char pad_len= AES_BLOCK_SIZE - (source_length - AES_BLOCK_SIZE*num_blocks);
memcpy(block, source, 16 -pad_len);
memset(block + AES_BLOCK_SIZE -pad_len, pad_len, pad_len);
char pad_len= AES_BLOCK_SIZE - (source_length - AES_BLOCK_SIZE*num_blocks);
memcpy(block, source, 16 -pad_len);
memset(block + AES_BLOCK_SIZE -pad_len, pad_len, pad_len);