QT String to char * adds extra characters
I have a qTextEdit
that I grab the text from (QString
) and convert to a char*
with this code:
QString msgQText = ui->textMsg->toPlainText();
size_t textSize = (size_t)msgQText.size();
if (textSize > 139) {
textSize = 139;
}
unsigned char * msgText = (unsigned char *)malloc(textSize);
memcpy(msgText, msgQText.toLocal8Bit().data(), textSize);
msgText[textSize] = '';
if (textSize > 0) {
Msg * newTextMsg = new Msg;
newTextMsg->type = 1; // text message type
newTextMsg->bitrate = 0;
newTextMsg->samplerate = 0;
newTextMsg->bufSize = (int)textSize;
newTextMsg->len = 0;
newTextMsg->buf = (char *)malloc(textSize);
memcpy((char *)newTextMsg->buf, (char *)msgText, textSize);
lPushToEnd(sendMsgList, newTextMsg, sizeof(Msg));
ui->sendRecList->addItem((char *)newTextMsg->buf);
ui->textMsg->clear();
}
I put the text into a qListBox
, but it shows up like
However, the character array, if I print it out, does not have the extra characters.
I have tried checking the "compile using UTF-8" option, but it doesn't make a difference.
Also, I send the text using RS232, and the receiver side also displays the extra characters.
The receiver code is here:
m_serial->waitForReadyRead(200);
const QByteArray data = m_serial->readAll();
if (data.size() > 0) {
qDebug() << "New serial data: " << data;
QString str = QString(data);
if (str.contains("0x6F8C32E90A")) {
qDebug() << "TEST SUCCESSFUL!";
}
return data.data();
} else {
return NULL;
}
qt
add a comment |
I have a qTextEdit
that I grab the text from (QString
) and convert to a char*
with this code:
QString msgQText = ui->textMsg->toPlainText();
size_t textSize = (size_t)msgQText.size();
if (textSize > 139) {
textSize = 139;
}
unsigned char * msgText = (unsigned char *)malloc(textSize);
memcpy(msgText, msgQText.toLocal8Bit().data(), textSize);
msgText[textSize] = '';
if (textSize > 0) {
Msg * newTextMsg = new Msg;
newTextMsg->type = 1; // text message type
newTextMsg->bitrate = 0;
newTextMsg->samplerate = 0;
newTextMsg->bufSize = (int)textSize;
newTextMsg->len = 0;
newTextMsg->buf = (char *)malloc(textSize);
memcpy((char *)newTextMsg->buf, (char *)msgText, textSize);
lPushToEnd(sendMsgList, newTextMsg, sizeof(Msg));
ui->sendRecList->addItem((char *)newTextMsg->buf);
ui->textMsg->clear();
}
I put the text into a qListBox
, but it shows up like
However, the character array, if I print it out, does not have the extra characters.
I have tried checking the "compile using UTF-8" option, but it doesn't make a difference.
Also, I send the text using RS232, and the receiver side also displays the extra characters.
The receiver code is here:
m_serial->waitForReadyRead(200);
const QByteArray data = m_serial->readAll();
if (data.size() > 0) {
qDebug() << "New serial data: " << data;
QString str = QString(data);
if (str.contains("0x6F8C32E90A")) {
qDebug() << "TEST SUCCESSFUL!";
}
return data.data();
} else {
return NULL;
}
qt
Note that you're writing off the end of the allocated buffer when you domsgText[textSize] = '';
. That's undefined behaviour.
– G.M.
Nov 13 '18 at 14:32
add a comment |
I have a qTextEdit
that I grab the text from (QString
) and convert to a char*
with this code:
QString msgQText = ui->textMsg->toPlainText();
size_t textSize = (size_t)msgQText.size();
if (textSize > 139) {
textSize = 139;
}
unsigned char * msgText = (unsigned char *)malloc(textSize);
memcpy(msgText, msgQText.toLocal8Bit().data(), textSize);
msgText[textSize] = '';
if (textSize > 0) {
Msg * newTextMsg = new Msg;
newTextMsg->type = 1; // text message type
newTextMsg->bitrate = 0;
newTextMsg->samplerate = 0;
newTextMsg->bufSize = (int)textSize;
newTextMsg->len = 0;
newTextMsg->buf = (char *)malloc(textSize);
memcpy((char *)newTextMsg->buf, (char *)msgText, textSize);
lPushToEnd(sendMsgList, newTextMsg, sizeof(Msg));
ui->sendRecList->addItem((char *)newTextMsg->buf);
ui->textMsg->clear();
}
I put the text into a qListBox
, but it shows up like
However, the character array, if I print it out, does not have the extra characters.
I have tried checking the "compile using UTF-8" option, but it doesn't make a difference.
Also, I send the text using RS232, and the receiver side also displays the extra characters.
