How to implement reading serial data with ANSI color codes and printing out to textbox in color

[lukutis222]

I am getting close to what I am trying to achieve and I have learnt a lot of things about QT while trying to achieve this. Currently, I am having issues of removing brackets("[" and "]") from the text that I receive. The messages that I receive from the remote device:

[1B][0;32mI (504) SEC_GATTS_DEMO: ESP_GATTS_REG_EVT[1B][0m

I have learnt how to replace characters before they are sent to the console for example removing the ANSI color code (0;32m)

const QByteArray data = serial->serial_connection.readAll();
QString DataAsString = QString(data);
DataAsString.replace(QRegularExpression("0;32m"), "");
ui->Console->insertPlainText(DataAsString);

I can also remove the ANSI color code using

DataAsString.replace(QRegularExpression("0;32m"), "");

However, there is this additional bracket that I am not certain where it comes from. Notice the [ and ] brackets highlighted with bold.
[1B] [ 0;32mI (504) SEC_GATTS_DEMO: ESP_GATTS_REG_EVT[1B] [ 0m

I would like to know how can I remove or replace it? This bracket octal code is \133 and I tried the following:

DataAsString.replace(QRegularExpression("\033\1330;32m"), "");
DataAsString.replace(QRegularExpression("\033[0;32m"), "");

But both does not seem to work for some reason. I am not sure why I cannot simple replace the brackets

[JonB]

@lukutis222
[ is a special character to mark the start of list of alternative characters to match till ]. So you need to do something to match a literal [ character.

• Try either \\[ or [[] in your C string for that. [EDIT Forum showing \\[ wrong on this line, I typed two \s, it shows two in preview mode but only one in final mode for some reason, grrr, this forum is very inconsistent in showing some literals inside backticks :( ]
• Personally I prefer \\033 (allow reg ex to see \033, which it interprets as octal character) over \033 (let C embed an actual ASCII 27 character in the string). Same for \133 -> \\133.

Perhaps play with these at regex101. Don't forget that if you are putting into a literal C string anything which works from there may need \ -> \\.

[mpergand]

@lukutis222

Unfortunatly what you're trying to do is not so trivial ...

Here a very basic attempt:

const char ESC=0x1b;            // escape char
const char* RESET="\033[0m";    // reset color

// basic 8 colors
const char *colors[]=
{
    "0;30","black",
    "0;31","red",
    "0;32","green",
    "0;33","yellow",
    "0;34","blue",
    "0;35","purple",
    "0;36","cyan",
    "0;37","white",
    nullptr,"black"
};


struct MsgAttr
{
        QString msg;
        QColor color;
};

bool parseMsg(const QByteArray& data, MsgAttr& attr)
{
    int index=0;
    // by default
    attr.color="black";
    attr.msg=data;
    const char* bytes=data.constData();     // use bytes data

    // search start/end of ansi color code
    if( (bytes[0] == ESC) && (bytes[1] =='[' ) )
        {
        index=2;

        while(bytes[index])   // search ending 'm'
            {
            if(bytes[index] == 'm') break;
            index++;
            }

        if(bytes[index] == 0) return false; // malformed msg
        }

    if(index>0)
        {
        QString colorStr=data.mid(2,index-2);
        int colorIndex=0;

        while(colors[colorIndex++])
            {
            if(colorStr == colors[colorIndex-1])
                attr.color=colors[colorIndex];
            }

        QString msg=data.mid(index+1);
        if(msg.endsWith(RESET))  // remove [0m
            msg.chop(strlen(RESET));

        attr.msg=msg;
        }

    return true;
}

// some text messages
   const char *msg[]=
   {
       "\033[0;30mBlack color\033[0m",
       "\033[0;31mRed color\033[0m",
       "\033[0;32mGreen color\033[0m",
       "\033[0;33mYellow color\033[0m",
       "\033[0;34mBlue color\033[0m",
       "\033[0;35mPurple color\033[0m",
       "\033[0;36mCyan color\033[0m",
       "\033[0;37mWhite color\033[0m",
       "no color",                     // no ansi color
       "\033[0;37mWhite color",        // no reset at the end
       "\033[0;37White color",         // malformed
       nullptr

