queue implementation in c using array

 // queue.cpp : Defines the entry point for the console application.  
 //  
 #include "stdafx.h"  
 #include <stdio.h>  
 #include <stdlib.h>  
 struct queue  
 {  
 int front;  
 int rear;  
 int a[5];  
 int capacity;  
 };  
 void enqueue(struct queue *q, int data)  
 {  
      if((q->front == ((q->rear+1)%q->capacity)))  
      {       
           printf("Queue full");  
           return ;  
      }  
      if(q->front == -1)  
      q->front=0;  
      q->rear = (++q->rear)%q->capacity;  
      q->a[q->rear]=data;  
      printf("front %d rear %d\n",q->front,q->rear);  
 }  
 void dequeue(struct queue *q)  
 {  
      if((q->front == -1) && (q->rear == -1))  
      {  
           printf("\n queue empty");  
           return;  
      }  
      if(q->front == q->rear)  
      {  
           q->front = -1;  
           q->rear = -1;  
           return;  
      }  
      q->front = (++q->front)%q->capacity;  
 }  
 void display(struct queue q)  
 {  
      if((q.front == -1) && (q.rear == -1))  
      {  
           printf("\n queue empty");  
           return;  
      }  
      for(int i=q.front;;i++)  
      {  
           i = i%(q.capacity);  
           printf("-%d-",q.a[i]);  
           if(i==q.rear)  
                break;  
      }  
 }  
 int main(int argc, char* argv[])  
 {  
      int ch=0, data = 0;  
      struct queue q;  
      q.capacity = 5;  
      q.front = -1;  
      q.rear = -1;  
      printf("1.enqueue\n2.dequeue\n3.display\n4.exit");  
      while(1)  
      {  
      printf("\nEnter the option!\n");  
      scanf("%d",&ch);  
      switch(ch)  
      {  
      case 1: printf("Enter data:");  
                scanf("%d",&data);  
                enqueue(&q,data);  
                break;  
      case 2: dequeue(&q);  
                break;  
      case 3: display(q);  
                break;  
      case 4: exit(0);  
      }  
      }       
      return 0;  
 }  

Different ways of compilations in android

Different compilations are used for android code

1. Compilation of complete code
$make
2. Compiling android kernel
$make bootimage
3. compiling system img
$make systemimage
4. compilation of an apk
open Android.mk of an apk
LOCAL_MODULE := xyz_module_name
$make xyz_module_name

5. mm is command to compile the indiviual modules . TO work this command first all the code should compile atleast once

how to compile SystemUI

Go to base SystemUI folder and type
$mm

SystemUI.apk is generated in out folder

//install to phone
adb root
adb remount
adb push SystemUI.apk /system/app/

adb reboot

Reverse single linked list.

#include<stdio.h>
#include<stdlib.h>
typedef struct node {
int data;
struct node *next;
};

struct node *head=NULL;

void push(int d)
{
struct node *tmp = (struct node *)malloc(sizeof(struct node*));
struct node *ptr = head;
if( head == NULL)
{
tmp->data = d;
tmp->next = NULL;
head = tmp;
} else {
tmp->data = d;
tmp->next = NULL;
while(ptr->next != NULL)
{
ptr = ptr->next;
}
ptr->next = tmp;
}
}

void display()
{
struct node *ptr = head;
while(ptr)
{
printf("%d",ptr->data);
ptr = ptr->next;
}
}

void delete(int n)
{
struct node *ptr=head;
struct node *pre;
int i=1;
if(head != NULL && n==1)
{
head = head->next;
free(ptr);
return;
}
while(ptr != NULL)
{
if(i == n)
{
pre->next = ptr->next;
free(ptr);
ptr=pre->next;
break;
}
pre= ptr;
ptr= ptr->next;
i++;
}
}

void reverse()
{
struct node *ptr=head;
struct node *tmp=NULL;
struct node *next=NULL;
while(ptr)
{
next = ptr->next;
ptr->next = tmp;
tmp=ptr;
ptr=next;
}
head = tmp;
}
main()
{
int d=0,i=0;
while(i<5)
{
i++;
scanf("%d",&d);
push(d);
}
display();
scanf("%d",&d);
delete(d);
display();
printf("reverse ");
reverse();
display();
}

delete nth element linked list

void delete(int n)
{
        struct node *ptr=head;
        struct node *pre;
        int i=1;
        if((ptr != NULL) && n == 1)
        {
                head = head->next;
                free(ptr);
                return;
        }
        while(ptr != NULL)
        {
                if(i == n)
                {
                        pre->next = ptr->next;
                        free(ptr);
                        ptr=pre->next;
                        break;
                }
                pre= ptr;
                ptr= ptr->next;
                i++;
        }
}

How to declare new system property in Android

Go to init.rc

//define property
setprop  sys.xyz 0

//use in your code
int ret;
char prop_value[MAX];
ret = property_get("sys.xyz",prop_value,NULL)

Auto indent of kernel code

sudo apt-get install indent

indent -linux file.c