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RarEntry::getCrc

(PECL rar >= 0.1)

RarEntry::getCrc — Get CRC of the entry

Açıklama

public RarEntry::getCrc(): string

Returns an hexadecimal string representation of the CRC of the archive entry.

Bağımsız Değişkenler

Bu işlevin bağımsız değişkeni yoktur.

Dönen Değerler

Returns the CRC of the archive entry or false on error.

Sürüm Bilgisi

Sürüm:	Açıklama
PECL rar 2.0.0	This method now returns correct values for multiple volume archives.

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User Contributed Notes 1 note

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aterlux at mail dot ru ¶

6 years ago


RarEntry::getCrc() returs a lowercase hex-string (e.g. 'bf6fa85c') the same as hash_... functions, using the same polynomial as 'crc32b' algorithm.
So, it can be used to check CRC after a stream unpacking:

<?php
  $archive_name = 'archive.rar';

  $entry_name = 'someentry.ext';

  $rar = RarArchive::open($archive_name) or die("Cannot open archive $archive_name");

  if ($rar->isBroken()) {
    die("The archive is broken!");
  }

  $entry = $rar->getEntry($entry_name) or die("Cannot find entry $entry_name");

  $stream = $entry->getStream() or die("Cannot open stream");

  $crc = hash_init('crc32b'); // Initializing the hash function

  while (!feof($stream)) {
    $s = fread($stream, 8192);
    if ($s === false) {
        // Error reading (do not use fread(...) or die(...), because fread can return '0'!)
      die('Error reading the compressed file.');
    }
    hash_update($crc, $s); // updating the hash

    // ...
    // Do whatever with the $s
  }

  fclose($stream);

  $got_crc = hash_final($crc);
  $need_crc = $entry->getCrc();

  print("Got CRC: $got_crc" . PHP_EOL);
  print("Need CRC: $need_crc" . PHP_EOL);

  if ($got_crc != $need_crc) {
    // rollback
    print("Sorry guys, the file was incorrect!" . PHP_EOL);
  } else {
    print("Everything is ok" . PHP_EOL);
  }
?>

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