mirror of
https://github.com/DCC-EX/CommandStation-EX.git
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106 lines
2.6 KiB
C++
106 lines
2.6 KiB
C++
/*
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* © 2020, Chris Harlow. All rights reserved.
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*
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* This file is part of DCC-EX CommandStation-EX
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*
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* This 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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* It 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 CommandStation. If not, see <https://www.gnu.org/licenses/>.
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*/
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#include "RingStream.h"
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#include "DIAG.h"
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RingStream::RingStream( const uint16_t len)
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{
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_len=len;
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_buffer=new byte[len];
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_pos_write=0;
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_pos_read=0;
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_buffer[0]=0;
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_overflow=false;
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_mark=0;
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_count=0;
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}
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size_t RingStream::write(uint8_t b) {
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if (_overflow) return 0;
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_buffer[_pos_write] = b;
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++_pos_write;
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if (_pos_write==_len) _pos_write=0;
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if (_pos_write==_pos_read) {
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_overflow=true;
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return 0;
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}
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_count++;
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return 1;
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}
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int RingStream::read() {
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if ((_pos_read==_pos_write) && !_overflow) return -1; // empty
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byte b=_buffer[_pos_read];
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_pos_read++;
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if (_pos_read==_len) _pos_read=0;
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_overflow=false;
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return b;
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}
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int RingStream::count() {
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return (read()<<8) | read();
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}
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int RingStream::freeSpace() {
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// allow space for client flag and length bytes
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if (_pos_read>_pos_write) return _pos_read-_pos_write-3;
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else return _len - _pos_write + _pos_read-3;
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}
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// mark start of message with client id (0...9)
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void RingStream::mark(uint8_t b) {
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_mark=_pos_write;
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write(b); // client id
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write((uint8_t)0); // count MSB placemarker
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write((uint8_t)0); // count LSB placemarker
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_count=0;
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}
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// peekTargetMark is used by the parser stash routines to know which client
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// to send a callback response to some time later.
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uint8_t RingStream::peekTargetMark() {
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return _buffer[_mark];
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}
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bool RingStream::commit() {
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if (_overflow) {
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DIAG(F("RingStream(%d) commit(%d) OVERFLOW"),_len, _count);
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// just throw it away
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_pos_write=_mark;
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_overflow=false;
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return false; // commit failed
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}
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if (_count==0) {
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// ignore empty response
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_pos_write=_mark;
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return true; // true=commit ok
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}
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// Go back to the _mark and inject the count 1 byte later
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_mark++;
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if (_mark==_len) _mark=0;
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_buffer[_mark]=highByte(_count);
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_mark++;
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if (_mark==_len) _mark=0;
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_buffer[_mark]=lowByte(_count);
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return true; // commit worked
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}
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