mirror of
https://github.com/DCC-EX/CommandStation-EX.git
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208 lines
6.2 KiB
C++
208 lines
6.2 KiB
C++
/*
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* © 2020-2021 Chris Harlow
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* 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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// NOTE: The use of a marker byte without an escape algorithm means
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// RingStream is unsuitable for binary data. Should binary data need to be
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// streamed it will be necessary to implementr an escape strategy to handle the
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// marker char when embedded in data.
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#include "RingStream.h"
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#include "DIAG.h"
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const byte FLASH_INSERT_MARKER=0xff;
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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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_flashInsert=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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// Ideally, I would prefer to override the Print:print(_FlashStringHelper) function
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// but the library authors omitted to make this virtual.
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// Therefore we obveride the only other simple function that has no side effects
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// in order that StringFormatter can recognise a RingStream and call its
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// printFlash() directly.
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int RingStream::availableForWrite() {
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return THIS_IS_A_RINGSTREAM;
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}
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size_t RingStream::printFlash(const FSH * flashBuffer) {
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// We are about to add a PROGMEM string to the buffer.
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// To save RAM we can insert a marker and the
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// progmem address into the buffer instead.
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// The buffer reading code must recognise this marker and
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// silently extract the progmem bytes.
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// In addition, we must make the count correct as if the
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// string had been embedded so that things like the wifi code
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// can read the expected count before reading the buffer.
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// Establish the actual length of the progmem string.
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char * flash=(char *)flashBuffer;
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int16_t plength=strlen_P(flash);
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if (plength==0) return 0; // just ignore empty string
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// Retain the buffer count as it will be modified by the marker+address insert
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int prevCount=_count;
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write(FLASH_INSERT_MARKER); // write the marker
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uintptr_t iFlash=reinterpret_cast<uintptr_t>(flash); // expect size match with pointer
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// write address bytes LSB first (size depends on CPU)
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for (byte f=0;f<sizeof(iFlash); f++) {
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write((byte) (iFlash & 0xFF));
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iFlash>>=8;
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}
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// correct the buffer count to reflect the flash length, not the marker/addr.
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_count=prevCount+plength;
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return plength;
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}
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int RingStream::read() {
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if (_flashInsert) {
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// we are reading out of a flash string
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byte fb=GETFLASH(_flashInsert);
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_flashInsert++;
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if (fb) return fb; // we have a byte from the flash
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// flash insert complete, clear and drop through to next buffer byte
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_flashInsert=NULL;
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}
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if ((_pos_read==_pos_write) && !_overflow) return -1; // empty
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byte b=readRawByte();
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if (b!=FLASH_INSERT_MARKER) return b;
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#ifndef ARDUINO_ARCH_ESP32
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// Detected a flash insert
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// read address bytes LSB first (size depends on CPU)
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uintptr_t iFlash=0;
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for (byte f=0; f<sizeof(iFlash); f++) {
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uintptr_t bf=readRawByte();
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bf&=0x00ff;
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bf<<= (8*f); // shift byte to correct position in iFlash
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iFlash |= bf;
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}
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_flashInsert=reinterpret_cast<char * >( iFlash);
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// and try again... so will read the first byte of the insert.
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return read();
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#else
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DIAG(F("Detected flash insert marker at pos %d but there should not be one"),_pos_read);
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return '\0';
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#endif
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}
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byte RingStream::readRawByte() {
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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 (readRawByte()<<8) | readRawByte();
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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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//DIAG(F("RS mark client %d at %d core %d"), b, _pos_write, xPortGetCoreID());
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_ringClient = 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 _ringClient;
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}
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void RingStream::info() {
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DIAG(F("Info len=%d count=%d pr=%d pw=%d m=%d"),_len, _count,_pos_read,_pos_write,_mark);
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}
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bool RingStream::commit() {
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_flashInsert=NULL; // prepared for first read
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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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//DIAG(F("RS commit count=0 rewind back to %d core %d"), _mark, xPortGetCoreID());
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// ignore empty response
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_pos_write=_mark;
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_ringClient = NO_CLIENT; //XXX make else clause later
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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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{ char s[_count+2];
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strncpy(s, (const char*)&(_buffer[_mark+1]), _count);
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s[_count]=0;
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//DIAG(F("RS commit count=%d core %d \"%s\""), _count, xPortGetCoreID(), s);
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}
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_ringClient = NO_CLIENT;
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return true; // commit worked
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}
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void RingStream::flush() {
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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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_flashInsert=NULL; // prepared for first read
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_ringClient = NO_CLIENT;
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}
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