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dfd1e745480fabd88139d2804acb90d5b6dc055e
secondo/Algebras/IMEX/aisdecode.cpp
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2026-01-23 17:03:45 +08:00

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/*
----
This file is part of SECONDO.
Copyright (C) 2017, University in Hagen,
Faculty of Mathematics and Computer Science,
Database Systems for New Applications.
SECONDO 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.
SECONDO 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 SECONDO; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
----
*/
#include "aisdecode.h"
#include <iostream>
#include <fstream>
#include <string>
#include <sstream>
#include <set>
#include <stdlib.h>
#include <bitset>
#include <vector>
#include <assert.h>
#include <map>
#include <stdint.h>
#include <algorithm>
namespace aisdecode{
/*
1 Auxiliary functions
*/
const char chartbl[] = "@ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"[\\]^- !\"#$%&`()*+,-./0123456789:;<=>?";
void trim(std::string& str, std::string whiteSpaces=" \r\n\t") {
std::string::size_type pos = str.find_last_not_of(whiteSpaces);
if(pos != std::string::npos) {
str.erase(pos + 1);
pos = str.find_first_not_of(whiteSpaces);
if(pos != std::string::npos){
str.erase(0, pos);
}
} else {
str.erase(str.begin(), str.end());
}
}
/*
2 Implementation of class Message
*/
template<int size>
void Message<size>::setMessage(const std::string& _msg){
msg = _msg;
size_t ssize = getStringSize();
if(msg.size() < ssize){
std::cerr << "expected minimum size is " << ssize << std::endl;
std::cerr << "got message of length " << msg.length() << std::endl;
throw 1001;
}
createMsg();
}
template<int size>
void Message<size>::createMsg(){
int s = getStringSize();
for(int i=0;i<s;i++){
unsigned long c = msg[i];
c = c - '0';
if(c>40) c = c - 8;
message = (message << 6);
message |= std::bitset<size>((unsigned long)c);
}
}
template<int size>
std::string Message<size>::extractString(int start, int end) const{
std::bitset<size> b = ((message >> (size - (end+1) ) ));
int len = (end - start) +1;
assert(len % 6 == 0); // must be a multiple of 6
len = len / 6; // number of chars
std::string chars(len,'@');
static std::bitset<size> mask(std::string("111111"));
for(int i=0;i<len;i++){
unsigned char c = (char)((b & mask).to_ulong());
assert(c<0xf3);
chars[len-(i+1)] = chartbl[c];
b = (b >> 6);
}
std::replace(chars.begin(), chars.end(),'@',' ');
trim(chars);
return chars;
}
template<int size>
double Message<size>::computeLat(unsigned int rlat) const{
if(rlat == 0x3412140){ // special value for nbot available
return 91;
}
int lat = rlat;
if(rlat >= 0x4000000){
lat = 0x8000000 - rlat;
lat = -lat;
}
return lat/600000.0;
}
template<int size>
double Message<size>::computeLon(unsigned int rlon) const{
if(rlon == 0x6791AC0){ // special value
return 181;
}
int lon = rlon;
if(rlon >= 0x8000000){
lon = 0x10000000 - rlon;
lon = -lon;
}
return lon / 600000.0;
}
template<int size>
std::string Message<size>::decodeText(const std::string& text) const{
std::string text2(text.length(),'@');
for(size_t i=0;i<text.length();i++){
char c = text[i] - '0';
if(c>40) c = c-8;
text2[i] = chartbl[(int)c];
}
return text2;
}
/*
3 Implementation of MultiLineMessage
*/
MultiLineMessage::MultiLineMessage(int fragmentcount, int fragmentnumber,
const std::string& fragment,
int messageId, const std::string& rcc){
for(int i=0;i<fragmentcount;i++){
fragments.push_back("");
}
fragments[fragmentnumber-1] = fragment;
fragmentsAvailable = 1;
this->message_Id = messageId;
this->rcc = rcc;
}
void MultiLineMessage::add(int fragmentcount, int fragmentnumber,
const std::string& fragment,
int messageId, const std::string& rcc){
if( ((size_t) fragmentcount != fragments.size())
