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queue.c
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435 lines (338 loc) · 6.94 KB
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/*
** SCCS ID: @(#)queue.c 1.1 4/17/15
**
** File: queue.c
**
** Author: CSCI-452 class of 20145
**
** Contributor:
**
** Description: Queue-related implementations
*/
#define __SP_KERNEL__
#include "common.h"
#include "types.h"
#include "stack.h"
#include "process.h"
#include "scheduler.h"
/*
** PRIVATE DEFINITIONS
*/
// number of qnodes to create
// need one per: PCB, stack, queue
// add a fudge factor
#define N_QNODES (N_PROCS + N_STACKS + N_QUEUES + 3)
/*
** PRIVATE DATA TYPES
*/
// structure of a qnode
typedef struct qnode {
void *key; // sorting key
void *data; // data queued
struct qnode *next; // link to successor
} qnode_t;
// now we can include queue.h to get the queue_t type
#include "queue.h"
// the actual queue definition
struct queue {
qnode_t *first; // head pointer
qnode_t *last; // tail pointer
comparef_t compare; // comparison function
uint32_t size; // queue length
};
/*
** PRIVATE GLOBAL VARIABLES
*/
static qnode_t *_free_qnodes; // list of available qnodes
static qnode_t _qnodes[N_QNODES]; // all qnodes in the system
static queue_t _free_queues; // queue of available queues
static struct queue _queues[N_QUEUES]; // all available queues
/*
** PUBLIC GLOBAL VARIABLES
*/
/*
** PRIVATE FUNCTIONS
*/
/*
** _compare_time()
**
** compare two keys as "time" values
*/
int _compare_time( void *qn1, void *qn2 ) {
uint32_t k1 = (uint32_t) qn1;
uint32_t k2 = (uint32_t) qn2;
return( k1 - k2 );
}
/*
** _qnode_dealloc()
**
** return a qnode to the free pool
*/
static void _qnode_dealloc( qnode_t *node ) {
#ifdef DEBUG
if( node == NULL ) {
_kpanic( "_qnode_dealloc", "NULL node" );
}
#endif
node->next = _free_qnodes;
_free_qnodes = node;
}
/*
** _qnode_alloc()
**
** obtain a qnode from the free pool
*/
static qnode_t *_qnode_alloc( void ) {
qnode_t *node;
node = _free_qnodes;
if( node != NULL ) {
_free_qnodes = node->next;
node->next = NULL;
}
return( node );
}
/*
** PUBLIC FUNCTIONS
*/
/*
** _queue_modinit()
**
** initialize the queue module
*/
void _queue_modinit( void ) {
_free_qnodes = NULL;
for( int i = 0; i < N_QNODES; ++i ) {
_qnode_dealloc( &_qnodes[i] );
}
// steal the first queue for _free_queues
_free_queues = &_queues[0];
_queue_init( _free_queues, 0 );
// add the rest to the free queue
for( int i = 1; i < N_QUEUES; ++i ) {
_queue_dealloc( &_queues[i] );
}
c_puts( " QUEUE" );
}
/*
** _queue_alloc()
**
** allocate a queue
**
** returns a pointer to the allocated queue, or NULL
*/
int _queue_alloc( queue_t locs[], int num ) {
int i;
for( i = 0; i < num; ++i ) {
// if none available, we're done
if( _queue_empty(_free_queues) ) {
break;
}
// allocate one
locs[i] = _queue_remove( _free_queues );
// if it didn't work, we're done
if( locs[i] == NULL ) {
break;
}
}
return( i );
}
/*
** _queue_dealloc()
**
** return a queue to the free list
*/
void _queue_dealloc( queue_t queue ) {
// sanity check: avoid deallocating a NULL pointer
if( queue == NULL ) {
// should this be an error?
