'＆'在C / C ++中做了什么以及它在perl中的等效运算符是什么？

Question

I'm writing a perl implementation of a protocol whose specification is given for C/C++ but I don't know much C.

What does the condition if ((flags & 0x400) != 0) mean? How do I do that in perl?

Is if ($flags == "\\x400") correct?

Answer 1

& is a bitwise AND. See Bitwise operators .

So flags is being treated as a series of bits, and then you AND it with something which has exactly the bit set that you want to check. If the result is non-zero, then the bit is set, otherwise the bit you were looking at isn't set. In particular, in your example 0x400 = 0100 0000 0000 is being used to check if the 11th bit is set (to 1) in flags .

Typically, you wouldn't use 0x400 but a named constant, so it is clear what that bit represents.

So if ($flags == "\\x400") isn't correct. See Working with bits in Perl .

A common example of bit-masking can be seen in Linux file permissions .

Answer 2

It's the bitwise AND operator in C\\C++ and Perl.

• Perl
• C\\C++

Answer 3

The & operator performs a bitwise AND. In your case, if ((flags & 0x400) != 0) checks whether the eleventh bit of the flags variable is not set to 0. You can do bitwise operations in Perl, too .

Answer 4

It's the bitwise AND. In Perl, the operator is "&" as well .

Answer 5

& is the bitwise and operator, basically this is a test to see if a specific bit is set in the flags . See the perl equivalents here: http://perldoc.perl.org/perlop.html#Bitwise-And