Decoder.php in Smart IP 6.2

Namespace

MaxMind\Db\Reader

File

includes/vendor/maxmind-db/reader/src/MaxMind/Db/Reader/Decoder.php

<?php

namespace MaxMind\Db\Reader;

use MaxMind\Db\Reader\InvalidDatabaseException;
use MaxMind\Db\Reader\Util;
class Decoder {
  private $fileStream;
  private $pointerBase;

  // This is only used for unit testing
  private $pointerTestHack;
  private $switchByteOrder;
  private $types = array(
    0 => 'extended',
    1 => 'pointer',
    2 => 'utf8_string',
    3 => 'double',
    4 => 'bytes',
    5 => 'uint16',
    6 => 'uint32',
    7 => 'map',
    8 => 'int32',
    9 => 'uint64',
    10 => 'uint128',
    11 => 'array',
    12 => 'container',
    13 => 'end_marker',
    14 => 'boolean',
    15 => 'float',
  );
  public function __construct($fileStream, $pointerBase = 0, $pointerTestHack = false) {
    $this->fileStream = $fileStream;
    $this->pointerBase = $pointerBase;
    $this->pointerTestHack = $pointerTestHack;
    $this->switchByteOrder = $this
      ->isPlatformLittleEndian();
  }
  public function decode($offset) {
    list(, $ctrlByte) = unpack('C', Util::read($this->fileStream, $offset, 1));
    $offset++;
    $type = $this->types[$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 == 'pointer') {
      list($pointer, $offset) = $this
        ->decodePointer($ctrlByte, $offset);

      // for unit testing
      if ($this->pointerTestHack) {
        return array(
          $pointer,
        );
      }
      list($result) = $this
        ->decode($pointer);
      return array(
        $result,
        $offset,
      );
    }
    if ($type == 'extended') {
      list(, $nextByte) = unpack('C', Util::read($this->fileStream, $offset, 1));
      $typeNum = $nextByte + 7;
      if ($typeNum < 8) {
        throw new InvalidDatabaseException("Something went horribly wrong in the decoder. An extended type " . "resolved to a type number < 8 (" . $this->types[$typeNum] . ")");
      }
      $type = $this->types[$typeNum];
      $offset++;
    }
    list($size, $offset) = $this
      ->sizeFromCtrlByte($ctrlByte, $offset);
    return $this
      ->decodeByType($type, $offset, $size);
  }
  private function decodeByType($type, $offset, $size) {
    switch ($type) {
      case 'map':
        return $this
          ->decodeMap($size, $offset);
      case 'array':
        return $this
          ->decodeArray($size, $offset);
      case 'boolean':
        return array(
          $this
            ->decodeBoolean($size),
          $offset,
        );
    }
    $newOffset = $offset + $size;
    $bytes = Util::read($this->fileStream, $offset, $size);
    switch ($type) {
      case 'utf8_string':
        return array(
          $this
            ->decodeString($bytes),
          $newOffset,
        );
      case 'double':
        $this
          ->verifySize(8, $size);
        return array(
          $this
            ->decodeDouble($bytes),
          $newOffset,
        );
      case 'float':
        $this
          ->verifySize(4, $size);
        return array(
          $this
            ->decodeFloat($bytes),
          $newOffset,
        );
      case 'bytes':
        return array(
          $bytes,
          $newOffset,
        );
      case 'uint16':
      case 'uint32':
        return array(
          $this
            ->decodeUint($bytes),
          $newOffset,
        );
      case 'int32':
        return array(
          $this
            ->decodeInt32($bytes),
          $newOffset,
        );
      case 'uint64':
      case 'uint128':
        return array(
          $this
            ->decodeBigUint($bytes, $size),
          $newOffset,
        );
      default:
        throw new InvalidDatabaseException("Unknown or unexpected type: " . $type);
    }
  }
  private function verifySize($expected, $actual) {
    if ($expected != $actual) {
      throw new InvalidDatabaseException("The MaxMind DB file's data section contains bad data (unknown data type or corrupt data)");
    }
  }
  private function decodeArray($size, $offset) {
    $array = array();
    for ($i = 0; $i < $size; $i++) {
      list($value, $offset) = $this
        ->decode($offset);
      array_push($array, $value);
    }
    return array(
      $array,
      $offset,
    );
  }
  private function decodeBoolean($size) {
    return $size == 0 ? false : true;
  }
  private function decodeDouble($bits) {