The receiver code is here:
m_serial->waitForReadyRead(200);
const QByteArray data = m_serial->readAll();
if (data.size() > 0) {
qDebug() << "New serial data: " << data;
QString str = QString(data);
if (str.contains("0x6F8C32E90A")) {
qDebug() << "TEST SUCCESSFUL!";
}
return data.data();
} else {
return NULL;
}
qt
I have a qTextEdit
that I grab the text from (QString
) and convert to a char*
with this code:
QString msgQText = ui->textMsg->toPlainText();
size_t textSize = (size_t)msgQText.size();
if (textSize > 139) {
textSize = 139;
}
unsigned char * msgText = (unsigned char *)malloc(textSize);
memcpy(msgText, msgQText.toLocal8Bit().data(), textSize);
msgText[textSize] = '';
if (textSize > 0) {
Msg * newTextMsg = new Msg;
newTextMsg->type = 1; // text message type
newTextMsg->bitrate = 0;
newTextMsg->samplerate = 0;
newTextMsg->bufSize = (int)textSize;
newTextMsg->len = 0;
newTextMsg->buf = (char *)malloc(textSize);
memcpy((char *)newTextMsg->buf, (char *)msgText, textSize);
lPushToEnd(sendMsgList, newTextMsg, sizeof(Msg));
ui->sendRecList->addItem((char *)newTextMsg->buf);
ui->textMsg->clear();
}
I put the text into a qListBox
, but it shows up like
However, the character array, if I print it out, does not have the extra characters.
I have tried checking the "compile using UTF-8" option, but it doesn't make a difference.
Also, I send the text using RS232, and the receiver side also displays the extra characters.
The receiver code is here:
m_serial->waitForReadyRead(200);
const QByteArray data = m_serial->readAll();
if (data.size() > 0) {
qDebug() << "New serial data: " << data;
QString str = QString(data);
if (str.contains("0x6F8C32E90A")) {
qDebug() << "TEST SUCCESSFUL!";
}
return data.data();
} else {
return NULL;
}
qt
qt
edited Nov 14 '18 at 5:33
AAEM
726318
726318
asked Nov 13 '18 at 14:11
HengyHengy
324
324
Note that you're writing off the end of the allocated buffer when you domsgText[textSize] = '';
. That's undefined behaviour.
– G.M.
Nov 13 '18 at 14:32
add a comment |
Note that you're writing off the end of the allocated buffer when you domsgText[textSize] = '';
. That's undefined behaviour.
– G.M.
Nov 13 '18 at 14:32
Note that you're writing off the end of the allocated buffer when you do
msgText[textSize] = '';
. That's undefined behaviour.– G.M.
Nov 13 '18 at 14:32
Note that you're writing off the end of the allocated buffer when you do
msgText[textSize] = '';
. That's undefined behaviour.– G.M.
Nov 13 '18 at 14:32
add a comment |
1 Answer
1
active
oldest
votes
There is a difference between the size of a QString
and the size of the QByteArray returned by toLocal8Bit()
. A QString
contains unicode text stored as UTF-16, while a QByteArray
is "just" a char
.
A QByteArray
is null-terminated, so you do not need to add it manually.
As @GM pointed out: msgText[textSize] = '';
is undefined behavior. You are writing to the textSize + 1
position of the msgText
array.
This position may be owned by something else and may be overwritten, so you end up with a non null terminated string.
This should work:
QByteArray bytes = msgQText.toLocal8Bit();
size_t textSize = (size_t)bytes.size() + 1; // Add 1 for the final ''
unsigned char * msgText = (unsigned char *) malloc(textSize);
memcpy(msgText, bytes.constData(), textSize);
Additional tips:
Prefer using const functions on Qt types that are copy-on-write, e.g. use
QBytearray::constData()
instead ofQByteArray::data()
. The non-const functions can cause a deep-copy of the object.Do not use
malloc()
and other C-style functions if possible. Here you could do:
unsigned char * msgText = new unsigned char[textSize];
and laterdelete msgText;
.Prefer using C++ casts (static_cast, reinterpret_cast, etc.) instead of C-style casts.
- You are making 2 copies of the text (2 calls to
memcpy
), given your code only 1 seem to be enough.
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
There is a difference between the size of a QString
and the size of the QByteArray returned by toLocal8Bit()
. A QString
contains unicode text stored as UTF-16, while a QByteArray
is "just" a char
.
A QByteArray
is null-terminated, so you do not need to add it manually.
As @GM pointed out: msgText[textSize] = '';
is undefined behavior. You are writing to the textSize + 1
position of the msgText
array.
This position may be owned by something else and may be overwritten, so you end up with a non null terminated string.
