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SBCS and MBCS data types

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Any Microsoft MBCS run-time library routine that handles only a single multibyte character, or a single byte of a multibyte character, expects an unsigned int argument (where 0x0000 <= character value <= 0xFFFF and 0x00 <= byte value <= 0xFF). An MBCS routine that handles multibyte bytes or characters in a string context expects a multibyte-character string to be represented as an unsigned char pointer.

Caution

Each byte of a multibyte character can be represented in an 8-bit char. However, an SBCS or MBCS single-byte character of type char with a value greater than 0x7F is negative. When such a character is converted directly to an int or a long, the result is sign-extended by the compiler and can therefore yield unexpected results.

It's best to represent a byte of a multibyte character as an 8-bit unsigned char. Or, to avoid a negative result, convert a single-byte character of type char to an unsigned char before converting it to an int or a long.

Because some SBCS string-handling functions take (signed) char* parameters, a type mismatch compiler warning will result when _MBCS is defined. There are three ways to avoid this warning, listed in order of efficiency:

  1. Use the type-safe inline functions in TCHAR.H. This behavior is the default.

  2. Use the direct macros in TCHAR.H by defining _MB_MAP_DIRECT on the command line. If you do, you must manually match types. This method is the fastest but isn't type-safe.

  3. Use the type-safe statically linked library functions in TCHAR.H. To do so, define the constant _NO_INLINING on the command line. This method is the slowest, but the most type-safe.

See also

Internationalization
Universal C runtime routines by category