C / C++ / MFC

Re: where did I do wrong? (myString class) Please help! I have to turn in tomorrow

21-May-04 18:45

I wrote a string class and try to test with a very simple driver program, but there are some erros, can somebody help me figure out my mistakes?

thank you!

--------------Configuration: main - Win32 Debug--------------------
Compiling...
main.cpp
Linking...
main.obj : error LNK2001: unresolved external symbol "public: __thiscall myString::~myString(void)" (??1myString@@QAE@XZ)
main.obj : error LNK2001: unresolved external symbol "class ostream & __cdecl operator<<(class ostream &,class myString const &)" (??6@YAAAVostream@@AAV0@ABVmyString@@@Z)
main.obj : error LNK2001: unresolved external symbol "public: __thiscall myString::myString(char const *)" (??0myString@@QAE@PBD@Z)
Debug/main.exe : fatal error LNK1120: 3 unresolved externals
Error executing link.exe.

main.exe - 4 error(s), 0 warning(s)
____________________________________________________________________________

myString.h file:

//myString

#ifndef MYSTRING_H
#define MYSTRING_H

#include<iostream.h>

class myString{

friend ostream &operator<<(ostream &, const myString &);
friend istream &operator>>(istream &, myString &);

public:

myString( const char * = "");
myString(const myString &);
~myString();
const myString &operator= (const myString &); //assign string
myString &operator+= (const myString &);
int operator! () const; //empty string
int operator== (const myString &) const;
int operator!= (const myString &) const;
int operator< (const myString &) const;
int operator> (const myString &) const;
int operator>= (const myString &) const;
int operator<= (const myString &) const;
char &operator[] (int);
myString &operator()(int, int);
int getLength() const;
// void toUpper (myString &);
// void toLower (myString &);

private:
char* sPtr;
int length;
};

#endif
________________________________________________________________________

myString.cpp file

//myString.cpp

#include<iostream.h>
#include<string.h>
#include<assert.h>
#include"myString.h"

myString::myString(const char *s)
{

lengh = strlen(s);
sPtr = new char[lengh +1];
assert(sPtr!=0);

strcpy(sPtr, s);
}
//convention constructor
myString::myString(const myString ©)
{
lengh = copy.length;
sptr = new char [length +1];
assert(sPtr!= 0 );
strcpy(sPtr, copy.sPtr);
}
//copy constructor
myString::~myString()
{
delete [] sPtr;
}
//destructor

const myString &myString::operator = (const myString &right)
{
if(&right! = this)
{
delete [] sPtr;
length = right.length;
sPtr = new char [length+1];
assert (sPtr!= 0);
strcpy(sPtr, right.sPtr);
}
else
cout<<"Attempted assignment of a String to itself\n";

return *this;
}
//operator =

myString &myString::operator+= (const myString &right)
{
char * tempPtr = sPtr;
length+= right.length;
sPtr = new char [length +1];
assert(sPtr!= 0);
strcpy(sPtr, tempPtr);
strcat(sPtr, right.Ptr);
delete[] tempPtr;
return *this;
}
//operator +=

int myString::operator! () const{return length == 0;}//empty

int myString::operator == (const String &right) const
{
return strcmp(sPtr, right,sPtr) == 0;
}

int myString::operator!= (const myString &right)const
{
return strcmp(sPtr, right.sPtr)!= 0;
}

int myString::operator< (const myString &right) const
{
return strcmp (sPtr, right.sPtr) < 0;
}

int myString::operator> (const myString &right) const
{
return strcmp (sPtr, right.sPtr) > 0;
}

int myString::operator>= (const myString &right) const
{
return strcmp (sPtr, right.sPtr) >= 0;
}

int myString::operator<= (const myString &right) const
{
return strcmp (sPtr, right.sPtr) <= 0;
}

char &myString:: operator[](int subscript)
{
assert(subscript >= 0 && subscript< length);

return sPtr[subscript];
}

myString &myString::operator() (int index, int subLengh)
{
assert(index >=0 && index<length &&sublength="">=0);

myString *subPtr = new myString;

assert(subPtr! = 0);

int size;

if((subLength == 0)||(index + subLength > length))

size = length - index+1;

else

size = subLength +1;

delete subPtr->sPtr;
subPtr->length = size;
subPtr-> = new char[size];
assert(subPtr->sPtr!=0);

for(int i = index, j = 0; i<index+size-1; i++,j++)
="" subptr-="">sPtr[j] = sPtr[i];

subPtr->sPtr[j] = '\0';

return *subPtr;
}

int myString::getLength()const{return length;}

ostream &operator<< (ostream &output, const myString &s)
{
output<<s.sptr;
return="" output;
}

istream="" &operator="">> (istream &input, myString &s)
{
static char temp[100];
input>>temp;

s=temp;

return input;
}

________________________________________________________________________

very simple main :

#include <iostream.h>
#include "myString.h"
#include <string.h>

int main()
{

myString s1("happy");

cout<

Maxwell Chen21-May-04 21:39

Re: where did I do wrong? (myString class) Please help! I have to turn in tomorrow

21-May-04 21:39

So is the modified code OK now? Big Grin | :-D

Maxwell Chen

foxele21-May-04 22:00

Re: where did I do wrong? (myString class) Please help! I have to turn in tomorrow

21-May-04 22:00

Thanks for the help, I haven't check it yet.

but I think it will work fine.

Thanks again

from foxele

foxele21-May-04 22:05

Re: where did I do wrong? (myString class) Please help! I have to turn in tomorrow

21-May-04 22:05

Can u send those modified code as attachment in header file and source file, cause I couldn't download them, I don't know why

thanks agian!

