libdecnumber/decContext.c

/* Decimal context module for the decNumber C Library.
   Copyright (C) 2005-2018 Free Software Foundation, Inc.
   Contributed by IBM Corporation.  Author Mike Cowlishaw.

   This file is part of GCC.

   GCC is free software; you can redistribute it and/or modify it under
   the terms of the GNU General Public License as published by the Free
   Software Foundation; either version 3, or (at your option) any later
   version.

   GCC is distributed in the hope that it will be useful, but WITHOUT ANY
   WARRANTY; without even the implied warranty of MERCHANTABILITY or
   FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   for more details.

Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.

You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
<http://www.gnu.org/licenses/>.  */

/* ------------------------------------------------------------------ */
/* Decimal Context module					      */
/* ------------------------------------------------------------------ */
/* This module comprises the routines for handling arithmetic	      */
/* context structures.						      */
/* ------------------------------------------------------------------ */

#include <string.h>	      /* for strcmp */
#ifdef DECCHECK
#include <stdio.h>	      /* for printf if DECCHECK */
#endif
#include "dconfig.h"	      /* for GCC definitions */
#include "decContext.h"       /* context and base types */
#include "decNumberLocal.h"   /* decNumber local types, etc. */

/* compile-time endian tester [assumes sizeof(Int)>1] */
static	const  Int mfcone=1;		     /* constant 1 */
static	const  Flag *mfctop=(const Flag *)&mfcone; /* -> top byte */
#define LITEND *mfctop		   /* named flag; 1=little-endian */

/* ------------------------------------------------------------------ */
/* round-for-reround digits					      */
/* ------------------------------------------------------------------ */
const uByte DECSTICKYTAB[10]={1,1,2,3,4,6,6,7,8,9}; /* used if sticky */

/* ------------------------------------------------------------------ */
/* Powers of ten (powers[n]==10**n, 0<=n<=9)			      */
/* ------------------------------------------------------------------ */
const uInt DECPOWERS[10]={1, 10, 100, 1000, 10000, 100000, 1000000,
			  10000000, 100000000, 1000000000};

/* ------------------------------------------------------------------ */
/* decContextClearStatus -- clear bits in current status	      */
/*								      */
/*  context is the context structure to be queried		      */
/*  mask indicates the bits to be cleared (the status bit that	      */
/*    corresponds to each 1 bit in the mask is cleared) 	      */
/*  returns context						      */
/*								      */
/* No error is possible.					      */
/* ------------------------------------------------------------------ */
decContext *decContextClearStatus(decContext *context, uInt mask) {
  context->status&=~mask;
  return context;
  } /* decContextClearStatus */

