php byte order conversion function

In any programming language, the concept of byte order (byte order) is very important. Especially in network programming, since communication must be cross-platform, it is necessary to understand the concept of byte order and related functions. In the PHP language, some functions are also provided to help us perform byte order conversion. This article will take a look at them together.

What is byte order

In computers, memory is stored in bytes (bytes). A byte is composed of 8 bits. In most computer architectures, bytes are stored in a little-endian manner, that is, the low-order bytes are stored first, followed by the high-order bytes. For example, if you want to store a 16-bit integer 0x1234, it is stored in the memory in the following way:

34 12

Of course, there are also some computer architectures, such as Motorola, that use large Big-endian storage, that is, the high-order byte is stored first, and the low-order byte is stored later.

In network transmission, since cross-platform communication is involved, byte order conversion is required. For example, an integer stored in little-endian mode needs to be converted into byte order when transmitted to a big-endian computer, otherwise the receiver will not be able to correctly parse the data.

PHP's byte order conversion function

In the PHP language, some functions are provided that can be used for byte order conversion. These functions can help us convert from network byte order (that is, big endian) to host byte order (that is, native byte order), or from host byte order to network byte order. The following are some commonly used PHP byte order conversion functions:

htonl()

This function can convert a 32-bit integer from host byte order to Network byte order.

int htonl (int $hostlong)

Parameter $hostlong is the 32-bit integer that needs to be converted. The return value is a converted 32-bit integer.

htons()

This function can convert a 16-bit short integer from host byte order to network byte order.

int htons (int $hostshort)

Parameter $hostshort is a 16-bit short integer that needs to be converted. The return value is a converted 16-bit short integer.

ntohl()

This function can convert a 32-bit integer from network byte order to host byte order.

int ntohl (int $netlong)

Parameter $netlong is the 32-bit integer that needs to be converted. The return value is a converted 32-bit integer.

ntohs()

This function can convert a 16-bit short integer from network byte order to host byte order.

int ntohs (int $netshort)

Parameter $netshort is a 16-bit short integer that needs to be converted. The return value is a converted 16-bit short integer.

Example Demonstration

The following uses an example to demonstrate the use of PHP's byte order conversion function.

Assume that a 32-bit integer needs to be converted to network byte order and transmitted over the network. The sender uses the following code for conversion and transmission:

// 要发送的32位整数
$data = 0x12345678;

// 转换为网络字节序
$data = htonl($data);

// 发送数据
socket_write($socket, $data, 4);

The receiver needs to convert the received data to host byte order, and can use the following code:

// 接收数据
$recvData = socket_read($socket, 4);

// 将网络字节序转换为主机字节序
$recvData = ntohl($recvData);

echo $recvData;

As can be seen from the above code , In network programming, the byte order conversion function is very important. In PHP, you can use the htonl(), htons(), ntohl(), ntohs() functions to do this conveniently Byte order conversion makes our network communication more reliable and stable.

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