i have a QByteArray like this:
// read file
QFile file("e:/test/test.dat");
if(!file.open(QIODevice::ReadOnly))return;
QByteArray ba = file.readAll();
Now I want to divide the ba variable into 8 parts. Each part must have a certain size. For example 100200 bytes. How to do this?
sorry for my english
You can split your byte array like this:
std::vector<QByteArray> parts;
static const int size = 100200;
assert(ba.size() >= size * 8); // Make sure you have enough bytes.
for (int i = 0; i < 8; ++i) {
parts.emplace_back(ba.mid(i * size, size));
}
Related
So I have a strange issue that when I read data (QDataStream) on a QTcpSocket: some of the data seems to be missing. The bytesAvailable() function will return the proper amount of bytes to be read, but QDataStream doesn't seem to hold all the bytes.
First of all, this is how the data looks:
bufferX always contains 768 floats and bufferY always contains 5376 floats. Therefore, I would expect the total data to be sent to be (excluding block size) : int + 768 floats + 5376 floats = 4 + 3072 + 21504 = 24580 bytes.
Now, here is the sender code:
void ClientSocket::serverTaskResult()
{
QByteArray block;
QDataStream out(&block, QIODevice::WriteOnly);
out.setVersion(QDataStream::Qt_DefaultCompiledVersion);
out << quint16(0);
out << mServerTask->getNPoints();
for (size_t i = 0; i < BUFFERX_SIZE; i++)
out << mServerTask->getBufferX(i);
for (size_t i = 0; i < BUFFERY_SIZE; i++)
out << mServerTask->getBufferY(i);
out.device()->seek(0);
out << quint16(block.size() - sizeof(quint16));
write(block);
out << quint16(0xFFFF);
}
And here is the receiver code:
void TestClient::recoverResult()
{
QDataStream in(&mTcpSocket);
in.setVersion(QDataStream::Qt_DefaultCompiledVersion);
float wBufferX[BUFFERX_SIZE];
float wBufferY[BUFFERY_SIZE];
int wNPoints;
forever{
if (mNextBlockSize == 0)
{
qint64 nBytesAvailable = mTcpSocket.bytesAvailable();
if (nBytesAvailable < sizeof(quint16))
break;
in >> mNextBlockSize;
}
if (mNextBlockSize == 0xFFFF)
{
closeConnection();
break;
}
if (mTcpSocket.bytesAvailable() < mNextBlockSize)
break;
for (size_t i = 0; i < BUFFERX_SIZE; i++)
in >> wBufferX[i];
for (size_t i = 0; i < BUFFERY_SIZE; i++)
in >> wBufferY[i];
in >> wNPoints;
mNextBlockSize = 0;
}
}
Now, the first odd thing I'm noticing is that nBytesAvailable always has a value of 49158, which is about double of what I'm expecting. How is it that I'm receiving twice as many bytes as expected?
Secondly, since I have all these bytes available, I would expect the QDataStream to be able to properly fill in the buffers. However, after anywhere between 315 and 350 floats, the QDataStream seems to contain unavailable data. That is, wBufferX will have defined (and correct) values in its first 315-350 indexes and unknown values afterwards. I don't understand how that is since bytesAvailable() clearly indicates that almost 50 000 bytes are on the socket. What am I missing?
Your help is greatly appreciated! Thanks!
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] = '\0';
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;
}
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] = '\0'; 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 '\0'
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 of QByteArray::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 later delete[] 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.
I was trying to write items to the EEPROM and later read them out. I was finding the reading back I was not getting the same as I put in at times. I narrow down to an example I can show you. Below I read into variables 2 address.
const int start_add_type = (EEPROM.length() - 10);
const int start_add_id = (EEPROM.length() - 4);
I then look at the value (via RS232)
Serial.begin(9600);
Serial.println(start_add_type);
Serial.println(start_add_id);
of them at the start of the setup() and see I get
1014
1020
I then look again at the end
Serial.println(start_add_type);
Serial.println(start_add_id);
and I get
1014
818
I cannot see why this should change. I did try calling them const e.g. const
const int start_add_type = (EEPROM.length() - 10);
const int start_add_id = (EEPROM.length() - 4);
but this gave the same result. So here I sit very puzzled at what I must have missed. Anyone got any idea?
