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// Emacs style mode select -*- C++ -*-
//-----------------------------------------------------------------------------
//
// Copyright(C) 2009 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
// 02111-1307, USA.
//
// DESCRIPTION:
// Queue of waiting callbacks, stored in a binary min heap, so that we
// can always get the first callback.
//
//-----------------------------------------------------------------------------
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "opl_queue.h"
#define MAX_OPL_QUEUE 64
typedef struct
{
opl_callback_t callback;
void *data;
unsigned int time;
} opl_queue_entry_t;
struct opl_callback_queue_s
{
opl_queue_entry_t entries[MAX_OPL_QUEUE];
unsigned int num_entries;
};
opl_callback_queue_t *OPL_Queue_Create(void)
{
opl_callback_queue_t *queue;
queue = malloc(sizeof(opl_callback_queue_t));
queue->num_entries = 0;
return queue;
}
void OPL_Queue_Destroy(opl_callback_queue_t *queue)
{
free(queue);
}
int OPL_Queue_IsEmpty(opl_callback_queue_t *queue)
{
return queue->num_entries == 0;
}
void OPL_Queue_Push(opl_callback_queue_t *queue,
opl_callback_t callback, void *data,
unsigned int time)
{
int entry_id;
if (queue->num_entries >= MAX_OPL_QUEUE)
{
fprintf(stderr, "OPL_Queue_Push: Exceeded maximum callbacks\n");
return;
}
// Add to last queue entry.
entry_id = queue->num_entries;
++queue->num_entries;
// Shift existing entries down in the heap.
while (entry_id > 0 && time < queue->entries[entry_id / 2].time)
{
memcpy(&queue->entries[entry_id],
&queue->entries[entry_id / 2],
sizeof(opl_queue_entry_t));
entry_id /= 2;
}
// Insert new callback data.
queue->entries[entry_id].callback = callback;
queue->entries[entry_id].data = data;
queue->entries[entry_id].time = time;
}
int OPL_Queue_Pop(opl_callback_queue_t *queue,
opl_callback_t *callback, void **data)
{
opl_queue_entry_t *entry;
int child1, child2;
int i, next_i;
// Empty?
if (queue->num_entries <= 0)
{
return 0;
}
// Store the result:
*callback = queue->entries[0].callback;
*data = queue->entries[0].data;
// Decrease the heap size, and keep pointer to the last entry in
// the heap, which must now be percolated down from the top.
--queue->num_entries;
entry = &queue->entries[queue->num_entries];
// Percolate down.
i = 0;
for (;;)
{
child1 = i * 2 + 1;
child2 = i * 2 + 2;
if (child1 < queue->num_entries
&& queue->entries[child1].time < entry->time)
{
// Left child is less than entry.
// Use the minimum of left and right children.
if (child2 < queue->num_entries
&& queue->entries[child2].time < queue->entries[child1].time)
{
next_i = child2;
}
else
{
next_i = child1;
}
}
else if (child2 < queue->num_entries
&& queue->entries[child2].time < entry->time)
{
// Right child is less than entry. Go down the right side.
next_i = child2;
}
else
{
// Finished percolating.
break;
}
// Percolate the next value up and advance.
memcpy(&queue->entries[i],
&queue->entries[next_i],
sizeof(opl_queue_entry_t));
i = next_i;
}
// Store the old last-entry at its new position.
memcpy(&queue->entries[i], entry, sizeof(opl_queue_entry_t));
return 1;
}
unsigned int OPL_Queue_Peek(opl_callback_queue_t *queue)
{
if (queue->num_entries > 0)
{
return queue->entries[0].time;
}
else
{
return 0;
}
}
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