97 lines
2.3 KiB
C
97 lines
2.3 KiB
C
/*
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#define PRT_EXIT
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#define PRT_ENTRY
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#define PRT_DBL
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CONVERTS FLOATING POINT TO EXTENDED FORMAT
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Two sizes of FLOATING Point are known:
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SINGLE and DOUBLE
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*/
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/********************************************************/
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/*
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It is not required to normalize in extended
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format, but it has been chosen to do so.
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Extended Format is as follows (at exit):
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->sign S000 0000 | 0000 0000 <SIGN>
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->exp 0EEE EEEE | EEEE EEEE <EXPONENT>
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->m1 LFFF FFFF | FFFF FFFF <L.Fraction>
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FFFF FFFF | FFFF FFFF <Fraction>
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->m2 FFFF FFFF | FFFF FFFF <Fraction>
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FFFF F000 | 0000 0000 <Fraction>
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*/
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/********************************************************/
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#include "FP_bias.h"
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#include "FP_shift.h"
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#include "FP_types.h"
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#include "get_put.h"
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/********************************************************/
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extend(from,to,size)
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_double *from;
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EXTEND *to;
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int size;
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{
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DOUBLE *f;
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register char *cpt1,*cpt2;
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unsigned long tmp;
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int leadbit = 0;
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#ifdef PRT_ENTRY
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write(2,"entry extend: ",14);
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#ifdef PRT_DBL
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prt_dbl(from,size);
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#else
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write(2,"\n",1);
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#endif PRT_DBL
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#endif PRT_ENTRY
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f = (DOUBLE *) from; /* local cast conversion */
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if (f->_s.p1.fract == 0L) {
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if (size == sizeof(SINGLE)) {
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zero: zrf_ext(to);
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goto ready;
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}
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else if (f->_s.p2 == 0L)
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goto zero;
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}
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/* there is a number to convert so lets get started */
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/* first extract the exponent; its always in the first two bytes */
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cpt1 = (char *) from;
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to->exp = uget2(cpt1);
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to->sign = (to->exp & 0x8000); /* set sign bit */
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to->exp ^= to->sign;
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if (size == sizeof(DOUBLE))
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to->exp >>= DBL_EXPSHIFT;
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else
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to->exp >>= SGL_EXPSHIFT;
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if (to->exp > 0)
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leadbit++; /* will set Lead bit later */
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to->m1 = get4(cpt1);
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if (size == sizeof(DOUBLE)) {
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to->m1 <<= DBL_M1LEFT; /* shift */
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to->exp -= DBL_BIAS; /* remove bias */
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cpt1 += 4;
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tmp = get4(cpt1);
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to->m1 |= (tmp>>DBL_RPACK); /* plus 10 == 32 */
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to->m2 = (tmp<<DBL_LPACK); /* plus 22 == 32 */
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}
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else { /* size == sizeof(SINGLE) */
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to->m1 <<= SGL_M1LEFT; /* shift */
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to->exp -= SGL_BIAS; /* remove bias */
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to->m2 = 0L;
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}
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to->m1 |= NORMBIT; /* set bit L */
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if (leadbit == 0) /* set or clear Leading Bit */
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to->m1 &= ~NORMBIT; /* clear bit L */
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ready:
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#ifdef PRT_EXIT
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prt_ext("exit extend:",to)
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#endif PRT_EXIT
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; /* end of print statement or null statement */
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}
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