On 30-Jul-08, at 5:20 PM, David Vazquez wrote:
gcry_error_t gcry_cipher_encrypt (gcry_cipher_hd_t H, unsigned char *out, size_t OUTSIZE, const unsigned char *IN, size_t INLEN)By the way, I think OUTSIZE argument is redundant. We can determine it for both methods. Is there any form We take advantage of this?
Does OUTSIZE not function as a guard to make it easier to avoid overflowing the 'out' buffer?
Looking at the documentation, 'in' can also be NULL in this call to request in-place encryption of the data already in the 'out' buffer, so a separate length is needed for that case. This doesn't have to propagated to the gnupdf api, of course.
Separate in and out buffer sizes can also simplify progress calculations for incremental processing through a ring buffer, since you can just pass the available input and output space and let the call make what progress it can. But it doesn't help if the call doesn't also return how much progress it made so you can advance the pointers. And because of the AES block padding, this isn't an entirely trivial calculation for encode, and is impossible to know ahead of time on decode.
-r