|| (fragmentnumber < 1)
|| ((size_t) fragmentnumber > fragments.size())
|| (fragments[fragmentnumber-1] !="")
|| (this->rcc != rcc) ){
throw 1002;
}
fragments[fragmentnumber-1] = fragment;
fragmentsAvailable++;
}
std::string MultiLineMessage::getMessage() const{
assert(isComplete());
std::stringstream ss;
for(size_t i=0;i<fragments.size();i++){
ss << fragments[i];
}
return ss.str();
}
/*
4 Message1-3
*/
void Message1_3::print()const{
std::cout << "-----------------------------------------------" << std::endl;
std::cout << "messagetype " << messageType << std::endl;
std::cout << "repeatIndicator " << repeatIndicator << std::endl;
std::cout << "mmsi " << mmsi << std::endl;
std::cout << "status " << status << std::endl;
std::cout << "rate of turn " << rot << std::endl;
std::cout << "speed over ground " << sog << std::endl;
std::cout << "accuracy " << accuracy << std::endl;
std::cout << "longitude " << longitude << std::endl;
std::cout << "latitude " << latitude << std::endl;
std::cout << "course over ground " << cog << std::endl;
std::cout << "heading " << heading << std::endl;
std::cout << "second " << second << std::endl;
std::cout << "maneuver " << maneuver << std::endl;
std::cout << "spare " << spare << std::endl;
std::cout << "raim " << raim << std::endl;
std::cout << "radio status " << rstatus << std::endl;
if(msg.length()>28){
std::cout << "more information available " << std::endl;
}
std::cout << "----------------------------------------------" << std::endl;
}
void Message1_3::extractInfos(){
messageType = extract(0,5);
repeatIndicator = extract(6,7);
mmsi = extract(8,37);
status = extract(38,41);
rot = extract(42,49);
sog = extract(50,59);
accuracy = extract(60,60);
unsigned int lon = extract(61,88);
longitude = computeLon(lon);
unsigned int lat = extract(89,115);
latitude = computeLat(lat);
cog = extract(116,127);
heading = extract(128,136);
second = extract(137,142);
maneuver = extract(143,144);
spare = extract(145,147);
raim = extract(148,148);
rstatus = extract(149,167);
}
/*
4 Message4
*/
void Message4::print()const{
std::cout << "--------------------------------------------" << std::endl;
std::cout << "type " << type << std::endl;
std::cout << "repeat " << repeat << std::endl;
std::cout << "mmsi " << mmsi << std::endl;
std::cout << "year " << year << std::endl;
std::cout << "month " << month << std::endl;
std::cout << "day " << day << std::endl;
std::cout << "hour " << hour << std::endl;
std::cout << "minute " << minute << std::endl;
std::cout << "second " << second << std::endl;
std::cout << "fix " << fix << std::endl;
std::cout << "longitude " << (longitude / 600000.0) << std::endl;
std::cout << "latitude " << (latitude / 600000.0) << std::endl;
std::cout << "epfd " << epfd << std::endl;
std::cout << "spare " << spare << std::endl;
std::cout << "raim " << raim << std::endl;
std::cout << "sotdma " << sotdma << std::endl;
if(msg.length()>28){
std::cout << "more information available " << std::endl;
}
std::cout << "--------------------------------------------" << std::endl;
}
void Message4::extractInfos(){
type = extract(0,5);
repeat = extract(6,7);
mmsi = extract(8,37);
year = extract(38,51);
month = extract(52,55);
day = extract(56,60);
hour = extract(61,65);
minute = extract(66,71);
second = extract(72,77);
fix = extract(78,78);
longitude = computeLon(extract(79,106));
latitude = computeLat(extract(107,133));
epfd = extract(134,137);
spare = extract(138,147);
raim = extract(148,148);
sotdma = extract(149,167);
assert(type==4);
}
/*
5 Message5
*/
void Message5::print() const{
std::cout << "--------------------------------------" << std::endl;
std::cout << "type : " << type << std::endl;
std::cout << "repeat : " << repeat << std::endl;
std::cout << "mmsi :" << mmsi << std::endl;
