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Differences Between: [Versions 310 and 403] [Versions 311 and 403] [Versions 39 and 403] [Versions 400 and 403]

   1  <?php
   2  
   3  declare(strict_types=1);
   4  
   5  namespace MaxMind\Db\Reader;
   6  
   7  // @codingStandardsIgnoreLine
   8  use RuntimeException;
   9  
  10  class Decoder
  11  {
  12      /**
  13       * @var resource
  14       */
  15      private $fileStream;
  16      /**
  17       * @var int
  18       */
  19      private $pointerBase;
  20      /**
  21       * @var float
  22       */
  23      private $pointerBaseByteSize;
  24      /**
  25       * This is only used for unit testing.
  26       *
  27       * @var bool
  28       */
  29      private $pointerTestHack;
  30      /**
  31       * @var bool
  32       */
  33      private $switchByteOrder;
  34  
  35      private const _EXTENDED = 0;
  36      private const _POINTER = 1;
  37      private const _UTF8_STRING = 2;
  38      private const _DOUBLE = 3;
  39      private const _BYTES = 4;
  40      private const _UINT16 = 5;
  41      private const _UINT32 = 6;
  42      private const _MAP = 7;
  43      private const _INT32 = 8;
  44      private const _UINT64 = 9;
  45      private const _UINT128 = 10;
  46      private const _ARRAY = 11;
  47      private const _CONTAINER = 12;
  48      private const _END_MARKER = 13;
  49      private const _BOOLEAN = 14;
  50      private const _FLOAT = 15;
  51  
  52      /**
  53       * @param resource $fileStream
  54       */
  55      public function __construct(
  56          $fileStream,
  57          int $pointerBase = 0,
  58          bool $pointerTestHack = false
  59      ) {
  60          $this->fileStream = $fileStream;
  61          $this->pointerBase = $pointerBase;
  62  
  63          $this->pointerBaseByteSize = $pointerBase > 0 ? log($pointerBase, 2) / 8 : 0;
  64          $this->pointerTestHack = $pointerTestHack;
  65  
  66          $this->switchByteOrder = $this->isPlatformLittleEndian();
  67      }
  68  
  69      public function decode(int $offset): array
  70      {
  71          $ctrlByte = \ord(Util::read($this->fileStream, $offset, 1));
  72          ++$offset;
  73  
  74          $type = $ctrlByte >> 5;
  75  
  76          // Pointers are a special case, we don't read the next $size bytes, we
  77          // use the size to determine the length of the pointer and then follow
  78          // it.
  79          if ($type === self::_POINTER) {
  80              [$pointer, $offset] = $this->decodePointer($ctrlByte, $offset);
  81  
  82              // for unit testing
  83              if ($this->pointerTestHack) {
  84                  return [$pointer];
  85              }
  86  
  87              [$result] = $this->decode($pointer);
  88  
  89              return [$result, $offset];
  90          }
  91  
  92          if ($type === self::_EXTENDED) {
  93              $nextByte = \ord(Util::read($this->fileStream, $offset, 1));
  94  
  95              $type = $nextByte + 7;
  96  
  97              if ($type < 8) {
  98                  throw new InvalidDatabaseException(
  99                      'Something went horribly wrong in the decoder. An extended type '
 100                      . 'resolved to a type number < 8 ('
 101                      . $type
 102                      . ')'
 103                  );
 104              }
 105  
 106              ++$offset;
 107          }
 108  
 109          [$size, $offset] = $this->sizeFromCtrlByte($ctrlByte, $offset);
 110  
 111          return $this->decodeByType($type, $offset, $size);
 112      }
 113  
 114      private function decodeByType(int $type, int $offset, int $size): array
 115      {
 116          switch ($type) {
 117              case self::_MAP:
 118                  return $this->decodeMap($size, $offset);
 119  
 120              case self::_ARRAY:
 121                  return $this->decodeArray($size, $offset);
 122  
 123              case self::_BOOLEAN:
 124                  return [$this->decodeBoolean($size), $offset];
 125          }
 126  
 127          $newOffset = $offset + $size;
 128          $bytes = Util::read($this->fileStream, $offset, $size);
 129  
 130          switch ($type) {
 131              case self::_BYTES:
 132              case self::_UTF8_STRING:
 133                  return [$bytes, $newOffset];
 134  
 135              case self::_DOUBLE:
 136                  $this->verifySize(8, $size);
