numeric.c

postgresql8.3.4源码,开源数据库

	i1 = res_rscale + var1->weight + 1;
	i2 = res_rscale + var2->weight + 1;
	for (i = res_ndigits - 1; i >= 0; i--)
	{
		i1--;
		i2--;
		if (i1 >= 0 && i1 < var1ndigits)
			carry += var1digits[i1];
		if (i2 >= 0 && i2 < var2ndigits)
			carry += var2digits[i2];

		if (carry >= 10)
		{
			res_digits[i] = carry - 10;
			carry = 1;
		}
		else
		{
			res_digits[i] = carry;
			carry = 0;
		}
	}

	while (res_ndigits > 0 && *res_digits == 0)
	{
		res_digits++;
		res_weight--;
		res_ndigits--;
	}
	while (res_ndigits > 0 && res_digits[res_ndigits - 1] == 0)
		res_ndigits--;

	if (res_ndigits == 0)
		res_weight = 0;

	digitbuf_free(result->buf);
	result->ndigits = res_ndigits;
	result->buf = res_buf;
	result->digits = res_digits;
	result->weight = res_weight;
	result->rscale = res_rscale;
	result->dscale = res_dscale;

	return 0;
}


/* ----------
 * sub_abs() -
 *
 *	Subtract the absolute value of var2 from the absolute value of var1
 *	and store in result. result might point to one of the operands
 *	without danger.
 *
 *	ABS(var1) MUST BE GREATER OR EQUAL ABS(var2) !!!
 * ----------
 */
static int
sub_abs(numeric *var1, numeric *var2, numeric *result)
{
	NumericDigit *res_buf;
	NumericDigit *res_digits;
	int			res_ndigits;
	int			res_weight;
	int			res_rscale;
	int			res_dscale;
	int			i,
				i1,
				i2;
	int			borrow = 0;

	/* copy these values into local vars for speed in inner loop */
	int			var1ndigits = var1->ndigits;
	int			var2ndigits = var2->ndigits;
	NumericDigit *var1digits = var1->digits;
	NumericDigit *var2digits = var2->digits;

	res_weight = var1->weight;
	res_rscale = Max(var1->rscale, var2->rscale);
	res_dscale = Max(var1->dscale, var2->dscale);
	res_ndigits = res_rscale + res_weight + 1;
	if (res_ndigits <= 0)
		res_ndigits = 1;

	if ((res_buf = digitbuf_alloc(res_ndigits)) == NULL)
		return -1;
	res_digits = res_buf;

	i1 = res_rscale + var1->weight + 1;
	i2 = res_rscale + var2->weight + 1;
	for (i = res_ndigits - 1; i >= 0; i--)
	{
		i1--;
		i2--;
		if (i1 >= 0 && i1 < var1ndigits)
			borrow += var1digits[i1];
		if (i2 >= 0 && i2 < var2ndigits)
			borrow -= var2digits[i2];

		if (borrow < 0)
		{
			res_digits[i] = borrow + 10;
			borrow = -1;
		}
		else
		{
			res_digits[i] = borrow;
			borrow = 0;
		}
	}

	while (res_ndigits > 0 && *res_digits == 0)
	{
		res_digits++;
		res_weight--;
		res_ndigits--;
	}
	while (res_ndigits > 0 && res_digits[res_ndigits - 1] == 0)
		res_ndigits--;

	if (res_ndigits == 0)
		res_weight = 0;

	digitbuf_free(result->buf);
	result->ndigits = res_ndigits;
	result->buf = res_buf;
	result->digits = res_digits;
	result->weight = res_weight;
	result->rscale = res_rscale;
	result->dscale = res_dscale;

	return 0;
}

/* ----------
 * add_var() -
 *
 *	Full version of add functionality on variable level (handling signs).
 *	result might point to one of the operands too without danger.
 * ----------
 */
int
PGTYPESnumeric_add(numeric *var1, numeric *var2, numeric *result)
{
	/*
	 * Decide on the signs of the two variables what to do
	 */
	if (var1->sign == NUMERIC_POS)
	{
		if (var2->sign == NUMERIC_POS)
		{
			/*
			 * Both are positive result = +(ABS(var1) + ABS(var2))
			 */
			if (add_abs(var1, var2, result) != 0)
				return -1;
			result->sign = NUMERIC_POS;
		}
		else
		{
			/*
			 * var1 is positive, var2 is negative Must compare absolute values
			 */
			switch (cmp_abs(var1, var2))
			{
				case 0:
					/* ----------
					 * ABS(var1) == ABS(var2)
					 * result = ZERO
					 * ----------
					 */
					zero_var(result);
					result->rscale = Max(var1->rscale, var2->rscale);
					result->dscale = Max(var1->dscale, var2->dscale);
					break;

