hash_update

(PHP 5 >= 5.1.2, PECL hash:1.1-1.5)

hash_update — Pump data into an active hashing context

Описание

bool hash_update ( resource $context , string $data )

Список параметров

context

Hashing context returned by hash_init().

data

Message to be included in the hash digest.

Возвращаемые значения

Returns TRUE.

Коментарии

Автор:
A simple example on incremental file hashing:

$fp = fopen($file, "r");
$ctx = hash_init('sha256');
while (!feof($fp)) {
    $buffer = fgets($fp, 65536);
    hash_update($ctx, $buffer);
}
$hash = hash_final($ctx, true);
fclose($fp);

While incremental hashing is quite slow, it's the easiest way to hash 
- parts of large files: I.e., a 700MB avi video uses first x bytes to store metadata, so in order to hash the avi's data only, you have to fseek to data start and use incremental hashing
- streaming data if php just proxies the data
- whenever it's inadequate or impossible to store the data being hashed into memory (i.e. because of their size) or on disc.
2006-07-24 21:19:26
http://php5.kiev.ua/manual/ru/function.hash-update.html

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