std::cout << "ais_version " << ais_version << std::endl;
std::cout << "imo " << imo << std::endl;
std::cout << "callSign " << callSign << std::endl;
std::cout << "vesselName " << vesselName << std::endl;
std::cout << "shiptype " << shipType << std::endl;
std::cout << "dimToBow " << dimToBow << std::endl;
std::cout << "dimToStern " << dimToStern << std::endl;
std::cout << "dimToPort " << dimToPort << std::endl;
std::cout << "dimToStarboard" << dimToStarboard << std::endl;
std::cout << "epfd " << epfd << std::endl;
std::cout << "month " << month << std::endl;
std::cout << "day " << day << std::endl;
std::cout << "hour " << hour << std::endl;
std::cout << "minute " << minute << std::endl;
std::cout << "draught " << draught << std::endl;
std::cout << "destination " << destination << std::endl;
std::cout << "dte " << dte << std::endl;
std::cout << "--------------------------------------" << std::endl;
}
void Message5::extractInfos(){
type = extract(0,5);
repeat = extract(6,7);
mmsi = extract(8,37);
ais_version = extract(38,39);
imo = extract(40,69);
callSign = extractString(70,111);
vesselName = extractString(112,231);
shipType = extract(232,239);
dimToBow = extract(240,248);
dimToStern = extract(249,257);
dimToPort = extract(258,263);
dimToStarboard = extract(264,269);
epfd = extract(270,273);
month = extract(274,277);
day = extract(278,282);
hour = extract(283,287);
minute = extract(288,293);
draught = extract(294,301);
destination = extractString(302,421);
dte = extract(422,422);
assert(type==5);
}
/*
6 Message9
*/
void Message9::print()const{
std::cout << "type " << type << std::endl;
std::cout << "repeat " << repeat << std::endl;
std::cout << "mmsi " << mmsi << std::endl;
std::cout << "alt " << alt << std::endl;
std::cout << "sog " << sog << std::endl;
std::cout << "accuracy " << accuracy << std::endl;
std::cout << "longitude " << longitude << std::endl;
std::cout << "latitude " << latitude << std::endl;
std::cout << "cog " << cog << std::endl;
std::cout << "second " << second << std::endl;
std::cout << "reserved " << reserved << std::endl;
std::cout << "dte " << dte << std::endl;
std::cout << "assigned " << assigned << std::endl;
std::cout << "raim " << raim << std::endl;
std::cout << "radio " << radio << std::endl;
}
void Message9::extractInfos(){
type = extract(0,5);
repeat = extract(6,7);
mmsi = extract(30,37);
alt = extract(38,49);
sog = extract(50,59);
accuracy = extract(60,60);
longitude = computeLon(extract(61,88));
latitude = computeLat(extract(89,115));
cog = extract(116,127);
second = extract(128,133);
reserved = extract(134,141);
dte = extract(142,142);
assigned = extract(146,146);
raim = extract(147,147);
radio = extract(148,167);
assert(type==9);
}
/*
8 Message12
*/
void Message12::print()const{
std::cout << "-----------------------------------" << std::endl;
std::cout << "type " << type << std::endl;
std::cout << "repeat " << repeat << std::endl;
std::cout << "source " << source_mmsi << std::endl;
std::cout << "sequence number " << sequence_number << std::endl;
std::cout << "dest " <<dest_mmsi << std::endl;
std::cout << "retransmit " << retransmit << std::endl;
std::cout << "text " << text << std::endl;
std::cout << "-----------------------------------" << std::endl;
}
void Message12::extractInfos(){
type = extract(0,5);
repeat = extract(6,7);
source_mmsi = extract(8,37);
sequence_number = extract(38,39);
dest_mmsi = extract(40,69);
retransmit = extract(70,70);
text = decodeText(omsg.substr(12));
assert(type==12);
}
/*
9 Message14
*/
void Message14::print()const{
std::cout << "---------------------------------" << std::endl;
std::cout << " type " << type << std::endl;
std::cout << " repeat " << repeat << std::endl;
std::cout << " mmsi " << mmsi << std::endl;
