176 lines
3.4 KiB
C
176 lines
3.4 KiB
C
/* $NetBSD: dolfptoa.c,v 1.3 2006/06/11 19:34:10 kardel Exp $ */
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/*
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* dolfptoa - do the grunge work of converting an l_fp number to decimal
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*/
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#include <stdio.h>
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#include "ntp_fp.h"
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#include "lib_strbuf.h"
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#include "ntp_string.h"
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#include "ntp_stdlib.h"
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char *
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dolfptoa(
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u_long fpi,
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u_long fpv,
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int neg,
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short ndec,
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int msec
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)
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{
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register u_char *cp, *cpend;
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register u_long lwork;
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register int dec;
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u_char cbuf[24];
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u_char *cpdec;
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char *buf;
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char *bp;
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/*
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* Get a string buffer before starting
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*/
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LIB_GETBUF(buf);
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/*
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* Zero the character buffer
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*/
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memset((char *) cbuf, 0, sizeof(cbuf));
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/*
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* safeguard against sign extensions and other mishaps on 64 bit platforms
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* the code following is designed for and only for 32-bit inputs and
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* only 32-bit worth of input are supplied.
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*/
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fpi &= 0xffffffff;
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fpv &= 0xffffffff;
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/*
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* Work on the integral part. This is biased by what I know
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* compiles fairly well for a 68000.
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*/
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cp = cpend = &cbuf[10];
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lwork = fpi;
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if (lwork & 0xffff0000) {
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register u_long lten = 10;
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register u_long ltmp;
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do {
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ltmp = lwork;
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lwork /= lten;
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ltmp -= (lwork << 3) + (lwork << 1);
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if (cp < cbuf) abort(); /* rather die a horrible death than trash the memory */
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*--cp = (u_char)ltmp;
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} while (lwork & 0xffff0000);
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}
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if (lwork != 0) {
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register u_short sten = 10;
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register u_short stmp;
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register u_short swork = (u_short)lwork;
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do {
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stmp = swork;
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swork = (u_short) (swork/sten);
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stmp = (u_short)(stmp - ((swork<<3) + (swork<<1)));
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if (cp < cbuf) abort(); /* rather die a horrible death than trash the memory */
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*--cp = (u_char)stmp;
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} while (swork != 0);
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}
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/*
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* Done that, now deal with the problem of the fraction. First
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* determine the number of decimal places.
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*/
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if (msec) {
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dec = ndec + 3;
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if (dec < 3)
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dec = 3;
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cpdec = &cbuf[13];
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} else {
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dec = ndec;
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if (dec < 0)
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dec = 0;
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cpdec = &cbuf[10];
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}
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if (dec > 12)
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dec = 12;
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/*
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* If there's a fraction to deal with, do so.
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*/
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if (fpv != 0) {
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l_fp work;
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work.l_ui = 0;
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work.l_uf = fpv;
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while (dec > 0) {
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l_fp ftmp;
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dec--;
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/*
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* The scheme here is to multiply the
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* fraction (0.1234...) by ten. This moves
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* a junk of BCD into the units part.
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* record that and iterate.
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*/
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work.l_ui = 0;
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L_LSHIFT(&work);
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ftmp = work;
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L_LSHIFT(&work);
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L_LSHIFT(&work);
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L_ADD(&work, &ftmp);
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*cpend++ = (u_char)work.l_ui;
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if (work.l_uf == 0)
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break;
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if (cpend > (cbuf + sizeof(cbuf))) abort(); /* rather die a horrible death than trash the memory */
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}
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/*
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* Rounding is rotten
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*/
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if (work.l_uf & 0x80000000) {
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register u_char *tp = cpend;
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*(--tp) += 1;
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while (*tp >= 10) {
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*tp = 0;
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*(--tp) += 1;
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};
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if (tp < cp)
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cp = tp;
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}
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}
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cpend += dec;
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/*
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* We've now got the fraction in cbuf[], with cp pointing at
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* the first character, cpend pointing past the last, and
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* cpdec pointing at the first character past the decimal.
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* Remove leading zeros, then format the number into the
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* buffer.
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*/
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while (cp < cpdec) {
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if (*cp != 0)
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break;
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cp++;
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}
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if (cp == cpdec)
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--cp;
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bp = buf;
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if (neg)
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*bp++ = '-';
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while (cp < cpend) {
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if (cp == cpdec)
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*bp++ = '.';
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*bp++ = (char)(*cp++ + '0'); /* ascii dependent? */
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}
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*bp = '\0';
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/*
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* Done!
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*/
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return buf;
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}
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