newlib/libc/stdlib/atof.c

   1 /*
   2 FUNCTION
   3    <<atof>>, <<atoff>>---string to double or float
   4
   5 INDEX
   6         atof
   7 INDEX
   8         atoff
   9
  10 SYNOPSIS
  11         #include <stdlib.h>
  12         double atof(const char *<[s]>);
  13         float atoff(const char *<[s]>);
  14
  15 DESCRIPTION
  16 <<atof>> converts the initial portion of a string to a <<double>>.
  17 <<atoff>> converts the initial portion of a string to a <<float>>.
  18
  19 The functions parse the character string <[s]>,
  20 locating a substring which can be converted to a floating-point
  21 value. The substring must match the format:
  22 . [+|-]<[digits]>[.][<[digits]>][(e|E)[+|-]<[digits]>]
  23 The substring converted is the longest initial
  24 fragment of <[s]> that has the expected format, beginning with
  25 the first non-whitespace character.  The substring
  26 is empty if <<str>> is empty, consists entirely
  27 of whitespace, or if the first non-whitespace character is
  28 something other than <<+>>, <<->>, <<.>>, or a digit.
  29
  30 <<atof(<[s]>)>> is implemented as <<strtod(<[s]>, NULL)>>.
  31 <<atoff(<[s]>)>> is implemented as <<strtof(<[s]>, NULL)>>.
  32
  33 RETURNS
  34 <<atof>> returns the converted substring value, if any, as a
  35 <<double>>; or <<0.0>>,  if no conversion could be performed.
  36 If the correct value is out of the range of representable values, plus
  37 or minus <<HUGE_VAL>> is returned, and <<ERANGE>> is stored in
  38 <<errno>>.
  39 If the correct value would cause underflow, <<0.0>> is returned
  40 and <<ERANGE>> is stored in <<errno>>.
  41
  42 <<atoff>> obeys the same rules as <<atof>>, except that it
  43 returns a <<float>>.
  44
  45 PORTABILITY
  46 <<atof>> is ANSI C. <<atof>>, <<atoi>>, and <<atol>> are subsumed by <<strod>>
  47 and <<strol>>, but are used extensively in existing code. These functions are
  48 less reliable, but may be faster if the argument is verified to be in a valid
  49 range.
  50
  51 Supporting OS subroutines required: <<close>>, <<fstat>>, <<isatty>>,
  52 <<lseek>>, <<read>>, <<sbrk>>, <<write>>.
  53 */
  54
  55
  56 #include <stdlib.h>
  57 #include <_ansi.h>
  58
  59 double
  60 atof (const char *s)
  61 {
  62   return strtod (s, NULL);
  63 }