/* $OpenBSD: atof-tahoe.c,v 1.2 1998/02/15 18:49:10 niklas Exp $ */ /* atof_tahoe.c - turn a string into a Tahoe floating point number Copyright (C) 1987 Free Software Foundation, Inc. */ /* This is really a simplified version of atof_vax.c. I glommed it wholesale and then shaved it down. I don't even know how it works. (Don't you find my honesty refreshing? bowen@cs.Buffalo.EDU (Devon E Bowen) I don't allow uppercase letters in the precision descrpitors. Ie 'f' and 'd' are allowed but 'F' and 'D' aren't */ #include "as.h" /* Precision in LittleNums. */ #define MAX_PRECISION (4) #define D_PRECISION (4) #define F_PRECISION (2) /* Precision in chars. */ #define D_PRECISION_CHARS (8) #define F_PRECISION_CHARS (4) /* Length in LittleNums of guard bits. */ #define GUARD (2) static const long int mask [] = { 0x00000000, 0x00000001, 0x00000003, 0x00000007, 0x0000000f, 0x0000001f, 0x0000003f, 0x0000007f, 0x000000ff, 0x000001ff, 0x000003ff, 0x000007ff, 0x00000fff, 0x00001fff, 0x00003fff, 0x00007fff, 0x0000ffff, 0x0001ffff, 0x0003ffff, 0x0007ffff, 0x000fffff, 0x001fffff, 0x003fffff, 0x007fffff, 0x00ffffff, 0x01ffffff, 0x03ffffff, 0x07ffffff, 0x0fffffff, 0x1fffffff, 0x3fffffff, 0x7fffffff, 0xffffffff }; /* Shared between flonum_gen2tahoe and next_bits */ static int bits_left_in_littlenum; static LITTLENUM_TYPE * littlenum_pointer; static LITTLENUM_TYPE * littlenum_end; #if __STDC__ == 1 int flonum_gen2tahoe(int format_letter, FLONUM_TYPE *f, LITTLENUM_TYPE *words); #else /* not __STDC__ */ int flonum_gen2tahoe(); #endif /* not __STDC__ */ static int next_bits (number_of_bits) int number_of_bits; { int return_value; if(littlenum_pointer= bits_left_in_littlenum) { return_value = mask [bits_left_in_littlenum] & * littlenum_pointer; number_of_bits -= bits_left_in_littlenum; return_value <<= number_of_bits; bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS - number_of_bits; littlenum_pointer --; if(littlenum_pointer>=littlenum_end) return_value |= ((*littlenum_pointer) >> (bits_left_in_littlenum)) & mask [number_of_bits]; } else { bits_left_in_littlenum -= number_of_bits; return_value = mask [number_of_bits] & ((*littlenum_pointer) >> bits_left_in_littlenum); } return (return_value); } static void make_invalid_floating_point_number (words) LITTLENUM_TYPE * words; { *words = 0x8000; /* Floating Reserved Operand Code */ } static int /* 0 means letter is OK. */ what_kind_of_float (letter, precisionP, exponent_bitsP) char letter; /* In: lowercase please. What kind of float? */ int * precisionP; /* Number of 16-bit words in the float. */ long int * exponent_bitsP; /* Number of exponent bits. */ { int retval; /* 0: OK. */ retval = 0; switch (letter) { case 'f': * precisionP = F_PRECISION; * exponent_bitsP = 8; break; case 'd': * precisionP = D_PRECISION; * exponent_bitsP = 8; break; default: retval = 69; break; } return (retval); } /***********************************************************************\ * * * Warning: this returns 16-bit LITTLENUMs, because that is * * what the VAX thinks in. It is up to the caller to figure * * out any alignment problems and to conspire for the bytes/word * * to be emitted in the right order. Bigendians beware! * * * \***********************************************************************/ char * /* Return pointer past text consumed. */ atof_tahoe (str, what_kind, words) char * str; /* Text to convert to binary. */ char what_kind; /* 'd', 'f', 'g', 'h' */ LITTLENUM_TYPE * words; /* Build the binary here. */ { FLONUM_TYPE f; LITTLENUM_TYPE bits [MAX_PRECISION + MAX_PRECISION + GUARD]; /* Extra bits for zeroed low-order bits. */ /* The 1st MAX_PRECISION are zeroed, */ /* the last contain flonum bits. */ char * return_value; int precision; /* Number of 16-bit words in the format. */ long int exponent_bits; return_value = str; f . low = bits + MAX_PRECISION; f . high = NULL; f . leader = NULL; f . exponent = NULL; f . sign = '\0'; if (what_kind_of_float (what_kind, & precision, & exponent_bits)) { return_value = NULL; /* We lost. */ make_invalid_floating_point_number (words); } if (return_value) { memset(bits, '\0', sizeof(LITTLENUM_TYPE) * MAX_PRECISION); /* Use more LittleNums than seems */ /* necessary: the highest flonum may have */ /* 15 leading 0 bits, so could be useless. */ f . high = f . low + precision - 1 + GUARD; if (atof_generic (& return_value, ".", "eE", & f)) { make_invalid_floating_point_number (words); return_value = NULL; /* we lost */ } else { if (flonum_gen2tahoe (what_kind, & f, words)) { return_value = NULL; } } } return (return_value); } /* * In: a flonum, a Tahoe floating point format. * Out: a Tahoe floating-point bit pattern. */ int /* 0: OK. */ flonum_gen2tahoe (format_letter, f, words) char format_letter; /* One of 'd' 'f'. */ FLONUM_TYPE * f; LITTLENUM_TYPE * words; /* Deliver answer here. */ { LITTLENUM_TYPE * lp; int precision; long int exponent_bits; int return_value; /* 0 == OK. */ return_value = what_kind_of_float(format_letter,&precision,&exponent_bits); if (return_value != 0) { make_invalid_floating_point_number (words); } else { if (f -> low > f -> leader) { /* 0.0e0 seen. */ memset(words, '\0', sizeof(LITTLENUM_TYPE) * precision); } else { long int exponent_1; long int exponent_2; long int exponent_3; long int exponent_4; int exponent_skippage; LITTLENUM_TYPE word1; /* JF: Deal with new Nan, +Inf and -Inf codes */ if(f->sign!