hash_update_stream
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.
hash_update
(PHP 5 >= 5.1.2, PECL hash:1.1-1.5)
hash_update — Pump data into an active hashing context
Opis
bool hash_update
( resource $context
, string $data
)
Parametry
- context
-
Hashing context returned by hash_init().
- data
-
Message to be included in the hash digest.
Zwracane wartości
Returns TRUE.
add a note
User Contributed Noteshash_update
Dainichi
25-Jul-2006 03:19
25-Jul-2006 03:19