On Wed, Dec 07, 2005 at 08:34:46PM -0800, Dan Kennedy wrote: > > To make it work in more than a superficial manner, you probably will > > need a good understanding of how structures are internally represented > > in C++ or C. You pass sqlite a pointer to the struct and tell it how > > long it is (using sizeof()). When you get the blob back, you then > > treat the data as an instance of your structure by casting it. > > I'm not sure this is always the best way to go. Any databases produced like > this will not be portable between architectures. In theory, they may not > be portable between compilers, but in practice you're probably Ok there.
A good caveat. If any of the members of your structure are more than one byte long (ie, an int) this approach will fail terribly if you create the database on a little-endian machine (Intel/PC) and then try to use it on a little-endian one (Motorola/Mac). But I decided to take the question as 'How do I', rather than 'Should I'. > Also, SQLite makes no guarantees as to the alignment of returned blobs. > This could cause a random crash somewhere down the line. You could get > around this by making a copy of the blob to memory obtained from malloc(). Can you offer more information about this? In what I'm working on, I am storing arrays of complex structures as blobs and then reconstituting them. I was concerned about alignment at one point, but it seems to be working without problems. Are there 'gotchas' that are likely to 'get me' in the future? This is server-side, and only for temporary data, so I'm not concerned about the endian-ness, only the alignment. Thanks! --nate
