I see a lot of templates and complicated data structures for implementing a circular buffer.
How do I code a simple integer circular buffer for 5 numbers?
I'm thinking in C is the most straightforward?
Thanks.
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7The complexity of the code goes up with how safe and robust you want it to be. Do you want it to prevent underflow/overflow, for instance?Oliver Charlesworth– Oliver Charlesworth2010-09-01 20:38:28 +00:00Commented Sep 1, 2010 at 20:38
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3Note: a circular (ring) buffer is different than a circular queue.Thomas Matthews– Thomas Matthews2010-09-01 20:42:32 +00:00Commented Sep 1, 2010 at 20:42
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I just need to store the 5 last values of some data, so whatever has a better design to do that.T.T.T.– T.T.T.2010-09-01 20:43:39 +00:00Commented Sep 1, 2010 at 20:43
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1@T.T.T. Do you need to retrieve them in a special order (FIFO, LIFO, no ordering) ?fjardon– fjardon2015-04-03 15:11:31 +00:00Commented Apr 3, 2015 at 15:11
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4 Answers
Have an array, buffer, of 5 integers. Have an index ind to the next element. When you add, do
buffer[ind] = value;
ind = (ind + 1) % 5;
2 Comments
photo_tom
From the personal experience file, you need to be careful that ind is not negative. If you change the second line to "ind = (max(0,ind) % 1) + 5;", you don't have to worry about negative values for ind.
Triskeldeian
Why don't you just set ind to be uint? That would solve your problem more efficiently if only additions are involved
Take an array, arr, an index idx, and a counter, num.
To insert foo, say arr[idx++] = foo; idx %= buffer_len; num++;.
To read out an item into foo, say foo = arr[(idx-num)%buffer_len]; num--;.
Add boundary checks.
1 Comment
user3467349
You don't need num and idx.
If the size and data type of your buffer are fixed, a simple array is all you need:
int buffer[5];
Add to that a couple pointers:
int* start = &buffer[0];
int* end = &buffer[4]+1;
int* input = start;
int* output = start;
Comments
int rI =0;
int wI=0;
#define FIFO_SIZE 3
int checkAvail()
{
int avail=0;
if(wI<rI)
avail= (rI-wI);
else
avail = (FIFO_SIZE-wI+rI);
return avail;
}
int addFIFO(int *a, int val)
{
if(checkAvail()>0)
{
a[wI]=val;
wI++;
if(wI>FIFO_SIZE)
wI=0;
}
else
{
printf("FIFO full");
}
return 0;
}
int remFIFO(int *a)
{
int val;
if((FIFO_SIZE-checkAvail()>0))
{
val =a[rI];
rI++;
if(rI>FIFO_SIZE)
rI=0;
}
else
{
printf("FIFO empty");
}
return 0;
}
int main(array<System::String ^> ^args)
{
int FIFO_ARRAY[FIFO_SIZE]={};
addFIFO(FIFO_ARRAY,1);
addFIFO(FIFO_ARRAY,2);
addFIFO(FIFO_ARRAY,3);
addFIFO(FIFO_ARRAY,4);
remFIFO(FIFO_ARRAY);
remFIFO(FIFO_ARRAY);
remFIFO(FIFO_ARRAY);
remFIFO(FIFO_ARRAY);
remFIFO(FIFO_ARRAY);
}
