Printable View
Hi All,
I have unsigned char * buffer in which some data are stored , now I want to move these all data to my CString variable for some operations.
I tried to copy but problem is that in my unsigned char * some data are padded as zero, So I hope that in CString it gets the null value so it can not copy whole data.
I tried to copy from unsigned char * to the CString using...
CString tmpMsg = CString(msg); // Here msg is the unsigned char *
Ashish
Don't try to use CString for containing binary data - it won't work. Tell us more about what you are doing and we can suggest alternatives.
So you want to copy a buffer to a CString variable and want to keep the characters that are set to 0. So that the string was something like this 'ABC\0\0DEF'. Is that correct?
In my unsigned char * buffer I have all char data, so I want all these data into my CString variable.
I tried to use memcpy() ,but it gives me the runtime error like....
TestRTMP.exe: 0xC0000005: Access violation reading location 0x49468964.
so plz help me.
Thanks.
when 0 value comes in CString it shows nothig(Just like blank space)...Quote:
Originally Posted by cilu
I m not getting that to much,but the problem is of zero value.
While it is technically possible to store a binary 0 in a CString you should not do it. There are too many problems that will be encountered. The bottom line is that most of the CString member functions (including the constructor you are trying to use) assume binary 0 is the end-of-string terminator and will fail for whatever purpose you intend. Once again, you need to re-think your application and use a container other than CString.
0xC0000005 is right, my suggestion is to use std::string for that purpose.
Regards,
Usman.
Although it's not a very brilliant idea, you can store any character including '\0' in a CString object as follows
With one condition: use that object only for storing; another subsequent call of one of CString methods may truncate it to the first '\0' value.Code:void CFoo::FillString(CString& str, unsigned char* msg, int length)
{
char* buffer = str.GetBufferSetLength(length);
memcpy(buffer, msg, length);
str.ReleaseBuffer(length);
}
UUUghhh!Quote:
Originally Posted by usman999_1
:rolleyes:Quote:
Originally Posted by ovidiucucu
I wouldn't use any kind of string, std, CString or anything else you find to store data that contains a NULL.
Right.
A possible better approach is to write your own "buffer" class like for example:
Code:class CBuffer
{
unsigned char* buffer;
unsigned int length;
public:
CBuffer() : buffer(NULL), length(0) {};
SetBuffer(unsigned char* src, unsigned int length);
unsigned int GetLength() const {return length;}
// and so on, and so on... all you need
};
What's wrong with std::string???Quote:
Originally Posted by GCDEF
Why do you think it's better than CString?Quote:
Originally Posted by usman999_1
What is the advantage of writing your own buffer class instead
of using std::string ???????????????????????
What is wrong with std::string???Quote:
Originally Posted by ovidiucucu
Try this
Now why would you need a buffer class with managing memory yourself???Code:
void DoSomethingWithBinaryData(char* szData, unsigned int nLen)
{
std::string BinaryData;
BinaryData.assign(szData, nLen);
// Now you have access to all those handy functions of std::string and what not
// And to get the data back
DoSomethingElseWithThisBinaryData(BinaryData.data(), BinaryData.size());
}
Regards,
Usman.
Depends how you're trying to use it. The data it contains wouldn't work with a lot of C style string functions. As long as you remember what you're doing with it I suppose you could avoid trouble, but a year from now when he forgets it's not compatible with regular const char* functions or future programmer don't know what he's up to, things will work as anticipated.Quote:
Originally Posted by usman999_1
Quote:
Originally Posted by GCDEF
But if the data contains embedded NULLS, it will not be compatible
with C stsyle string functions to start with. So how does using
std::string make it worse ? Plus you can use the string member
functions and algorithms to search/replace etc.
Well, I dont want to start this CString vs std::string debate all over again. CString is better for MFC functions requiring CString. But CString is designed and should be used as C++ version of c-string (null terminated string), while std::string is more versatile & can act a buffer (for binary or null-terminated data) and provides you will a good api to access and manipulate it.Quote:
Originally Posted by ovidiucucu
My 2 cents....
Regards,
Usman.
Nothing. It can store binary data using the proper member functions, as you've demonstrated.Quote:
Originally Posted by usman999_1
I think it's just the name "std::string" that gives the impression "it stores only null-terminated strings".
Now it looks "nicer" to say "BufferHandler x" instead of "std::string x".Code:typedef std::string BufferHandler;
//...
BufferHandler buf;
Regards,
Paul McKenzie
Because it's not intuitively obvious to a programmer that sting data will contain embedded nulls. Another programmer may come along and use c_str() method to pass the contents to another function for example. Very few programmers are going to look at any kind of string object and expect its data to contain embedded nulls.Quote:
Originally Posted by Philip Nicoletti
But it is not "intuitively obvious" that an char array will contain
embedded nulls either. If the function that you send the data to
works with NULL terminated strings, it will not work "properly" ...
regardless of whether it is a std::string , CString, custom buffer,
or raw character array.
As I have demonstated in my first post, CString isn't obviously containing "only null-terminated strings". Can be also just an impression of outside-MFC visitors. ;)Quote:
Originally Posted by Paul McKenzie