943,616 Members | Top Members by Rank

Ad:
  • C Discussion Thread
  • Unsolved
  • Views: 10558
  • C RSS
Sep 12th, 2003
0

Array limit

Expand Post »
#include <iostream>
#include <conio.h>

void input(char *str) {
bool quit = 0;
unsigned char key;
for(int i = 0;quit != 1;) {
key = getch();
switch(key) {
case 8: // Backspace
if (i > 0) {
i--;
*str--;
std::cout << "\b \b";
}
else
putch('\a');
break;
case 13: // Enter
*str = '\0';
putch('\n');
quit = 1;
break;
default:
*str = key;
putch(key);
i++;
*str++;
break;
}
}
}

int main() {
char string[40];
std::cout << ">";
input(string);
std::cout << string;
getch();
return 0;
}

I am working on a function that will take input from the user and store it in a string. One problem I face is when the user enters more than the size of the char array. I could set up the input function to take two arguments, the second being the size of the array, but I want to find a more simple way. I want the program to work out how big the array is without me telling it. Does anyone have any suggestions?
Similar Threads
Reputation Points: 10
Solved Threads: 0
Newbie Poster
rknight is offline Offline
3 posts
since Sep 2003
Sep 12th, 2003
0

Re: Array limit

I haven't done work with strings in a long while, but could u by any chance use string.h with getline?

Check out this reference site: http://www.msoe.edu/eecs/ce/courseinfo/stl/string.htm
Administrator
Staff Writer
Reputation Points: 1422
Solved Threads: 162
The Queen of DaniWeb
cscgal is offline Offline
13,645 posts
since Feb 2002
Sep 16th, 2003
0

Re: Re: Array limit

Use dynamic memory allocation.
In C++ (didn't test):

char * getstring()
{
fflush (stdin); //don't have to do it
char * string=NULL;
char * temp=NULL;
int size =2
scanf(""); //to get buffer input
char ch;
do
{
delete [] string;
string = new char[size];
memcpy (string, temp, sizeof(temp));
delete[]temp;
ch = getc(stdin);
string[size-2] =ch;
temp = new char [size];
memcpy(temp, string, sizeof (string));
size++;
} while (ch!='\n'); //change the quiting value if you want to whatever
return string;
}
void main (void)
{
char * string = getstring();
}
Reputation Points: 13
Solved Threads: 0
Junior Poster in Training
Valmian is offline Offline
82 posts
since Sep 2003
Sep 16th, 2003
0

Re: Re: Re: Array limit

You're using C++ but you are using the std:string? #include <string>

If you want to do strings C-style which is a pointer to an array of chars like you have you first want to malloc() and then when you want to allocate more space you want to realloc().
Reputation Points: 44
Solved Threads: 1
Junior Poster
subtronic is offline Offline
117 posts
since Aug 2003
Sep 16th, 2003
0

Re: Re: Re: Re: Array limit

I know, I just had like 1 min so I wrote what came first to my mind.. anyways, I am known to use classes, new/delete and all else in C. (i never took time to learn iostream etc.. but I like objects.. my first though is C)
Ilya
Reputation Points: 13
Solved Threads: 0
Junior Poster in Training
Valmian is offline Offline
82 posts
since Sep 2003
Oct 4th, 2003
0

Re: Array limit

Quote originally posted by Valmian ...
Use dynamic memory allocation.
In C++ (didn't test):

char * getstring()
{
fflush (stdin); //don't have to do it
char * string=NULL;
char * temp=NULL;
int size =2
scanf(""); //to get buffer input
char ch;
do
{
delete [] string;
string = new char[size];
memcpy (string, temp, sizeof(temp));
delete[]temp;
ch = getc(stdin);
string[size-2] =ch;
temp = new char [size];
memcpy(temp, string, sizeof (string));
size++;
} while (ch!='\n'); //change the quiting value if you want to whatever
return string;
}
void main (void)
{
char * string = getstring();
}
Valmian, I really don't wish to be unkind, but it has to be said, the code you posted is horrible. I can't begin to imagine how someone trying to seek advice here would manage with such code, but the problems it introduces would be beyond most of the beginners that come here seeking help, for sure.