#include "EEPROM.h"
int start_add_type = (EEPROM.length() - 10);
int start_add_id = (EEPROM.length() - 4);
char ID[7] = "ENCPG2";
char Stored_ID[5];
char Input[10];
//String Type;
void setup()
{
Serial.begin(9600);
Serial.println(start_add_type);
Serial.println(start_add_id);
// start_add = (EEPROM.length() - 10); // use this method to be PCB independent.
for (int i = 0; i < 6; i++)
{
Stored_ID[i] = EEPROM.read(start_add_type + i); // Read the ID into the EEPROM.
}
if (Stored_ID != ID) // Check if the one we have got is the same as the one in this code ID[7]
{
for (int i = 0; i < 6; i++)
{
EEPROM.write(start_add_type + i, ID[i]); // Write the ID into the EEPROM.
}
}
Serial.println(start_add_type);
Serial.println(start_add_id);
}
void loop()
{
}
You are overwriting your memory in this loop:
for (int i = 0; i < 6; i++)
{
Stored_ID[i] = EEPROM.read(start_add_type + i);
}
Stored_ID array is 5 bytes long, so writing to Stored_ID[5] will rewrite also the start_add_id variable, thus the weird value 818, which equals to 0x0332 HEX and 0x32 is the '2' character of your ID
For fixing this issue, declare Stored_ID in this way:
char Stored_ID[6];
if (Stored_ID != ID)
This is nonsense: You compare two different addresses, which are never equal. If you want to compare the content, you should do it in a loop. (e.g. directly when reading the EEPROM value into Stored_ID[i] )
Alternatively, Stored_ID could be a 0-terminated text as well and you might use
if (strcmp(Stored_ID, ID) != 0)
I am trying to reconstruct an image from a file which is in Intel hex 386 format. After parsing the file all the data I am copying to a QByteArray and same array is used to create a QImage Object. But whatever image is which I got after reconstructing is not perfect. I am getting blue color instead of black, edges are not clear etc. The text file which I am parsing is a ram memory dump from STM32F4 controller (arm).The image is stored in RGB565 format.
Code to create the image:
{
QString strFilename;
Hex386Parser oFileParser;
strFilename = QFileDialog::getOpenFileName(this,"Select a file", QDir::homePath());
oFileParser.parseFile(strFilename, oByteArray);
QImage image(320, 240, QImage::Format_RGB16);
for (int y = 0; y < image.height(); y++)
{
memcpy(image.scanLine(y), oByteArray.constData() + y * image.bytesPerLine(),
image.bytesPerLine());
}
qDebug() <<"Size of the byte array is " <<oByteArray.size();
QLabel *label = new QLabel();
label->setPixmap(QPixmap::fromImage(image));
label->show();
}
Code to used to parse the file:
#define QT_NO_CAST_TO_ASCII
void Hex386Parser::parseFile(QString strFilename,QByteArray& ref_ByteArray)
{
QFile oFile(strFilename);
std::stringstream sstr;
QString strLength;
int unLength = 0, unAddress = 0,unDescriptor =0xFFFF,nIndex =0,nlineno=0;
if (oFile.open((QIODevice::ReadOnly | QIODevice::Text)))
{
QTextStream in(&oFile);
while (!in.atEnd())
{
QString line = in.readLine();
nIndex = 0;
nlineno++;
//unsigned char *pCharFrame = (unsigned char *)line.toStdString().c_str();
if (':' != line.at(nIndex))
{
// file corrupted
return;
}
nIndex++;
{
strLength = line.mid(nIndex, 2);
sstr << strLength.toStdString();
sstr << std::hex;
sstr >> unLength; // get length of the record
strLength.clear();
sstr.clear();
}
nIndex += 2;
unAddress = line.mid(nIndex,4).toInt(); // get address bytes
nIndex +=4;
unDescriptor = line.mid(nIndex, 2).toInt(); // get data descriptor
nIndex += 2;
switch(unDescriptor)
{
case data_record:
ref_ByteArray.append((line.mid(nIndex, unLength )));
// add data to bytearray
break;
case end_of_file_record:
break;
case extended_segment_address_record:
break;
case extended_linear_address_record:
break;
case start_linear_address_record:
break;
}
}
oFile.close();
}
}
What am I doing wrong??
