/* atof_tahoe.c - turn a string into a Tahoe floating point number Copyright (C) 1987, 1998 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? Devon E Bowen I don't allow uppercase letters in the precision descrpitors. i.e. '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 < littlenum_end) return 0; if (number_of_bits >= 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; { /* Floating Reserved Operand Code. */ *words = 0x8000; } static int /* 0 means letter is OK. */ what_kind_of_float (letter, precisionP, exponent_bitsP) /* In: lowercase please. What kind of float? */ char letter; /* Number of 16-bit words in the float. */ int *precisionP; /* Number of exponent bits. */ long int *exponent_bitsP; { 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)) { /* We lost. */ return_value = NULL; 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); /* We lost. */ return_value = NULL; } 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; } /* 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 0. * 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 ? 0 : _("Bad call to md_atof()"); }