PHP pack, unpack binary stream Interface application example

At work, I also learned that Pack,unpack,ord is powerful for binary byte processing. Let me introduce them to you. In our work, there is not much estimation of their use. I am in a recent job, because the communication needs to use the binary stream, and then the interface is received in PHP. At that time, a lot of information was consulted. Because they are really less used, they are seldom used by friends in their work. At work, I also learned that Pack,unpack,ord is powerful for binary byte processing. Let me introduce them to you.

pacrk Function Description : This function is used to compress data into a string in place.

Syntax : Pack (format,args+)

Parameters	Describe
Format	Necessary. Specifies the format to use when wrapping the data.
args+	Optional. Specifies one or more parameters that are packaged.

Character	Description
A	Fills the string blank with a NULL character
A	Fills the string blank with space characters (spaces)
H	16 string, low in front
H	16 string, high in front
C	Character with number
C	No number character
S	Number of short integers (16 bits, depending on the computer's bit order)
S	No number short integer (16 bits, depending on the computer's bit order)
N	unsigned short integers (16-bit, high-order in the back)
V	No number short integers (16 bits, low in the back order)
I	Number of integers (depending on the order and scope of the computer)
I	unsigned integers (depending on the computer's order and range)
L	Number of long integers (32 bits, depending on the computer's bit order)
L	unsigned long integers (32 bits, depending on the computer's bit order)
N	unsigned short integers (32-bit, high-order in the back)
V	No number short integers (32 bits, low in the back order)
F	Single-precision floating-point number (depending on the computer's range)
D	Times the exact floating point number (depending on the computer's range)
X	Vacancy
X	Rewind One
@	Fill in the NULL character to the absolute position

Unpack Function Description: This function is used to extract the data of the bit string

Syntax : Unpack (format,args+)

Parameters	Describe
Format	Necessary. Specifies the format to use when wrapping the data.
args+	Optional. Specifies one or more parameters that are packaged.

The parameters are the same as the pack.

Ord function Description: Returns the Acill code value of the corresponding character

Syntax : Ord ($character);

Example Description:

<?php
A character
$str = (Pack ("A *", "China"));
echo $str, "=", strlen ($STR), "Byte \ n";
Getascill ($STR);
H character
$str = (Pack ("h*", "Fffe"));
echo $str, "=", strlen ($STR), "Byte \ n";
Getascill ($STR);
C character
$str = (Pack ("c*", "55", "56", "57"));
echo $str, "=", strlen ($STR), "Byte \ n";
Getascill ($STR);

I-character short-shaped 32-bit 4-byte 64-bit 8-byte
$str = (Pack ("I", "100"));
echo $str, "=", strlen ($STR), "Byte \ n";
Getascill ($STR);

s character short shaping 2 bytes
$str = (Pack ("s", "100"));
echo $str, "=", strlen ($STR), "Byte \ n";
Getascill ($STR);

L character-length shaping 4 bytes
$str = (Pack ("L", "100"));
echo $str, "=", strlen ($STR), "Byte \ n";
Getascill ($STR);

F-character single-precision floating-point 4 bytes
$str = (Pack ("F", "100"));
echo $str, "=", strlen ($STR), "Byte \ n";
Getascill ($STR);

D-character double-precision floating-point 8 bytes
$str = (Pack ("D", "100"));
echo $str, "=", strlen ($STR), "Byte \ n";
Getascill ($STR);

function Getascill ($STR)
{
$arr =str_split ($STR);
foreach ($arr as $v)
{
echo $v, "=", Ord ($v), "\ n";
}
echo "=============\r\n\r\n";
}
?>

With the above example, we can see that the same string, stored in a different format, consumes a different number of bytes. It can also be seen here that saving characters in different formats can save space for storage. and start the unreadable encryption effect. Suddenly think of a bit, Design database field type problems, if a field is just: 10-bit length integer type. We set it to reshape: 256*256*256*256 is 4 bytes, if set to 10 length string. That accounts for 10 bytes. The whole digestive space is twice times the size. Setting the correct character type is a great help in improving database performance. Oh, a little off-topic ...

A case analysis of PHP processing byte code communication
Just said pack function: space-saving, encrypted format

Here are 2 examples to illustrate, interface development requirements:

Parameters	Describe
User name	20 bytes, character type
Password	10 bytes, Character type
Age	1 bytes, no character char type
Date of birth	4 bytes, integer (19800101)
Mailbox	50 bytes, string
Between fields: "\" split

A, pack Packaging

[PHP]View Plaincopyprint?

2. $code =Array (
6. "username" = =Array ("A20","Zhang San adfb12"),
10. "Pass" =Array ("A10","asdf* #1"),
14. "Age" = =Array ("C", "All"),
18. "Birthday" = =Array ("I","19900101"),
22. "Email" = =Array ("A50","[email protected]"));
26. $stream =join ("n", Packbyarr ($code));
30. Echo $stream,strlen ($stream);
38. File_put_contents ("C:/1.txt",$stream); //Save the stream for easy reading below.
46. function Packbyarr ($arr) {
50. $ATARR =Array ();
54. foreach ($arr as $k = =$v) {
58. $ATARR []=pack ($v [0],$v [1]);
62. }
66. return $ATARR;
70. }
74. function Getascill ($str) {
78. $arr =str_split ($str);
82. foreach ($arr as $v) {
86. echo $v,"=", Ord ($v),"\ n";
90. }
94. }

The entire length is 89 bytes, because it is split with "\". With the above output, some string output can be read, the others have become garbled. This is what I said can be kept secret effect reason.
B, unpack unpacking
The unpacking needs to be read in a packaged manner, the length of the read, what type to read, and the same as the packing rules.

[PHP]View Plaincopyprint?

2. $code =Array (
6. "username" = =Array ("A20"),
10. "Pass" =Array ("A10"),
14. "Age" = =Array ("C"),
18. "Birthday" = =Array ("I"),
22. "Email" = =Array ("A50"));
26. $stream =file_get_contents ("C:/1.txt");
30. Var_dump (Packbyarr ($stream,$code));
34. function Packbyarr ($str,$code) {
38. $ARR =explode ("n",$str);
42. $ATARR =Array ();
46. $i = 0;
50. foreach ($code as $k = =$v) {
54. $ATARR [$k]=unpack ($v [0],$Arr [$i]);
58. $i + +;
62. }
66. return $ATARR;
70. }

PHP pack, unpack binary stream interface application instance