This should work:
QByteArray bytes = msgQText.toLocal8Bit();
size_t textSize = (size_t)bytes.size() + 1; // Add 1 for the final ''
unsigned char * msgText = (unsigned char *) malloc(textSize);
memcpy(msgText, bytes.constData(), textSize);
Additional tips:
Prefer using const functions on Qt types that are copy-on-write, e.g. use
QBytearray::constData()
instead ofQByteArray::data()
. The non-const functions can cause a deep-copy of the object.Do not use
malloc()
and other C-style functions if possible. Here you could do:
unsigned char * msgText = new unsigned char[textSize];
and laterdelete msgText;
.Prefer using C++ casts (static_cast, reinterpret_cast, etc.) instead of C-style casts.
- You are making 2 copies of the text (2 calls to
memcpy
), given your code only 1 seem to be enough.
add a comment |
There is a difference between the size of a QString
and the size of the QByteArray returned by toLocal8Bit()
. A QString
contains unicode text stored as UTF-16, while a QByteArray
is "just" a char
.
A QByteArray
is null-terminated, so you do not need to add it manually.
As @GM pointed out: msgText[textSize] = '';
is undefined behavior. You are writing to the textSize + 1
position of the msgText
array.
This position may be owned by something else and may be overwritten, so you end up with a non null terminated string.
This should work:
QByteArray bytes = msgQText.toLocal8Bit();
size_t textSize = (size_t)bytes.size() + 1; // Add 1 for the final ''
unsigned char * msgText = (unsigned char *) malloc(textSize);
memcpy(msgText, bytes.constData(), textSize);
Additional tips:
Prefer using const functions on Qt types that are copy-on-write, e.g. use
QBytearray::constData()
instead ofQByteArray::data()
. The non-const functions can cause a deep-copy of the object.Do not use
malloc()
and other C-style functions if possible. Here you could do:
unsigned char * msgText = new unsigned char[textSize];
and laterdelete msgText;
.Prefer using C++ casts (static_cast, reinterpret_cast, etc.) instead of C-style casts.
- You are making 2 copies of the text (2 calls to
memcpy
), given your code only 1 seem to be enough.
add a comment |
There is a difference between the size of a QString
and the size of the QByteArray returned by toLocal8Bit()
. A QString
contains unicode text stored as UTF-16, while a QByteArray
is "just" a char
.
A QByteArray
is null-terminated, so you do not need to add it manually.
As @GM pointed out: msgText[textSize] = '';
is undefined behavior. You are writing to the textSize + 1
position of the msgText
array.
This position may be owned by something else and may be overwritten, so you end up with a non null terminated string.
This should work:
QByteArray bytes = msgQText.toLocal8Bit();
size_t textSize = (size_t)bytes.size() + 1; // Add 1 for the final ''
unsigned char * msgText = (unsigned char *) malloc(textSize);
memcpy(msgText, bytes.constData(), textSize);
Additional tips:
Prefer using const functions on Qt types that are copy-on-write, e.g. use
QBytearray::constData()
instead ofQByteArray::data()
. The non-const functions can cause a deep-copy of the object.Do not use
malloc()
and other C-style functions if possible. Here you could do:
unsigned char * msgText = new unsigned char[textSize];
and laterdelete msgText;
.Prefer using C++ casts (static_cast, reinterpret_cast, etc.) instead of C-style casts.
- You are making 2 copies of the text (2 calls to
memcpy
), given your code only 1 seem to be enough.
There is a difference between the size of a QString
and the size of the QByteArray returned by toLocal8Bit()
. A QString
contains unicode text stored as UTF-16, while a QByteArray
is "just" a char
.
A QByteArray
is null-terminated, so you do not need to add it manually.
As @GM pointed out: msgText[textSize] = '';
is undefined behavior. You are writing to the textSize + 1
position of the msgText
array.
This position may be owned by something else and may be overwritten, so you end up with a non null terminated string.
This should work:
QByteArray bytes = msgQText.toLocal8Bit();
size_t textSize = (size_t)bytes.size() + 1; // Add 1 for the final ''
unsigned char * msgText = (unsigned char *) malloc(textSize);
memcpy(msgText, bytes.constData(), textSize);
Additional tips:
Prefer using const functions on Qt types that are copy-on-write, e.g. use
QBytearray::constData()
instead ofQByteArray::data()
. The non-const functions can cause a deep-copy of the object.Do not use
malloc()
and other C-style functions if possible. Here you could do:
unsigned char * msgText = new unsigned char[textSize];
and laterdelete msgText;
.Prefer using C++ casts (static_cast, reinterpret_cast, etc.) instead of C-style casts.
- You are making 2 copies of the text (2 calls to
memcpy
), given your code only 1 seem to be enough.
answered Nov 13 '18 at 15:29
Benjamin TBenjamin T
5,1031027
5,1031027
add a comment |
add a comment |
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Note that you're writing off the end of the allocated buffer when you do
msgText[textSize] = '';
. That's undefined behaviour.– G.M.
Nov 13 '18 at 14:32