/* ------------------------------------------------------------------ */
/* decContextDefault -- initialize a context structure		      */
/*								      */
/*  context is the structure to be initialized			      */
/*  kind selects the required set of default values, one of:	      */
/*	DEC_INIT_BASE	    -- select ANSI X3-274 defaults	      */
/*	DEC_INIT_DECIMAL32  -- select IEEE 754 defaults, 32-bit       */
/*	DEC_INIT_DECIMAL64  -- select IEEE 754 defaults, 64-bit       */
/*	DEC_INIT_DECIMAL128 -- select IEEE 754 defaults, 128-bit      */
/*	For any other value a valid context is returned, but with     */
/*	Invalid_operation set in the status field.		      */
/*  returns a context structure with the appropriate initial values.  */
/* ------------------------------------------------------------------ */
decContext * decContextDefault(decContext *context, Int kind) {
  /* set defaults... */
  context->digits=9;			     /* 9 digits */
  context->emax=DEC_MAX_EMAX;		     /* 9-digit exponents */
  context->emin=DEC_MIN_EMIN;		     /* .. balanced */
  context->round=DEC_ROUND_HALF_UP;	     /* 0.5 rises */
  context->traps=DEC_Errors;		     /* all but informational */
  context->status=0;			     /* cleared */
  context->clamp=0;			     /* no clamping */
  #if DECSUBSET
  context->extended=0;			     /* cleared */
  #endif
  switch (kind) {
    case DEC_INIT_BASE:
      /* [use defaults] */
      break;
    case DEC_INIT_DECIMAL32:
      context->digits=7;		     /* digits */
      context->emax=96; 		     /* Emax */
      context->emin=-95;		     /* Emin */
      context->round=DEC_ROUND_HALF_EVEN;    /* 0.5 to nearest even */
      context->traps=0; 		     /* no traps set */
      context->clamp=1; 		     /* clamp exponents */
      #if DECSUBSET
      context->extended=1;		     /* set */
      #endif
      break;
    case DEC_INIT_DECIMAL64:
      context->digits=16;		     /* digits */
      context->emax=384;		     /* Emax */
      context->emin=-383;		     /* Emin */
      context->round=DEC_ROUND_HALF_EVEN;    /* 0.5 to nearest even */
      context->traps=0; 		     /* no traps set */
      context->clamp=1; 		     /* clamp exponents */
      #if DECSUBSET
      context->extended=1;		     /* set */
      #endif
      break;
    case DEC_INIT_DECIMAL128:
      context->digits=34;		     /* digits */
      context->emax=6144;		     /* Emax */
      context->emin=-6143;		     /* Emin */
      context->round=DEC_ROUND_HALF_EVEN;    /* 0.5 to nearest even */
      context->traps=0; 		     /* no traps set */
      context->clamp=1; 		     /* clamp exponents */
      #if DECSUBSET
      context->extended=1;		     /* set */
      #endif
      break;

    default:				     /* invalid Kind */
      /* use defaults, and .. */
      decContextSetStatus(context, DEC_Invalid_operation); /* trap */
    }

  return context;} /* decContextDefault */

/* ------------------------------------------------------------------ */
/* decContextGetRounding -- return current rounding mode	      */
/*								      */
/*  context is the context structure to be queried		      */
/*  returns the rounding mode					      */
/*								      */
/* No error is possible.					      */
/* ------------------------------------------------------------------ */
enum rounding decContextGetRounding(decContext *context) {
  return context->round;
  } /* decContextGetRounding */

/* ------------------------------------------------------------------ */
/* decContextGetStatus -- return current status 		      */
/*								      */
/*  context is the context structure to be queried		      */
/*  returns status						      */
/*								      */
/* No error is possible.					      */
/* ------------------------------------------------------------------ */
uInt decContextGetStatus(decContext *context) {
  return context->status;
  } /* decContextGetStatus */

/* ------------------------------------------------------------------ */
/* decContextRestoreStatus -- restore bits in current status	      */
/*								      */
/*  context is the context structure to be updated		      */
/*  newstatus is the source for the bits to be restored 	      */
/*  mask indicates the bits to be restored (the status bit that       */
/*    corresponds to each 1 bit in the mask is set to the value of    */
/*    the correspnding bit in newstatus)			      */
/*  returns context						      */
/*								      */
/* No error is possible.					      */
/* ------------------------------------------------------------------ */
decContext *decContextRestoreStatus(decContext *context,
				    uInt newstatus, uInt mask) {
  context->status&=~mask;		/* clear the selected bits */
  context->status|=(mask&newstatus);	/* or in the new bits */
  return context;
  } /* decContextRestoreStatus */

/* ------------------------------------------------------------------ */
/* decContextSaveStatus -- save bits in current status		      */
/*								      */
/*  context is the context structure to be queried		      */
/*  mask indicates the bits to be saved (the status bits that	      */
/*    correspond to each 1 bit in the mask are saved)		      */
/*  returns the AND of the mask and the current status		      */
/*								      */
/* No error is possible.					      */
/* ------------------------------------------------------------------ */
uInt decContextSaveStatus(decContext *context, uInt mask) {
  return context->status&mask;
  } /* decContextSaveStatus */