   };

   MsgAttr attr;

   int m=0;
   while(msg[m])
       {
       bool ok=parseMsg(msg[m],attr);
       qDebug()<<"ok="<<ok<<"color="<<attr.color<<attr.msg;
       m++;
       }

console logs:

ok= true color= QColor(ARGB 1, 0, 0, 0) "Black color"
ok= true color= QColor(ARGB 1, 1, 0, 0) "Red color"
ok= true color= QColor(ARGB 1, 0, 0.501961, 0) "Green color"
ok= true color= QColor(ARGB 1, 1, 1, 0) "Yellow color"
ok= true color= QColor(ARGB 1, 0, 0, 1) "Blue color"
ok= true color= QColor(ARGB 1, 0.501961, 0, 0.501961) "Purple color"
ok= true color= QColor(ARGB 1, 0, 1, 1) "Cyan color"
ok= true color= QColor(ARGB 1, 1, 1, 1) "White color"
ok= true color= QColor(ARGB 1, 0, 0, 0) "no color"
ok= true color= QColor(ARGB 1, 1, 1, 1) "White color"
ok= false color= QColor(ARGB 1, 0, 0, 0) "\u001B[0;37White color"

This example supposes ansi colors are in the form 0;3x
but it could be 3x;0 as well.
see here:
https://gist.github.com/JBlond/2fea43a3049b38287e5e9cefc87b2124
http://jafrog.com/2013/11/23/colors-in-terminal.html

As I said, it's not trivial ;)

[lukutis222]

@JonB

Hello. It has been a while and I have learnt a couple of things since the last time. Since I have changed the logic of incoming data parsing ( using readAll instead of readLine ), the previous solution was no longer valid. I have come up with a simillar solution, It feels like I am very close to achieving what I want but not quite there yet.

My readData function:

    QString error_match = QString("\033\1330;31m");// error
    QString info_match = QString("\033\1330;32m"); // info
    QString warning_match = QString("\033\1330;33m"); //warning



void MainWindow::readData()
{

    // save the scrollbar position
    QScrollBar *scrollbar = ui->Console_read_2->verticalScrollBar();
    bool scrollbarAtBottom  = (scrollbar->value() >= (scrollbar->maximum() - 4));
    int scrollbarPrevValue = scrollbar->value();


    // this moves the cursor to the bottom to avoid writing data in the middle of the console
    QTextCursor cursor = ui->Console_read_2->textCursor();
    cursor.clearSelection();
    cursor.movePosition(QTextCursor::End);
    ui->Console_read_2->setTextCursor(cursor);
    
    QByteArray data = serial_local->serial_connection.readAll(); //read all data
    QString DataAsString = QString(data); // covert  qbytearray to string
    DataAsString.replace("\r", "\n"); // replay ce all \r with \n
    QStringList myStringList = DataAsString.split("\n"); // split all data to multiple lines

    for(int i =0;i < myStringList.length();i++)
    {
        myStringList[i] +=  "\n"; // append new line
        qDebug("myStringList[%i]=%s \n",i,myStringList.at(i).toStdString().c_str());

        //CAPTURE INFO LOGS
        if(myStringList.at(i).contains(info_match)){
            ui->Console_read_2->setTextColor(QColor(0,128,0)); // 'custom' color
            ui->Console_read_2->insertPlainText(myStringList.at(i));
            continue;

        }
         //CAPTURE WARNING LOGS
        else if(myStringList.at(i).contains(warning_match)){
            ui->Console_read_2->setTextColor(QColor(255,165,0)); // 'custom' color
            ui->Console_read_2->insertPlainText(myStringList.at(i));
            continue;

