Combining curl to read the stream and calculate the hash value dynamically

In PHP, the hash_update_stream function is a method for dynamically updating hash values, especially when processing stream data. Combined with curl , it can realize the hash value calculation in real time when downloading large files or streaming data. In this article, we will explore how to use hash_update_stream and curl to achieve this.

1. What is hash_update_stream ?

The hash_update_stream function is one of the built-in hash functions in PHP, which is used to gradually update hash calculations. This means that when we process a large amount of data streams, we can gradually calculate the hash value of the file without loading the entire file into memory. Its syntax is as follows:

 bool hash_update_stream ( resource $context , resource $stream )

• $context : The hash context resource that was initialized using hash_init() .

• $stream : The resource of the data stream, usually created through a file or network stream.

2. What is curl ?

curl is a powerful PHP extension that allows you to interact with different network resources through URLs. Through curl , we can send requests to the server and receive responses, supporting multiple protocols such as HTTP, HTTPS, FTP, etc. In our application scenario, curl can be used to download remote resources and hand over the data stream to the hash_update_stream function for hash calculation.

3. Example: Use hash_update_stream and curl to calculate hash values ​​dynamically

In this example, we will use curl to download the file dynamically and calculate the hash value of the file in real time in combination with the hash_update_stream function.

Step 1: Initialize the hash context

First, we need to initialize a hash context. We can choose commonly used hashing algorithms, such as sha256 .

 $hashContext = hash_init('sha256'); // initialization sha256 Hash context

Step 2: Initialize the curl session

Next, we will initialize the session using curl and set the corresponding options to get the data stream of the remote file.

 $url = "http://example.com/largefile"; // Files to be downloaded URL
$ch = curl_init($url); // initialization curl Session

// set up curl Options
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true); // Returns the response instead of direct output
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true); // Support redirection
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false); // prohibit SSL Certificate verification（Suitable for self-signed certificates）

// Open the file stream to get data
$stream = curl_exec($ch);

Step 3: Dynamically read the stream and update the hash value

Now, we can use the hash_update_stream function to pass the data stream obtained by curl to perform real-time hash calculations.

 if ($stream) {
    $fp = fopen('php://memory', 'r+'); // Create memory streams
    fwrite($fp, $stream); // Write downloaded content to memory stream
    rewind($fp); // Return the stream pointer to the starting position

    // use hash_update_stream Dynamically update hash value
    hash_update_stream($hashContext, $fp); 

    fclose($fp); // Close the stream
}

Step 4: Complete hash calculation

Finally, we can get the final hash value through hash_final() .