No offence, but at the very least I would suggest that if you post code here for people you ought to try compiling it first to check that it'll at least get past your compiler. Failing to do that can leave a poor noob struggling for hours, or days even, trying to overcome the problems in your code.

On top of that, it's clear from your code that you're not sufficiently experienced in C++ to offer advice of the nature you attempted to provide, you're punching above your weight.

All credit to you for coming here and trying to help people, I think that's great. With respect, it might be better if you gained more experience before trying to help further, otherwise you can end up doing more harm than good.

No offence intended.
Bob
Team Colleague
Reputation Points: 15
Solved Threads: 2
Junior Poster
Bob is offline Offline
129 posts
since Feb 2003
Oct 6th, 2003
0

Re: Array limit

Quote originally posted by Valmian ...
I know, I just had like 1 min so I wrote what came first to my mind.. anyways, I am known to use classes, new/delete and all else in C. (i never took time to learn iostream etc.. but I like objects.. my first though is C)
Ilya
In all honesty, I'm using C++ with C too right now because I'm writing a binary file reader to read and load Lightwave objects into a C++ class/object representation (so I can start using my Lightwave models in various applications). In fact, because most all APIs are written in C, like the Python C API and the MySQL C API (not to mention OpenGL), when you're wanting to write a psuedo-OO program (as C++ isn't completely OO) and don't want to bother learning Objective-C which is a pain in the ass, it's probably the only viable way to go (unless you switch programmin languages) -- In my years of working at the Los Alamos National Labs, you'd be so suprised to see how ugly, yet operational most code is. When writing a game engine, its been my experience (not that I have a lot of experience writing game engines), that OO is the best way to go and C++ really lends itself nicely to important OO concepts like inheritance and polymorphism and object message passing (although error handling is less than desirable). For example, there are some things that I need to do with polymorphic STL maps (with dynamic casting) for run-time "type reconstruction".. On the other side though, I hate using cout/cin (because I know for a fact they're just sitting on top of printf which is a far more superior function adding overhead (but you're right, I'm using the STL and C++, why should I be concerned about saving on overhead!!! Hehe)...

So its OK to be a code-******* as long as you have a clear objective and a purpose for doing so. I think the fact that you're being lazy about your code design will kick you in the ass repeatedly for projects to come. Memory management is something a lot of programmers just don't get and I really think we can attribute a lot of the confusion to deceptively simply commands like new/delete and garbage collectors like the one in Java.

Learn about what each type means in terms of memory usage, where it exists in user space, etc. For instance, writing a loader for binary 3d files requires me to work closely with a spec which involves bitmasking out flags, reading in numbers that could either be either sizeof(char) (which is a constant across all C compilers thank god), sizeof(short), sizeof(int), or sizeof(float)..... I have to take into consideration bit-ordering, since the file is Big-Endian, I have to do byte_swaps and byte_swapping a float is a little tricky because I'm using a x86 processor which is (stupidly) Little-Endian. Good exercise in understanding bytes/bits handling and memory allocation.
Last edited by subtronic; Oct 6th, 2003 at 1:16 pm.
Reputation Points: 44
Solved Threads: 1
Junior Poster
subtronic is offline Offline
117 posts
since Aug 2003
Oct 7th, 2003
0

Re: Array limit

Thank you everyone for your help. By the sounds of things, dynamic memory allocation sounds like the best choice. I think one of the main things I wanted to know was if it was possible to find out how much an array can hold by using a pointer; and it looks as if you can’t.

Now about the mixture of c and c++ in my code…………..I must confess that my knowledge in c++ is very small. At the moment I am putting bits of c++ into my c programs to get a taste of what it’s like.
Reputation Points: 10
Solved Threads: 0
Newbie Poster
rknight is offline Offline
3 posts
since Sep 2003

This thread is more than three months old

No one has posted to this discussion for at least three months. Please let old threads die and do not reply to them unless you feel you have something new and valuable to contribute that absolutely must be added to make the discussion complete. Otherwise, please start a new thread in this forum instead.
Message:
Previous Thread in C Forum Timeline: wsaData : undeclared identifier
Next Thread in C Forum Timeline: C Help!!!





About Us | Contact Us | Advertise | Acceptable Use Policy
Forum Index | Build Custom RSS Feed


Follow us on Twitter


© 2011 DaniWeb® LLC