On Apr 14, 2009, at 12:48 PM, Richard Dauben wrote:
> After successfully reading from a blob sequentially to a buffer in
> Objective C
> the buffer seems to be altered such that it can no longer be
> accessed from
> memory.... Is there some kind of special buffer type that I should
> be using?
> Here is sample of my code:
>
> int success;
> NSData *inBuffer;
> success = sqlite3_blob_read(blobData, inBuffer, intByteCount,
> intOffsetInBlob);
>
> After running this code, success == SQLITE_OK. Prior to reading the
> blob,
> inBuffer behaves normally. Afterward, it no longer behaves like a
> buffer, and I
> cannot get any valid data from it. I have set intByteCount to make
> sure it is
> smaller than the number of bytes in the Blob, and intOffsetInBlob = 0
sqlite3_blob_read expects a valid pointer pointing to an allocated
buffer, but you're passing it an uninitialized NSData pointer.
Something like this ought to work:
int success;
NSMutableData *inBuffer = [NSMutableData dataWithLength:intByteCount];
if (inBuffer)
success = sqlite3_blob_read(blobData, [inBuffer mutableBytes],
intBytesCount, intOffsetInBlob);
You'll probably also need to dispose of the NSMutableData object when
you're through with it.
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