Convert float to QbyteArray
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Why do you want to store a float in a QByteArray?
You used the wrong QDataStream constructor. The one you used is for reading a QByteArray (please read the documentation at http://qt-project.org/doc/qt-5.1/qtcore/qdatastream.html ). To write, you need QDataStream(QByteArray * a, QIODevice::OpenMode mode) -- Andre's example should have two arguments.
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Hi, because I want to use QtSerialPort to write data to slave device.The one argument of QtSeriaLPort::write() is QbyteArray, so I need to transform my data to QbyteArray.
I change my code like follows, it is still a little weird. There are indeed four bytes in the result, but how to verify these bytes are my float variable?? I also used the other way to catch these bytes, the result is different with I use QDAtaStream to get.Which one is correct!??
method 1
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float data = 3.54;
QByteArray result;
QDataStream s(&result,QIODevice::ReadWrite);
s.setFloatingPointPrecision(QDataStream::SinglePrecision);
s << data;
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method 2
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float data = 3.54;
QByteArray t2;
t2.append(reinterpret_cast<const char*>(&data), sizeof(data));
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Method 3:
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float data = 3.54;
QString temp = QString::number(data);
QByteArray result = temp.data();
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I know which method is I want. It's method 2. Because I use following code to verify
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float data = 3.54;
QByteArray t2;
t2.append(reinterpret_cast<const char*>(&data), sizeof(data));
char tempdata[4] = {0};
for(int i =0; i < t2.length(); i++)
tempdata[i] = t2[i];
float answerPtr = (float)&tempdata;
float result = *answerPtr;
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The result will be 3.54.Thanks for suggestion from everyone gave: ). -
[quote author="Ivan1120" date="1380167106"]I know which method is I want. It's method 2. Because I use following code to verify
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float data = 3.54;
QByteArray t2;
t2.append(reinterpret_cast<const char*>(&data), sizeof(data));
char tempdata[4] = {0};
for(int i =0; i < t2.length(); i++)
tempdata[i] = t2[i];
float answerPtr = (float)&tempdata;
float result = *answerPtr;
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The result will be 3.54.Thanks for suggestion from everyone gave: ).[/quote]
Also read this: http://stackoverflow.com/questions/2724359/are-there-any-modern-platforms-with-non-ieee-c-c-float-formatsIt describes possible issues when sending float data as raw bytes between different platforms. Your master and slave might not implement float the same way.