return;
}
// clear the queue
_memset( (void *) queue, sizeof(struct queue), 0 );
// put it back on the free list
_queue_insert( _free_queues, (void *) queue, 0 );
}
/*
** _queue_init()
**
** initialize the supplied queue
*/
void _queue_init( queue_t queue, comparef_t compare ) {
#ifdef DEBUG
if( queue == NULL ) {
_kpanic( "_queue_init", "NULL queue" );
}
#endif
queue->first = NULL;
queue->last = NULL;
queue->size = 0;
queue->compare = compare;
}
/*
** _queue_remove()
**
** remove the first element from the queue
**
** returns the thing that was removed, or NULL
*/
void *_queue_remove( queue_t queue ) {
qnode_t *node;
void *data;
#ifdef DEBUG
if( queue == NULL ) {
_kpanic( "_queue_remove", "NULL queue" );
}
#endif
if( queue->first == NULL ) {
return( NULL );
}
node = queue->first;
queue->first = node->next;
if( queue->first == NULL ) {
queue->last = NULL;
}
queue->size -= 1;
data = node->data;
_qnode_dealloc( node );
return( data );
}
/*
** _queue_insert()
**
** insert the supplied data value into the queue, ordering the
** queue using its built-in comparison function
*/
void _queue_insert( queue_t queue, void *data, void *key ) {
qnode_t *node;
#ifdef DEBUG
if( queue == NULL ) {
_kpanic( "_queue_insert", "NULL queue" );
}
#endif
node = _qnode_alloc();
if( node == NULL ) {
_kpanic( "_queue_insert", "NULL qnode" );
}
node->data = data;
node->key = key;
if( _queue_empty(queue) ) {
queue->first = node;
queue->last = node;
queue->size = 1;
return;
}
if( queue->compare == NULL ) {
queue->last->next = node;
queue->last = node;
queue->size += 1;
return;
}
qnode_t *prev, *curr;
prev = NULL;
curr = queue->first;
while( curr != NULL &&
queue->compare(node->key,curr->key) >= 0 ) {
prev = curr;
curr = curr->next;
}
/*
** prev curr meaning
** ==============================================
** NULL !NULL add at front: new -> curr, first -> new
** NULL NULL error??? cannot happen???
** !NULL !NULL add in middle: new -> curr, prev -> new
** !NULL NULL add at end: new -> NULL, prev -> new, last -> new
*/
node->next = curr;
if( prev == NULL ) {
queue->first = node;
} else {
prev->next = node;
}
if( curr == NULL ) {
queue->last = node;
}
queue->size += 1;
}
/*
** _queue_empty()
**
** determine whether or not the supplied queue is empty
*/
bool_t _queue_empty( queue_t queue ) {
return( queue->first == NULL );
}
/*
** _queue_size()
**
** return the number of elements in the supplied queue
*/
uint32_t _queue_size( queue_t queue ) {
return( queue->size );
}
/*
** _queue_kpeek()
**
** peek at the first element in the queue
**
** returns the key associated with that element
*/
void *_queue_kpeek( queue_t queue ) {
#ifdef DEBUG
if( queue == NULL ) {
_kpanic( "_queue_kpeek", "NULL queue" );
}
#endif
if( _queue_empty(queue) ) {
return( NULL );
}
return( queue->first->key );
}
/*
** _queue_dpeek()
**
** peek at the first element in the queue
**
** returns the data associated with that element
*/
void *_queue_dpeek( queue_t queue ) {
#ifdef DEBUG
if( queue == NULL ) {
_kpanic( "_queue_dpeek", "NULL queue" );
}
#endif
if( _queue_empty(queue) ) {
return( NULL );
}
return( queue->first->data );
}
/*
** _queue_dump(which,queue)
**
** dump the contents of the specified queue to the console
*/
void _queue_dump( char *which, queue_t queue ) {
qnode_t *tmp;
int i;
c_printf( "%s: ", which );
if( queue == NULL ) {
c_puts( "NULL???" );
return;
}
c_printf( "first %08x last %08x comp %08x (%d items)\n",
(uint32_t) queue->first, (uint32_t) queue->last,
(uint32_t) queue->compare, queue->size );
if( _queue_size(queue) > 0 ) {
c_puts( " data: " );
i = 0;
for( tmp = queue->first; tmp != NULL; tmp = tmp->next ) {
c_printf( " [%x,%x]", (uint32_t) tmp->key,
(uint32_t) tmp->data );
if( ++i > 10 ) break;
}
if( tmp != NULL ) {
c_puts( " ..." );
}
c_puts( "\n" );
}
}