        }
        //CAPTURE ERROR LOGS
        else if(myStringList.at(i).contains(error_match)){
            ui->Console_read_2->setTextColor(QColor(255,0,0)); // 'custom' color
            ui->Console_read_2->insertPlainText(myStringList.at(i));
            continue;

        }
        //All other data with ANSI code is printed in black color
        else{
            ui->Console_read_2->setTextColor(Qt::white); //by default the text will be black
            ui->Console_read_2->insertPlainText(myStringList.at(i));
            continue;

        }

    }


    if (scrollbarAtBottom)
    {
        ui->Console_read_2->ensureCursorVisible();
    }
    else
    {
        ui->Console_read_2->verticalScrollBar()->setValue(scrollbarPrevValue);
    }


}

The external device that I am connected to is sending me bunch of data every 2 seconds

        ESP_LOGI("INFO","this is info log1"); 
        ESP_LOGW("WARNING","this is warning log1");
        ESP_LOGE("ERROR","this is error log1");
        ESP_LOGI("INFO","this is very very very very long info log2");
        ESP_LOGW("WARNING","this is very very very very long warning log2");
        ESP_LOGE("ERROR","this is very very very long error log2");
        ESP_LOGI("INFO","this is info log3");
        ESP_LOGW("WARNING","this is warning log3");
        ESP_LOGE("ERROR","this is error log3");
        printf("This is normal message without ANSI color code \n");
        delay(2000);

My current problems:

• Since I use readAll, there is no guarantee that I will complete line. For example. You can see that in my for loop, I am printing each detected line that I have split with \n:

QStringList myStringList = DataAsString.split("\n"); // split all data to multiple lines

    for(int i =0;i < myStringList.length();i++)
    {
        myStringList[i] +=  "\n"; // append new line
        qDebug("myStringList[%i]=%s \n",i,myStringList.at(i).toStdString().c_str());

On the console application, I see the following:

myStringList[0]=[0;32mI (10872) INFO: this is info log1[0m
 
myStringList[1]=
 
myStringList[2]=[0;33mW (10872) W
 
myStringList[0]=ARNING: this is warning log1[0m
 
myStringList[1]=
 
myStringList[2]=[0;31mE (10872) ERROR: this i
 
myStringList[0]=s error log1[0m
 
myStringList[1]=
 
myStringList[2]=[0;32mI (10872) INFO: this is very very very 
 
myStringList[0]=very long info log2[0m
 
myStringList[1]=
 
myStringList[2]=[0;33mW (10872) WARNING: this is very 
 
myStringList[0]=very very very long warning log2[0m
 
myStringList[1]=
 
myStringList[2]=[0;31mE (10882) ERROR: th
 
myStringList[0]=is is very very very long error log2[0m
 
myStringList[1]=
 
myStringList[2]=[0;32mI (10892) INFO:
 
myStringList[0]= this is info log3[0m
 
myStringList[1]=
 
myStringList[2]=[0;33mW (10892) WARNING: this is warnin
 
myStringList[0]=g log3[0m
 
myStringList[1]=
 
myStringList[2]=[0;31mE (10892) ERROR: this is error log3[0m
 
myStringList[3]=
 
myStringList[4]=This
 
myStringList[0]= is normal message without ANSI color code 
 
myStringList[1]=
 
myStringList[2]=
 
myStringList[0]=[0;32mI (12902) INFO: this is info log1[0m
 
myStringList[1]=
 
myStringList[2]=[0;33mW (12902) W

Lets look at first 4 lines very closely:

myStringList[0]=[0;32mI (10872) INFO: this is info log1[0m
 
myStringList[1]=
 
myStringList[2]=[0;33mW (10872) W
 
myStringList[0]=ARNING: this is warning log1[0m

As you can see from above, I split my data into multiple lines but the line 3 (myStringList[2]) is incomplete. Hence the next line after this one will be also incomplete and will not match with the color code sequence due to the begining lost in the previous line.

