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221 lines
9.9 KiB
�
221 lines
9.9 KiB
�
/* ------------------------------------------------------------------ */
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/* Packed Decimal conversion module */
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/* ------------------------------------------------------------------ */
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/* Copyright (c) IBM Corporation, 2000, 2002. All rights reserved. */
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/* */
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/* This software is made available under the terms of the */
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/* ICU License -- ICU 1.8.1 and later. */
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/* */
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/* The description and User's Guide ("The decNumber C Library") for */
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/* this software is called decNumber.pdf. This document is */
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/* available, together with arithmetic and format specifications, */
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/* testcases, and Web links, on the General Decimal Arithmetic page. */
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/* */
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/* Please send comments, suggestions, and corrections to the author: */
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/* mfc@uk.ibm.com */
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/* Mike Cowlishaw, IBM Fellow */
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/* IBM UK, PO Box 31, Birmingham Road, Warwick CV34 5JL, UK */
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/* ------------------------------------------------------------------ */
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/* This module comprises the routines for Packed Decimal format */
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/* numbers. Conversions are supplied to and from decNumber, which in */
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/* turn supports: */
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/* conversions to and from string */
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/* arithmetic routines */
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/* utilities. */
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/* Conversions from decNumber to and from densely packed decimal */
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/* formats are provided by the decimal32 through decimal128 modules. */
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/* ------------------------------------------------------------------ */
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#include <string.h> // for NULL
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#include "decNumber.h" // base number library
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#include "decPacked.h" // packed decimal
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#include "decNumberLocal.h" // decNumber local types, etc.
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/* ------------------------------------------------------------------ */
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/* decPackedFromNumber -- convert decNumber to BCD Packed Decimal */
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/* */
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/* bcd is the BCD bytes */
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/* length is the length of the BCD array */
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/* scale is the scale result */
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/* dn is the decNumber */
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/* returns bcd, or NULL if error */
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/* */
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/* The number is converted to a BCD packed decimal byte array, */
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/* right aligned in the bcd array, whose length is indicated by the */
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/* second parameter. The final 4-bit nibble in the array will be a */
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/* sign nibble, C (1100) for + and D (1101) for -. Unused bytes and */
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/* nibbles to the left of the number are set to 0. */
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/* */
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/* scale is set to the scale of the number (this is the exponent, */
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/* negated). To force the number to a specified scale, first use the */
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/* decNumberRescale routine, which will round and change the exponent */
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/* as necessary. */
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/* */
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/* If there is an error (that is, the decNumber has too many digits */
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/* to fit in length bytes, or it is a NaN or Infinity), NULL is */
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/* returned and the bcd and scale results are unchanged. Otherwise */
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/* bcd is returned. */
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/* ------------------------------------------------------------------ */
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uByte * decPackedFromNumber(uByte *bcd, Int length, Int *scale,
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const decNumber *dn) {
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const Unit *up=dn->lsu; // Unit array pointer
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uByte obyte, *out; // current output byte, and where it goes
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Int indigs=dn->digits; // digits processed
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uInt cut=DECDPUN; // downcounter per Unit
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uInt u=*up; // work
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uInt nib; // ..
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#if DECDPUN<=4
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uInt temp; // ..
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#endif
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if (dn->digits>length*2-1 // too long ..
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||(dn->bits & DECSPECIAL)) return NULL; // .. or special -- hopeless
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if (dn->bits&DECNEG) obyte=DECPMINUS; // set the sign ..
