EXC_BAD_ACCESS in attempt to rewrite NSString ComponentsSeparatedByString: - objective-c

Question

I'm writing an objective-C program to deal with trajectories of Biomolecules with XCODE 4.3.1 and ARC. I need to read PDB files, i.e. parse large quantities of text formatted data. I'm very disappointed by NSString inefficiency and was trying to write a C-equivalent of componentsSeparatedByString:. The algorithm works just fine with NSString and NSMutableArrays, but i'm having a hard time using char* and char**.
Unfortunately, I'm getting an EXC_BAD_ACCESS error. The strange thing is that i get the error for i=68103 and j=68049 (does these number ring a bell for you ?), which means it worked for some time before crashing. The error is "static" (always block at the same (i,j) numbers). The array seems to work just fine(NSLog on its values before crash).
As it seems, I'm not very experienced with C-code and the subtlety behind pointers, but I would definitely be glad to hear your suggestions to make it work ! Thanks !
Heres the code :
+(char**) componentsSeparedByNewLineCEQUIV:(const char*)aChar:(int*)numWord
{ // char* aChar : my file, is typically 3 millions characters
int j=-1; //Last non space character
int i; //Scanned character
int len=strlen(aChar);
char** stringArray=malloc((*numWord)*sizeof(char*));
for (i=0;i<len; i++)
{ if (aChar[i]==10)
{
if ( j!=-1)
{
char* buffer2=malloc(i-j+1);
strcpy(buffer2, strndup(aChar+j, i-j));
stringArray[i]=malloc(sizeof(char)*strlen(buffer2)+1); //EXC_BAD_ACCESS HERE
strcpy(stringArray[i], buffer2);
}
j=-1;
}
else if (j==-1)
{j=i;}
}
if (j!=-1)
{ char* buffer2=malloc(i-j+1);
strcpy(buffer2, strndup(aChar+j, i-j));
stringArray[i]=malloc(strlen(buffer2)+1);
strcpy(stringArray[i], buffer2);
}
return stringArray;
}

Answer 1

You're probably not the first person to have this problem :)
Why not just use strtok?
PS What analysis showed that NSString was your problem?

Answer 2

I don't know why the error is at the line above of where it should be.However you are copying a string that is not allocated.
stringArray[i] is not allocated when you copy on it buffer2, allocate it:
if ( j!=-1)
{
char* buffer2=malloc(i-j+1);
strcpy(buffer2, strndup(aChar+j, i-j));
stringArray[i]=malloc(sizeof(char)*strlen(buffer2)+1); //EXC_BAD_ACCESS HERE
stringArray[i]=(char*)malloc( (strlen(buffer2)+1)*sizeof(char)); // Allocate the string
strcpy(stringArray[i], buffer2);
}

Answer 3

First: if Im not totaly wrong, but i think you are consuming at least 4-times as much memory as you need to:
You are using malloc for creating buffer2 and also using strndup for getting the wanted chars. strndup does exactly what you want, but in one step. char* buffer2 = strndup(aChar+j, i-j) should be your first step. Even worse in the next two line you are essential doing the same again. So i think what you are really want is stringArray[i] = strndup(aChar+j, i-j). To look at memory Problems: all the functions use errno to indicate memory allocating failure.
Second: Your functions does not return the number of components, so your stringArray may contain some garbage without knowing.
Third: strlen is expensive and you do not need it, just use for(int i = 0; aChar[i] != '\0'; i++)

Answer 4

Update for everyone who might be interested : this is a working version, using strtok which can be useful, although i'm still interested in response on my code.
This code have been tested 5 times faster (125ms vs 581ms) than [astring componentsSeparatedByString:#"\n"] ...
+(char**)componentsSeparatedByNewLine:(const char*)aChar:(int*)numWord
{
int i;
int j=0;
int len = strlen(aChar);
*numWord=1;
for (i=0;i<len; i++)
{
if (aChar[i]==10) *numWord=*numWord+1; //change 10 for any other character (ASCII for space)
}
char** stringArray=malloc((*numWord)*sizeof(char*));
char* pch;
char* aChar2=malloc(len+1);
strcpy(aChar2,aChar);
pch = strtok(aChar2,"\n");
while (pch != NULL)
{
stringArray[j]=(char*)malloc( (strlen(pch)+1)*sizeof(char));
strcpy(stringArray[j], pch);
//NSLog(#"%s",stringArray[j]);
j=j+1;
pch = strtok (NULL, "\n");
}
return stringArray;
}