				case 1:
					/* ----------
					 * ABS(var1) > ABS(var2)
					 * result = +(ABS(var1) - ABS(var2))
					 * ----------
					 */
					if (sub_abs(var1, var2, result) != 0)
						return -1;
					result->sign = NUMERIC_POS;
					break;

				case -1:
					/* ----------
					 * ABS(var1) < ABS(var2)
					 * result = -(ABS(var2) - ABS(var1))
					 * ----------
					 */
					if (sub_abs(var2, var1, result) != 0)
						return -1;
					result->sign = NUMERIC_NEG;
					break;
			}
		}
	}
	else
	{
		if (var2->sign == NUMERIC_POS)
		{
			/* ----------
			 * var1 is negative, var2 is positive
			 * Must compare absolute values
			 * ----------
			 */
			switch (cmp_abs(var1, var2))
			{
				case 0:
					/* ----------
					 * ABS(var1) == ABS(var2)
					 * result = ZERO
					 * ----------
					 */
					zero_var(result);
					result->rscale = Max(var1->rscale, var2->rscale);
					result->dscale = Max(var1->dscale, var2->dscale);
					break;

				case 1:
					/* ----------
					 * ABS(var1) > ABS(var2)
					 * result = -(ABS(var1) - ABS(var2))
					 * ----------
					 */
					if (sub_abs(var1, var2, result) != 0)
						return -1;
					result->sign = NUMERIC_NEG;
					break;

				case -1:
					/* ----------
					 * ABS(var1) < ABS(var2)
					 * result = +(ABS(var2) - ABS(var1))
					 * ----------
					 */
					if (sub_abs(var2, var1, result) != 0)
						return -1;
					result->sign = NUMERIC_POS;
					break;
			}
		}
		else
		{
			/* ----------
			 * Both are negative
			 * result = -(ABS(var1) + ABS(var2))
			 * ----------
			 */
			if (add_abs(var1, var2, result) != 0)
				return -1;
			result->sign = NUMERIC_NEG;
		}
	}

	return 0;
}


/* ----------
 * sub_var() -
 *
 *	Full version of sub functionality on variable level (handling signs).
 *	result might point to one of the operands too without danger.
 * ----------
 */
int
PGTYPESnumeric_sub(numeric *var1, numeric *var2, numeric *result)
{
	/*
	 * Decide on the signs of the two variables what to do
	 */
	if (var1->sign == NUMERIC_POS)
	{
		if (var2->sign == NUMERIC_NEG)
		{
			/* ----------
			 * var1 is positive, var2 is negative
			 * result = +(ABS(var1) + ABS(var2))
			 * ----------
			 */
			if (add_abs(var1, var2, result) != 0)
				return -1;
			result->sign = NUMERIC_POS;
		}
		else
		{
			/* ----------
			 * Both are positive
			 * Must compare absolute values
			 * ----------
			 */
			switch (cmp_abs(var1, var2))
			{
				case 0:
					/* ----------
					 * ABS(var1) == ABS(var2)
					 * result = ZERO
					 * ----------
					 */
					zero_var(result);
					result->rscale = Max(var1->rscale, var2->rscale);
					result->dscale = Max(var1->dscale, var2->dscale);
					break;

				case 1:
					/* ----------
					 * ABS(var1) > ABS(var2)
					 * result = +(ABS(var1) - ABS(var2))
					 * ----------
					 */
					if (sub_abs(var1, var2, result) != 0)
						return -1;
					result->sign = NUMERIC_POS;
					break;

				case -1:
					/* ----------
					 * ABS(var1) < ABS(var2)
					 * result = -(ABS(var2) - ABS(var1))
					 * ----------
					 */
					if (sub_abs(var2, var1, result) != 0)
						return -1;
					result->sign = NUMERIC_NEG;
					break;
			}
		}
	}
	else
	{
		if (var2->sign == NUMERIC_NEG)
		{
			/* ----------
			 * Both are negative
			 * Must compare absolute values
			 * ----------
			 */
			switch (cmp_abs(var1, var2))
			{
				case 0:
					/* ----------
					 * ABS(var1) == ABS(var2)
					 * result = ZERO
					 * ----------
					 */
					zero_var(result);
					result->rscale = Max(var1->rscale, var2->rscale);
					result->dscale = Max(var1->dscale, var2->dscale);
					break;

				case 1:
					/* ----------
					 * ABS(var1) > ABS(var2)
					 * result = -(ABS(var1) - ABS(var2))
					 * ----------
					 */
					if (sub_abs(var1, var2, result) != 0)
						return -1;
					result->sign = NUMERIC_NEG;
					break;