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else obyte=DECPPLUS;
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*scale=-dn->exponent; // .. and scale
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// loop from lowest (rightmost) byte
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out=bcd+length-1; // -> final byte
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for (; out>=bcd; out--) {
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if (indigs>0) {
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if (cut==0) {
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up++;
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u=*up;
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cut=DECDPUN;
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}
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#if DECDPUN<=4
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temp=(u*6554)>>16; // fast /10
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nib=u-X10(temp);
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u=temp;
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#else
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nib=u%10; // cannot use *6554 trick :-(
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u=u/10;
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#endif
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obyte|=(nib<<4);
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indigs--;
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cut--;
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}
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*out=obyte;
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obyte=0; // assume 0
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if (indigs>0) {
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if (cut==0) {
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up++;
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u=*up;
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cut=DECDPUN;
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}
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#if DECDPUN<=4
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temp=(u*6554)>>16; // as above
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obyte=(uByte)(u-X10(temp));
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u=temp;
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#else
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obyte=(uByte)(u%10);
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u=u/10;
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#endif
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indigs--;
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cut--;
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}
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} // loop
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return bcd;
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} // decPackedFromNumber
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/* ------------------------------------------------------------------ */
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/* decPackedToNumber -- convert BCD Packed Decimal to a decNumber */
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/* */
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/* bcd is the BCD bytes */
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/* length is the length of the BCD array */
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/* scale is the scale associated with the BCD integer */
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/* dn is the decNumber [with space for length*2 digits] */
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/* returns dn, or NULL if error */
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/* */
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/* The BCD packed decimal byte array, together with an associated */
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/* scale, is converted to a decNumber. The BCD array is assumed full */
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/* of digits, and must be ended by a 4-bit sign nibble in the least */
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/* significant four bits of the final byte. */
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/* */
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/* The scale is used (negated) as the exponent of the decNumber. */
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/* Note that zeros may have a sign and/or a scale. */
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/* */
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/* The decNumber structure is assumed to have sufficient space to */
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/* hold the converted number (that is, up to length*2-1 digits), so */
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/* no error is possible unless the adjusted exponent is out of range, */
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/* no sign nibble was found, or a sign nibble was found before the */
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/* final nibble. In these error cases, NULL is returned and the */
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/* decNumber will be 0. */
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/* ------------------------------------------------------------------ */
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decNumber * decPackedToNumber(const uByte *bcd, Int length,
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const Int *scale, decNumber *dn) {
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const uByte *last=bcd+length-1; // -> last byte
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const uByte *first; // -> first non-zero byte
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uInt nib; // work nibble
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Unit *up=dn->lsu; // output pointer
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Int digits; // digits count
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Int cut=0; // phase of output
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decNumberZero(dn); // default result
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last=&bcd[length-1];
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nib=*last & 0x0f; // get the sign
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if (nib==DECPMINUS || nib==DECPMINUSALT) dn->bits=DECNEG;
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else if (nib<=9) return NULL; // not a sign nibble
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// skip leading zero bytes [final byte is always non-zero, due to sign]
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for (first=bcd; *first==0;) first++;
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digits=(last-first)*2+1; // calculate digits ..
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if ((*first & 0xf0)==0) digits--; // adjust for leading zero nibble
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if (digits!=0) dn->digits=digits; // count of actual digits [if 0,
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// leave as 1]
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// check the adjusted exponent; note that scale could be unbounded
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dn->exponent=-*scale; // set the exponent
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if (*scale>=0) { // usual case
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if ((dn->digits-*scale-1)<-DECNUMMAXE) { // underflow
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decNumberZero(dn);
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return NULL;}
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}
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else { // -ve scale; +ve exponent
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// need to be careful to avoid wrap, here, also BADINT case
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if ((*scale<-DECNUMMAXE) // overflow even without digits
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|| ((dn->digits-*scale-1)>DECNUMMAXE)) { // overflow
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decNumberZero(dn);
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return NULL;}
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}
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if (digits==0) return dn; // result was zero
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// copy the digits to the number's units, starting at the lsu
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// [unrolled]
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for (;;) { // forever
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// left nibble first
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nib=(unsigned)(*last & 0xf0)>>4;
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// got a digit, in nib
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if (nib>9) {decNumberZero(dn); return NULL;}
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if (cut==0) *up=(Unit)nib;
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else *up=(Unit)(*up+nib*DECPOWERS[cut]);
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digits--;
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if (digits==0) break; // got them all
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cut++;
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if (cut==DECDPUN) {
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up++;
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cut=0;
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}
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last--; // ready for next
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nib=*last & 0x0f; // get right nibble
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if (nib>9) {decNumberZero(dn); return NULL;}
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// got a digit, in nib
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if (cut==0) *up=(Unit)nib;
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else *up=(Unit)(*up+nib*DECPOWERS[cut]);
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digits--;
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if (digits==0) break; // got them all
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cut++;
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if (cut==DECDPUN) {
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up++;
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cut=0;
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}
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} // forever
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return dn;
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} // decPackedToNumber
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