Access violation on copying array contents.

Dear experts:
Hope you can point my error here. This function of mine receives an
array of length 32 and then the for loop adds some scrambled characters
at patterns. I think, I can not read the array w[] beyond 32 , but dont
know how to achieve the result. Thanks a lot for help !

void scramble( char *w, int key)
{
x = key; // key = (0-9)
int len = strlen(w);
cout << "length is:" << len << endl; // 32
len = (len + len/x); // 48
cout << "length is:" << len << endl;
char s[] = "@#$"; //array to hold scramble characters
int n = strlen(s);
int i,j,k,m=0;
char * c;
c = new char[len+1];
memset(c, 0, sizeof(c));
//if (c == NULL) exit(1);
for (i=0,j=0,k=0; i<len-1; i++){
if(k<x) {
c[j++] = w[i];k++;
}
else {
if(m<n)
c[j++] = s[m++];
else {
c[j++] = s[0]; m = 1;}
c[j++]=w[i]; k=1; }
}
cout << "scrambled output is :" << c << endl;
delete c;
}

The output is this, which is desired but it has run time error as
mentioned.
input is : ba ced fhgi kzl nmpo qsr tvuxwzy
scrambled output is :ba@ c#ed$ f@hg#i $kz@l #nm$po@ q#sr$ t@vu#xw$zy@

re: Access violation on copying array contents.

dbuser wrote:[color=blue]
> Hope you can point my error here. This function of mine receives an
> array of length 32 and then the for loop adds some scrambled characters
> at patterns. I think, I can not read the array w[] beyond 32 , but dont
> know how to achieve the result. Thanks a lot for help !
>
> void scramble( char *w, int key)[/color]

If 'w' is the array the bounds of which you're not supposed to cross,
then this function needs to know the bounds -- pass the actual size of
that array into the function, as another argument.
[color=blue]
> {
> x = key; // key = (0-9)[/color]

Where is 'x' declared? Is it a global variable?
[color=blue]
> int len = strlen(w);
> cout << "length is:" << len << endl; // 32[/color]

Is '32' what it prints out?
[color=blue]
> len = (len + len/x); // 48[/color]

What does '48' mean? x == 2? What is 'len' now?
[color=blue]
> cout << "length is:" << len << endl;[/color]

Does it print 48 here?
[color=blue]
> char s[] = "@#$"; //array to hold scramble characters[/color]

Four letters is the size of your 's' array.
[color=blue]
> int n = strlen(s);[/color]

n is 3.
[color=blue]
> int i,j,k,m=0;
> char * c;[/color]

Why not merge the two statements into one?
[color=blue]
> c = new char[len+1];
> memset(c, 0, sizeof(c));[/color]

sizeof(c) is 4. You really need to do 'memset(c, 0, len+1)' here.
[color=blue]
> //if (c == NULL) exit(1);[/color]
^^^^^^^^^^^^^^^^^^^^^^^^^
Get rid of this comment, it has no value.
[color=blue]
> for (i=0,j=0,k=0; i<len-1; i++){
> if(k<x) {
> c[j++] = w[i];k++;[/color]

So, you copy the characters if 'k' is smaller than the 'key'. IOW, you
leave up to 'key' characters unchanged.
[color=blue]
> }
> else {[/color]

Otherwise...
[color=blue]
> if(m<n)
> c[j++] = s[m++];[/color]

You insert a scrambled character until they are all used up (m>=n)
[color=blue]
> else {
> c[j++] = s[0]; m = 1;}[/color]

Otherwise you start over...
[color=blue]
> c[j++]=w[i]; k=1; }[/color]

... and still append the source character...
[color=blue]
> }
> cout << "scrambled output is :" << c << endl;
> delete c;[/color]

delete[] c;
[color=blue]
> }
>
> The output is this, which is desired but it has run time error as
> mentioned.
> input is : ba ced fhgi kzl nmpo qsr tvuxwzy
> scrambled output is :ba@ c#ed$ f@hg#i $kz@l #nm$po@ q#sr$ t@vu#xw$zy@[/color]

Well, your calculation of 'len' may be a bit flawed. Try adding 1 to it.

V

re: Access violation on copying array contents.

dbuser wrote:[color=blue]
> Dear experts:
> Hope you can point my error here. This function of mine receives an
> array of length 32 and then the for loop adds some scrambled characters
> at patterns. I think, I can not read the array w[] beyond 32 , but dont
> know how to achieve the result. Thanks a lot for help !
>
> void scramble( char *w, int key)
> {
> x = key; // key = (0-9)
> int len = strlen(w);
> cout << "length is:" << len << endl; // 32
> len = (len + len/x); // 48[/color]
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ replace with
int newLen = (len + len/x);[color=blue]
> cout << "length is:" << len << endl;
> char s[] = "@#$"; //array to hold scramble characters
> int n = strlen(s);
> int i,j,k,m=0;
> char * c;
> c = new char[len+1];[/color]
^^^^^^^^^^^^^^^^^^^ c = new char[newLen + 1];[color=blue]
> memset(c, 0, sizeof(c));[/color]
^^^^^^^ sizeof(c) is 4 on 32 bit machines
memset(c, 0, newLen + 1);
[color=blue]
> //if (c == NULL) exit(1);
> for (i=0,j=0,k=0; i<len-1; i++){
> if(k<x) {
> c[j++] = w[i];k++;
> }
> else {
> if(m<n)
> c[j++] = s[m++];
> else {
> c[j++] = s[0]; m = 1;}
> c[j++]=w[i]; k=1; }
> }
> cout << "scrambled output is :" << c << endl;
> delete c;[/color]
^^^^^^^^^^^^^^^^^^^^
delete[] c;
[color=blue]
> }
>
> The output is this, which is desired but it has run time error as
> mentioned.
> input is : ba ced fhgi kzl nmpo qsr tvuxwzy
> scrambled output is :ba@ c#ed$ f@hg#i $kz@l #nm$po@ q#sr$ t@vu#xw$zy@[/color]

work on the indentation style. also, write one statement per line.

your for loop was running 48 times, and J was incremented 2 some times
(that is how it works) so you were writing past the end of newly
allocated memory for c

/dan

re: Access violation on copying array contents.

Thanks a lot for your valuable suggestions. I corrected mistakes but to
fix run time error, I had to read source array upto its own length like
this:
for (i=0,j=0,k=0,p=0; i<newLen,p<len; i++,p++){
if(k<x) {
c[j++] = w[p];k++;
}
else {
if(m<n)
c[j++] = s[m++];
else {
c[j++] = s[0];
m = 1;
}
c[j++]=w[p];
k=1;
}
}

re: Access violation on copying array contents.

dbuser schrieb:[color=blue]
> Thanks a lot for your valuable suggestions. I corrected mistakes but to
> fix run time error, I had to read source array upto its own length like
> this:
> for (i=0,j=0,k=0,p=0; i<newLen,p<len; i++,p++){[/color]
^^^^^^^^^^^^^^
Do you mean (i<newLen && p<len) or (i<newLen || p<len)?
The comma operator throws away the result of the first part.
[color=blue]
> if(k<x) {
> c[j++] = w[p];k++;
> }
> else {
> if(m<n)
> c[j++] = s[m++];
> else {
> c[j++] = s[0];
> m = 1;
> }
> c[j++]=w[p];
> k=1;
> }
> }
>[/color]

Th.