='-' && f->sign!='+') { make_invalid_floating_point_number(words); return return_value; } /* * All tahoe floating_point formats have: * Bit 15 is sign bit. * Bits 14:n are excess-whatever exponent. * Bits n-1:0 (if any) are most significant bits of fraction. * Bits 15:0 of the next word are the next most significant bits. * And so on for each other word. * * So we need: number of bits of exponent, number of bits of * mantissa. */ bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS; littlenum_pointer = f -> leader; littlenum_end = f->low; /* Seek (and forget) 1st significant bit */ for (exponent_skippage = 0; ! next_bits(1); exponent_skippage ++) { } exponent_1 = f -> exponent + f -> leader + 1 - f -> low; /* Radix LITTLENUM_RADIX, point just higher than f -> leader. */ exponent_2 = exponent_1 * LITTLENUM_NUMBER_OF_BITS; /* Radix 2. */ exponent_3 = exponent_2 - exponent_skippage; /* Forget leading zeros, forget 1st bit. */ exponent_4 = exponent_3 + (1 << (exponent_bits - 1)); /* Offset exponent. */ if (exponent_4 & ~ mask [exponent_bits]) { /* * Exponent overflow. Lose immediately. */ make_invalid_floating_point_number (words); /* * We leave return_value alone: admit we read the * number, but return a floating exception * because we can't encode the number. */ } else { lp = words; /* Word 1. Sign, exponent and perhaps high bits. */ /* Assume 2's complement integers. */ word1 = ((exponent_4 & mask [exponent_bits]) << (15 - exponent_bits)) | ((f -> sign == '+') ? 0 : 0x8000) | next_bits (15 - exponent_bits); * lp ++ = word1; /* The rest of the words are just mantissa bits. */ for (; lp < words + precision; lp++) { * lp = next_bits (LITTLENUM_NUMBER_OF_BITS); } if (next_bits (1)) { /* * Since the NEXT bit is a 1, round UP the mantissa. * The cunning design of these hidden-1 floats permits * us to let the mantissa overflow into the exponent, and * it 'does the right thing'. However, we lose if the * highest-order bit of the lowest-order word flips. * Is that clear? */ unsigned long int carry; /* #if (sizeof(carry)) < ((sizeof(bits[0]) * BITS_PER_CHAR) + 2) Please allow at least 1 more bit in carry than is in a LITTLENUM. We need that extra bit to hold a carry during a LITTLENUM carry propagation. Another extra bit (kept 0) will assure us that we don't get a sticky sign bit after shifting right, and that permits us to propagate the carry without any masking of bits. #endif */ for (carry = 1, lp --; carry && (lp >= words); lp --) { carry = * lp + carry; * lp = carry; carry >>= LITTLENUM_NUMBER_OF_BITS; } if ( (word1 ^ *words) & (1 << (LITTLENUM_NUMBER_OF_BITS - 1)) ) { make_invalid_floating_point_number (words); /* * We leave return_value alone: admit we read the * number, but return a floating exception * because we can't encode the number. */ } } /* if (we needed to round up) */ } /* if (exponent overflow) */ } /* if (0.0e0) */ } /* if (float_type was OK) */ return (return_value); } /* * md_atof() * * In: input_line_pointer -> the 1st character of a floating-point * number. * 1 letter denoting the type of statement that wants a * binary floating point number returned. * Address of where to build floating point literal. * Assumed to be 'big enough'. * Address of where to return size of literal (in chars). * * Out: Input_line_pointer -> of next char after floating number. * Error message, or "". * Floating point literal. * Number of chars we used for the literal. */ char * md_atof (what_statement_type, literalP, sizeP) char what_statement_type; char * literalP; int * sizeP; { LITTLENUM_TYPE words [MAX_PRECISION]; register char kind_of_float; register int number_of_chars; register LITTLENUM_TYPE * littlenum_pointer; switch (what_statement_type) { case 'f': /* .ffloat */ case 'd': /* .dfloat */ kind_of_float = what_statement_type; break; default: kind_of_float = 0; break; }; if (kind_of_float) { register LITTLENUM_TYPE * limit; input_line_pointer = atof_tahoe (input_line_pointer, kind_of_float, words); /* * The atof_tahoe() builds up 16-bit numbers. * Since the assembler may not be running on * a different-endian machine, be very careful about * converting words to chars. */ number_of_chars = (kind_of_float == 'f' ? F_PRECISION_CHARS : (kind_of_float == 'd' ? D_PRECISION_CHARS : 0)); know(number_of_chars<=MAX_PRECISION*sizeof(LITTLENUM_TYPE)); limit = words + (number_of_chars / sizeof(LITTLENUM_TYPE)); for (littlenum_pointer = words; littlenum_pointer < limit; littlenum_pointer ++) { md_number_to_chars(literalP,*littlenum_pointer, sizeof(LITTLENUM_TYPE)); literalP += sizeof(LITTLENUM_TYPE); }; } else { number_of_chars = 0; }; * sizeP = number_of_chars; return (kind_of_float ? "" : "Bad call to md_atof()"); } /* md_atof() */ /* atof_tahoe.c */