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hash_update_stream() is a function in PHP that is used to hash the data stream. This function is part of the hash extension in PHP, which provides a more efficient way to calculate when hashing large amounts of data. This function is usually used in scenarios where the hash value needs to be updated step by step, rather than reading the entire data at once.
The hash_update_stream() function gradually updates the hash value by processing the data stream. This is very effective for handling large files or getting data from network streams, as the data can be read block by block and updated hash without loading all data into memory. This function is usually used in conjunction with hash_init() and hash_final() to complete the hash calculation process.
bool hash_update_stream ( resource $context , resource $stream [, int $length ] )
$context : is a hash context resource initialized by the hash_init() function.
$stream : The stream resource to read data can be a file stream, a network stream, etc.
$length : Optional parameter, specifying the number of bytes to be read.
The hash_update_stream() function can be used to handle multiple types of resources. The following are the resource types supported by this function:
File flow resources
This is the most common resource type and is suitable for file read operations. You can open the file stream through functions such as fopen() or file_get_contents() and pass it to the hash_update_stream() function. In this way, the function will gradually read the file content and update the hash value.
Sample code:
$file = fopen('http://m66.net/somefile.txt', 'r'); // Open the file stream
$hash_context = hash_init('sha256'); // Initialize hash context
hash_update_stream($hash_context, $file); // Update hash
fclose($file); // Close the file stream
Network flow resources
hash_update_stream() also supports updating hash values from network resource streams. This resource type can open a network connection through the fopen() function. For example, you can open an HTTP stream and read the data step by step.
Sample code:
$url = 'http://m66.net/somefile.txt';
$stream = fopen($url, 'r'); // OpenURLflow
$context = hash_init('sha256'); // Initialize hash context
hash_update_stream($context, $stream); // 逐步Update hash值
fclose($stream); // 关闭flow
Standard input stream
On the command line, PHP can handle standard input streams. hash_update_stream() also supports hash updates to standard input streams (such as streams obtained through php://stdin ).
Sample code:
$stdin = fopen('php://stdin', 'r'); // Open标准输入flow
$context = hash_init('sha256'); // Initialize hash context
hash_update_stream($context, $stdin); // 逐步Update hash值
fclose($stdin); // 关闭标准输入flow
Memory stream (via php://temp or php://memory)
You can also use PHP's memory streaming resources (for example via php://temp or php://memory ). These streams can store temporary data and are ideal for processing small to medium amounts of data.
Sample code:
$memory_stream = fopen('php://temp', 'r+'); // Open内存flow
fwrite($memory_stream, 'Hello, this is a test string.');
rewind($memory_stream); // 重置flow指针到开始位置
$context = hash_init('sha256'); // Initialize hash context
hash_update_stream($context, $memory_stream); // 逐步Update hash值
fclose($memory_stream); // 关闭内存flow
The hash_update_stream() function can handle a variety of types of stream resources, including file streams, network streams, standard input streams, and memory streams. Whether you are reading files from disk, getting data from the network, or processing temporary data in memory, you can use this function to gradually update the hash value. This makes it very efficient and efficient when handling large files or getting data streams in real time.