				case -1:
					/* ----------
					 * ABS(var1) < ABS(var2)
					 * result = +(ABS(var2) - ABS(var1))
					 * ----------
					 */
					if (sub_abs(var2, var1, result) != 0)
						return -1;
					result->sign = NUMERIC_POS;
					break;
			}
		}
		else
		{
			/* ----------
			 * var1 is negative, var2 is positive
			 * result = -(ABS(var1) + ABS(var2))
			 * ----------
			 */
			if (add_abs(var1, var2, result) != 0)
				return -1;
			result->sign = NUMERIC_NEG;
		}
	}

	return 0;
}

/* ----------
 * mul_var() -
 *
 *	Multiplication on variable level. Product of var1 * var2 is stored
 *	in result.	Accuracy of result is determined by global_rscale.
 * ----------
 */
int
PGTYPESnumeric_mul(numeric *var1, numeric *var2, numeric *result)
{
	NumericDigit *res_buf;
	NumericDigit *res_digits;
	int			res_ndigits;
	int			res_weight;
	int			res_sign;
	int			i,
				ri,
				i1,
				i2;
	long		sum = 0;
	int			global_rscale = var1->rscale + var2->rscale;

	res_weight = var1->weight + var2->weight + 2;
	res_ndigits = var1->ndigits + var2->ndigits + 1;
	if (var1->sign == var2->sign)
		res_sign = NUMERIC_POS;
	else
		res_sign = NUMERIC_NEG;

	if ((res_buf = digitbuf_alloc(res_ndigits)) == NULL)
		return -1;
	res_digits = res_buf;
	memset(res_digits, 0, res_ndigits);

	ri = res_ndigits;
	for (i1 = var1->ndigits - 1; i1 >= 0; i1--)
	{
		sum = 0;
		i = --ri;

		for (i2 = var2->ndigits - 1; i2 >= 0; i2--)
		{
			sum += res_digits[i] + var1->digits[i1] * var2->digits[i2];
			res_digits[i--] = sum % 10;
			sum /= 10;
		}
		res_digits[i] = sum;
	}

	i = res_weight + global_rscale + 2;
	if (i >= 0 && i < res_ndigits)
	{
		sum = (res_digits[i] > 4) ? 1 : 0;
		res_ndigits = i;
		i--;
		while (sum)
		{
			sum += res_digits[i];
			res_digits[i--] = sum % 10;
			sum /= 10;
		}
	}

	while (res_ndigits > 0 && *res_digits == 0)
	{
		res_digits++;
		res_weight--;
		res_ndigits--;
	}
	while (res_ndigits > 0 && res_digits[res_ndigits - 1] == 0)
		res_ndigits--;

	if (res_ndigits == 0)
	{
		res_sign = NUMERIC_POS;
		res_weight = 0;
	}

	digitbuf_free(result->buf);
	result->buf = res_buf;
	result->digits = res_digits;
	result->ndigits = res_ndigits;
	result->weight = res_weight;
	result->rscale = global_rscale;
	result->sign = res_sign;
	result->dscale = var1->dscale + var2->dscale;

	return 0;
}

/*
 * Default scale selection for division
 *
 * Returns the appropriate display scale for the division result,
 * and sets global_rscale to the result scale to use during div_var.
 *
 * Note that this must be called before div_var.
 */
static int
select_div_scale(numeric *var1, numeric *var2, int *rscale)
{
	int			weight1,
				weight2,
				qweight,
				i;
	NumericDigit firstdigit1,
				firstdigit2;
	int			res_dscale;
	int			res_rscale;

	/*
	 * The result scale of a division isn't specified in any SQL standard. For
	 * PostgreSQL we select a display scale that will give at least
	 * NUMERIC_MIN_SIG_DIGITS significant digits, so that numeric gives a
	 * result no less accurate than float8; but use a scale not less than
	 * either input's display scale.
	 */

	/* Get the actual (normalized) weight and first digit of each input */

	weight1 = 0;				/* values to use if var1 is zero */
	firstdigit1 = 0;
	for (i = 0; i < var1->ndigits; i++)
	{
		firstdigit1 = var1->digits[i];
		if (firstdigit1 != 0)
		{
			weight1 = var1->weight - i;
			break;
		}
	}

	weight2 = 0;				/* values to use if var2 is zero */
	firstdigit2 = 0;
	for (i = 0; i < var2->ndigits; i++)
	{
		firstdigit2 = var2->digits[i];
		if (firstdigit2 != 0)
		{
			weight2 = var2->weight - i;
			break;
		}
	}

	/*
	 * Estimate weight of quotient.  If the two first digits are equal, we
	 * can't be sure, but assume that var1 is less than var2.
	 */
	qweight = weight1 - weight2;
	if (firstdigit1 <= firstdigit2)
		qweight--;