44. Peek N Bytes from Circular Buffer

#include <stdio.h>

typedef struct {
    int buffer[10];
    int head;
    int tail;
    int count;
    int capacity;
} CircularBuffer;

// Function to peek at the next n bytes without modifying the buffer
void peek_bytes(CircularBuffer *cb, int n) {
    for (int i = 0; i < n; i++) {
        if ((*cb).count <= i) {
            printf("NULL");
        } else {
            int index = ((*cb).tail + i) % (*cb).capacity;
            printf("%d", (*cb).buffer[index]);
        }
        if(i < n-1){
            printf(" ");
        }
    }
}
 
int main() {
    CircularBuffer cb = {
        .buffer = {10, 20, 30, 40, 50, 60, 70, 80, 90, 100},
        .head = 3,
        .tail = 7,
        .count = 6,
        .capacity = 10
    };

    int n;
    scanf("%d", &n);

    peek_bytes(&cb, n);

    return 0;
}

A circular buffer maintains a fixed-size memory array efficiently.

Peeking allows inspecting elements without removing or modifying the buffer state — commonly used in protocol detection, timeout handling, or pre-processing.

Solution Logic:

• Loop n times
• If the current index i is within the available count:
  • Compute peek index: (tail + i) % capacity
  • Print the value at that position
• Else:
  • Print "NULL"

No change is made to the tail, head, or count.

Alternate Solution

void peek_bytes(CircularBuffer *cb, int n) {
    int i = 0, temp = (*cb).tail;
    while (i < n) {
        if (i >= (*cb).count) {
            printf("NULL");
        } else {
            printf("%d", (*cb).buffer[temp]);
            temp = (temp + 1) % (*cb).capacity;
        }
        if(i < n-1){
            printf(" ");
        }
        i++;
    }
}