mirror of
https://github.com/scummvm/scummvm.git
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145 lines
3.2 KiB
C++
145 lines
3.2 KiB
C++
/* ScummVM - Graphic Adventure Engine
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*
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* ScummVM is the legal property of its developers, whose names
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* are too numerous to list here. Please refer to the COPYRIGHT
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* file distributed with this source distribution.
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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*/
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/*
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* Based on ScottFree interpreter version 1.14 developed by Swansea
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* University Computer Society without disassembly of any other game
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* drivers, only of game databases as permitted by EEC law (for purposes
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* of compatibility).
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*
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* Licensed under GPLv2
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*
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* https://github.com/angstsmurf/spatterlight/tree/master/terps/scott
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*/
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#include "glk/scott/ring_buffer.h"
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namespace Glk {
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namespace Scott {
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// The hidden definition of our circular buffer structure
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struct CircularBuf {
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uint8_t *_buffer;
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size_t _head;
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size_t _tail;
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size_t _max; // of the buffer
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bool _full;
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};
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// Return a pointer to a struct instance
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cbuf_handle_t circularBufInit(uint8_t *buffer, size_t size) {
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cbuf_handle_t cbuf = new CircularBuf;
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cbuf->_buffer = buffer;
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cbuf->_max = size;
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circularBufReset(cbuf);
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return cbuf;
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}
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void circularBufReset(cbuf_handle_t me) {
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me->_head = 0;
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me->_tail = 0;
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me->_full = false;
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}
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void circularBufFree(cbuf_handle_t me) {
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delete me;
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}
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bool circularBufFull(cbuf_handle_t me) {
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return me->_full;
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}
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bool circularBufEmpty(cbuf_handle_t me) {
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return (!me->_full && (me->_head == me->_tail));
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}
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size_t circularBufCapacity(cbuf_handle_t me) {
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return me->_max;
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}
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size_t circularBufSize(cbuf_handle_t me) {
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size_t size = me->_max;
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if (!me->_full) {
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if (me->_head >= me->_tail) {
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size = (me->_head - me->_tail);
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} else {
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size = (me->_max + me->_head - me->_tail);
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}
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}
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return size;
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}
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static void advancePointer(cbuf_handle_t me) {
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if (me->_full) {
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if (++(me->_tail) == me->_max) {
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me->_tail = 0;
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}
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}
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if (++(me->_head) == me->_max) {
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me->_head = 0;
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}
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me->_full = (me->_head == me->_tail);
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}
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static void retreatPointer(cbuf_handle_t me) {
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me->_full = false;
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if (++(me->_tail) == me->_max) {
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me->_tail = 0;
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}
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}
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int circularBufPut(cbuf_handle_t me, uint8_t x, uint8_t y) {
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int r = -1;
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if (!circularBufFull(me)) {
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me->_buffer[me->_head] = x;
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advancePointer(me);
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if (!circularBufFull(me)) {
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me->_buffer[me->_head] = y;
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advancePointer(me);
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r = 0;
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}
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}
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return r;
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}
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int circularBufGet(cbuf_handle_t me, int *x, int *y) {
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int r = -1;
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if (!circularBufEmpty(me)) {
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*x = me->_buffer[me->_tail];
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retreatPointer(me);
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if (!circularBufEmpty(me)) {
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*y = me->_buffer[me->_tail];
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retreatPointer(me);
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r = 0;
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}
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}
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return r;
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}
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} // End of namespace Scott
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} // End of namespace Glk
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