<?php
namespace Aws\Api\Parser;
use \Iterator;
use Aws\Api\DateTimeResult;
use GuzzleHttp\Psr7;
use Psr\Http\Message\StreamInterface;
use Aws\Api\Parser\Exception\ParserException;
/**
* @internal Implements a decoder for a binary encoded event stream that will
* decode, validate, and provide individual events from the stream.
*/
class DecodingEventStreamIterator implements Iterator
{
const HEADERS = 'headers';
const PAYLOAD = 'payload';
const LENGTH_TOTAL = 'total_length';
const LENGTH_HEADERS = 'headers_length';
const CRC_PRELUDE = 'prelude_crc';
const BYTES_PRELUDE = 12;
const BYTES_TRAILING = 4;
private static $preludeFormat = [
self::LENGTH_TOTAL => 'decodeUint32',
self::LENGTH_HEADERS => 'decodeUint32',
self::CRC_PRELUDE => 'decodeUint32',
];
private static $lengthFormatMap = [
1 => 'decodeUint8',
2 => 'decodeUint16',
4 => 'decodeUint32',
8 => 'decodeUint64',
];
private static $headerTypeMap = [
0 => 'decodeBooleanTrue',
1 => 'decodeBooleanFalse',
2 => 'decodeInt8',
3 => 'decodeInt16',
4 => 'decodeInt32',
5 => 'decodeInt64',
6 => 'decodeBytes',
7 => 'decodeString',
8 => 'decodeTimestamp',
9 => 'decodeUuid',
];
/** @var StreamInterface Stream of eventstream shape to parse. */
private $stream;
/** @var array Currently parsed event. */
private $currentEvent;
/** @var int Current in-order event key. */
private $key;
/** @var resource|\HashContext CRC32 hash context for event validation */
private $hashContext;
/** @var int $currentPosition */
private $currentPosition;
/**
* DecodingEventStreamIterator constructor.
*
* @param StreamInterface $stream
*/
public function __construct(StreamInterface $stream)
{
$this->stream = $stream;
$this->rewind();
}
private function parseHeaders($headerBytes)
{
$headers = [];
$bytesRead = 0;
while ($bytesRead < $headerBytes) {
list($key, $numBytes) = $this->decodeString(1);
$bytesRead += $numBytes;
list($type, $numBytes) = $this->decodeUint8();
$bytesRead += $numBytes;
$f = self::$headerTypeMap[$type];
list($value, $numBytes) = $this->{$f}();
$bytesRead += $numBytes;
if (isset($headers[$key])) {
throw new ParserException('Duplicate key in event headers.');
}
$headers[$key] = $value;
}
return [$headers, $bytesRead];
}
private function parsePrelude()
{
$prelude = [];
$bytesRead = 0;
$calculatedCrc = null;
foreach (self::$preludeFormat as $key => $decodeFunction) {
if ($key === self::CRC_PRELUDE) {
$hashCopy = hash_copy($this->hashContext);
$calculatedCrc = hash_final($this->hashContext, true);
$this->hashContext = $hashCopy;
}
list($value, $numBytes) = $this->{$decodeFunction}();
$bytesRead += $numBytes;
$prelude[$key] = $value;
}
if (unpack('N', $calculatedCrc)[1] !== $prelude[self::CRC_PRELUDE]) {
throw new ParserException('Prelude checksum mismatch.');
}
return [$prelude, $bytesRead];
}
private function parseEvent()
{
$event = [];
if ($this->stream->tell() < $this->stream->getSize()) {
$this->hashContext = hash_init('crc32b');
$bytesLeft = $this->stream->getSize() - $this->stream->tell();
list($prelude, $numBytes) = $this->parsePrelude();
if ($prelude[self::LENGTH_TOTAL] > $bytesLeft) {
throw new ParserException('Message length too long.');
}
$bytesLeft -= $numBytes;
if ($prelude[self::LENGTH_HEADERS] > $bytesLeft) {
throw new ParserException('Headers length too long.');
}
list(
$event[self::HEADERS],
$numBytes
) = $this->parseHeaders($prelude[self::LENGTH_HEADERS]);
$event[self::PAYLOAD] = Psr7\Utils::streamFor(
