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Re: How is perl able to handle the null byte?

by Joost (Canon)
on Jun 15, 2006 at 18:52 UTC ( #555581=note: print w/replies, xml ) Need Help??

in reply to How is perl able to handle the null byte?

Yup, C treats a 0 byte as the end of a string. And yes perl is written in C. However, perl strings are not C strings.

In C a string is nothing more than a pointer to the first character of the string. C can't know how long a string is except by counting all the characters from the start until the first 0 byte. You need to know the length of a string in order to do things like copy or compare them.

Perl's strings are C structs that include (amongst other things) a pointer to the first character, AND the length of the string. Since perl doesn't need a special terminating character you can use 0 characters in the middle of a string too.

Note that internally perl strings are still 0-terminated in order to facilitate interoperation with functions that expect C style strings. Also note that sending strings with embedded 0 characters to system calls or XS libraries does not always work as you'd expect, though all the buildin string and IO operations (regexes, print etc) should work correctly.

  • Comment on Re: How is perl able to handle the null byte?

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Re^2: How is perl able to handle the null byte?
by muba (Priest) on Jun 15, 2006 at 18:56 UTC
    A struct is basically like creating your own data type, right?

    However, I understand now. That was fairly simple, actually...
    Thank you!

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