postgresql/src/include/utils/numeric.h

/*-------------------------------------------------------------------------
 *
 * numeric.h
 *	  Definitions for the exact numeric data type of Postgres
 *
 * Original coding 1998, Jan Wieck.  Heavily revised 2003, Tom Lane.
 *
 * Copyright (c) 1998-2012, PostgreSQL Global Development Group
 *
 * src/include/utils/numeric.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef _PG_NUMERIC_H_
#define _PG_NUMERIC_H_

#include "fmgr.h"

/*
 * Hardcoded precision limit - arbitrary, but must be small enough that
 * dscale values will fit in 14 bits.
 */
#define NUMERIC_MAX_PRECISION		1000

/*
 * Internal limits on the scales chosen for calculation results
 */
#define NUMERIC_MAX_DISPLAY_SCALE	NUMERIC_MAX_PRECISION
#define NUMERIC_MIN_DISPLAY_SCALE	0

#define NUMERIC_MAX_RESULT_SCALE	(NUMERIC_MAX_PRECISION * 2)

/*
 * For inherently inexact calculations such as division and square root,
 * we try to get at least this many significant digits; the idea is to
 * deliver a result no worse than float8 would.
 */
#define NUMERIC_MIN_SIG_DIGITS		16

/* The actual contents of Numeric are private to numeric.c */
struct NumericData;
typedef struct NumericData *Numeric;

/*
 * fmgr interface macros
 */

#define DatumGetNumeric(X)		  ((Numeric) PG_DETOAST_DATUM(X))
#define DatumGetNumericCopy(X)	  ((Numeric) PG_DETOAST_DATUM_COPY(X))
#define NumericGetDatum(X)		  PointerGetDatum(X)
#define PG_GETARG_NUMERIC(n)	  DatumGetNumeric(PG_GETARG_DATUM(n))
#define PG_GETARG_NUMERIC_COPY(n) DatumGetNumericCopy(PG_GETARG_DATUM(n))
#define PG_RETURN_NUMERIC(x)	  return NumericGetDatum(x)

/*
 * Utility functions in numeric.c
 */
extern bool numeric_is_nan(Numeric num);
int32		numeric_maximum_size(int32 typmod);
extern char *numeric_out_sci(Numeric num, int scale);

#endif   /* _PG_NUMERIC_H_ */