• Another issue is that when I split data using:

QStringList myStringList = DataAsString.split("\n"); // split all data to multiple lines,

I can see that almost every other line in my for loop is empty. Is that expected and this is how split works? I feel like it is inefficient and causes additional for loop cycles to go through all lines.

• Is it correct to manually insert new line after every line?

    QStringList myStringList = DataAsString.split("\n"); // split all data to multiple lines
    for(int i =0;i < myStringList.length();i++)
    {
        myStringList[i] +=  "\n"; // append new line

Notice that after I split data into different lines with \n delimiter, I also append \n to the very end of it. If I do not do that, the data will be printed in console without any endlines

According to my understanding, in order to solve my problem I need to know where exactly does the new line starts and I am not sure how can I do that with readAll.

[JonB]

@lukutis222
It's a long post, so here are couple of observations.

I think you might be the same guy who has been asking about "reading lines" in another thread, since I recognise

QStringList myStringList = DataAsString.split("\n"); // split all data to multiple lines,

I did not know you are also the guy for this thread. Are you?? That person was saying incoming lines could end either in \n or in \r (which worries me). Is that you too, or quite separate?

Since I have changed the logic of incoming data parsing ( using readAll instead of readLine )
Since I use readAll, there is no guarantee that I will complete line.
According to my understanding, in order to solve my problem I need to know where exactly does the new line starts and I am not sure how can I do that with readAll.

Indeed, and you will want to code (correctly) for that. I do not know why you are no longer using readLine(), unless you are the other guy with the \r/\n issue. If you need to use readAll() you need to do a proper job to replace readLine/canReadLine(). And I suspect you are not.

Consider input of, say, "Line 1\nLine 2\n Line". The last line does not have a trailing \n, and hence is not complete. That means you must not process it yet as a complete line, you can process the first 2 lines there but must "buffer" the 3rd line to allow further characters to arrive at a future time.

You are using split("\n") to split your input into a list of lines. This is not good enough here. The problem is it will return 3 lines for the list, but you cannot tell from it that the third line did not end in a \n. If the input had been "Line 1\nLine 2\n Line\n" --- note now the trailing \n at the end making the last line complete --- you would get exactly the same result back from split(). So it's not good (precise) enough for this task.

readLine/canReadLine() would not have used split(). It would not divide all its input into lines, it would only have looked for the first newline in the string and dealt with that. Use e.g. QString::indexOf() or QByteArray::indexOf() to search for the first \n in the input. If there is not one then canReadLine() returns false, and you should not call readLine() yet, see how the docs state:

Note that on sequential devices, data may not be immediately available, which may result in a partial line being returned. By calling the canReadLine() function before reading, you can check whether a complete line (including the newline character) can be read.

If it does have a \n then readLine() can be called. Its job is to read up to and including the first \n and return that segment, while removing that from its currently buffered input, so that only the stuff after that \n remain to be read at a future time.

You need to implement similar. And if you are the person who wants to treat \rs like \ns deal with \r instead of \n as the first end-of-line marker appropriately.

I can see that almost every other line in my for loop is empty. Is that expected and this is how split works?

split() does not insert anything into your input/the resulting lines, and does not produce any empty/blank lines which are not in the input. If you are the person who claims that your input has "lines" ending in \r as well as in \n, and if you are presently replacing all \rs by \ns, I said I was never happy with that. If you actually have \r\n at the end of lines you will end up with \n\n and that will cause an unintended blank line. If you are not that person then:

Is it correct to manually insert new line after every line?
myStringList[i] += "\n"; // append new line

That depends on what you will do with the myStringList[] lines. If you append a \n here then you must not also output them with an explicit \n, or use some kind of "writeLine()", as that will lead to a double newline. But since you say

I also append \n to the very end of it. If I do not do that, the data will be printed in console without any endlines

I don't think you are doing that. So cannot answer where blank lines are coming from, analyze your input carefully.