 137  
 138                  return [$this->decodeDouble($bytes), $newOffset];
 139  
 140              case self::_FLOAT:
 141                  $this->verifySize(4, $size);
 142  
 143                  return [$this->decodeFloat($bytes), $newOffset];
 144  
 145              case self::_INT32:
 146                  return [$this->decodeInt32($bytes, $size), $newOffset];
 147  
 148              case self::_UINT16:
 149              case self::_UINT32:
 150              case self::_UINT64:
 151              case self::_UINT128:
 152                  return [$this->decodeUint($bytes, $size), $newOffset];
 153  
 154              default:
 155                  throw new InvalidDatabaseException(
 156                      'Unknown or unexpected type: ' . $type
 157                  );
 158          }
 159      }
 160  
 161      private function verifySize(int $expected, int $actual): void
 162      {
 163          if ($expected !== $actual) {
 164              throw new InvalidDatabaseException(
 165                  "The MaxMind DB file's data section contains bad data (unknown data type or corrupt data)"
 166              );
 167          }
 168      }
 169  
 170      private function decodeArray(int $size, int $offset): array
 171      {
 172          $array = [];
 173  
 174          for ($i = 0; $i < $size; ++$i) {
 175              [$value, $offset] = $this->decode($offset);
 176              $array[] = $value;
 177          }
 178  
 179          return [$array, $offset];
 180      }
 181  
 182      private function decodeBoolean(int $size): bool
 183      {
 184          return $size !== 0;
 185      }
 186  
 187      private function decodeDouble(string $bytes): float
 188      {
 189          // This assumes IEEE 754 doubles, but most (all?) modern platforms
 190          // use them.
 191          [, $double] = unpack('E', $bytes);
 192  
 193          return $double;
 194      }
 195  
 196      private function decodeFloat(string $bytes): float
 197      {
 198          // This assumes IEEE 754 floats, but most (all?) modern platforms
 199          // use them.
 200          [, $float] = unpack('G', $bytes);
 201  
 202          return $float;
 203      }
 204  
 205      private function decodeInt32(string $bytes, int $size): int
 206      {
 207          switch ($size) {
 208              case 0:
 209                  return 0;
 210  
 211              case 1:
 212              case 2:
 213              case 3:
 214                  $bytes = str_pad($bytes, 4, "\x00", \STR_PAD_LEFT);
 215  
 216                  break;
 217  
 218              case 4:
 219                  break;
 220  
 221              default:
 222                  throw new InvalidDatabaseException(
 223                      "The MaxMind DB file's data section contains bad data (unknown data type or corrupt data)"
 224                  );
 225          }
 226  
 227          [, $int] = unpack('l', $this->maybeSwitchByteOrder($bytes));
 228  
 229          return $int;
 230      }
 231  
 232      private function decodeMap(int $size, int $offset): array
 233      {
 234          $map = [];
 235  
 236          for ($i = 0; $i < $size; ++$i) {
 237              [$key, $offset] = $this->decode($offset);
 238              [$value, $offset] = $this->decode($offset);
 239              $map[$key] = $value;
 240          }
 241  
 242          return [$map, $offset];
 243      }
 244  
 245      private function decodePointer(int $ctrlByte, int $offset): array
 246      {
 247          $pointerSize = (($ctrlByte >> 3) & 0x3) + 1;
 248  
 249          $buffer = Util::read($this->fileStream, $offset, $pointerSize);
 250          $offset = $offset + $pointerSize;
 251  
 252          switch ($pointerSize) {
 253              case 1:
 254                  $packed = \chr($ctrlByte & 0x7) . $buffer;
 255                  [, $pointer] = unpack('n', $packed);
 256                  $pointer += $this->pointerBase;
 257  
 258                  break;
 259  
 260              case 2:
 261                  $packed = "\x00" . \chr($ctrlByte & 0x7) . $buffer;
 262                  [, $pointer] = unpack('N', $packed);
 263                  $pointer += $this->pointerBase + 2048;
 264  
 265                  break;
 266  
 267              case 3:
 268                  $packed = \chr($ctrlByte & 0x7) . $buffer;
 269  
 270                  // It is safe to use 'N' here, even on 32 bit machines as the
 271                  // first bit is 0.
