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decContext.c
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decContext.c
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/* ------------------------------------------------------------------ */
/* Decimal Context module */
/* ------------------------------------------------------------------ */
/* Copyright (c) IBM Corporation, 2000, 2009. All rights reserved. */
/* */
/* This software is made available under the terms of the */
/* ICU License -- ICU 1.8.1 and later. */
/* */
/* The description and User's Guide ("The decNumber C Library") for */
/* this software is called decNumber.pdf. This document is */
/* available, together with arithmetic and format specifications, */
/* testcases, and Web links, on the General Decimal Arithmetic page. */
/* */
/* Please send comments, suggestions, and corrections to the author: */
/* [email protected] */
/* Mike Cowlishaw, IBM Fellow */
/* IBM UK, PO Box 31, Birmingham Road, Warwick CV34 5JL, UK */
/* ------------------------------------------------------------------ */
/* This module comprises the routines for handling arithmetic */
/* context structures. */
/* ------------------------------------------------------------------ */
#include <string.h> // for strcmp
#include <stdio.h> // for printf if DECCHECK
#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) { // always refer to this
#if DECPRINT
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