Summary: Get rid of split("\n"), do it properly with e.g. indexOf() just getting the next line out of your buffer and leaving all further stuff to be read/dealt with later.

[lukutis222]

@JonB said in How to implement reading serial data with ANSI color codes and printing out to textbox in color:

readLine()

Yes I am the same guy who want to treat \r like \n and that is exactly the reason why I no longer can use readLine/canReadLine(). I thought posting in this existing thread made more sense than the other one for some reason.
From what I understand, the only way to handle incoming serial data with \r \n is to use readAll but that brings a bunch of new problems that I did not have when using readLine/canReadLine().

I will go through your suggestions very closely and see if I can come up with something clever.. Thank you very much !

UPDATE

• Regarding the every other line in the loop emtpy

You were totally right regarding \n\n. Some data that I read comes with \r\n hence that results with \n\n..

I am now looking into your suggestions about indexOf()

[JonB]

@lukutis222 said in How to implement reading serial data with ANSI color codes and printing out to textbox in color:

Yes I am the same guy who want to treat \r like \n and that is exactly the reason why I no longer can use readLine/canReadLine(). I thought posting in this existing thread made more sense than the other one for some reason.

Ah ha! :) Agreed about continuing your question in this thread, just it would have helped if you had referenced that thread in this one now so that I/people would know! They are related because of your situation.

Now you have a real problem :( Per what you have said/"claimed" that your lines could be terminated by any of just \n, just \r or \r\n. Consider receiving "Line 1\r". Is this a complete line ready to be processed, or is it a partial line waiting for a \n to arrive later? The answer is you cannot tell, you do not know whether the next character will or won't be a \n. So you have a problem with this line, which would require careful coding, and would certainly defeat readLine().

Stop what you are coding now! Go back and look carefully at all the bytes you actually receive (without trying to break them into lines, for now). readLine() can deal with just \n at the end of a line. It can also deal with \r\n (we might take some further action on this, but it will be treated as a line). But it cannot deal with your claim that some lines end in only \r. Come back as & when you are sure whether you really have a \r and no following \n to be treated as a "complete line", or whether actually it's always \r\n....

[lukutis222]

@JonB

Hello. The reason why I want to be able to parse \n, \r and the combination of the two because I want to make my terminal as bulletproof and as much universal as possible.

I have used many terminals such as PuTTy, Termite, MobaXterm and every terminal had disatvantages, for example:

• Termite - not supporting color codes. The controllers that I program always printing in color so its very convenient for me to see different logs in different colors.

• PuTTy - supports color codes but is only for reading the data. It does not allow to write data to external device

• MobaXterm - Supports color codes and seems to work very nicely, however, I didint find a way to write serial data to external device and only reading...

Hence for my first QT project I have decided to create this terminal because I thought it would be good C++ experience and I also I want this terminal to rule them all!

When I am programming my own device, I can sure use only \n. But lets assume some other guy connects its weird device with my terminal and his device only prints with \r.

[JonB]

@lukutis222
Then to cater for "just \n, just \r or \r\n" you will have to code appropriately, you can't use readLine() and you will have to do the necessary coding yourself (remember what I said about the "ambiguity" of the input read into the buffer ending in just \r). That is the answer.

[lukutis222]

@JonB

I was also not aware that readAll() automatically inserts \r in between different lines.

My remote device is sending the following data:

        printf("This is normal message1 without ANSI color code \n");
        printf("This is normal message2 without ANSI color code \n");
        printf("This is normal message3 without ANSI color code \n");
        printf("This is normal message4 without ANSI color code \n");
        printf("This is normal message5 without ANSI color code \n");
        printf("This is normal message6 without ANSI color code \n");
        printf("This is normal message7 without ANSI color code \n");
        printf("This is normal message8 without ANSI color code \n");
delay(2000);

As you can see from above, I use only \n termination.