 272                  [, $pointer] = unpack('N', $packed);
 273                  $pointer += $this->pointerBase + 526336;
 274  
 275                  break;
 276  
 277              case 4:
 278                  // We cannot use unpack here as we might overflow on 32 bit
 279                  // machines
 280                  $pointerOffset = $this->decodeUint($buffer, $pointerSize);
 281  
 282                  $pointerBase = $this->pointerBase;
 283  
 284                  if (\PHP_INT_MAX - $pointerBase >= $pointerOffset) {
 285                      $pointer = $pointerOffset + $pointerBase;
 286                  } else {
 287                      throw new RuntimeException(
 288                          'The database offset is too large to be represented on your platform.'
 289                      );
 290                  }
 291  
 292                  break;
 293  
 294              default:
 295                  throw new InvalidDatabaseException(
 296                      'Unexpected pointer size ' . $pointerSize
 297                  );
 298          }
 299  
 300          return [$pointer, $offset];
 301      }
 302  
 303      // @phpstan-ignore-next-line
 304      private function decodeUint(string $bytes, int $byteLength)
 305      {
 306          if ($byteLength === 0) {
 307              return 0;
 308          }
 309  
 310          $integer = 0;
 311  
 312          // PHP integers are signed. PHP_INT_SIZE - 1 is the number of
 313          // complete bytes that can be converted to an integer. However,
 314          // we can convert another byte if the leading bit is zero.
 315          $useRealInts = $byteLength <= \PHP_INT_SIZE - 1
 316              || ($byteLength === \PHP_INT_SIZE && (\ord($bytes[0]) & 0x80) === 0);
 317  
 318          for ($i = 0; $i < $byteLength; ++$i) {
 319              $part = \ord($bytes[$i]);
 320  
 321              // We only use gmp or bcmath if the final value is too big
 322              if ($useRealInts) {
 323                  $integer = ($integer << 8) + $part;
 324              } elseif (\extension_loaded('gmp')) {
 325                  $integer = gmp_strval(gmp_add(gmp_mul((string) $integer, '256'), $part));
 326              } elseif (\extension_loaded('bcmath')) {
 327                  $integer = bcadd(bcmul((string) $integer, '256'), (string) $part);
 328              } else {
 329                  throw new RuntimeException(
 330                      'The gmp or bcmath extension must be installed to read this database.'
 331                  );
 332              }
 333          }
 334  
 335          return $integer;
 336      }
 337  
 338      private function sizeFromCtrlByte(int $ctrlByte, int $offset): array
 339      {
 340          $size = $ctrlByte & 0x1F;
 341  
 342          if ($size < 29) {
 343              return [$size, $offset];
 344          }
 345  
 346          $bytesToRead = $size - 28;
 347          $bytes = Util::read($this->fileStream, $offset, $bytesToRead);
 348  
 349          if ($size === 29) {
 350              $size = 29 + \ord($bytes);
 351          } elseif ($size === 30) {
 352              [, $adjust] = unpack('n', $bytes);
 353              $size = 285 + $adjust;
 354          } else {
 355              [, $adjust] = unpack('N', "\x00" . $bytes);
 356              $size = $adjust + 65821;
 357          }
 358  
 359          return [$size, $offset + $bytesToRead];
 360      }
 361  
 362      private function maybeSwitchByteOrder(string $bytes): string
 363      {
 364          return $this->switchByteOrder ? strrev($bytes) : $bytes;
 365      }
 366  
 367      private function isPlatformLittleEndian(): bool
 368      {
 369          $testint = 0x00FF;
 370          $packed = pack('S', $testint);
 371  
 372          return $testint === current(unpack('v', $packed));
 373      }
 374  }