The line contains hex string data representations where each byte is coded as two characters.
You want binary bytes. So, 2 * unLength symbols should be read from line. Then, that data string should converted to binary, for example:
{
case data_record:
QByteArray hex = line.mid(nIndex, 2 * unLength ).toLatin1();
QByteArray binary = QByteArray::fromHex(hex);
ref_ByteArray.append(binary);
...
}
Pointer related question. I'm going through some example code that currently reads in data from a file called dataFile into a buffer. The reading is done inside a loop as follows:
unsigned char* buffer = (unsigned char*)malloc(1024*768*);
fread(buffer,1,1024*768,dataFile);
redPointer = buffer;
bluePointer = buffer+1024;
greenPointer = buffer+768;
Now, I want to try and write the entire contents of the array buffer to a file, so that I can save just those discrete images (and not have a large file). However, I am not entirely sure how to go about doing this.
I was trying to cout statements, however I get a print-out of garbage characters on the console and also a beep from the PC. So then I end my program.
Is there an alternative method other than this:
for (int i=0; i < (1024*768); i++) {
fprintf(myFile, "%6.4f , ", buffer[i]);
}
By declaring your buffer as a char*, any pointer arithmatic or array indexes will use sizeof(char) to calculate the offset. A char is 1 byte (8 bits).
I'm not sure what you are trying to do with the data in your buffer. Here are some ideas:
Print the value of each byte in decimal, encoded as ASCII text:
for (int i=0; i < (1024*768); i++) {
fprintf(myFile, "%d , ", buffer[i]);
}
Print the value of each byte in hexadecimal, encoded in ASCII text:
for (int i=0; i < (1024*768); i++) {
fprintf(myFile, "%x , ", buffer[i]);
}
Print the value of each floating point number, in decimal, encoded in ASCII text (I think my calculation of the array index is correct to process adjacent non-overlapping memory locations for each float):
for (int i=0; i < (1024*768); i += sizeof(float)) {
fprintf(myFile, "%6.4f , ", buffer[i]);
}
Split the buffer into three files, each one from a non-overlapping section of the buffer:
fwrite(redPointer, sizeof(char), 768, file1);
fwrite(greenPointer, sizeof(char), 1024-768, file2);
fwrite(bluePointer, sizeof(char), (1024*768)-1024, file3);
Reference for fwrite. Note that for the count parameter I simply hard-coded the offsets that you had hard-coded in your question. One could also subtract certain of the pointers to calculate the number of bytes in each region. Note also that the contents of these three files will only be sensible if those are sensibly independent sections of the original data.
Maybe this gives you some ideas.
Updated: so I created a complete program to compile and test the formatting behavior. This only prints the first 20 items from the buffer. It compiles (with gcc -std=c99) and runs. I created the file /tmp/data using ghex and simply filled in some random data.
#include <stdlib.h>
#include <stdio.h>
int main()
{
FILE* dataFile = fopen("/tmp/data", "rb");
if (dataFile == NULL)
{
printf("fopen() failed");
return -2;
}
unsigned char* buffer = (unsigned char*)malloc(1024*768);
if (buffer == NULL)
{
printf("malloc failed");
return -1;
}
const int bytesRead = fread(buffer,1,1024*768,dataFile);
printf("fread() read %d bytes\n", bytesRead);
// release file handle
fclose(dataFile); dataFile = NULL;
printf("\nDecimal:\n");
for (int i=0; i < (1024*768); i++) {
printf("%hd , ", buffer[i]);
if (i > 20) { break; }
}
printf("\n");
printf("\nHexadecimal:\n");
for (int i=0; i < (1024*768); i++) {
printf("%#0hx , ", buffer[i]);
if (i > 20) { break; }
}
printf("\n");
printf("\nFloat:\n");
for (int i=0; i < (1024*768); i += sizeof(float)) {
printf("%6.4f , ", (float)buffer[i]);
if (i > 20) { break; }
}
printf("\n");
return 0;
}