/* ------------------------------------------------------------------ */
/* decContextSetRounding -- set current rounding mode		      */
/*								      */
/*  context is the context structure to be updated		      */
/*  newround is the value which will replace the current mode	      */
/*  returns context						      */
/*								      */
/* No error is possible.					      */
/* ------------------------------------------------------------------ */
decContext *decContextSetRounding(decContext *context,
				  enum rounding newround) {
  context->round=newround;
  return context;
  } /* decContextSetRounding */

/* ------------------------------------------------------------------ */
/* decContextSetStatus -- set status and raise trap if appropriate    */
/*								      */
/*  context is the context structure to be updated		      */
/*  status  is the DEC_ exception code				      */
/*  returns the context structure				      */
/*								      */
/* Control may never return from this routine, if there is a signal   */
/* handler and it takes a long jump.				      */
/* ------------------------------------------------------------------ */
decContext * decContextSetStatus(decContext *context, uInt status) {
  context->status|=status;
  if (status & context->traps) raise(SIGFPE);
  return context;} /* decContextSetStatus */

/* ------------------------------------------------------------------ */
/* decContextSetStatusFromString -- set status from a string + trap   */
/*								      */
/*  context is the context structure to be updated		      */
/*  string is a string exactly equal to one that might be returned    */
/*	      by decContextStatusToString			      */
/*								      */
/*  The status bit corresponding to the string is set, and a trap     */
/*  is raised if appropriate.					      */
/*								      */
/*  returns the context structure, unless the string is equal to      */
/*    DEC_Condition_MU or is not recognized.  In these cases NULL is  */
/*    returned. 						      */
/* ------------------------------------------------------------------ */
decContext * decContextSetStatusFromString(decContext *context,
					   const char *string) {
  if (strcmp(string, DEC_Condition_CS)==0)
    return decContextSetStatus(context, DEC_Conversion_syntax);
  if (strcmp(string, DEC_Condition_DZ)==0)
    return decContextSetStatus(context, DEC_Division_by_zero);
  if (strcmp(string, DEC_Condition_DI)==0)
    return decContextSetStatus(context, DEC_Division_impossible);
  if (strcmp(string, DEC_Condition_DU)==0)
    return decContextSetStatus(context, DEC_Division_undefined);
  if (strcmp(string, DEC_Condition_IE)==0)
    return decContextSetStatus(context, DEC_Inexact);
  if (strcmp(string, DEC_Condition_IS)==0)
    return decContextSetStatus(context, DEC_Insufficient_storage);
  if (strcmp(string, DEC_Condition_IC)==0)
    return decContextSetStatus(context, DEC_Invalid_context);
  if (strcmp(string, DEC_Condition_IO)==0)
    return decContextSetStatus(context, DEC_Invalid_operation);
  #if DECSUBSET
  if (strcmp(string, DEC_Condition_LD)==0)
    return decContextSetStatus(context, DEC_Lost_digits);
  #endif
  if (strcmp(string, DEC_Condition_OV)==0)
    return decContextSetStatus(context, DEC_Overflow);
  if (strcmp(string, DEC_Condition_PA)==0)
    return decContextSetStatus(context, DEC_Clamped);
  if (strcmp(string, DEC_Condition_RO)==0)
    return decContextSetStatus(context, DEC_Rounded);
  if (strcmp(string, DEC_Condition_SU)==0)
    return decContextSetStatus(context, DEC_Subnormal);
  if (strcmp(string, DEC_Condition_UN)==0)
    return decContextSetStatus(context, DEC_Underflow);
  if (strcmp(string, DEC_Condition_ZE)==0)
    return context;
  return NULL;	/* Multiple status, or unknown */
  } /* decContextSetStatusFromString */

