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/*
* Copyright (c) 2012 Itay Duvdevani
* All rights reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#include "queue.h"
#if defined(__18CXX)
#pragma udata
#endif
/* queue buffer */
static volatile char queue[QUEUE_SIZE];
/* last position read */
static volatile BYTE read_head;
/* next position to write to */
static volatile BYTE write_head;
#if defined(__18CXX)
#pragma code
#endif
/* mask to AND with, to modulu a number to queue size */
/* we're assuming the queue size is a power of 2 */
#define QUEUE_SIZE_MASK (QUEUE_SIZE - 1)
#define INCREMENT_MODULU(x) ((x + 1) & QUEUE_SIZE_MASK)
void QueueInit(void) {
read_head = 0; /* this is the last position read */
write_head = 1; /* this is the next position to write to */
}
void QueuePut(char data) {
if (write_head == read_head) {
/* discard overflowing data */
return;
}
/* write, then increment */
queue[write_head] = data;
write_head = INCREMENT_MODULU(write_head);
}
BOOL QueueHas(void) {
return write_head != INCREMENT_MODULU(read_head);
}
char QueueGet(void) {
/* move to new read position first */
read_head = INCREMENT_MODULU(read_head);
return queue[read_head];
}
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