Maxwell Chen21-May-04 22:11

Re: where did I do wrong? (myString class) Please help! I have to turn in tomorrow

21-May-04 22:11

I did send them in attachment form. Check the lower part of the mail! There are [Download] links. Big Grin | :-D

In the email...

My texts,

(blue line) Your text...

(Still blue line) Your original attachment texts...

Do you Yahoo!?

(No blue line since here) My attachments!

Maxwell Chen

Maxwell Chen21-May-04 22:07

Re: where did I do wrong? (myString class) Please help! I have to turn in tomorrow

21-May-04 22:07

I have sent you another email about the reason having written the email address that way ... Big Grin | :-D

Maxwell Chen

foxele22-May-04 17:21

Re: where did I do wrong? (myString class) Please help! I have to turn in tomorrow

22-May-04 17:21

Maxwell, did you test the myString class with your c++ compiler?

I still got the same four errors about my destructor and operator<< and constructor. If it works fine in your computer, then it is the problem of my compiler.

Please let me know .

Thank You So Much

from foxele

Maxwell Chen22-May-04 22:18

creating an application that runs in the background

22-May-04 22:18

foxele wrote:
Maxwell, did you test the myString class with your c++ compiler?

I still got the same four errors about my destructor and operator<< and constructor. If it works fine in your computer, then it is the problem of my compiler.

Please let me know .

Yes, with Visual C++ 6.0, I built it, and ran it. The code compiled without any error or warning. And the output was correct ("Happy"... something).

Are you sure that you've downloaded the correct code? Or you just made a mistake that you copied the original code included in the text part of the reply? Or you didn't replace the code in the project with new one?

Check the comments in the cpp file. I have moved some comments from the end of function bodies to the beginning of function bodies. If it is such kind, then it's a new one. For example:

// Conventional constructor <br />
myString::myString()<br />
{<br />
  // ...<br />
}

To isolate the problem from your making a mistake replacing files or your compiler's got problem, this time I will send you the whole project in ZIP form.

Please visit WinZip[^] to get a zip tool. Thanks.

Maxwell Chen

shals16921-May-04 18:36

shals169

21-May-04 18:36

I have created an application.While running and applcation I would like to run another application (exe) using Shell.But I want that application to run in the background i.e. no dialogs or documents associated with it.I don't want the user to know that this application is running.SO how can I create such and application that runs in the backdrop.

Re: creating an application that runs in the background

Dominik Reichl22-May-04 0:53

Dominik Reichl

22-May-04 0:53

Use CreateProcess and set the wShowWindow member of the STARTUPINFO member to SW_HIDE.

Best regards,
Dominik

_outp(0x64, 0xAD);
and
__asm mov al, 0xAD __asm out 0x64, al
do the same... but what do they do??
(doesn't work on NT)

binary contents in a CString

(Steven Hicks)ⁿ⁺¹21-May-04 17:54

(Steven Hicks)ⁿ⁺¹

21-May-04 17:54

I have a download function that returns the contents in a CString (it mostly downloads text), for simplicities sake I would like to use it to download JPGs (binary content) how can I get the binary contents from teh download function without messing it up when it downloads text and be able to send it to WriteBinaryToFile as the correct size.

CString Download(CString m_strURL); //returns the content
void WriteBinaryToFile(CString m_strFileName, CString m_strFileContents);
(this is specifies the binary flag in the CFile options)

-Steven Hicks

CPA

CodeProjectAddict

Actual Linux Penguins were harmed in the creation of this message.

More tutorials: Ltpb.8m.com: Tutorials |404Browser.com (Download Link)

Andrew Quinn AUS21-May-04 22:57

Andrew Quinn AUS

21-May-04 22:57

Steve,

Please be aware that if the file contents contains a zero (null) within the contents, then CString will only give you contents upto the null value.

Do you know the lengths of the files you're downloading?

If I was you, I'd look at CHttpFile. Here's the MSDN link.

Hope this helps,
Andy

Prakash Nadar22-May-04 2:10

Prakash Nadar

22-May-04 2:10

You should not use binary value with CString, must use a buffer of TCHAR to collect the info.

I'll write a suicide note on a hundred dollar bill - Dire Straits

Gary R. Wheeler23-May-04 12:35

Gary R. Wheeler

23-May-04 12:35

Personally, I would modify your Download function to return an object, something like the following:

class DownloadObject {
public:
    DownloadObject(char *text);
    DownloadObject(unsigned char *data,int size);
    ~DownloadObject();
    enum Type { Text, Binary };
    Type GetType() const;
    bool GetAsText(CString &text) const;
    bool GetAsBinary(unsigned char **binary,int *size);
private:
    Type _Type;
    unsigned char *_Data;
    int _Size;
};

This object contains an arbitrary sequence of bytes, that the creator of the object (e.g. the Download function) can specify to be of type 'Text' or 'Binary'. The creator specifies the type of object based on which constructor he uses. When the object is returned to the caller of the Download function, that function can determine the type of data using the supplied member functions, something like this:

DownloadObject *Download(CString URL);
//...
DownloadObject *object = Download(example_URL);
CString text;
unsigned char *data;
int size;
if (object != NULL) {
    switch (object->GetType()) {
        case DownloadObject::Text:
            object->GetText(text);
            //...
            break;
        case DownloadObject::Binary:
            object->GetBinary(&data,&size);
            //...
            break;
    }
    delete object;
}

Note that I've modified the definition of the Download function to return a pointer to a DownloadObject. If the return value is NULL, that can be an error indication.

I think this is a better approach than overloading the CString class. While CString does let you store binary data of arbitrary length which includes '\0' characters, it's primary purpose is to hold text data. Using it to contain binary data confuses the programmers who come after you.

Software Zen: delete this;