/* ------------------------------------------------------------------ */
/* decContextSetStatusFromStringQuiet -- set status from a string     */
/*								      */
/*  context is the context structure to be updated		      */
/*  string is a string exactly equal to one that might be returned    */
/*	      by decContextStatusToString			      */
/*								      */
/*  The status bit corresponding to the string is set; no trap is     */
/*  raised.							      */
/*								      */
/*  returns the context structure, unless the string is equal to      */
/*    DEC_Condition_MU or is not recognized.  In these cases NULL is  */
/*    returned. 						      */
/* ------------------------------------------------------------------ */
decContext * decContextSetStatusFromStringQuiet(decContext *context,
						const char *string) {
  if (strcmp(string, DEC_Condition_CS)==0)
    return decContextSetStatusQuiet(context, DEC_Conversion_syntax);
  if (strcmp(string, DEC_Condition_DZ)==0)
    return decContextSetStatusQuiet(context, DEC_Division_by_zero);
  if (strcmp(string, DEC_Condition_DI)==0)
    return decContextSetStatusQuiet(context, DEC_Division_impossible);
  if (strcmp(string, DEC_Condition_DU)==0)
    return decContextSetStatusQuiet(context, DEC_Division_undefined);
  if (strcmp(string, DEC_Condition_IE)==0)
    return decContextSetStatusQuiet(context, DEC_Inexact);
  if (strcmp(string, DEC_Condition_IS)==0)
    return decContextSetStatusQuiet(context, DEC_Insufficient_storage);
  if (strcmp(string, DEC_Condition_IC)==0)
    return decContextSetStatusQuiet(context, DEC_Invalid_context);
  if (strcmp(string, DEC_Condition_IO)==0)
    return decContextSetStatusQuiet(context, DEC_Invalid_operation);
  #if DECSUBSET
  if (strcmp(string, DEC_Condition_LD)==0)
    return decContextSetStatusQuiet(context, DEC_Lost_digits);
  #endif
  if (strcmp(string, DEC_Condition_OV)==0)
    return decContextSetStatusQuiet(context, DEC_Overflow);
  if (strcmp(string, DEC_Condition_PA)==0)
    return decContextSetStatusQuiet(context, DEC_Clamped);
  if (strcmp(string, DEC_Condition_RO)==0)
    return decContextSetStatusQuiet(context, DEC_Rounded);
  if (strcmp(string, DEC_Condition_SU)==0)
    return decContextSetStatusQuiet(context, DEC_Subnormal);
  if (strcmp(string, DEC_Condition_UN)==0)
    return decContextSetStatusQuiet(context, DEC_Underflow);
  if (strcmp(string, DEC_Condition_ZE)==0)
    return context;
  return NULL;	/* Multiple status, or unknown */
  } /* decContextSetStatusFromStringQuiet */

/* ------------------------------------------------------------------ */
/* decContextSetStatusQuiet -- set status without trap		      */
/*								      */
/*  context is the context structure to be updated		      */
/*  status  is the DEC_ exception code				      */
/*  returns the context structure				      */
/*								      */
/* No error is possible.					      */
/* ------------------------------------------------------------------ */
decContext * decContextSetStatusQuiet(decContext *context, uInt status) {
  context->status|=status;
  return context;} /* decContextSetStatusQuiet */

/* ------------------------------------------------------------------ */
/* decContextStatusToString -- convert status flags to a string       */
/*								      */
/*  context is a context with valid status field		      */
/*								      */
/*  returns a constant string describing the condition.  If multiple  */
/*    (or no) flags are set, a generic constant message is returned.  */
/* ------------------------------------------------------------------ */
const char *decContextStatusToString(const decContext *context) {
  Int status=context->status;

