MemIOCallback::read has a integer overflow bug

[fatshi]

function MemIOCallback::read at line 70 has an integer overflow:

POC code as below:

#include "ebml/MemIOCallback.h"

using namespace libebml;

int main() {
    char buff[128] = {};
    MemIOCallback memoryBuffer;

    memoryBuffer.write(buff, 124);

    char outBuff[128];
    memoryBuffer.read(outBuff, 0xfffffffffffffff0);

    return 0;
}

terminal output is:

Process finished with exit code 139 (interrupted by signal 11: SIGSEGV)

[robUx4]

Indeed, thanks a lot for this finding! There was also some potential issue when writing.