$this->readAndHashBytes(
$prelude[self::LENGTH_TOTAL] - self::BYTES_PRELUDE
- $numBytes - self::BYTES_TRAILING
)
);
$calculatedCrc = hash_final($this->hashContext, true);
$messageCrc = $this->stream->read(4);
if ($calculatedCrc !== $messageCrc) {
throw new ParserException('Message checksum mismatch.');
}
}
return $event;
}
// Iterator Functionality
/**
* @return array
*/
public function current()
{
return $this->currentEvent;
}
/**
* @return int
*/
public function key()
{
return $this->key;
}
public function next()
{
$this->currentPosition = $this->stream->tell();
if ($this->valid()) {
$this->key++;
$this->currentEvent = $this->parseEvent();
}
}
public function rewind()
{
$this->stream->rewind();
$this->key = 0;
$this->currentPosition = 0;
$this->currentEvent = $this->parseEvent();
}
/**
* @return bool
*/
public function valid()
{
return $this->currentPosition < $this->stream->getSize();
}
// Decoding Utilities
private function readAndHashBytes($num)
{
$bytes = $this->stream->read($num);
hash_update($this->hashContext, $bytes);
return $bytes;
}
private function decodeBooleanTrue()
{
return [true, 0];
}
private function decodeBooleanFalse()
{
return [false, 0];
}
private function uintToInt($val, $size)
{
$signedCap = pow(2, $size - 1);
if ($val > $signedCap) {
$val -= (2 * $signedCap);
}
return $val;
}
private function decodeInt8()
{
$val = (int)unpack('C', $this->readAndHashBytes(1))[1];
return [$this->uintToInt($val, 8), 1];
}
private function decodeUint8()
{
return [unpack('C', $this->readAndHashBytes(1))[1], 1];
}
private function decodeInt16()
{
$val = (int)unpack('n', $this->readAndHashBytes(2))[1];
return [$this->uintToInt($val, 16), 2];
}
private function decodeUint16()
{
return [unpack('n', $this->readAndHashBytes(2))[1], 2];
}
private function decodeInt32()
{
$val = (int)unpack('N', $this->readAndHashBytes(4))[1];
return [$this->uintToInt($val, 32), 4];
}
private function decodeUint32()
{
return [unpack('N', $this->readAndHashBytes(4))[1], 4];
}
private function decodeInt64()
{
$val = $this->unpackInt64($this->readAndHashBytes(8))[1];
return [$this->uintToInt($val, 64), 8];
}
private function decodeUint64()
{
return [$this->unpackInt64($this->readAndHashBytes(8))[1], 8];
}
private function unpackInt64($bytes)
{
if (version_compare(PHP_VERSION, '5.6.3', '<')) {
$d = unpack('N2', $bytes);
return [1 => $d[1] << 32 | $d[2]];
}
return unpack('J', $bytes);
}
private function decodeBytes($lengthBytes=2)
{
if (!isset(self::$lengthFormatMap[$lengthBytes])) {
throw new ParserException('Undefined variable length format.');
}
$f = self::$lengthFormatMap[$lengthBytes];
list($len, $bytes) = $this->{$f}();
return [$this->readAndHashBytes($len), $len + $bytes];
}
private function decodeString($lengthBytes=2)
{
if (!isset(self::$lengthFormatMap[$lengthBytes])) {
throw new ParserException('Undefined variable length format.');
}
$f = self::$lengthFormatMap[$lengthBytes];
list($len, $bytes) = $this->{$f}();
return [$this->readAndHashBytes($len), $len + $bytes];
}
private function decodeTimestamp()
{
list($val, $bytes) = $this->decodeInt64();
return [
DateTimeResult::createFromFormat('U.u', $val / 1000),
$bytes
];
}
private function decodeUuid()
{
$val = unpack('H32', $this->readAndHashBytes(16))[1];
return [
substr($val, 0, 8) . '-'
. substr($val, 8, 4) . '-'
. substr($val, 12, 4) . '-'
. substr($val, 16, 4) . '-'
. substr($val, 20, 12),
16
];
}
}