- number_of_digits_to_use = number_of_digits_available;
- }
- decimal_exponent += number_of_digits_before_decimal - number_of_digits_to_use;
-
- more_than_enough_bits_for_digits
- = ((((double)number_of_digits_to_use) * LOG_TO_BASE_2_OF_10) + 1);
- more_than_enough_littlenums_for_digits
- = ( more_than_enough_bits_for_digits
- / LITTLENUM_NUMBER_OF_BITS
- )
- + 2;
-
- /*
- * Compute (digits) part. In "12.34E56" this is the "1234" part.
- * Arithmetic is exact here. If no digits are supplied then
- * this part is a 0 valued binary integer.
- * Allocate room to build up the binary number as littlenums.
- * We want this memory to disappear when we leave this function.
- * Assume no alignment problems => (room for n objects) ==
- * n * (room for 1 object).
- */
-
- size_of_digits_in_littlenums = more_than_enough_littlenums_for_digits;
- size_of_digits_in_chars = size_of_digits_in_littlenums
- * sizeof( LITTLENUM_TYPE );
- digits_binary_low = (LITTLENUM_TYPE *)
- alloca (size_of_digits_in_chars);
- bzero ((char *)digits_binary_low, size_of_digits_in_chars);
-
- /* Digits_binary_low[] is allocated and zeroed. */
-
- {
- /*
- * Parse the decimal digits as if * digits_low was in the units position.
- * Emit a binary number into digits_binary_low[].
- *
- * Use a large-precision version of:
- * (((1st-digit) * 10 + 2nd-digit) * 10 + 3rd-digit ...) * 10 + last-digit
- */
-
- char * p;
- char c;
- int count; /* Number of useful digits left to scan. */
-
- for (p = first_digit, count = number_of_digits_to_use;
- count;
- p ++, -- count)
- {
- c = * p;
- if (isdigit(c))
- {
- /*
- * Multiply by 10. Assume can never overflow.
- * Add this digit to digits_binary_low[].
- */
-
- long carry;
- LITTLENUM_TYPE * littlenum_pointer;
- LITTLENUM_TYPE * littlenum_limit;
-
- littlenum_limit
- = digits_binary_low
- + more_than_enough_littlenums_for_digits
- - 1;
- carry = c - '0'; /* char -> binary */
- for (littlenum_pointer = digits_binary_low;
- littlenum_pointer <= littlenum_limit;
- littlenum_pointer ++)
- {
- long work;
-
- work = carry + 10 * (long)(*littlenum_pointer);
- * littlenum_pointer = work & LITTLENUM_MASK;
- carry = work >> LITTLENUM_NUMBER_OF_BITS;
- }
- if (carry != 0)
- {
- /*
- * We have a GROSS internal error.
- * This should never happen.
- */
- as_fatal("failed sanity check."); /* RMS prefers abort() to any message. */
- }
- }
- else
- {
- ++ count; /* '.' doesn't alter digits used count. */
- } /* if valid digit */
- } /* for each digit */
- }
-
- /*
- * Digits_binary_low[] properly encodes the value of the digits.
- * Forget about any high-order littlenums that are 0.
- */
- while (digits_binary_low [size_of_digits_in_littlenums - 1] == 0
- && size_of_digits_in_littlenums >= 2)
- size_of_digits_in_littlenums --;
-
- digits_flonum . low = digits_binary_low;
- digits_flonum . high = digits_binary_low + size_of_digits_in_littlenums - 1;
- digits_flonum . leader = digits_flonum . high;
- digits_flonum . exponent = 0;
- /*
- * The value of digits_flonum . sign should not be important.
- * We have already decided the output's sign.
- * We trust that the sign won't influence the other parts of the number!
- * So we give it a value for these reasons:
- * (1) courtesy to humans reading/debugging
- * these numbers so they don't get excited about strange values
- * (2) in future there may be more meaning attached to sign,
- * and what was
- * harmless noise may become disruptive, ill-conditioned (or worse)
- * input.
- */
- digits_flonum . sign = '+';
-
- {
- /*
- * Compute the mantssa (& exponent) of the power of 10.
- * If sucessful, then multiply the power of 10 by the digits
- * giving return_binary_mantissa and return_binary_exponent.
- */
-
- LITTLENUM_TYPE *power_binary_low;
- int decimal_exponent_is_negative;
- /* This refers to the "-56" in "12.34E-56". */
- /* FALSE: decimal_exponent is positive (or 0) */
- /* TRUE: decimal_exponent is negative */
- FLONUM_TYPE temporary_flonum;
- LITTLENUM_TYPE *temporary_binary_low;
- int size_of_power_in_littlenums;
- int size_of_power_in_chars;
-
- size_of_power_in_littlenums = precision;
- /* Precision has a built-in fudge factor so we get a few guard bits. */
-
-
- decimal_exponent_is_negative = decimal_exponent < 0;
- if (decimal_exponent_is_negative)
- {
- decimal_exponent = - decimal_exponent;
- }
- /* From now on: the decimal exponent is > 0. Its sign is seperate. */
-
- size_of_power_in_chars
- = size_of_power_in_littlenums
- * sizeof( LITTLENUM_TYPE ) + 2;
- power_binary_low = (LITTLENUM_TYPE *) alloca ( size_of_power_in_chars );
- temporary_binary_low = (LITTLENUM_TYPE *) alloca ( size_of_power_in_chars );
- bzero ((char *)power_binary_low, size_of_power_in_chars);
- * power_binary_low = 1;
- power_of_10_flonum . exponent = 0;
- power_of_10_flonum . low = power_binary_low;
- power_of_10_flonum . leader = power_binary_low;
- power_of_10_flonum . high = power_binary_low + size_of_power_in_littlenums - 1;
- power_of_10_flonum . sign = '+';
- temporary_flonum . low = temporary_binary_low;
- temporary_flonum . high = temporary_binary_low + size_of_power_in_littlenums - 1;
- /*
- * (power) == 1.
- * Space for temporary_flonum allocated.
- */
-
- /*
- * ...
- *
- * WHILE more bits
- * DO find next bit (with place value)
- * multiply into power mantissa
- * OD
- */
- {
- int place_number_limit;
- /* Any 10^(2^n) whose "n" exceeds this */
- /* value will fall off the end of */
- /* flonum_XXXX_powers_of_ten[]. */
- int place_number;
- const FLONUM_TYPE * multiplicand; /* -> 10^(2^n) */
-
- place_number_limit = table_size_of_flonum_powers_of_ten;
- multiplicand
- = ( decimal_exponent_is_negative
- ? flonum_negative_powers_of_ten
- : flonum_positive_powers_of_ten);
- for (place_number = 1; /* Place value of this bit of exponent. */
- decimal_exponent; /* Quit when no more 1 bits in exponent. */
- decimal_exponent >>= 1
- , place_number ++)
- {
- if (decimal_exponent & 1)
- {
- if (place_number > place_number_limit)
- {
- /*
- * The decimal exponent has a magnitude so great that
- * our tables can't help us fragment it. Although this
- * routine is in error because it can't imagine a
- * number that big, signal an error as if it is the
- * user's fault for presenting such a big number.
- */
- return_value = ERROR_EXPONENT_OVERFLOW;
- /*
- * quit out of loop gracefully
- */
- decimal_exponent = 0;
- }
- else
- {