How can I insert null bytes in to std::string?

[Pep]

I have to interface to an older library that uses strings and there is
no alternative. I need to pass a string that is padded with null
bytes. So how can I append these null bytes to the std::string?

Yes I know it would be better to use something like a vector but I do
not have that option.

Yes I know that I will not be able to use std::string.c_s tr() but will
instead have to use std:;string.get Data().

TIA.

[Victor Bazarov]

Pep wrote:

I have to interface to an older library that uses strings and there is
no alternative. I need to pass a string that is padded with null
bytes. So how can I append these null bytes to the std::string?

Probably using "append" member... Have you RTFM?

Yes I know it would be better to use something like a vector but I do
not have that option.

In your case it probably does not matter. Why do you think that 'vector'
has any advantage?

Yes I know that I will not be able to use std::string.c_s tr() but will
instead have to use std:;string.get Data().

Just like with a 'vector', you can always use the address of the first
char...

V
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[Pep]

Victor Bazarov wrote:

Pep wrote:

I have to interface to an older library that uses strings and there is
no alternative. I need to pass a string that is padded with null
bytes. So how can I append these null bytes to the std::string?

Probably using "append" member... Have you RTFM?

Yes but it was suggested to me that there was a way that did not
involve using append, so as I could not find any way I decided to ask
if anyone knew of one of those "tricks".

Guess it will have to be append then.

Yes I know it would be better to use something like a vector but I do
not have that option.

In your case it probably does not matter. Why do you think that 'vector'
has any advantage?

I read something in a previous posting that suggested vectors would be
better though as you, I do not understand how other than perhaps the
poster meant that you should not in theory have nulls in strings.

>

Yes I know that I will not be able to use std::string.c_s tr() but will
instead have to use std:;string.get Data().

Just like with a 'vector', you can always use the address of the first
char...

For some reason I opted for the getData being better than c_str as it
implies it is the correct method by it's name.

>
V
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Thanks for the help.

[Daniel T.]

In article <eb**********@n ews.datemas.de> ,
"Victor Bazarov" <v.********@com Acast.netwrote:

Yes I know that I will not be able to use std::string.c_s tr() but will
instead have to use std:;string.get Data().

Just like with a 'vector', you can always use the address of the first
char...

Really? I didn't think the standard guaranteed that a std::string was
contiguous like vector is?

[Daniel T.]

In article <11************ **********@i3g2 000cwc.googlegr oups.com>,
"Pep" <pe**********@y ahoo.co.ukwrote :

I have to interface to an older library that uses strings and there is
no alternative. I need to pass a string that is padded with null
bytes. So how can I append these null bytes to the std::string?

The above doesn't quite make sense. C strings can't have null bytes in
the middle of them so why would you need to append null bites? If you
are talking about the null at the end of the string, then the
member-function c_str() does that for you, you don't need to.

Yes I know it would be better to use something like a vector but I do
not have that option.

I'm personally not so sure that it would be better to use "something
like a vector" but you know your problem space better than us.

Yes I know that I will not be able to use std::string.c_s tr() but will
instead have to use std:;string.get Data().

Why can't you use c_str()? The only difference between c_str() and
data() [not getData()] is that c_str appends a null on the end. Isn't
that what you want?

[Victor Bazarov]

Daniel T. wrote:

In article <eb**********@n ews.datemas.de> ,
"Victor Bazarov" <v.********@com Acast.netwrote:

>>Yes I know that I will not be able to use std::string.c_s tr() but
will instead have to use std:;string.get Data().

Just like with a 'vector', you can always use the address of the
first char...

Really? I didn't think the standard guaranteed that a std::string was
contiguous like vector is?

No, there is no such guarantee, you're correct (at least I can't find it).

V
--
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[Victor Bazarov]

Pep wrote:

[...]
For some reason I opted for the getData

You mean 'data()', of course, no? 'data()' and 'c_str()' are essentially
the same.

V
--
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[peter koch]

Daniel T. wrote:

In article <11************ **********@i3g2 000cwc.googlegr oups.com>,
"Pep" <pe**********@y ahoo.co.ukwrote :

I have to interface to an older library that uses strings and there is
no alternative. I need to pass a string that is padded with null
bytes. So how can I append these null bytes to the std::string?

The above doesn't quite make sense. C strings can't have null bytes in
the middle of them so why would you need to append null bites? If you
are talking about the null at the end of the string, then the
member-function c_str() does that for you, you don't need to.

This is not true - sort of anyway:

char const* weird_hello = "Weird \0hello";

does contain an embedded null and if'd call it a C-string you surely
are wrong! ;-)
I've seen a list of lines being defined with a \0 separating each
string and using an empty string as a terminator. Something like 'H'
'e' 'l' 'l' 'o' 0 'W' 'o' 'r' 'l' 'd' '!' 0 0.

My guess is the OP wanted to have two nulls at the end of the string-
Another possibility is that the interface expects the string in a
fixed-length buffer and the buffer to be containing zeroes at the end
of the string. You believe I'm kidding, but I've actually witnessed
such an interface once.

>

Yes I know it would be better to use something like a vector but I do
not have that option.

I'm personally not so sure that it would be better to use "something
like a vector" but you know your problem space better than us.

Yes I know that I will not be able to use std::string.c_s tr() but will
instead have to use std:;string.get Data().

/Peter

[Alf P. Steinbach]

* Victor Bazarov:

Daniel T. wrote:

>In article <eb**********@n ews.datemas.de> ,
"Victor Bazarov" <v.********@com Acast.netwrote:

>>>Yes I know that I will not be able to use std::string.c_s tr() but
will instead have to use std:;string.get Data().
Just like with a 'vector', you can always use the address of the
first char...

Really? I didn't think the standard guaranteed that a std::string was
contiguous like vector is?

No, there is no such guarantee, you're correct (at least I can't find it).

Pete Becker posted earlier (many months ago, early March?) that this
guarantee for std::basic_stri ng was approved that day by the Library
Working Group and would be voted into the Working Draft, as I understood
it the next day or week or so, so presumably it has been so voted, and
will be present in C++0x.

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[Daniel T.]

In article <11************ *********@m73g2 000cwd.googlegr oups.com>,
"peter koch" <pe************ ***@gmail.comwr ote:

Daniel T. wrote:

In article <11************ **********@i3g2 000cwc.googlegr oups.com>,
"Pep" <pe**********@y ahoo.co.ukwrote :

I have to interface to an older library that uses strings and there is
no alternative. I need to pass a string that is padded with null
bytes. So how can I append these null bytes to the std::string?

The above doesn't quite make sense. C strings can't have null bytes in
the middle of them so why would you need to append null bites? If you
are talking about the null at the end of the string, then the
member-function c_str() does that for you, you don't need to.

This is not true - sort of anyway:

char const* weird_hello = "Weird \0hello";

does contain an embedded null and if'd call it a C-string you surely
are wrong! ;-)

I'd call that two c-strings, but I grant that you may very well be right
and this is exactly what the OP wants.