In-depth analysis of PHP reading binary stream (C language structure struct data file)_PHP tutorial

Although php is developed in C language, what puzzles me is that php does not provide direct support for the structure struct.
However, PHP provides pack and unpack functions for converting binary data and PHP internal data:

Copy code Code As follows:

string pack ( string $format [, mixed $args [, mixed $...]] )
//Pack given arguments into binary string according to format.
array unpack ( string $format, string $data )
//Unpacks from a binary string into an array according to the given format.

Among them, $format is similar to the pack format in perl , there are some as follows (Chinese is added by me, any inaccuracies are welcome):
a NUL-padded string, that is, "
But something very Faint happened. I don’t know if it is a strpos bug or a substr bug (in fact, you will know after testing it, but I am too lazy to try). Some strings are fine, but some strings can only get null values ​​(i.e. $ name == "). I was very depressed, and then I found a strtok function, and now there is no problem.
It’s hard for everyone to read so much, so let’s write a complete PHP to read the binary data stream (C language structure struct Data) file sample code:
First is the C struct definition example. For demonstration, I will write a simpler one. In fact, there should be no problem if you compare it with the $format format table above:



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The code is as follows:


struct BIANBIAN {
char name[10];
char pass[33];
int age;
unsigned char flag;
};


For example, there is a "file.dat" file, the content of which is composed of the N BIANBIAN structures above:

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The code is as follows:

//Determine $format based on struct below. Note that the int type is related to the machine environment. My 32-bit Linux is 4 lengths
$format = 'a10name/a33pass/ iage/Cflag';
//Determine how many bytes of length a struct occupies. This is not needed if you just read a single structure.
$length = 10 + 33 + 4 + 1;
// You can also use fopen + fread + fclose, but file_get_contents is more efficient because it can be mmap
$data = file_get_contents('file.dat', 'r');
for ($i = 0, $c = strlen($data); $i < $c; $i += $length) {
$bianbian = unpack("$format", $data);
//reference passing is only supported by PHP 5 Yes, if you use php4, you have to use other methods
foreach ($bianbian as &$value) {
if (is_string($value)) {
$value = strtok($value, "



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TechArticleAlthough php is developed in C language, what puzzles me is that php does not provide support for the structure struct Direct support. However, PHP provides pack and unpack functions for binary data (...