  /* test the five IEEE first, as some of the others are ambiguous when */
  /* DECEXTFLAG=0 */
  if (status==DEC_Invalid_operation    ) return DEC_Condition_IO;
  if (status==DEC_Division_by_zero     ) return DEC_Condition_DZ;
  if (status==DEC_Overflow	       ) return DEC_Condition_OV;
  if (status==DEC_Underflow	       ) return DEC_Condition_UN;
  if (status==DEC_Inexact	       ) return DEC_Condition_IE;

  if (status==DEC_Division_impossible  ) return DEC_Condition_DI;
  if (status==DEC_Division_undefined   ) return DEC_Condition_DU;
  if (status==DEC_Rounded	       ) return DEC_Condition_RO;
  if (status==DEC_Clamped	       ) return DEC_Condition_PA;
  if (status==DEC_Subnormal	       ) return DEC_Condition_SU;
  if (status==DEC_Conversion_syntax    ) return DEC_Condition_CS;
  if (status==DEC_Insufficient_storage ) return DEC_Condition_IS;
  if (status==DEC_Invalid_context      ) return DEC_Condition_IC;
  #if DECSUBSET
  if (status==DEC_Lost_digits	       ) return DEC_Condition_LD;
  #endif
  if (status==0 		       ) return DEC_Condition_ZE;
  return DEC_Condition_MU;  /* Multiple errors */
  } /* decContextStatusToString */

/* ------------------------------------------------------------------ */
/* decContextTestEndian -- test whether DECLITEND is set correctly    */
/*								      */
/*  quiet is 1 to suppress message; 0 otherwise 		      */
/*  returns 0 if DECLITEND is correct				      */
/*	    1 if DECLITEND is incorrect and should be 1 	      */
/*	   -1 if DECLITEND is incorrect and should be 0 	      */
/*								      */
/* A message is displayed if the return value is not 0 and quiet==0.  */
/*								      */
/* No error is possible.					      */
/* ------------------------------------------------------------------ */
Int decContextTestEndian(Flag quiet) {
  Int res=0;		      /* optimist */
  uInt dle=(uInt)DECLITEND;   /* unsign */
  if (dle>1) dle=1;	      /* ensure 0 or 1 */

  if (LITEND!=DECLITEND) {
    if (!quiet) {
#if DECCHECK
      const char *adj;
      if (LITEND) adj="little";
	     else adj="big";
      printf("Warning: DECLITEND is set to %d, but this computer appears to be %s-endian\n",
	     DECLITEND, adj);
#endif
      }
    res=(Int)LITEND-dle;
    }
  return res;
  } /* decContextTestEndian */

/* ------------------------------------------------------------------ */
/* decContextTestSavedStatus -- test bits in saved status	      */
/*								      */
/*  oldstatus is the status word to be tested			      */
/*  mask indicates the bits to be tested (the oldstatus bits that     */
/*    correspond to each 1 bit in the mask are tested)		      */
/*  returns 1 if any of the tested bits are 1, or 0 otherwise	      */
/*								      */
/* No error is possible.					      */
/* ------------------------------------------------------------------ */
uInt decContextTestSavedStatus(uInt oldstatus, uInt mask) {
  return (oldstatus&mask)!=0;
  } /* decContextTestSavedStatus */

/* ------------------------------------------------------------------ */
/* decContextTestStatus -- test bits in current status		      */
/*								      */
/*  context is the context structure to be updated		      */
/*  mask indicates the bits to be tested (the status bits that	      */
/*    correspond to each 1 bit in the mask are tested)		      */
/*  returns 1 if any of the tested bits are 1, or 0 otherwise	      */
/*								      */
/* No error is possible.					      */
/* ------------------------------------------------------------------ */
uInt decContextTestStatus(decContext *context, uInt mask) {
  return (context->status&mask)!=0;
  } /* decContextTestStatus */

/* ------------------------------------------------------------------ */
/* decContextZeroStatus -- clear all status bits		      */
/*								      */
/*  context is the context structure to be updated		      */
/*  returns context						      */
/*								      */
/* No error is possible.					      */
/* ------------------------------------------------------------------ */
decContext *decContextZeroStatus(decContext *context) {
  context->status=0;
  return context;
  } /* decContextZeroStatus */