312 lines
8.5 KiB
PHP
312 lines
8.5 KiB
PHP
<?php
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namespace MaxMind\Db\Reader;
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class Decoder
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{
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private $fileStream;
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private $pointerBase;
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// This is only used for unit testing
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private $pointerTestHack;
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private $switchByteOrder;
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private $types = [
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0 => 'extended',
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1 => 'pointer',
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2 => 'utf8_string',
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3 => 'double',
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4 => 'bytes',
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5 => 'uint16',
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6 => 'uint32',
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7 => 'map',
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8 => 'int32',
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9 => 'uint64',
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10 => 'uint128',
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11 => 'array',
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12 => 'container',
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13 => 'end_marker',
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14 => 'boolean',
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15 => 'float',
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];
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public function __construct(
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$fileStream,
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$pointerBase = 0,
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$pointerTestHack = false
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) {
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$this->fileStream = $fileStream;
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$this->pointerBase = $pointerBase;
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$this->pointerTestHack = $pointerTestHack;
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$this->switchByteOrder = $this->isPlatformLittleEndian();
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}
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public function decode($offset)
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{
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list(, $ctrlByte) = unpack(
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'C',
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Util::read($this->fileStream, $offset, 1)
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);
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$offset++;
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$type = $this->types[$ctrlByte >> 5];
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// Pointers are a special case, we don't read the next $size bytes, we
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// use the size to determine the length of the pointer and then follow
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// it.
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if ($type === 'pointer') {
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list($pointer, $offset) = $this->decodePointer($ctrlByte, $offset);
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// for unit testing
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if ($this->pointerTestHack) {
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return [$pointer];
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}
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list($result) = $this->decode($pointer);
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return [$result, $offset];
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}
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if ($type === 'extended') {
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list(, $nextByte) = unpack(
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'C',
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Util::read($this->fileStream, $offset, 1)
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);
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$typeNum = $nextByte + 7;
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if ($typeNum < 8) {
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throw new InvalidDatabaseException(
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'Something went horribly wrong in the decoder. An extended type '
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. 'resolved to a type number < 8 ('
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. $this->types[$typeNum]
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. ')'
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);
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}
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$type = $this->types[$typeNum];
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$offset++;
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}
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list($size, $offset) = $this->sizeFromCtrlByte($ctrlByte, $offset);
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return $this->decodeByType($type, $offset, $size);
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}
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private function decodeByType($type, $offset, $size)
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{
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switch ($type) {
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case 'map':
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return $this->decodeMap($size, $offset);
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case 'array':
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return $this->decodeArray($size, $offset);
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case 'boolean':
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return [$this->decodeBoolean($size), $offset];
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}
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$newOffset = $offset + $size;
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$bytes = Util::read($this->fileStream, $offset, $size);
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switch ($type) {
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case 'utf8_string':
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return [$this->decodeString($bytes), $newOffset];
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case 'double':
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$this->verifySize(8, $size);
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return [$this->decodeDouble($bytes), $newOffset];
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case 'float':
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$this->verifySize(4, $size);
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return [$this->decodeFloat($bytes), $newOffset];
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case 'bytes':
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return [$bytes, $newOffset];
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case 'uint16':
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case 'uint32':
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return [$this->decodeUint($bytes), $newOffset];
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case 'int32':
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return [$this->decodeInt32($bytes), $newOffset];
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case 'uint64':
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case 'uint128':
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return [$this->decodeBigUint($bytes, $size), $newOffset];
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default:
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throw new InvalidDatabaseException(
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'Unknown or unexpected type: ' . $type
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);
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}
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}
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private function verifySize($expected, $actual)
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{
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if ($expected !== $actual) {
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throw new InvalidDatabaseException(
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"The MaxMind DB file's data section contains bad data (unknown data type or corrupt data)"
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);
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}
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}
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private function decodeArray($size, $offset)
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{
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$array = [];
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for ($i = 0; $i < $size; $i++) {
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list($value, $offset) = $this->decode($offset);
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array_push($array, $value);
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}
