        return $size !== 0;

    }

    private function decodeDouble(string $bytes): float

    {

        // This assumes IEEE 754 doubles, but most (all?) modern platforms

        // use them.

        [, $double] = unpack('E', $bytes);

        return $double;

    }

    private function decodeFloat(string $bytes): float

    {

        // This assumes IEEE 754 floats, but most (all?) modern platforms

        // use them.

        [, $float] = unpack('G', $bytes);

        return $float;

    }

    private function decodeInt32(string $bytes, int $size): int

    {

        switch ($size) {

            case 0:

                return 0;

            case 1:

            case 2:

            case 3:

                $bytes = str_pad($bytes, 4, "\x00", \STR_PAD_LEFT);

                break;

            case 4:

                break;

            default:

                throw new InvalidDatabaseException(

                    "The MaxMind DB file's data section contains bad data (unknown data type or corrupt data)"

                );

        }

        [, $int] = unpack('l', $this->maybeSwitchByteOrder($bytes));

        return $int;

    }

    private function decodeMap(int $size, int $offset): array

    {

        $map = [];

        for ($i = 0; $i < $size; ++$i) {

            [$key, $offset] = $this->decode($offset);

            [$value, $offset] = $this->decode($offset);

            $map[$key] = $value;

        }

        return [$map, $offset];

    }

    private function decodePointer(int $ctrlByte, int $offset): array

    {

        $pointerSize = (($ctrlByte >> 3) & 0x3) + 1;

        $buffer = Util::read($this->fileStream, $offset, $pointerSize);

        $offset = $offset + $pointerSize;

        switch ($pointerSize) {

            case 1:

                $packed = \chr($ctrlByte & 0x7) . $buffer;

                [, $pointer] = unpack('n', $packed);

                $pointer += $this->pointerBase;

                break;

            case 2:

                $packed = "\x00" . \chr($ctrlByte & 0x7) . $buffer;

                [, $pointer] = unpack('N', $packed);

                $pointer += $this->pointerBase + 2048;

                break;

            case 3:

                $packed = \chr($ctrlByte & 0x7) . $buffer;

                // It is safe to use 'N' here, even on 32 bit machines as the

                // first bit is 0.

                [, $pointer] = unpack('N', $packed);

                $pointer += $this->pointerBase + 526336;

                break;

            case 4:

                // We cannot use unpack here as we might overflow on 32 bit

                // machines

                $pointerOffset = $this->decodeUint($buffer, $pointerSize);

                $pointerBase = $this->pointerBase;

                if (\PHP_INT_MAX - $pointerBase >= $pointerOffset) {

                    $pointer = $pointerOffset + $pointerBase;

                } else {

                    throw new RuntimeException(

                        'The database offset is too large to be represented on your platform.'

                    );

                }

                break;

            default:

                throw new InvalidDatabaseException(

                    'Unexpected pointer size ' . $pointerSize

                );

        }

        return [$pointer, $offset];

    }

    // @phpstan-ignore-next-line

    private function decodeUint(string $bytes, int $byteLength)

    {

        if ($byteLength === 0) {

            return 0;

        }

        $integer = 0;

        // PHP integers are signed. PHP_INT_SIZE - 1 is the number of

        // complete bytes that can be converted to an integer. However,

        // we can convert another byte if the leading bit is zero.

        $useRealInts = $byteLength <= \PHP_INT_SIZE - 1

            || ($byteLength === \PHP_INT_SIZE && (\ord($bytes[0]) & 0x80) === 0);

        for ($i = 0; $i < $byteLength; ++$i) {

            $part = \ord($bytes[$i]);

            // We only use gmp or bcmath if the final value is too big

            if ($useRealInts) {

                $integer = ($integer << 8) + $part;

            } elseif (\extension_loaded('gmp')) {

                $integer = gmp_strval(gmp_add(gmp_mul((string) $integer, '256'), $part));

            } elseif (\extension_loaded('bcmath')) {

                $integer = bcadd(bcmul((string) $integer, '256'), (string) $part);

            } else {

                throw new RuntimeException(

                    'The gmp or bcmath extension must be installed to read this database.'

                );

            }

        }

        return $integer;

    }

    private function sizeFromCtrlByte(int $ctrlByte, int $offset): array

    {

        $size = $ctrlByte & 0x1F;

        if ($size < 29) {

            return [$size, $offset];

        }

        $bytesToRead = $size - 28;

        $bytes = Util::read($this->fileStream, $offset, $bytesToRead);

        if ($size === 29) {

            $size = 29 + \ord($bytes);

        } elseif ($size === 30) {

            [, $adjust] = unpack('n', $bytes);

            $size = 285 + $adjust;

        } else {

            [, $adjust] = unpack('N', "\x00" . $bytes);

            $size = $adjust + 65821;

        }

        return [$size, $offset + $bytesToRead];

    }

    private function maybeSwitchByteOrder(string $bytes): string

    {

        return $this->switchByteOrder ? strrev($bytes) : $bytes;

    }

    private function isPlatformLittleEndian(): bool

    {

        $testint = 0x00FF;

        $packed = pack('S', $testint);

        return $testint === current(unpack('v', $packed));

    }

}