On Oct 30, 2013, at 6:36 PM, Chan, Jack wrote:
> Hi,
>
> I'm having trouble initializing a TMemoryBuffer with contents. I serialized
> an object (a ContactsList object) with TCompactProtocol and then wrote it out
> as a file to disk. Now, I'm trying to read that file and create the same
> object, but it appears that when I call the object's .read() function, it
> says "No more data to read." I suspect that I did not correctly initialize
> the TMemoryBuffer with anything. Here is what I'm doing:
>
> // contacts_bin is a std::string that is read in from disk and is a binary
> string encoded with TCompactProtocol)
> // contacts_bin_copy is a copy of contacts_bin except it's a char* instead of
> a std::string.
> ContactsList object;
> shared_ptr<TMemoryBuffer> transportIn(new TMemoryBuffer((unsigned
> char*)contacts_bin_copy, contacts_bin.size()));
> shared_ptr<TCompactProtocol> protocolIn(new TCompactProtocol(transportIn));
> object.read(protocolIn.get());
>
> So, I am creating a new TMemoryBuffer by providing a string and the size of
> that string to the constructor. I might not be doing it right, which is why
> I'm getting problems. Might the buffer have nothing in it because I did not
> change the memory policy to COPY? If that's the case, what's the correct code
> that will do it?
>
> Thanks,
> Jack
>
Hi Jack,
Here's a function we use to do something very similar:
template <class T>
void readThriftObjFromBuffer(const void* inBuffer, const size_t
inBufferSize,
T&
outThriftStruct)
{
// Instance the memory buffer and simple binary protocol, then
read the structure from it.
boost::shared_ptr<TMemoryBuffer> memoryBuffer( new
TMemoryBuffer(const_cast<uint8_t*>(reinterpret_cast<const uint8_t*>(inBuffer)),
inBufferSize, TMemoryBuffer::OBSERVE) );
boost::shared_ptr<TProtocol> binaryProtocol( new
TBinaryProtocol(memoryBuffer) );
outThriftStruct.read(binaryProtocol.get());
}
It seems to me that what you're doing should work.
Have you verified that your write really worked and that contacts_bin_copy
really points to a string that has nonzero size?
- Rush
