diff options
Diffstat (limited to 'opl/opl_queue.c')
| -rw-r--r-- | opl/opl_queue.c | 192 |
1 files changed, 192 insertions, 0 deletions
diff --git a/opl/opl_queue.c b/opl/opl_queue.c new file mode 100644 index 00000000..6639eee5 --- /dev/null +++ b/opl/opl_queue.c @@ -0,0 +1,192 @@ +// 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; + } +} + |