newlib/libc/ctype/tolower.c

   1 /*
   2 FUNCTION
   3         <<tolower>>, <<tolower_l>>---translate characters to lowercase
   4
   5 INDEX
   6         tolower
   7
   8 INDEX
   9         tolower_l
  10
  11 INDEX
  12         _tolower
  13
  14 SYNOPSIS
  15         #include <ctype.h>
  16         int tolower(int <[c]>);
  17         int _tolower(int <[c]>);
  18
  19         #include <ctype.h>
  20         int tolower_l(int <[c]>, locale_t <[locale]>);
  21
  22
  23 DESCRIPTION
  24 <<tolower>> is a macro which converts uppercase characters to lowercase,
  25 leaving all other characters unchanged.  It is only defined when
  26 <[c]> is an integer in the range <<EOF>> to <<255>>.
  27
  28 <<tolower_l>> is like <<tolower>> but performs the function based on the
  29 locale specified by the locale object locale.  If <[locale]> is
  30 LC_GLOBAL_LOCALE or not a valid locale object, the behaviour is undefined.
  31
  32 You can use a compiled subroutine instead of the macro definition by
  33 undefining this macro using `<<#undef tolower>>' or `<<#undef tolower_l>>'.
  34
  35 <<_tolower>> performs the same conversion as <<tolower>>, but should
  36 only be used when <[c]> is known to be an uppercase character (<<A>>--<<Z>>).
  37
  38 RETURNS
  39 <<tolower>>, <<tolower_l>> return the lowercase equivalent of <[c]> when
  40 <[c]> is an uppercase character, and <[c]> otherwise.
  41
  42 <<_tolower>> returns the lowercase equivalent of <[c]> when it is a
  43 character between <<A>> and <<Z>>.  If <[c]> is not one of these
  44 characters, the behaviour of <<_tolower>> is undefined.
  45
  46 PORTABILITY
  47 <<tolower>> is ANSI C.  <<_tolower>> is not recommended for portable programs.
  48 <<tolower_l>> is POSIX-1.2008.
  49
  50 No supporting OS subroutines are required.
  51 */
  52
  53 #include <_ansi.h>
  54 #include <ctype.h>
  55 #if defined (_MB_EXTENDED_CHARSETS_ISO) || defined (_MB_EXTENDED_CHARSETS_WINDOWS)
  56 #include <limits.h>
  57 #include <stdio.h>
  58 #include <stdlib.h>
  59 #include <wctype.h>
  60 #include <wchar.h>
  61 #endif
  62
  63 #undef tolower
  64 int
  65 tolower (int c)
  66 {
  67 #if defined (_MB_EXTENDED_CHARSETS_ISO) || defined (_MB_EXTENDED_CHARSETS_WINDOWS)
  68   if ((unsigned char) c <= 0x7f)
  69     return isupper (c) ? c - 'A' + 'a' : c;
  70   else if (c != EOF && MB_CUR_MAX == 1 && isupper (c))
  71     {
  72       char s[MB_LEN_MAX] = { c, '\0' };
  73       wchar_t wc;
  74       if (mbtowc (&wc, s, 1) >= 0
  75           && wctomb (s, (wchar_t) towlower ((wint_t) wc)) == 1)
  76         c = (unsigned char) s[0];
  77     }
  78   return c;
  79 #else
  80   return isupper(c) ? (c) - 'A' + 'a' : c;
  81 #endif
  82 }