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return [$array, $offset];
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}
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private function decodeBoolean($size)
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{
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return $size === 0 ? false : true;
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}
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private function decodeDouble($bits)
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{
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// XXX - Assumes IEEE 754 double on platform
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list(, $double) = unpack('d', $this->maybeSwitchByteOrder($bits));
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return $double;
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}
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private function decodeFloat($bits)
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{
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// XXX - Assumes IEEE 754 floats on platform
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list(, $float) = unpack('f', $this->maybeSwitchByteOrder($bits));
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return $float;
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}
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private function decodeInt32($bytes)
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{
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$bytes = $this->zeroPadLeft($bytes, 4);
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list(, $int) = unpack('l', $this->maybeSwitchByteOrder($bytes));
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return $int;
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}
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private function decodeMap($size, $offset)
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{
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$map = [];
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for ($i = 0; $i < $size; $i++) {
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list($key, $offset) = $this->decode($offset);
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list($value, $offset) = $this->decode($offset);
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$map[$key] = $value;
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}
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return [$map, $offset];
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}
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private $pointerValueOffset = [
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1 => 0,
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2 => 2048,
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3 => 526336,
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4 => 0,
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];
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private function decodePointer($ctrlByte, $offset)
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{
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$pointerSize = (($ctrlByte >> 3) & 0x3) + 1;
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$buffer = Util::read($this->fileStream, $offset, $pointerSize);
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$offset = $offset + $pointerSize;
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$packed = $pointerSize === 4
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? $buffer
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: (pack('C', $ctrlByte & 0x7)) . $buffer;
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$unpacked = $this->decodeUint($packed);
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$pointer = $unpacked + $this->pointerBase
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+ $this->pointerValueOffset[$pointerSize];
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return [$pointer, $offset];
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}
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private function decodeUint($bytes)
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{
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list(, $int) = unpack('N', $this->zeroPadLeft($bytes, 4));
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return $int;
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}
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private function decodeBigUint($bytes, $byteLength)
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{
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$maxUintBytes = log(PHP_INT_MAX, 2) / 8;
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if ($byteLength === 0) {
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return 0;
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}
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$numberOfLongs = ceil($byteLength / 4);
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$paddedLength = $numberOfLongs * 4;
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$paddedBytes = $this->zeroPadLeft($bytes, $paddedLength);
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$unpacked = array_merge(unpack("N$numberOfLongs", $paddedBytes));
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$integer = 0;
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// 2^32
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$twoTo32 = '4294967296';
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foreach ($unpacked as $part) {
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// We only use gmp or bcmath if the final value is too big
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if ($byteLength <= $maxUintBytes) {
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$integer = ($integer << 32) + $part;
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} elseif (extension_loaded('gmp')) {
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$integer = gmp_strval(gmp_add(gmp_mul($integer, $twoTo32), $part));
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} elseif (extension_loaded('bcmath')) {
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$integer = bcadd(bcmul($integer, $twoTo32), $part);
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} else {
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throw new \RuntimeException(
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'The gmp or bcmath extension must be installed to read this database.'
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);
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}
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}
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return $integer;
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}
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private function decodeString($bytes)
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{
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// XXX - NOOP. As far as I know, the end user has to explicitly set the
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// encoding in PHP. Strings are just bytes.
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return $bytes;
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}
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private function sizeFromCtrlByte($ctrlByte, $offset)
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{
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$size = $ctrlByte & 0x1f;
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$bytesToRead = $size < 29 ? 0 : $size - 28;
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$bytes = Util::read($this->fileStream, $offset, $bytesToRead);
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$decoded = $this->decodeUint($bytes);
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if ($size === 29) {
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$size = 29 + $decoded;
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} elseif ($size === 30) {
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$size = 285 + $decoded;
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} elseif ($size > 30) {
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$size = ($decoded & (0x0FFFFFFF >> (32 - (8 * $bytesToRead))))
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+ 65821;
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}
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return [$size, $offset + $bytesToRead];
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}
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private function zeroPadLeft($content, $desiredLength)
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{
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return str_pad($content, $desiredLength, "\x00", STR_PAD_LEFT);
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}
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private function maybeSwitchByteOrder($bytes)
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{
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return $this->switchByteOrder ? strrev($bytes) : $bytes;
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}
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private function isPlatformLittleEndian()
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{
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$testint = 0x00FF;
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$packed = pack('S', $testint);
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return $testint === current(unpack('v', $packed));
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}
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}
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