hash_update_stream() – Populate an Active Hash Context from an Open Stream (PHP)

The PHP function hash_update_stream() reads data from an open stream and feeds it into an active hash context, allowing incremental hashing of large data sources.

Signature:

int hash_update_stream(resource $context, resource $handle[, int $length = -1])

Parameters:

context : the hash context resource returned by hash_init().

handle : an open file handle representing the stream to read from.

length (optional): the maximum number of bytes to copy from the handle; default -1 means read until EOF.

Return value: the number of bytes actually read from the handle and added to the hash context.

Example:

<?php
$fp = tmpfile();
fwrite($fp, 'The quick brown fox jumped over the lazy dog.');
rewind($fp);
$ctx = hash_init('md5');
hash_update_stream($ctx, $fp);
echo hash_final($ctx);
?>

The script outputs the MD5 hash of the string, for example:

5c6ffbdd40d9556b73a21e63c3e0e904