ConFoo 2025

RarEntry::getCrc

(PECL rar >= 0.1)

RarEntry::getCrcGet CRC of the entry

Description

public RarEntry::getCrc(): string

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

Parameters

This function has no parameters.

Return Values

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

Changelog

Version Description
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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