std::cout << " text " << text << std::endl;
std::cout << "---------------------------------" << std::endl;
}
void Message14::extractInfos(){
type = extract(0,5);
repeat = extract(6,7);
mmsi = extract(8,37);
//std::cout << "tbit = " << tbit << std::endl;
text = extractString(40,1007-2);
int textlength = omsg.length() - 8;
text = text.substr(0,textlength);
assert(type==14);
}
/*
10 Message18
*/
void Message18::print()const{
std::cout << "type " << type << std::endl;
std::cout << "repeat " << repeat << std::endl;
std::cout << "mmsi " << mmsi << std::endl;
std::cout << "reserved1 " << reserved1 << std::endl;
std::cout << "sog " << sog << std::endl;
std::cout << "accuracy " << accuracy << std::endl;
std::cout << "longitude " << longitude << std::endl;
std::cout << "latitude " << latitude << std::endl;
std::cout << "cog " << cog << std::endl;
std::cout << "heading " << heading << std::endl;
std::cout << "second " << second << std::endl;
std::cout << "reserved2 " << reserved2 << std::endl;
std::cout << "cs " << cs << std::endl;
std::cout << "display " << display << std::endl;
std::cout << "dsc " << dsc << std::endl;
std::cout << "band " << band << std::endl;
std::cout << "msg22 " << msg22 << std::endl;
std::cout << "assigned " << assigned << std::endl;
std::cout << "raim " << raim << std::endl;
std::cout << "radio " << radio << std::endl;
}
void Message18::extractInfos(){
type = extract(0,5);
repeat = extract(6,7);
mmsi = extract(8,37);
reserved1 = extract(38,45);
sog = extract(46,55);
accuracy = extract(56,56);
longitude = computeLon(extract(57,84));
latitude = computeLat(extract(85,111));
cog = extract(112,123);
heading = extract(124,132);
second = extract(133,138);
reserved2 = extract(139,140);
cs = extract(141,141);
display = extract(142,142);
dsc = extract(143,143);
band = extract(144,144);
msg22 = extract(145,145);
assigned = extract(146,146);
raim = extract(147,147);
radio = extract(148,167);
assert(type==18);
}
/*
11 Message19
*/
void Message19::print()const{
std::cout << "type" << type << std::endl;
std::cout << "repeat" << repeat << std::endl;
std::cout << "mmsi " << mmsi << std::endl;
std::cout << "reserved " << reserved << std::endl;
std::cout << "sog " << sog << std::endl;
std::cout << "accuracy " << accuracy << std::endl;
std::cout << "longitude " << longitude << std::endl;
std::cout << "latitude " << latitude << std::endl;
std::cout << "cog " << cog << std::endl;
std::cout << "heading " << heading << std::endl;
std::cout << "second " << second << std::endl;
std::cout << "reserved2 " << reserved2 << std::endl;
std::cout << "name " << name << std::endl;
std::cout << "shiptype " << shiptype << std::endl;
std::cout << "dimToBow " << dimToBow << std::endl;
std::cout << "dimToStern " << dimToStern << std::endl;
std::cout << "dimToPort " << dimToPort << std::endl;
std::cout << "dimToStarboard " << dimToStarboard << std::endl;
std::cout << "epfd " << epfd << std::endl;
std::cout << "raim " << raim << std::endl;
std::cout << "dte " << dte << std::endl;
std::cout << "assigned " << assigned << std::endl;
}
void Message19::extractInfos(){
type = extract(0,5);
repeat = extract(6,7);
mmsi = extract(8,37);
reserved = extract(38,45);
sog = extract(46,55);
accuracy = extract(56,56);
longitude = computeLon(extract(57,84));
latitude = computeLat(extract(85,111));
cog = extract(112,123);
heading = extract(124,132);
second = extract(133,138);
reserved2 = extract(139,142);
name = extractString(143,262);
shiptype = extract(263,270);
dimToBow = extract(271,279);
dimToStern = extract(280,288);
dimToPort = extract(289,294);
dimToStarboard = extract(295,300);
epfd = extract(301,304);
raim = extract(305,305);
dte = extract(306,306);
assigned = extract(307,307);
assert(type==19);
}
/*
13 Message24
*/
