I have some code which uses the sqlite3_blob_write() function, but I
observe some odd behaviour.
When I pass it a QVector (Qt vector class - similar to std::vector,
contiguous memory) of a class C (for example) when the vector is of
significant size (over 200 entries), towards the end of the blob, the
data is just set to 0 - rather than the values in the vector members.
Class C just consists of 6 floats and a short (as well as some functions
in its definition). The precise point where this happens in the blob
seems to vary between machines.
I have checked the sqlite limits and the blob handle is of the desired
size. I pass the function the value of constData() which returns a
const pointer to the data in the vector.
The call is as follows
(body is a QVector<C>,
i_blobHandle is sqlite3_blob* where sqlite3_blob_bytes(i_blobHandle) ==
( length of vector * size of class C in bytes) )
sqlite3_blob_write(i_blobHandle, (body.constData()), ( body.size() *
SIZE_OF_C ), 0);
If I immediately read the blob afterwards as follows
QVector<C> rmcv_d(body.size());
sqlite3_blob_read(i_blobHandle, (rmcv_d.constData()), (body.size()*
SIZE_OF_C), 0);
for ( int rmcv_a(0); rmcv_a < rmcv_d.size(); ++rmcv_a )
{
if( d != body[rmcv_a] )
{
// GET HERE AROUND THE rmcv_a == 230 mark (though this varies)
}
}
Has anybody seen this type of behaviour before? Is it a known
limitation/bug with BLOB writing? If I write the items one at a time in
a loop, there is no problem. But I thought to save time, passing in the
address of the vector would be enough - yet it behaves in this odd way.
Any feedback appreciated.
R
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