"std::vector<unsigned char>" - what is it?

[Bobrick]

Hi.

I'm in the process of making a GUI for a function someone else wrote,
and i've come across a type i'm unfamiliar with, namely
"std::vector<unsigned char>". I need to get the contents of this
variable into a form I can display in a text box, but i'm not sure what
to expect inside of the variable, whether I can just treat it like an
array e.t.c. Any help would be appreciated.

Thanks,

Bob

[Peter Jansson]

Bobrick wrote:

Hi.

I'm in the process of making a GUI for a function someone else wrote,
and i've come across a type i'm unfamiliar with, namely
"std::vector<unsigned char>". I need to get the contents of this
variable into a form I can display in a text box, but i'm not sure what
to expect inside of the variable, whether I can just treat it like an
array e.t.c. Any help would be appreciated.

Thanks,

Bob

It is a vector of unsigned char's. You can treat is as an array as follows:

std::vector<unsigned charvar;
const std::vector<unsigned char>::size_type N(var.size());
// Write it to cout and to a string:
std::ostringstream s;
for(int i=0;i<N;i++)
{
// Notice the [i]
std::cout<<var[i]<<'\n';
s<<var[i];
}
std::cout<<s.str()<<'\n';
Sincerely,

Peter Jansson
http://www.p-jansson.com/
http://www.jansson.net/

[Colander]

Hi There,

I'm in the process of making a GUI for a function someone else wrote,
and i've come across a type i'm unfamiliar with, namely
"std::vector<unsigned char>". I need to get the contents of this
variable into a form I can display in a text box, but i'm not sure what
to expect inside of the variable, whether I can just treat it like an
array e.t.c. Any help would be appreciated.

If you have the time, have a look at the following page:
http://www.sgi.com/tech/stl/

If you have less time, look at:
http://www.sgi.com/tech/stl/Vector.html

Greets,
Bas

[Alf P. Steinbach]

* Peter Jansson:

Bobrick wrote:

>Hi.

I'm in the process of making a GUI for a function someone else wrote,
and i've come across a type i'm unfamiliar with, namely
"std::vector<unsigned char>". I need to get the contents of this
variable into a form I can display in a text box, but i'm not sure what
to expect inside of the variable, whether I can just treat it like an
array e.t.c. Any help would be appreciated.

Thanks,

Bob

It is a vector of unsigned char's. You can treat is as an array as follows:

std::vector<unsigned charvar;
const std::vector<unsigned char>::size_type N(var.size());
// Write it to cout and to a string:
std::ostringstream s;
for(int i=0;i<N;i++)
{
// Notice the [i]
std::cout<<var[i]<<'\n';
s<<var[i];
}
std::cout<<s.str()<<'\n';

It's also possible that the vector is meant to directly represent a
string. In which case the simplest way to convert it to the string
format required by the OP's text box depends on that string format.
Converting to a std::string by copying (inefficient but works):

std::string s( v.begin(), v.end() );

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Q: Why is it such a bad thing?
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[Jim Langston]

"Bobrick" <pu******@gmail.comwrote in message
news:11**********************@51g2000cwl.googlegro ups.com...

Hi.

I'm in the process of making a GUI for a function someone else wrote,
and i've come across a type i'm unfamiliar with, namely
"std::vector<unsigned char>". I need to get the contents of this
variable into a form I can display in a text box, but i'm not sure what
to expect inside of the variable, whether I can just treat it like an
array e.t.c. Any help would be appreciated.

Thanks,

Bob

The vector itself you can pretty much treat as an array. The contents of
the unsigned chars will be values from 0 to 255. What those represent, I
don't know. Are they characters? Are they values? You'll have to look at
the way it's used to determine that.

The fact that it's unsigned char instead of plain char would lead me to
suspect it's used for it's values. Many ways to iterate through a vector.
The one that most C programs would understand would be:

// presume Array is std::vector<unsigned char>
for ( size_t i = 0; i < Array.size(); ++i )
std::cout << Array[i] << "\n";

Or you can iterate using iterators:
for ( std::vector<unsigned char>::iterator it = Array.begin(); it !=
Array.end(); ++it )
std::cout << *it << "\n";

In addition, an arrays memory is guaranteed to be contiguous.

unsigned char* vecp = &(Array[0]); // grab address of first unsigned char
for ( size_t i = 0; i < Array.size(); ++i )
std::cout << *(vecp + i) << "\n";