Detailed explanation of PHP's bz2 compression extension tool

In daily development and computer use, we often come into contact with some compression and decompression tools. PHP has also prepared many related operation expansion packages for us, and there are directly available functions that can easily operate some compression and decompression functions.

Install the extension

The installation of this extension requires the system to have bzip2-devel. So we need to first install the system with the support of this software package, and then this extension is released with the PHP installation package, so we just need to compile PHP and add the corresponding compilation command in ./configure.

# yum install bzip2-devel
# ./configure xxxx --with-bz2
# make && make install

Basic Operation

Bzip2 provides not many functions, and it is very simple. The first thing we look at is saving strings into a file.

$bz = bzopen('/tmp/', 'w');
// -rw-r--r-- 1 root root 14 Jun 28 09:51 

$text = "This is Bz Compress";
bzwrite($bz, $text);
// -rw-r--r-- 1 root root 59 Jun 28 09:53 

bzclose($bz);

$bz = bzopen('/tmp/', 'r');

$v = bzread($bz);
echo $v, PHP_EOL;
// This is Bz Compress

bzclose($bz);

Just like the file operation function, we need to first open the file through bzopen() to obtain the handle. Then use bzwrite() to write to the file and bzread() to read the file. Finally, use bzclose() to close the file.

What you need to note here is that the second parameter of bzopen(), that is, the file is opened, and can only write "w" or "r" . It has no other types and cannot be read and written at the same time, that is, it cannot be written in the form "wr". So after we finish writing the file, we have to use "r" to open the file before we can read it.

Read length settings

$bz = bzopen('/tmp/', 'r');

$v = bzread($bz, 10);
echo $v, PHP_EOL;
// This is Bz

$v = bzread($bz);
echo $v, PHP_EOL;
//  Compress

bzclose($bz);

The second parameter of bzread() is the optional byte length, the default is 1024, and the maximum 8192 uncompressed bytes can be read in at a time.

String encoding

The Bzip2 extension also provides us with functions that directly encode strings. It does not need to be stored in the file every time. If it is the same string, the functions encoded using the string and the content output to the file are the same garbled binary content.

$str = "Test compress String";

$bzstr = bzcompress($str, 9);
echo $bzstr, PHP_EOL;
// BZh91AY&amp;SY��J���@
//
// �� 1
// df����2�h&gt;.�p�!��//

$newStr = bzdecompress($bzstr);
echo $newStr, PHP_EOL;

$chineseStr = "test";
$bzstr = bzcompress($chineseStr, 9);
echo bzdecompress($bzstr), PHP_EOL;

bzcompress() is used to encode and compress the string. The second parameter is the compression ratio, and 9 is the highest level. The encoded content is non-human binary garbled content. bzdecompress() is used to decode encoded content. I believe many friends have discovered that this can be used for encrypted transmission of some confidential content. At the same time, in the test code, we can see that it also supports Chinese normally.

error message

Finally, let's take a look at the error handling function of Bzip2.

$bz = bzopen('/tmp/', 'r');
bzwrite($bz, 'aaa');
print_r(bzerror($bz));
// Array
// (
//     [errno] => -1
//     [errstr] => SEQUENCE_ERROR
// )

echo bzerrno($bz), PHP_EOL; // -1
echo bzerrstr($bz), PHP_EOL; // SEQUENCE_ERROR

bzclose($bz);

We first constructed a wrong environment. After using "r" to open the file and obtain the handle, write to the file. bzerror() will return an array of error messages containing error numbers and error messages. bzerrno() and bzerrstr() return the error number and the error content separately. Three very simple and easy to understand functions.

Summarize

This extension is still very simple. The most important thing is that the compressed file type Bzip2 is not a very commonly used type, so not many people may know it. But we still found a little surprise from it, that is, it provides string codec functions, and these two functions can indeed be used as means of information encryption in some scenarios.

Test code:

/zhangyue0503/dev-blog/blob/master/php/202006/source/PHP%E7%9A%84Bzip2%E5%8E%8B%E7%BC%A9%E6%89%A9%E5%B1%95%E5%B7%A5%E5%85%

Reference documentation:

/manual/zh/book.

The above is the detailed explanation of PHP's bz2 compression extension tool. For more information about php bz2 extension, please follow my other related articles!