    // XXX - Assumes IEEE 754 double on platform
    list(, $double) = unpack('d', $this
      ->maybeSwitchByteOrder($bits));
    return $double;
  }
  private function decodeFloat($bits) {

    // XXX - Assumes IEEE 754 floats on platform
    list(, $float) = unpack('f', $this
      ->maybeSwitchByteOrder($bits));
    return $float;
  }
  private function decodeInt32($bytes) {
    $bytes = $this
      ->zeroPadLeft($bytes, 4);
    list(, $int) = unpack('l', $this
      ->maybeSwitchByteOrder($bytes));
    return $int;
  }
  private function decodeMap($size, $offset) {
    $map = array();
    for ($i = 0; $i < $size; $i++) {
      list($key, $offset) = $this
        ->decode($offset);
      list($value, $offset) = $this
        ->decode($offset);
      $map[$key] = $value;
    }
    return array(
      $map,
      $offset,
    );
  }
  private $pointerValueOffset = array(
    1 => 0,
    2 => 2048,
    3 => 526336,
    4 => 0,
  );
  private function decodePointer($ctrlByte, $offset) {
    $pointerSize = ($ctrlByte >> 3 & 0x3) + 1;
    $buffer = Util::read($this->fileStream, $offset, $pointerSize);
    $offset = $offset + $pointerSize;
    $packed = $pointerSize == 4 ? $buffer : pack('C', $ctrlByte & 0x7) . $buffer;
    $unpacked = $this
      ->decodeUint($packed);
    $pointer = $unpacked + $this->pointerBase + $this->pointerValueOffset[$pointerSize];
    return array(
      $pointer,
      $offset,
    );
  }
  private function decodeUint($bytes) {
    list(, $int) = unpack('N', $this
      ->zeroPadLeft($bytes, 4));
    return $int;
  }
  private function decodeBigUint($bytes, $byteLength) {
    $maxUintBytes = log(PHP_INT_MAX, 2) / 8;
    if ($byteLength == 0) {
      return 0;
    }
    $numberOfLongs = ceil($byteLength / 4);
    $paddedLength = $numberOfLongs * 4;
    $paddedBytes = $this
      ->zeroPadLeft($bytes, $paddedLength);
    $unpacked = array_merge(unpack("N{$numberOfLongs}", $paddedBytes));
    $integer = 0;

    // 2^32
    $twoTo32 = '4294967296';
    foreach ($unpacked as $part) {

      // We only use gmp or bcmath if the final value is too big
      if ($byteLength <= $maxUintBytes) {
        $integer = ($integer << 32) + $part;
      }
      elseif (extension_loaded('gmp')) {
        $integer = gmp_strval(gmp_add(gmp_mul($integer, $twoTo32), $part));
      }
      elseif (extension_loaded('bcmath')) {
        $integer = bcadd(bcmul($integer, $twoTo32), $part);
      }
      else {
        throw new \RuntimeException('The gmp or bcmath extension must be installed to read this database.');
      }
    }
    return $integer;
  }
  private function decodeString($bytes) {

    // XXX - NOOP. As far as I know, the end user has to explicitly set the
    // encoding in PHP. Strings are just bytes.
    return $bytes;
  }
  private function sizeFromCtrlByte($ctrlByte, $offset) {
    $size = $ctrlByte & 0x1f;
    $bytesToRead = $size < 29 ? 0 : $size - 28;
    $bytes = Util::read($this->fileStream, $offset, $bytesToRead);
    $decoded = $this
      ->decodeUint($bytes);
    if ($size == 29) {
      $size = 29 + $decoded;
    }
    elseif ($size == 30) {
      $size = 285 + $decoded;
    }
    elseif ($size > 30) {
      $size = ($decoded & 0xfffffff >> 32 - 8 * $bytesToRead) + 65821;
    }
    return array(
      $size,
      $offset + $bytesToRead,
    );
  }
  private function zeroPadLeft($content, $desiredLength) {
    return str_pad($content, $desiredLength, "\0", STR_PAD_LEFT);
  }
  private function maybeSwitchByteOrder($bytes) {
    return $this->switchByteOrder ? strrev($bytes) : $bytes;
  }
  private function isPlatformLittleEndian() {
    $testint = 0xff;
    $packed = pack('S', $testint);
    return $testint === current(unpack('v', $packed));
  }

}

Classes

Name	Description
Decoder