src/libpq/include/utils/numeric.h

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/*-------------------------------------------------------------------------
 *
 * numeric.h
 *        Definitions for the exact numeric data type of Postgres
 *
 * Original coding 1998, Jan Wieck.  Heavily revised 2003, Tom Lane.
 *
 * Copyright (c) 1998-2005, PostgreSQL Global Development Group
 *
 * $PostgreSQL: pgsql/src/include/utils/numeric.h,v 1.20 2005/01/01 05:43:09 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#ifndef _PG_NUMERIC_H_
#define _PG_NUMERIC_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


/*
 * Sign values and macros to deal with packing/unpacking n_sign_dscale
 */
#define NUMERIC_SIGN_MASK       0xC000
#define NUMERIC_POS                     0x0000
#define NUMERIC_NEG                     0x4000
#define NUMERIC_NAN                     0xC000
#define NUMERIC_DSCALE_MASK 0x3FFF
#define NUMERIC_SIGN(n)         ((n)->n_sign_dscale & NUMERIC_SIGN_MASK)
#define NUMERIC_DSCALE(n)       ((n)->n_sign_dscale & NUMERIC_DSCALE_MASK)
#define NUMERIC_IS_NAN(n)       (NUMERIC_SIGN(n) != NUMERIC_POS &&      \
                                                         NUMERIC_SIGN(n) != NUMERIC_NEG)


/*
 * The Numeric data type stored in the database
 *
 * NOTE: by convention, values in the packed form have been stripped of
 * all leading and trailing zero digits (where a "digit" is of base NBASE).
 * In particular, if the value is zero, there will be no digits at all!
 * The weight is arbitrary in that case, but we normally set it to zero.
 */
typedef struct NumericData
{
        int32           varlen;                 /* Variable size (std varlena header) */
        int16           n_weight;               /* Weight of 1st digit  */
        uint16          n_sign_dscale;  /* Sign + display scale */
        char            n_data[1];              /* Digits (really array of NumericDigit) */
} NumericData;

typedef NumericData *Numeric;

#define NUMERIC_HDRSZ   (sizeof(int32) + sizeof(int16) + sizeof(uint16))


/*
 * 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)

#endif   /* _PG_NUMERIC_H_ */