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Diffstat (limited to 'stdlib/strtod.c')
| -rw-r--r-- | stdlib/strtod.c | 1027 |
1 files changed, 1027 insertions, 0 deletions
diff --git a/stdlib/strtod.c b/stdlib/strtod.c new file mode 100644 index 0000000..d647753 --- /dev/null +++ b/stdlib/strtod.c @@ -0,0 +1,1027 @@ +/* Read decimal floating point numbers. +Copyright (C) 1995 Free Software Foundation, Inc. +Contributed by Ulrich Drepper. + +This file is part of the GNU C Library. + +The GNU C Library is free software; you can redistribute it and/or +modify it under the terms of the GNU Library General Public License as +published by the Free Software Foundation; either version 2 of the +License, or (at your option) any later version. + +The GNU C Library is distributed in the hope that it will be useful, +but WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +Library General Public License for more details. + +You should have received a copy of the GNU Library General Public +License along with the GNU C Library; see the file COPYING.LIB. If +not, write to the Free Software Foundation, Inc., 675 Mass Ave, +Cambridge, MA 02139, USA. */ + +/* Configuration part. These macros are defined by `strtold.c' and `strtof.c' + to produce the `long double' and `float' versions of the reader. */ +#ifndef FLOAT +#define FLOAT double +#define FLT DBL +#define STRTOF strtod +#define MPN2FLOAT __mpn_construct_double +#define FLOAT_HUGE_VAL HUGE_VAL +#endif +/* End of configuration part. */ + +#include <ctype.h> +#include <errno.h> +#include <float.h> +#include <localeinfo.h> +#include <math.h> +#include <stdlib.h> +#include "../stdio/gmp.h" +#include "../stdio/gmp-impl.h" +#include <gmp-mparam.h> +#include "../stdio/longlong.h" +#include "../stdio/fpioconst.h" + +/* #define NDEBUG 1 */ +#include <assert.h> + + +/* Constants we need from float.h; select the set for the FLOAT precision. */ +#define MANT_DIG FLT##_MANT_DIG +#define MAX_EXP FLT##_MAX_EXP +#define MIN_EXP FLT##_MIN_EXP +#define MAX_10_EXP FLT##_MAX_10_EXP +#define MIN_10_EXP FLT##_MIN_10_EXP +#define MAX_10_EXP_LOG FLT##_MAX_10_EXP_LOG + + +/* Function to construct a floating point number from an MP integer + containing the fraction bits, a base 2 exponent, and a sign flag. */ +extern FLOAT MPN2FLOAT (mp_srcptr mpn, int exponent, int negative); + +/* Definitions according to limb size used. */ +#if BITS_PER_MP_LIMB == 32 +# define MAX_DIG_PER_LIMB 9 +# define MAX_FAC_PER_LIMB 1000000000L +#elif BITS_PER_MP_LIMB == 64 +# define MAX_DIG_PER_LIMB 19 +# define MAX_FAC_PER_LIMB 10000000000000000000L +#else +# error "mp_limb size " BITS_PER_MP_LIMB "not accounted for" +#endif + + +/* Local data structure. */ +static const mp_limb _tens_in_limb[MAX_DIG_PER_LIMB] = +{ 0, 10, 100, + 1000, 10000, 100000, + 1000000, 10000000, 100000000 +#if BITS_PER_MP_LIMB > 32 + , 1000000000, 10000000000, 100000000000, + 1000000000000, 10000000000000, 100000000000000, + 1000000000000000, 10000000000000000, 100000000000000000, + 1000000000000000000 +#endif +#if BITS_PER_MP_LIMB > 64 + #error "Need to expand tens_in_limb table to" MAX_DIG_PER_LIMB +#endif +}; + +#ifndef howmany +#define howmany(x,y) (((x)+((y)-1))/(y)) +#endif +#define SWAP(x, y) ({ typeof(x) _tmp = x; x = y; y = _tmp; }) + +#define NDIG (MAX_10_EXP - MIN_10_EXP + 2 * MANT_DIG) +#define RETURN_LIMB_SIZE howmany (MANT_DIG, BITS_PER_MP_LIMB) + +#define RETURN(val,end) \ + do { if (endptr != 0) *endptr = (char *) end; return val; } while (0) + +/* Maximum size necessary for mpn integers to hold floating point numbers. */ +#define MPNSIZE (howmany (MAX_EXP + MANT_DIG, BITS_PER_MP_LIMB) + 1) +/* Declare an mpn integer variable that big. */ +#define MPN_VAR(name) mp_limb name[MPNSIZE]; mp_size_t name##size +/* Copy an mpn integer value. */ +#define MPN_ASSIGN(dst, src) \ + memcpy (dst, src, (dst##size = src##size) * sizeof (mp_limb)) + + +/* Return a floating point number of the needed type according to the given + multi-precision number after possible rounding. */ +static inline FLOAT +round_and_return (mp_limb *retval, int exponent, int negative, + mp_limb round_limb, mp_size_t round_bit, int more_bits) +{ + if (exponent < MIN_EXP) + { + mp_size_t shift = MIN_EXP - 1 - exponent; + + if (shift >= MANT_DIG) + { + errno = EDOM; + return 0.0; + } + + more_bits |= (round_limb & ((1 << round_bit) - 1)) != 0; + if (shift >= BITS_PER_MP_LIMB) + { + round_limb = retval[(shift - 1) / BITS_PER_MP_LIMB]; + round_bit = (shift - 1) % BITS_PER_MP_LIMB; +#if RETURN_LIMB_SIZE <= 2 + assert (RETURN_LIMB_SIZE == 2); + more_bits |= retval[0] != 0; + retval[0] = retval[1]; + retval[1] = 0; +#else + int disp = shift / BITS_PER_MP_LIMB; + int i = 0; + while (retval[i] == 0 && i < disp) + ++i; + more_bits |= i < disp; + for (i = disp; i < RETURN_LIMB_SIZE; ++i) + retval[i - disp] = retval[i]; + MPN_ZERO (&retval[RETURN_LIMB_SIZE - disp], disp); +#endif + shift %= BITS_PER_MP_LIMB; + } + else + { + round_limb = retval[0]; + round_bit = shift - 1; + } + (void) __mpn_rshift (retval, retval, RETURN_LIMB_SIZE, shift); + exponent = MIN_EXP - 2; + } + + if ((round_limb & (1 << round_bit)) != 0 && + (more_bits || (retval[0] & 1) != 0 || + (round_limb & ((1 << round_bit) - 1)) != 0)) + { + mp_limb cy = __mpn_add_1 (retval, retval, RETURN_LIMB_SIZE, 1); + if (cy || (retval[RETURN_LIMB_SIZE - 1] + & (1 << (MANT_DIG % BITS_PER_MP_LIMB))) != 0) + { + ++exponent; + (void) __mpn_rshift (retval, retval, RETURN_LIMB_SIZE, 1); + retval[RETURN_LIMB_SIZE - 1] |= 1 << (MANT_DIG % BITS_PER_MP_LIMB); + } + } + + if (exponent > MAX_EXP) + return negative ? -FLOAT_HUGE_VAL : FLOAT_HUGE_VAL; + + return MPN2FLOAT (retval, exponent, negative); +} + + +/* Read a multi-precision integer starting at STR with exactly DIGCNT digits + into N. Return the size of the number limbs in NSIZE at the first + character od the string that is not part of the integer as the function + value. If the EXPONENT is small enough to be taken as an additional + factor for the resulting number (see code) multiply by it. */ +static inline const char * +str_to_mpn (const char *str, int digcnt, mp_limb *n, mp_size_t *nsize, + int *exponent) +{ + /* Number of digits for actual limb. */ + int cnt = 0; + mp_limb low = 0; + mp_limb base; + + *nsize = 0; + assert (digcnt > 0); + do + { + if (cnt == MAX_DIG_PER_LIMB) + { + if (*nsize == 0) + n[0] = low; + else + { + mp_limb cy; + cy = __mpn_mul_1 (n, n, *nsize, MAX_FAC_PER_LIMB); + cy += __mpn_add_1 (n, n, *nsize, low); + if (cy != 0) + n[*nsize] = cy; + } + ++(*nsize); + cnt = 0; + low = 0; + } + + /* There might be thousands separators or radix characters in the string. + But these all can be ignored because we know the format of the number + is correct and we have an exact number of characters to read. */ + while (!isdigit (*str)) + ++str; + low = low * 10 + *str++ - '0'; + ++cnt; + } + while (--digcnt > 0); + + if (*exponent > 0 && cnt + *exponent <= MAX_DIG_PER_LIMB) + { + low *= _tens_in_limb[*exponent]; + base = _tens_in_limb[cnt + *exponent]; + *exponent = 0; + } + else + base = _tens_in_limb[cnt]; + + if (*nsize == 0) + { + n[0] = low; + *nsize = 1; + } + else + { + mp_limb cy; + cy = __mpn_mul_1 (n, n, *nsize, base); + cy += __mpn_add_1 (n, n, *nsize, low); + if (cy != 0) + n[(*nsize)++] = cy; + } + return str; +} + + +/* Shift {PTR, SIZE} COUNT bits to the left, and fill the vacated bits + with the COUNT most significant bits of LIMB. + + Tege doesn't like this function so I have to write it here myself. :) + --drepper */ +static inline void +__mpn_lshift_1 (mp_limb *ptr, mp_size_t size, unsigned int count, mp_limb limb) +{ + if (count == BITS_PER_MP_LIMB) + { + /* Optimize the case of shifting by exactly a word: + just copy words, with no actual bit-shifting. */ + mp_size_t i; + for (i = size - 1; i > 0; --i) + ptr[i] = ptr[i - 1]; + ptr[0] = limb; + } + else + { + (void) __mpn_lshift (ptr, ptr, size, count); + ptr[0] |= limb >> (BITS_PER_MP_LIMB - count); + } +} + + +/* Return a floating point number with the value of the given string NPTR. + Set *ENDPTR to the character after the last used one. If the number is + smaller than the smallest representable number, set `errno' to ERANGE and + return 0.0. If the number is too big to be represented, set `errno' to + ERANGE and return HUGE_VAL with the approriate sign. */ +FLOAT +STRTOF (nptr, endptr) + const char *nptr; + char **endptr; +{ + int negative; /* The sign of the number. */ + MPN_VAR (num); /* MP representation of the number. */ + int exponent; /* Exponent of the number. */ + + /* When we have to compute fractional digits we form a fraction with a + second multi-precision number (and we sometimes need a second for + temporary results). */ + MPN_VAR (den); + + /* Representation for the return value. */ + mp_limb retval[RETURN_LIMB_SIZE]; + /* Number of bits currently in result value. */ + int bits; + + /* Running pointer after the last character processed in the string. */ + const char *cp; + /* Start of significant part of the number. */ + const char *startp; + /* Points at the character following the integer and fractional digits. */ + const char *expp; + /* Total number of digit and number of digits in integer part. */ + int dig_no, int_no; + /* Contains the last character read. */ + char c; + + /* The radix character of the current locale. */ + wchar_t decimal; +#ifdef USE_GROUPING + /* The thousands character of the current locale. */ + wchar_t thousands; + /* The numeric grouping specification of the current locale, + in the format described in <locale.h>. */ + const char *grouping; + + /* Check the grouping of the integer part at [BEGIN,END). + Return zero iff a separator is found out of place. */ + int grouping_ok (const char *begin, const char *end) + { + if (grouping) + while (end > begin) + { + const char *p = end; + do + --p; + while (*p != thousands && p > begin); + if (end - 1 - p != *grouping++) + return 0; /* Wrong number of digits in this group. */ + end = p; /* Correct group; trim it off the end. */ + + if (*grouping == 0) + --grouping; /* Same grouping repeats in next iteration. */ + else if (*grouping == CHAR_MAX || *grouping < 0) + { + /* No further grouping allowed. */ + while (end > begin) + if (*--end == thousands) + return 0; + } + } + return 1; + } + /* Return with no conversion if the grouping of [STARTP,CP) is bad. */ +#define CHECK_GROUPING if (! grouping_ok (startp, cp)) RETURN (0.0, nptr); else + + grouping = _numeric_info->grouping; /* Cache the grouping info array. */ + if (*grouping <= 0 || *grouping == CHAR_MAX) + grouping = NULL; + else + { + /* Figure out the thousands seperator character. */ + if (mbtowc (&thousands_sep, _numeric_info->thousands_sep, + strlen (_numeric_info->thousands_sep)) <= 0) + thousands = (wchar_t) *_numeric_info->thousands_sep; + if (thousands == L'\0') + grouping = NULL; + } +#else +#define grouping NULL +#define thousands L'\0' +#define CHECK_GROUPING ((void) 0) +#endif + + /* Find the locale's decimal point character. */ + if (mbtowc (&decimal, _numeric_info->decimal_point, + strlen (_numeric_info->decimal_point)) <= 0) + decimal = (wchar_t) *_numeric_info->decimal_point; + + + /* Prepare number representation. */ + exponent = 0; + negative = 0; + bits = 0; + + /* Parse string to get maximal legal prefix. We need the number of + characters of the interger part, the fractional part and the exponent. */ + cp = nptr - 1; + /* Ignore leading white space. */ + do + c = *++cp; + while (isspace (c)); + + /* Get sign of the result. */ + if (c == '-') + { + negative = 1; + c = *++cp; + } + else if (c == '+') + c = *++cp; + + /* Return 0.0 if no legal string is found. + No character is used even if a sign was found. */ + if (!isdigit (c)) + RETURN (0.0, nptr); + + /* Record the start of the digits, in case we will check their grouping. */ + startp = cp; + + /* Ignore leading zeroes. This helps us to avoid useless computations. */ + while (c == '0' || (thousands != L'\0' && c == thousands)) + c = *++cp; + + CHECK_GROUPING; + + /* If no other digit but a '0' is found the result is 0.0. + Return current read pointer. */ + if (!isdigit (c) && c != decimal) + RETURN (0.0, cp); + + /* Remember first significant digit and read following characters until the + decimal point, exponent character or any non-FP number character. */ + startp = cp; + dig_no = 0; + while (dig_no < NDIG || + /* If parsing grouping info, keep going past useful digits + so we can check all the grouping separators. */ + grouping) + { + if (isdigit (c)) + ++dig_no; + else if (thousands == L'\0' || c != thousands) + /* Not a digit or separator: end of the integer part. */ + break; + c = *++cp; + } + + CHECK_GROUPING; + + if (dig_no >= NDIG) + /* Too many digits to be representable. Assigning this to EXPONENT + allows us to read the full number but return HUGE_VAL after parsing. */ + exponent = MAX_10_EXP; + + /* We have the number digits in the integer part. Whether these are all or + any is really a fractional digit will be decided later. */ + int_no = dig_no; + + /* Read the fractional digits. */ + if (c == decimal) + { + if (isdigit (cp[1])) + { + ++cp; + do + { + ++dig_no; + c = *++cp; + } + while (isdigit (c)); + } + } + + /* Remember start of exponent (if any). */ + expp = cp; + + /* Read exponent. */ + if (tolower (c) == 'e') + { + int exp_negative = 0; + + c = *++cp; + if (c == '-') + { + exp_negative = 1; + c = *++cp; + } + else if (c == '+') + c = *++cp; + + if (isdigit (c)) + { + do + { + if ((!exp_negative && exponent * 10 + int_no > MAX_10_EXP) + || (exp_negative + && exponent * 10 + int_no > -MIN_10_EXP + MANT_DIG)) + /* The exponent is too large/small to represent a valid + number. */ + { + FLOAT retval; + + /* Overflow or underflow. */ + errno = ERANGE; + retval = (exp_negative ? 0.0 : + negative ? -FLOAT_HUGE_VAL : FLOAT_HUGE_VAL); + + /* Accept all following digits as part of the exponent. */ + do + ++cp; + while (isdigit (*cp)); + + RETURN (retval, cp); + /* NOTREACHED */ + } + + exponent *= 10; + exponent += c - '0'; + c = *++cp; + } + while (isdigit (c)); + } + else + cp = expp; + + if (exp_negative) + exponent = -exponent; + } + + /* We don't want to have to work with trailing zeroes after the radix. */ + if (dig_no > int_no) + { + while (expp[-1] == '0') + { + --expp; + --dig_no; + } + assert (dig_no >= int_no); + } + + /* The whole string is parsed. Store the address of the next character. */ + if (endptr) + *endptr = (char *) cp; + + if (dig_no == 0) + return 0.0; + + /* Now we have the number of digits in total and the integer digits as well + as the exponent and its sign. We can decide whether the read digits are + really integer digits or belong to the fractional part; i.e. we normalize + 123e-2 to 1.23. */ + { + register int incr = exponent < 0 ? MAX (-int_no, exponent) + : MIN (dig_no - int_no, exponent); + int_no += incr; + exponent -= incr; + } + + if (int_no + exponent > MAX_10_EXP) + { + errno = ERANGE; + return negative ? -FLOAT_HUGE_VAL : FLOAT_HUGE_VAL; + } + + if (int_no - dig_no + exponent < MIN_10_EXP - MANT_DIG) + { + errno = ERANGE; + return 0.0; + } + + if (int_no > 0) + { + /* Read the integer part as a multi-precision number to NUM. */ + startp = str_to_mpn (startp, int_no, num, &numsize, &exponent); + + if (exponent > 0) + { + /* We now multiply the gained number by the given power of ten. */ + mp_limb *psrc = num; + mp_limb *pdest = den; + int expbit = 1; + const struct mp_power *ttab = &_fpioconst_pow10[0]; + + assert (exponent < (1 << (MAX_10_EXP_LOG + 1))); + do + { + if ((exponent & expbit) != 0) + { + mp_limb cy; + exponent ^= expbit; + + /* FIXME: not the whole multiplication has to be done. + If we have the needed number of bits we only need the + information whether more non-zero bits follow. */ + if (numsize >= ttab->arraysize - 2) + cy = __mpn_mul (pdest, psrc, numsize, + &ttab->array[2], ttab->arraysize - 2); + else + cy = __mpn_mul (pdest, &ttab->array[2], + ttab->arraysize - 2, + psrc, numsize); + numsize += ttab->arraysize - 2; + if (cy == 0) + --numsize; + SWAP (psrc, pdest); + } + expbit <<= 1; + ++ttab; + } + while (exponent != 0); + + if (psrc == den) + memcpy (num, den, numsize * sizeof (mp_limb)); + } + + /* Determine how many bits of the result we already have. */ + count_leading_zeros (bits, num[numsize - 1]); + bits = numsize * BITS_PER_MP_LIMB - bits; + + /* We