OS/2 codes: How to support DBCS #1 Determine if DBCS env

Most of OS/2 users are in SBCS countries. Naturally, many OS/2 programs are developed in their countries. And those programs lack DBCS support. To begin with this article, I'll write a series of articles for DBCS support.

How to determine if DBCS environment

OS/2 is based on a code page. And OS/2 provides many APIs for a code page. Out of these, you can use DosQueryDBCSEnv() to determine if DBCS environment because DBCS code pages provides the ranges of DBCS lead-bytes.

This is a syntax for DosQueryDBCSEnv().

Obtains a DBCS (double-byte character set) environmental vector that resides in the country file.

#define INCL_DOSNLS
#include <os2.h>

ULONG           cb;    /*  The length, in bytes, of the data area (pBuf) provided by the caller. */
PCOUNTRYCODE    pcc;   /*  A pointer to the COUNTRYCODE structure in which the country code and code page are identified. */
PCHAR           pBuf;  /*  The data area where the country-dependent information for the DBCS environmental vector is returned. */
APIRET          ulrc;  /*  Return Code. */

ulrc = DosQueryDBCSEnv(cb, pcc, pBuf);

Reference : http://cyberkinetica.homeunix.net/os2tk45/cp1/1126_L2H_DosQueryDBCSEnvSynta.html

Note: You can see the explanation for parameters by clicking them.

As you see, if country of *pcc is set to 0, then a default system country code is used. And if codepage of *pcc is set to 0, then a current process code page is used.

If returned buffer has two bytes of zero, then it means SBCS env, otherwise DBCS env.

Here is a function to determine if DBCS env by using the above.

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#define INCL_DOSNLS #include <os2.h> int isDBCSEnv( void ) {     COUNTRYCODE cc = { 0, };     UCHAR       uchDBCSLead[ 12 ];     return DosQueryDBCSEnv( sizeof( uchDBCSLead ), &cc, uchDBCSLead ) == 0 &&            ( uchDBCSLead[ 0 ] || uchDBCSLead[ 1 ]); } #include <stdio.h> int main( void ) {     printf("Is DBCS env ? %s\n", isDBCSEnv() ? "Yes" : "No");     return 0; }

// ----- 2015/01/12

Locale version

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#include <stdlib.h> int isDBCSEnv( void ) {     /* Do not consider unicodes such as UTF-8, UCS-2. */     return MB_CUR_MAX > 1; }

Note: MB_CUR_MAX is affected by LC_CTYPE category not a process code page. By the way, a program starts with "C" or "POSIX" locale. That is, SBCS. So if you want to set a locale which you want, you should use setlocale(). And if a second parameter is an empty string(""), then a locale is set to a process locale. For example

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#include <locale.h> int main( void ) {     setlocale( LC_ALL, "");     ... }