memcpy returning incorrect results - c++

Question

This test example I've made works as expected:
FLAC__int32 array[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
FLAC__int32 const *const handle(array);
FLAC__int32 temp[10];
std::vector<FLAC__int32> base;
base.resize(10);
memcpy(&base[0], handle, 10 * sizeof(FLAC__int32));
for (size_t i(0); i < 10; i++)
cout << endl << "[ " << i << " ] " << base[i];
However, with the code below, I can't get the memcpy to work correctly. How do I correct this so that memcpy makes correct copies of the buffer?
Note: _buffer contains binary data which was decoder by libFLAC.
FLAC__StreamDecoderWriteStatus
Source::write_callback
(FLAC__Frame const* _frame, FLAC__int32 const *const _buffer[])
{
cout << endl << "Head index [ " << index_ << " ].";
memcpy(&data_[index_], &_buffer[0], _frame->header.blocksize *
sizeof(FLAC__int32));
index_ += _frame->header.blocksize;
cout << endl << "Tail index [ " << index_ << " ].";
for(size_t i(0); i < 400; i++) {
cout << endl << "Buff [ " << i << " ] " << _buffer[i];
cout << endl << "Data [ " << i << " ] " << data_[i];
} // jump
return FLAC__STREAM_DECODER_WRITE_STATUS_CONTINUE;
} // main
And below is how I resize the vector and reset the index:
void
Source::metadata_callback (const ::FLAC__StreamMetadata *metadata)
{
...
total_samples_ = metadata->data.stream_info.total_samples;
...
data_.resize(total_samples_); index_ = 0;
} // main

Answer 1

You want a deep copy (that is, you want to copy the FLAC__int32 values, not the pointers to them), and you don't seem to care whether you construct a container of those values or of pointers to those values. So memcpy is the wrong tool. Let's start with a very simple case:
void foo(int * buf)
{
int data = *buf;
}
Then try copying an array to a vector:
void foo(int * buf[])
{
vector<int> data(10);
for(unsigned int k=0; k<3; ++k)
data[k] = *buf[k];
}
Then the full solution:
FLAC__StreamDecoderWriteStatus Source::write_callback(FLAC__Frame const* _frame, FLAC__int32 const *const _buffer[])
{
cout << endl << "Head index [ " << index_ << " ].";
data_.resize(_frame->header.blocksize);
for(size_t k=0; k<_frame->header.blocksize; ++k)
{
data_[index_+k] = *_buffer[k];
}
index_ += _frame->header.blocksize;
cout << endl << "Tail index [ " << index_ << " ].";
for(size_t i(0); i < 400; i++)
{
cout << endl << "Buff [ " << i << " ] " << *_buffer[i];
cout << endl << "Data [ " << i << " ] " << data_[i];
}
return FLAC__STREAM_DECODER_WRITE_STATUS_CONTINUE;
}