[PHP知识库]Shmop demo

<?php
/**
 * Shmop demo
 *
 * $ ipcs -m
 * ------ Shared Memory Segments --------
 * key        shmid      owner      perms      bytes      nattch     status      
 * 0x5102031f 32787      user       600        3208       1                       
 * 0x00000000 32814      user       600        524288     2          dest         
 * 0x2a020da2 32828      user       644        1024       0
 */
header('Content-Type: text/plain');

function block_check(int $max_size, string &$block): bool
{
    $size = strlen($block);
    if ($size <= 32 || $size != $max_size) {
        return false;
    }
    $md5 = substr($block, 0, 32);
    if (empty($md5)) {
        return false;
    }
    $playload = substr($block, 32);
    if (empty($playload)) {
        return false;
    }
    return $md5 === md5($playload);
}

function block_data_write(int $max_size, string &$block, string $data): string
{
    $body = strlen($data) . '|' . $data;
    $len = strlen($body);
    if (32 + $len > $max_size) {
        throw new Exception('Too much data.');
    }
    $playload = str_pad($body, $max_size - 32, ' ');
    return $block = md5($playload) . $playload;
}

function block_data_read(int $max_size, string &$block): string
{
    if (!block_check($max_size, $block) || strlen($block) != $max_size) {
        return '';
    }
    $data_length = '';
    $data_start = 32;
    for ($i = 32; $i < $max_size && $block[$i] != '|'; $i++) {
        $data_length .= $block[$i];
        $data_start = $i + 2;
    }
    return substr($block, $data_start, $data_length);
}

function block_data(int $max_size, string &$block, ?string $data = null): string
{
    return is_null($data) ? block_data_read($max_size, $block) : block_data_write($max_size, $block, $data);
}

$max_size = 1024;

$key = ftok(__FILE__, '*');
if (-1 == $key) {
    echo 'ftok fail';
    exit(1);
}

echo 'Key: ' . $key . PHP_EOL;

$shmop = shmop_open($key, 'c', 0644, $max_size);
if (false === $shmop) {
    echo 'shmop_open fail';
    exit(1);
}

$save_data = shmop_read($shmop, 0, 0);
if (false === $save_data) {
    echo 'shmop_read fail' . PHP_EOL;
} else {
    echo base64_encode($save_data) . PHP_EOL;
    $inside_message = block_data($max_size, $save_data);
    if (empty($inside_message)) {
        $inside_message = 'Hello, shmop.';
        echo "Write: $inside_message" . PHP_EOL;
        $shmop_write_data = '';
        block_data($max_size, $shmop_write_data, $inside_message);
        shmop_write($shmop, $shmop_write_data, 0);
    } else {
        echo "Read: $inside_message" . PHP_EOL;
    }
}

//shmop_delete($shmop);
shmop_close($shmop);