ret = ctx->bn + (ctx->tos++);
BIGNUM *BN_CTX_get(BN_CTX *ctx)	{	BIGNUM *ret;	/* Note: If BN_CTX_get is ever changed to allocate BIGNUMs dynamically,	 * make sure that if BN_CTX_get fails once it will return NULL again	 * until BN_CTX_end is called.  (This is so that callers have to check	 * only the last return value.)	 */	if (ctx->depth > BN_CTX_NUM_POS || ctx->tos >= BN_CTX_NUM)		{		if (!ctx->too_many)			{			BNerr(BN_F_BN_CTX_GET,BN_R_TOO_MANY_TEMPORARY_VARIABLES);			/* disable error code until BN_CTX_end is called: */			ctx->too_many = 1;			}		return NULL;		}	ret = ctx->bn + (ctx->tos++);	/* always return a 'zeroed' bignum */	BN_zero(ret);	return ret;	}