In my readData() funciton I do the following(Notice that I do not replace \r with \n at the moment)

    QByteArray data = serial_local->serial_connection.readAll(); //read all data
    QString DataAsString = QString(data); // covert  qbytearray to string
    uint16_t received_data_length = DataAsString.length();
    //DataAsString.replace("\r", "\n"); // replay ce all \r with \n
    qDebug("****FULL DATA***** = %s \n",DataAsString.toStdString().c_str());
    qDebug("*****FULL DATA length***** = %u \n",received_data_length);
    //print all raw bytes
    for(int i = 0; i <received_data_length;i++){
        qDebug("%u\n",DataAsString[i]);
    }

The application output:

****FULL DATA***** = This is normal message1 without ANSI color code 
This is normal 
*****FULL DATA length***** = 64 
84
104
105
115
32
105
115
32
110
111
114
109
97
108
32
109
101
115
115
97
103
101
49
32
119
105
116
104
111
117
116
32
65
78
83
73
32
99
111
108
111
114
32
99
111
100
101
32
13
10
84
104
105
115
32
105
115
32
110
111
114
109
97
108

Notice that there is decimal 13 and 10 (carriage return and new line). I am trying to understand how did carriage return appear here if I do not send it.

This is confusing because I do not know if I should do indexOf('\n') or indexOf('\r'). If readAll automatically inserts \r between different lines it would make more sense to detect a complete line with \r

[Christian Ehrlicher]

@lukutis222 said in How to implement reading serial data with ANSI color codes and printing out to textbox in color:

I was also not aware that readAll() automatically inserts \r in between different lines.

readAll() does not modify any data read from the io device.

[lukutis222]

@Christian-Ehrlicher
I cannot wrap my head around how does \r appear in the serial data then... The remote device that I am connected to only sends \n

[Christian Ehrlicher]

@lukutis222 said in How to implement reading serial data with ANSI color codes and printing out to textbox in color:

I cannot wrap my head around how does \r appear in the serial data then...

Please output the QByteArray data, not the one converted to QString (for whatever reason binary data should be converted to a QString though).

[lukutis222]

@Christian-Ehrlicher

    QByteArray data = serial_local->serial_connection.readAll(); //read all data
    QString DataAsString = QString(data); // covert  qbytearray to string
    uint16_t received_data_length = DataAsString.length();

    for(int i = 0; i <received_data_length;i++){
        qDebug("%u\n",DataAsString[i]);
    }
    qDebug("****RAW DATA***** \n");
    for(int i = 0; i <data.length();i++){
        qDebug("%u\n",data[i]);
    }

Both identical.
Does that mean that my remote device "secretly" slips in another \r without me even wanting ?

[Christian Ehrlicher]

@lukutis222 said in How to implement reading serial data with ANSI color codes and printing out to textbox in color:

Does that mean that my remote device "secretly" slips in another \r without me even wanting ?

Yes

[lukutis222]

I think I managed to achieve what I want (didint test 100% but I believe I am getting very close). I want to share the current logic, perhaps you can advise on how to improve it.

void MainWindow::readData()
{
    // save the scrollbar position
    QScrollBar *scrollbar = ui->Console_read_2->verticalScrollBar();
    bool scrollbarAtBottom  = (scrollbar->value() >= (scrollbar->maximum() - 4));
    int scrollbarPrevValue = scrollbar->value();

    // this moves the cursor to the bottom to avoid writing data in the middle of the console
    QTextCursor cursor = ui->Console_read_2->textCursor();
    cursor.clearSelection();
    cursor.movePosition(QTextCursor::End);
    ui->Console_read_2->setTextCursor(cursor);

    QByteArray data = serial_local->serial_connection.readAll(); //read all data
    QString DataAsString = QString(data); // covert  qbytearray to string
    static QString incomplete_line = nullptr; // hold information about the last incomplete line
    uint16_t beggining_pointer = 0; // save the beggining pointer
    