void Message24::print()const{
std::cout << "type " << type << std::endl;
std::cout << "repeat " << repeat << std::endl;
std::cout << "mmsi " << mmsi << std::endl;
std::cout << "partno " << partno << std::endl;
std::cout << "shipsname " << shipsname << std::endl;
std::cout << "shiptype " << shiptype << std::endl;
std::cout << "vendorid " << vendorid << std::endl;
std::cout << "model " << model << std::endl;
std::cout << "serial " << serial << std::endl;
std::cout << "callsign " << callsign << std::endl;
std::cout << "dimToBow " << dimToBow << std::endl;
std::cout << "dimToStern " << dimToStern << std::endl;
std::cout << "dimToPort " << dimToPort << std::endl;
std::cout << "dimToStarboard " << dimToStarboard << std::endl;
std::cout << "mothership_mmsi " << mothership_mmsi << std::endl;
}
void Message24::extractInfos(){
type = extract(0,5);
repeat = extract(6,7);
mmsi = extract(8,37);
partno = extract(38,39);
shipsname = extractString(40,159);
shiptype = extract(40,47);
vendorid = extract(48,65);
model = extract(66,69);
serial = extract(70,89);
callsign = extractString(90,131);
dimToBow = extract(132,140);
dimToStern = extract(141,149);
dimToPort = extract(150,155);
dimToStarboard = extract(156,161);
mothership_mmsi = extract(132,161);
assert(type==24);
}
/*
20 class aisdecoder
*/
aisdecoder::aisdecoder(const std::string& filename) {
in.open(filename.c_str(),std::ios::in);
buffer = 0;
if(in){
const int FILE_BUFFER_SIZE = 10485760;
buffer = new char[FILE_BUFFER_SIZE];
in.rdbuf()->pubsetbuf(buffer, FILE_BUFFER_SIZE);
}
}
MessageBase* aisdecoder::getNextMessage(){
while(!in.eof() && in.good()){
getline(in,line);
MessageBase* msg = 0;
try{
msg = decodeLine(line,0);
} catch(...){
std::cerr << "Exception during decoding line " << line << std::endl;
}
if(msg){
return msg;
}
}
try{
in.close();
} catch(...) {}
return 0;
}
MessageBase* aisdecoder::getNextMessage(const int type){
while(!in.eof() && in.good()){
getline(in,line);
MessageBase* msg = 0;
try{
msg = decodeLine(line,type);
} catch(...){
std::cerr << "Exception during decoding line " << line << std::endl;
}
if(msg){
return msg;
}
}
try{
in.close();
} catch(...) {}
return 0;
}
MessageBase* aisdecoder::decodeLine(const std::string& line, const int type){
if(line.size()==0){ // ignore empty lines
return 0;
}
size_t pos = line.find(",");
if(pos==std::string::npos){
std::cerr << "invalid line format, no comma inside" << std::endl;
std::cerr << "line is " << line << std::endl;
return 0;
}
std::string talker = line.substr(0,pos);
if(talker.length()==6 && talker[0]=='!' && talker.substr(3,2)=="VD"){
return decodevdms(line, type);
} else if(talker=="$PVOL"){
return 0; // heartbeat message, ignore
} else {
std::cerr << "unknown talker: " << talker << std::endl;
return 0;
}
}
MessageBase* aisdecoder::decodevdms(const std::string& line, const int type){
std::string talker = line.substr(1,2);
size_t pos1 = 0;
size_t pos2 = line.find(",");
std::string tmp;
if(!getNextPart(line,pos1,pos2,tmp)){
std::cerr << "cannot extract framecount" << std::endl;
std::cerr << "line is " << line << std::endl;
return 0;
}
int fragmentcount = str2int(tmp);
if(!getNextPart(line,pos1,pos2,tmp)){
std::cerr << "cannot extract frame number in line '"
<< line << "'" << std::endl;
std::cerr << "line is " << line << std::endl;
return 0;
}
int fragmentnumber = str2int(tmp);
if(!getNextPart(line,pos1,pos2,tmp)){
std::cerr << "cannot extract message id" << std::endl;
std::cerr << "line is " << line << std::endl;
return 0;
}
int messageId = str2int(tmp);
if(!getNextPart(line,pos1,pos2,tmp)){
std::cerr << "cannot extract radio channel code" << std::endl;
std::cerr << "line is " << line << std::endl;
return 0;
}
std::string rcc = tmp;
if(!getNextPart(line,pos1,pos2,tmp)){
