Convert wchar t to char

Question

I was wondering is it safe to do so   wchar t wide      something     assert wide  gt   0  amp  amp  wide  lt  256  amp  amp    char myChar   static cast lt char gt  wide     If I am pretty sure the wide char will fall within ASCII range

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A short function I wrote a while back to pack a wchar t array into a char array   Characters that aren t on the ANSI code page  0-127  are replaced by     characters  and it handles surrogate pairs correctly   size t to narrow const wchar t   src  char   dest  size t dest len     size t i    wchar t code     i   0     while  src i       0   amp  amp  i  lt   dest len - 1        code   src i       if  code  lt  128        dest i    char code       else        dest i               if  code  gt   0xD800  amp  amp  code  lt   0xD8FF             lead surrogate  skip the next code unit  which is the trail         i              i           dest i      0      return i - 1

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Here s another way of doing it  remember to use free   on the result   char  wchar to char const wchar t  pwchar           get the number of characters in the string      int currentCharIndex   0      char currentChar   pwchar currentCharIndex        while  currentChar      0                 currentCharIndex            currentChar   pwchar currentCharIndex              const int charCount   currentCharIndex   1          allocate a new block of memory size char  1 byte  instead of wide char  2 bytes      char  filePathC    char  malloc sizeof char    charCount        for  int i   0  i  lt  charCount  i                     convert to char  1 byte          char character   pwchar i             filePathC   character           filePathC    sizeof char              filePathC      0        filePathC -   sizeof char    charCount        return filePathC

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Technically   char  could have the same range as either  signed char  or  unsigned char    For the unsigned characters  your range is correct  theoretically  for signed characters  your condition is wrong   In practice  very few compilers will object - and the result will be the same   Nitpick  the last  amp  amp  in the assert is a syntax error   Whether the assertion is appropriate depends on whether you can afford to crash when the code gets to the customer  and what you could or should do if the assertion condition is violated but the assertion is not compiled into the code   For debug work  it seems fine  but you might want an active test after it for run-time checking too

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An easy way is            wstring your wchar in ws  lt your wchar gt            string your wchar in str your wchar in ws begin    your wchar in ws end             char  your wchar in char    your wchar in str c str      I m using this method for years

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You are looking for wctomb    it s in the ANSI standard  so you can count on it  It works even when the wchar t uses a code above 255  You almost certainly do not want to use it     wchar t is an integral type  so your compiler won t complain if you actually do   char x    char wc    but because it s an integral type  there s absolutely no reason to do this  If you accidentally read Herbert Schildt s C  The Complete Reference  or any C book based on it  then you re completely and grossly misinformed  Characters should be of type int or better  That means you should be writing this   int x   getchar      and not this   char x   getchar        lt - WRONG       As far as integral types go  char is worthless  You shouldn t make functions that take parameters of type char  and you should not create temporary variables of type char  and the same advice goes for wchar t as well   char  may be a convenient typedef for a character string  but it is a novice mistake to think of this as an  array of characters  or a  pointer to an array of characters  - despite what the cdecl tool says  Treating it as an actual array of characters with nonsense like this   for int i   0  s i     i      wchar t wc   s i     char c   doit wc     out i    c      is absurdly wrong  It will not do what you want  it will break in subtle and serious ways  behave differently on different platforms  and you will most certainly confuse the hell out of your users  If you see this  you are trying to reimplement wctombs   which is part of ANSI C already  but it s still wrong   You re really looking for iconv    which converts a character string from one encoding  even if it s packed into a wchar t array   into a character string of another encoding   Now go read this  to learn what s wrong with iconv

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Why not just use a library routine wcstombs

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assert is for ensuring that something is true in a debug mode  without it having any effect in a release build  Better to use an if statement and have an alternate plan for characters that are outside the range  unless the only way to get characters outside the range is through a program bug   Also  depending on your character encoding  you might find a difference between the Unicode characters 0x80 through 0xff and their char version

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one could also convert wchar t --  wstring  --  string --  char      wchar t wide  wstring wstrValue  wstrValue 0    wide  string strValue  strValue assign wstrValue begin    wstrValue end         convert wstring to string  char char value   strValue 0

User · Answer

In general  no  int wchar t 255      int char 255   of course  but that just means they have the same int value  They may not represent the same characters   You would see such a discrepancy in the majority of Windows PCs  even  For instance  on Windows Code page 1250  char 0xFF  is the same character as wchar t 0x02D9   dot above   not wchar t 0x00FF   small y with diaeresis    Note that it does not even hold for the ASCII range  as C   doesn t even require ASCII  On IBM systems in particular you may see that  A     65

[c++] Convert wchar_t to char

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