    DataAsString.replace("\r", "\n"); // replace all \r with \n
    DataAsString.replace("\n\n", "\n"); // this ensures that all double \n\n (if exist) will be replaces with just a single \n

    int index = DataAsString.indexOf('\n');
    
    while (index != -1) {
        QString complete_line = DataAsString.mid(beggining_pointer, index-(beggining_pointer)); // index is where the \n was found in the string.
        complete_line = incomplete_line+complete_line; // append beggining of incomplete line to complete line (initially incomplete line will be empty)
        incomplete_line = nullptr; // reset the incomplete line after each append because its no longer relevant
        Format_and_insert(complete_line); // insert data to console
        beggining_pointer = index+1; // increment beggining pointer to the location where the previous \n was found because this will now be our beggining pointer
        index = DataAsString.indexOf('\n', index+1);

    }

     incomplete_line = DataAsString.mid(beggining_pointer, DataAsString.length()); // after going through every line, take the last beggining pointer and read till the end of string.

    if (scrollbarAtBottom)
    {
        ui->Console_read_2->ensureCursorVisible();
    }
    else
    {
        ui->Console_read_2->verticalScrollBar()->setValue(scrollbarPrevValue);
    }


}

I am reading line by line and when I find an uncomplete line, I save it in the incomplete_line buffer and use it on the next iteration.

[Christian Ehrlicher]

And now you're again simulating readLine()/canReadLine()...

[JonB]

@Christian-Ehrlicher
Which is what OP is wanting to do. His problem is that he wishes to treat \r, without requiring a following \n, as a line end. I have verified that Qt code for all of canReadLine/readLine/readLineData() have \n hard-coded in their logic. It is not possible to use these existing ones if you want to treat a bare \r as an acceptable line-ender. (In fact, he wishes to treat any/all of \n, \r or \r\n as line terminators, which complicates things.) While the proposed code above is "rough and ready", and has some flaws, and I personally was not prepared to write the full code of what he wants, if he is happy with this "approximation" it would seem that it would give him what he wants.

Of course, if he did not insist on accepting \r as a line terminator it would be a whole lot simpler....

[Christian Ehrlicher]

@JonB Overread this.

Still the code looks ugly and over-complicated

void parseBuffer()
{
  auto findNextSeparator = [](const QByteArray &ba, int startOfs) {
    for (int i = startOfs; i < ba.size(); ++i) {
      auto c = ba[i];
      if (c == '\n' || c == '\r') {
        return i;
      }
    }
    return -1;
  };
  auto fromIdx = 0;
  idx = findNextSeparator(m_buffer, fromIdx );
  while (idx >= 0) {
    auto line = m_buffer.mid(fromIdx , idx - fromIdx);
    if (!line.isEmpty())
      emit newLineReceived(line);
    fromIdx = idx + 1;
  }
  m_buffer = m_buffer.mid(fromIdx);
}

Did not check if '\r' or '\n' is in the 'line' buffer - maybe this needs a +/-1 adjustment.

[JonB]

@Christian-Ehrlicher
Please do not take this wrong, but your code is a touch simplistic. I don't blame you, as I was not prepared to write a comprehensive implementation!

Per the user's requirements, for example it fails to distinguish between incoming \r\n --- one line --- versus \n\n --- a line followed by a genuine blank line. It also does not deal with end-of-file at the end of a final line which has no \r or \n. It does not tell the OP when he needs to call readAll() to fetch more characters for the buffer, and address what to do if that returns eof. It does not deal well with the (unlikely but possible?) case where a readAll() returns a line ending in \r because that is all that has been received so far, when in fact the next character received in the future will be a \n after the \r. I am not saying his code deals with all of these cases either!

All of which is what I thought about when deciding whether I wished to offer the full, robust code, and decided not to... :)

Nonetheless, perhaps the OP will adapt your code to whatever situations he wants to cover.