std::cerr << "cannot extract message " << std::endl;
std::cerr << "line is " << line << std::endl;
return 0;
}
std::string msg = tmp;
if(msg.length()<1){
return 0;
}
// extract type and filter out if type not fits
int t = msg[0] - '0';
if(t>40) t -= 8;
if(type>0 && t!=type){
return 0;
}
pos1 = pos2;
pos1++;
pos2 = line.find(",",pos1);
std::string fill = pos2==std::string::npos
? line.substr(pos1, std::string::npos)
: line.substr(pos1, pos2-pos1);
if(fill.size()!=4){
std::cerr << "invalid length of fill" << std::endl;
std::cerr << "fill is " << fill << std::endl;
std::cerr << "line is " << line << std::endl;
return 0;
}
if( fill[1] != '*'){
std::cerr << "missing '*' in last field" << std::endl;
std::cerr << "line is " << line << std::endl;
return 0;
}
int check = atoi(("0x"+fill.substr(2)).c_str());
std::string rest = pos2 == std::string::npos
? line.substr(pos1,std::string::npos)
: "";
return decodeLine(talker, fragmentcount, fragmentnumber, messageId, rcc,
msg, fill[0]-'0', check, rest);
}
MessageBase* aisdecoder::decodeLine(std::string& talker,
int fragmentcount,
int fragmentnumber,
int messageId,
std::string& rcc,
std::string& msg,
int fill,
int check,
std::string& rest){
if(fragmentcount > 1){
if(incompleteMessages.find(messageId)==incompleteMessages.end()){
MultiLineMessage mlm(fragmentcount, fragmentnumber, msg, messageId,rcc);
incompleteMessages[messageId] = mlm;
} else {
try{
incompleteMessages[messageId].add(fragmentcount, fragmentnumber,
msg, messageId,rcc);
} catch(int err){
incompleteMessages.erase(messageId);
MultiLineMessage mlm(fragmentcount, fragmentnumber, msg,
messageId,rcc);
incompleteMessages[messageId] = mlm;
}
}
MultiLineMessage mlm = incompleteMessages[messageId];
if(mlm.isComplete()){
incompleteMessages.erase(messageId);
return decode(mlm);
}
return 0;
}
if(msg.length() < 1){
std::cerr << "empty message" << std::endl;
return 0;
}
int messagenumber = msg[0] - 48;
if(messagenumber > 40){
messagenumber = messagenumber - 8;
}
if(messagenumber <1 || messagenumber > 27){
std::cerr << "invalid message number " << messagenumber << std::endl;
return 0;
}
return decode(messagenumber, msg);
}
MessageBase* aisdecoder::decode(const MultiLineMessage& mlm){
assert(mlm.isComplete());
std::string msg = mlm.getMessage();
if(msg.size()<1){
std::cerr << "found empty multi line message";
return 0;
}
int messagenumber = msg[0] - 48;
if(messagenumber > 40){
messagenumber = messagenumber - 8;
}
return decode(messagenumber,msg);
}
MessageBase* aisdecoder::decode(const int messagenumber,
const std::string& msg) {
try{
switch(messagenumber){
case 1:
case 2:
case 3: return new Message1_3(msg);
case 4: return new Message4(msg);
case 5: return new Message5(msg);
case 9: return new Message9(msg);
case 12: return new Message12(msg);
case 14: return new Message14(msg);
case 18: return new Message18(msg);
case 19: return new Message19(msg);
case 24: return new Message24(msg);
default: std::cerr << "aisdecoder: message type " << messagenumber
<< "not implemented yet" << std::endl;
return 0;
}
} catch(int ex){
std::cerr << "exception during processing message " << messagenumber
<< std::endl;
std::cerr << "message is " << msg << std::endl;
std::cerr << "message's length : " << msg.length() << std::endl;
std::cerr << "Exception is " << ex << std::endl;
return 0;
} catch(...){
std::cerr << " unknown exception during processing message "
<< messagenumber << std::endl;
return 0;
}
return 0;
}
bool aisdecoder::getNextPart(const std::string& line, size_t& pos1,
size_t&pos2, std::string& result){
pos1 = pos2;
pos1++;
pos2 = line.find(",",pos1);
if(pos2==std::string::npos){
result = "";
return false;
}
result = line.substr(pos1, pos2-pos1);
return true;
}
} // end of namespace
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