www.pudn.com > pthread_examples.rar > queue.c

/* queue.c 
** Copyright 2000 Daniel Robbins, Gentoo Technologies, Inc. 
** Author: Daniel Robbins 
** Date: 16 Jun 2000 
** 
** This set of queue functions was originally thread-aware.  I 
** redesigned the code to make this set of queue routines 
** thread-ignorant (just a generic, boring yet very fast set of queue 
** routines).  Why the change?  Because it makes more sense to have 
** the thread support as an optional add-on.  Consider a situation 
** where you want to add 5 nodes to the queue.  With the 
** thread-enabled version, each call to queue_put() would 
** automatically lock and unlock the queue mutex 5 times -- that's a 
** lot of unnecessary overhead.  However, by moving the thread stuff 
** out of the queue routines, the caller can lock the mutex once at 
** the beginning, then insert 5 items, and then unlock at the end. 
** Moving the lock/unlock code out of the queue functions allows for 
** optimizations that aren't possible otherwise.  It also makes this 
** code useful for non-threaded applications. 
** 
** We can easily thread-enable this data structure by using the 
** data_control type defined in control.c and control.h.  */ 
 
#include  
#include "queue.h" 
 
void queue_init(queue *myroot) { 
  myroot->head=NULL; 
  myroot->tail=NULL; 
} 
 
void queue_put(queue *myroot,node *mynode) { 
  mynode->next=NULL; 
  if (myroot->tail!=NULL) 
    myroot->tail->next=mynode; 
  myroot->tail=mynode; 
  if (myroot->head==NULL) 
    myroot->head=mynode; 
} 
 
node *queue_get(queue *myroot) { 
  //get from root 
  node *mynode; 
  mynode=myroot->head; 
  if (myroot->head!=NULL) 
    myroot->head=myroot->head->next; 
  return mynode; 
}