CODEWITHSUNDEEP
carraysdynamiclinked-list
PandaRaid
PandaRaid

Reputation: 628

Linked List in Contiguous Memory Space

I have been looking into some code for measuring latencies and one of the methods I came across deals with iterating through a linked list that is confined to a dynamically allocated memory space. I understand traditional linked lists pretty well and I understand dynamically allocated arrays, but putting the two together is throwing me through a loop. This may seem like a relatively basic question but I am not great with c and for whatever reason I am having a hard time constructing it.

I wanted to make strides of 128 bytes so I tried doing the following (I know I am probably way off base but I needed to start somewhere)

char** randomArray = malloc(accessSize);    //allocate space for linked list
char** start=randomArray;               //header for base adress
char** iterate;                         //iterator
char** end =randomArray+accessSize;     //end address
for(iterate=start; iterate < end; iterate+=128){
    *iterate = iterate+128;                 //step through in strides of 128 bytes, assign next addr to current value
}

*iterate=start;     //linked list is circular, assign last element to first

I had no idea what data type to point to, normally you allocate space for a struct but that space already exists.

I then thought I would iterate through it as follows

for(counter = 0; counter < LotsOfAccess; counter++){
     start = (char**) *start;
}

Well this didn't even work slightly for me and I can't seem to find out why. Does any have any suggestions for the proper way of implementing this or what I might be doing wrong?

Upvotes: 0

Views: 1210

Answers (1)

PandaRaid
PandaRaid

Reputation: 628

Well did't get many bites on this one but I still think its a useful question so I will post what I did!

To create the linked list with strides of 128 bytes in a dynamically allocated space I did:

char * randomArray = malloc(accessSize*sizeof(char));
int counter;
char ** head = (char **) randomArray;
char ** iterate = head;
for(counter=0; counter < accessSize; counter+=128){
    (*iterate) = &randomArray[counter+128];
    iterate+=(128/sizeof iterate);
}
*iterate = head;

To traverse I did:

iterate = head;   
for(counter=0; counter < NUM_ACCESSES; counter++){
    iterate = *iterate;
}

Upvotes: 1

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