不能使用大尺寸的QByteArray作为QString

Question

I have big char* object. When I write this array to file, the size of this file is 63.7 MB. I receive QByteArray object from this object like this

QByteArray outputDataByteArray(outputData, outputSize);

If I try to send this object to function as QString parameter, I receive

Invalid parameter passed to C runtime function.

While debugging I noticed that it crash after calling function with this array as input parameter, but does not come in this function.

I tried something like this

outputDataByteArray.append("\0");

according to documentation information, that

Warning: A byte array created with fromRawData() is not null-terminated, unless the raw data contains a 0 character at position size. While that does not matter for QDataStream or functions like indexOf() , passing the byte array to a function accepting a const char * expected to be '\\0' -terminated will fail.

But it didn't help me.

On small size of data all work fine.

Edition:

This is some function I receive QBytearray in it (all work fine):

uncompress(const QByteArray &inputByteArray, bool *ok)
{
if (ok != NULL)
    *ok = false;

const char *inputData = inputByteArray.data();

char *outputData = NULL;
qint64 outputSize   = 0;

for (int i = 0; i < CHUNK_COUNT_MAX; i++)
{
    const int outputSizeMax = CHUNKSIZE * (i + 1);
    outputData = new char[outputSizeMax];


    outputSize = LZ4_decompress_safe_withPrefix64k(inputData, outputData, inputByteArray.length(), outputSizeMax);

    if (outputSize < 0)
    {
        delete [] outputData;
        outputData = NULL;
    }
    else
    {
        break;
    }
}

if (outputData == NULL)
    return QByteArray();

QFile file("C:/Users/HOME/file.txt");
if(file.open(QIODevice::WriteOnly))
{
    file.write(outputData, outputSize);
}
file.close();

QByteArray outputDataByteArray(outputData, outputSize);

outputDataByteArray.append("\0");

delete [] outputData;

if (ok != NULL)
    *ok = true;

return outputDataByteArray;

}

But, if I try to to call another function with this array as parameter:

parse(outputDataByteArray, ok);

I receive what I wrote above.

Addition: It does not come in this function but defination of function that i send QByteArray as parameter:

parse(const QString &json, bool &success)
{
    success = true;
    if(!json.isNull() || !json.isEmpty())
    {
            QString data = json;

            int index = 0;


            QVariant value = Json::parseValue(data, index, success);


            return value;
    }
    else
    {
        return QVariant();
    }
}

Answer 1

You are calling LZ4_decompress_safe_withPrefix64k with:

char *outputData = NULL;

And, this function's definitions is like this:

int LZ4_decompress_safe_withPrefix64k(const char* source, char* dest, int compressedSize, int maxOutputSize)
{
    return LZ4_decompress_generic(source, dest, compressedSize, maxOutputSize, endOnInputSize, full, 0, withPrefix64k, (BYTE*)dest - 64 KB, NULL, 64 KB);
}

And, the definition of LZ4_decompress_generic doesn't have any allocation code for your output buffer. See definition of LZ4_decompress_generic .

It is simply typecasted in line # 1129 :

BYTE* op = (BYTE*) dest;

And, it is further used throughout the definition of this function eg memcpy , LZ4_wildCopy , LZ4_copy8 , etc.

So, it's invalid memory that is being pointed by your output buffer pointer. You need to allocate its memory before passing it to the function. In addition to it, you need validate a pointer before passing it to other function. You may use asserts or if checks to validate this.

Hope that would help.