have already the first BITS bits of the result. Together with + the information whether more non-zero bits follow this is enough + to determine the result. */ + if (bits > MANT_DIG) + { + const mp_size_t least_idx = (bits - MANT_DIG) / BITS_PER_MP_LIMB; + const mp_size_t least_bit = (bits - MANT_DIG) % BITS_PER_MP_LIMB; + const mp_size_t round_idx = least_bit == 0 ? least_idx - 1 + : least_idx; + const mp_size_t round_bit = least_bit == 0 ? BITS_PER_MP_LIMB - 1 + : least_idx - 1; + int i; + + if (least_bit == 0) + memcpy (retval, &num[least_idx], + RETURN_LIMB_SIZE * sizeof (mp_limb)); + else + (void) __mpn_rshift (retval, &num[least_idx], + numsize - least_idx + 1, least_bit); + + /* Check whether any limb beside the ones in RETVAL are non-zero. */ + for (i = 0; num[i] == 0; ++i) + ; + + return round_and_return (retval, bits - 1, negative, + num[round_idx], round_bit, + int_no < dig_no || i < round_idx); + /* NOTREACHED */ + } + else if (dig_no == int_no) + { + const mp_size_t target_bit = (MANT_DIG - 1) % BITS_PER_MP_LIMB; + const mp_size_t is_bit = (bits - 1) % BITS_PER_MP_LIMB; + + if (target_bit == is_bit) + { + memcpy (&retval[RETURN_LIMB_SIZE - numsize], num, + numsize * sizeof (mp_limb)); + /* FIXME: the following loop can be avoided if we assume a + maximal MANT_DIG value. */ + MPN_ZERO (retval, RETURN_LIMB_SIZE - numsize); + } + else if (target_bit > is_bit) + { + (void) __mpn_lshift (&retval[RETURN_LIMB_SIZE - numsize], + num, numsize, target_bit - is_bit); + /* FIXME: the following loop can be avoided if we assume a + maximal MANT_DIG value. */ + MPN_ZERO (retval, RETURN_LIMB_SIZE - numsize); + } + else + { + mp_limb cy; + assert (numsize < RETURN_LIMB_SIZE); + + cy = __mpn_rshift (&retval[RETURN_LIMB_SIZE - numsize], + num, numsize, is_bit - target_bit); + retval[RETURN_LIMB_SIZE - numsize - 1] = cy; + /* FIXME: the following loop can be avoided if we assume a + maximal MANT_DIG value. */ + MPN_ZERO (retval, RETURN_LIMB_SIZE - numsize - 1); + } + + return round_and_return (retval, bits - 1, negative, 0, 0, 0); + /* NOTREACHED */ + } + + /* Store the bits we already have. */ + memcpy (retval, num, numsize * sizeof (mp_limb)); +#if RETURN_LIMB_SIZE > 1 + if (numsize < RETURN_LIMB_SIZE) + retval[numsize] = 0; +#endif + } + + /* We have to compute at least some of the fractional digits. */ + { + /* We construct a fraction and the result of the division gives us + the needed digits. The denominator is 1.0 multiplied by the + exponent of the lowest digit; i.e. 0.123 gives 123 / 1000 and + 123e6 gives 123 / 1000000. */ + + int expbit; + int cnt; + mp_limb cy; + mp_limb *psrc = den; + mp_limb *pdest = num; + int neg_exp = dig_no - int_no - exponent; + const struct mp_power *ttab = &_fpioconst_pow10[0]; + + assert (dig_no > int_no && exponent <= 0); + + /* Construct the denominator. */ + densize = 0; + expbit = 1; + do + { + if ((neg_exp & expbit) != 0) + { + mp_limb cy; + neg_exp ^= expbit; + + if (densize == 0) + memcpy (psrc, &ttab->array[2], + (densize = ttab->arraysize - 2) * sizeof (mp_limb)); + else + { + cy = __mpn_mul (pdest, &ttab->array[2], ttab->arraysize - 2, + psrc, densize); + densize += ttab->arraysize - 2; + if (cy == 0) + --densize; + SWAP (psrc, pdest); + } + } + expbit <<= 1; + ++ttab; + } + while (neg_exp != 0); + + if (psrc == num) + memcpy (den, num, densize * sizeof (mp_limb)); + + /* Read the fractional digits from the string. */ + (void) str_to_mpn (startp, dig_no - int_no, num, &numsize, &exponent); + + + /* We now have to shift both numbers so that the highest bit in the + denominator is set. In the same process we copy the numerator to + a high place in the array so that the division constructs the wanted + digits. This is done by a "quasi fix point" number representation. + + num: ddddddddddd . 0000000000000000000000 + |--- m ---| + den: ddddddddddd n >= m + |--- n ---| + */ + + count_leading_zeros (cnt, den[densize - 1]); + + (void) __mpn_lshift (den, den, densize, cnt); + cy = __mpn_lshift (num, num, numsize, cnt); + if (cy != 0) + num[numsize++] = cy; + + /* Now we are ready for the division. But it is not necessary to + do a full multi-precision division because we only need a small + number of bits for the result. So we do not use __mpn_divmod + here but instead do the division here by hand and stop whenever + the needed number of bits is reached. The code itself comes + from the GNU MP Library by Torbj\"orn Granlund. */ + + exponent = bits; + + switch (densize) + { + case 1: + { + mp_limb d, n, quot; + int used = 0; + + n = num[0]; + d = den[0]; + assert (numsize == 1 && n < d); + + do + { + udiv_qrnnd (quot, n, n, 0, d); + +#define got_limb \ + if (bits == 0) \ + { \ + register int cnt; \ + if (quot == 0) \ + cnt = BITS_PER_MP_LIMB; \ + else \ + count_leading_zeros (cnt, quot); \ + exponent -= cnt; \ + if (BITS_PER_MP_LIMB - cnt > MANT_DIG) \ + { \ + used = cnt + MANT_DIG; \ + retval[0] = quot >> (BITS_PER_MP_LIMB - used); \ + bits -= BITS_PER_MP_LIMB - used; \ + } \ + else \ + { \ + /* Note that we only clear the second element. */ \ + retval[1] = 0; \ + retval[0] = quot; \ + bits -= cnt; \ + } \ + } \ + else if (bits + BITS_PER_MP_LIMB <= MANT_DIG) \ + __mpn_lshift_1 (retval, RETURN_LIMB_SIZE, BITS_PER_MP_LIMB, \ + quot); \ + else \ + { \ + used = MANT_DIG - bits; \ + if (used > 0) \ + __mpn_lshift_1 (retval, RETURN_LIMB_SIZE, used, quot); \ + } \ + bits += BITS_PER_MP_LIMB + + got_limb; + } + while (bits <= MANT_DIG); + + return round_and_return (retval, exponent - 1, negative, + quot, BITS_PER_MP_LIMB - 1 - used, + n != 0); + } + case 2: + { + mp_limb d0, d1, n0, n1; + mp_limb quot = 0; + int used = 0; + + d0 = den[0]; + d1 = den[1]; + + if (numsize < densize) + { + if (bits <= 0) + exponent -= BITS_PER_MP_LIMB; + else + { + if (bits + BITS_PER_MP_LIMB <= MANT_DIG) + __mpn_lshift_1 (retval, RETURN_LIMB_SIZE, + BITS_PER_MP_LIMB, 0); + else + { + used = MANT_DIG - bits; + if (used > 0) + __mpn_lshift_1 (retval, RETURN_LIMB_SIZE, used, 0); + } + bits += BITS_PER_MP_LIMB; + } + n1 = num[0]; + n0 = 0; + } + else + { + n1 = num[1]; + n0 = num[0]; + } + + while (bits <= MANT_DIG) + { + mp_limb r; + + if (n1 == d1) + { + /* QUOT should be either 111..111 or 111..110. We need + special treatment of this rare case as normal division + would give overflow. */ + quot = ~(mp_limb) 0; + + r = n0 + d1; + if (r < d1) /* Carry in the addition? */ + { + add_ssaaaa (n1, n0, r - d0, 0, 0, d0); + goto have_quot; + } + n1 = d0 - (d0 != 0); + n0 = -d0; + } + else + { + udiv_qrnnd (quot, r, n1, n0, d1); + umul_ppmm (n1, n0, d0, quot); + } + + q_test: + if (n1 > r || (n1 == r && n0 > 0)) + { + /* The estimated QUOT was too large. */ + --quot; + + sub_ddmmss (n1, n0, n1, n0, 0, d0); + r += d1; + if (r >= d1) /* If not carry, test QUOT again. */ + goto q_test; + } + sub_ddmmss (n1, n0, r, 0, n1, n0); + + have_quot: + got_limb; + } + + return round_and_return (retval, exponent - 1, negative, + quot, BITS_PER_MP_LIMB - 1 - used, + n1 != 0 || n0 != 0); + } + default: + { + int i; + mp_limb cy, dX, d1, n0, n1; + mp_limb quot = 0; + int used = 0; + + dX = den[densize - 1]; + d1 = den[densize - 2]; + + /* The division does not work if the upper limb of the two-limb + numerator is greater than the denominator. */ + if (num[numsize - 1] > dX) + num[numsize++] = 0; + + if (numsize < densize) + { + mp_size_t empty = densize - numsize; + + if (bits <= 0) + { + register int i; + for (i = numsize; i > 0; --i) + num[i + empty] = num[i - 1]; + MPN_ZERO (num, empty + 1); + exponent -= empty * BITS_PER_MP_LIMB; + } + else + { + if (bits + empty * BITS_PER_MP_LIMB <= MANT_DIG) + { + /* We make a difference here because the compiler + cannot optimize the `else' case that good and + this reflects all currently used FLOAT types + and GMP implementations. */ + register int i; +#if RETURN_LIMB_SIZE <= 2 + assert (empty == 1); + __mpn_lshift_1 (retval, RETURN_LIMB_SIZE, + BITS_PER_MP_LIMB, 0); +#else + for (i = RETURN_LIMB_SIZE; i > empty; --i) + retval[i] = retval[i - empty]; +#endif + retval[1] = 0; + for (i = numsize; i > 0; --i) + num[i + empty] = num[i - 1]; + MPN_ZERO (num, empty + 1); + } + else + { + used = MANT_DIG - bits; + if (used >= BITS_PER_MP_LIMB) + { + register int i; + (void) __mpn_lshift (&retval[used + / BITS_PER_MP_LIMB], + retval, RETURN_LIMB_SIZE, + used % BITS_PER_MP_LIMB); + for (i = used / BITS_PER_MP_LIMB; i >= 0; --i) + retval[i] = 0; + } + else if (used > 0) + __mpn_lshift_1 (retval, RETURN_LIMB_SIZE, used, 0); + } + bits += empty * BITS_PER_MP_LIMB; + } + } + else + { + int i; + assert (numsize == densize); + for (i = numsize; i > 0; --i) + num[i] = num[i - 1]; + } + + den[densize] = 0; + n0 = num[densize]; + + while (bits <= MANT_DIG) + { + if (n0 == dX) + /* This might over-estimate QUOT, but it's probably not + worth the extra code here to find out. */ + quot = ~(mp_limb) 0; + else + { + mp_limb r; + + udiv_qrnnd (quot, r, n0, num[densize - 1], dX); + umul_ppmm (n1, n0, d1, quot); + + while (n1 > r || (n1 == r && n0 > num[densize - 2])) + { + --quot; + r += dX; + if (r < dX) /* I.e. "carry in previous addition?" */ + break; + n1 -= n0 < d1; + n0 -= d1; + } + } + + /* Possible optimization: We already have (q * n0) and (1 * n1) + after the calculation of QUOT. Taking advantage of this, we + could make this loop make two iterations less. */ + + cy = __mpn_submul_1 (num, den, densize + 1, quot); + + if (num[densize] != cy) + { + cy = __mpn_add_n (num, num, den, densize); + assert (cy != 0); + --quot; + } + n0 = num[densize] = num[densize - 1]; + for (i = densize - 1; i > 0; --i) + num[i] = num[i - 1]; + + got_limb; + } + + for (i = densize - 1; num[i] != 0 && i >= 0; --i) + ; + return round_and_return (retval, exponent - 1, negative, + quot, BITS_PER_MP_LIMB - 1 - used, + i >= 0); + } + } + } + + /* NOTREACHED */ +} |