116 lines
2.5 KiB
C
116 lines
2.5 KiB
C
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/*
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** dbcs.c - DBCS functions for DOS apps.
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**
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** Written by RokaH and DavidDi.
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*/
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/* Headers
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**********/
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#include <dos.h>
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#include <ctype.h>
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#include <dbcs.h>
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/*
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** int IsDBCSLeadByte(unsigned char uch);
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**
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** Check to see if a character is a DBCS lead byte.
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**
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** Arguments: uch - charcter to examine
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**
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** Returns: int - 1 if the character is a DBCS lead byte. 0 if not.
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**
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** Globals: none
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*/
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int IsDBCSLeadByte(unsigned char uch)
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{
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static unsigned char far *DBCSLeadByteTable = 0;
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union REGS inregs, outregs;
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struct SREGS segregs;
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unsigned char far *puch;
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if (DBCSLeadByteTable == 0)
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{
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/*
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** Get DBCS lead byte table. This function has been supported since
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** DBCS MS-DOS 2.21.
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*/
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inregs.x.ax = 0x6300;
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intdosx(&inregs, &outregs, &segregs);
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FP_OFF(DBCSLeadByteTable) = outregs.x.si;
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FP_SEG(DBCSLeadByteTable) = segregs.ds;
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}
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/* See if the given byte is in any of the table's lead byte ranges. */
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for (puch = DBCSLeadByteTable; puch[0] || puch[1]; puch += 2)
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if (uch >= puch[0] && uch <= puch[1])
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return(1);
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return(0);
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}
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/*
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** unsigned char *AnsiNext(unsigned char *puch);
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**
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** Moves to the next character in a string.
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**
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** Arguments: puch - pointer to current location in string
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**
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** Returns: char * - Pointer to next character in string.
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**
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** Globals: none
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**
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** N.b., if puch points to a null character, AnsiNext() will return puch.
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*/
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unsigned char far *AnsiNext(unsigned char far *puch)
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{
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if (*puch == '\0')
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return(puch);
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else if (IsDBCSLeadByte(*puch))
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puch++;
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puch++;
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return(puch);
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}
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/*
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** unsigned char *AnsiPrev(unsigned char *psz, unsigned char *puch);
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**
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** Moves back one character in a string.
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**
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** Arguments: psz - pointer to start of string
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** puch - pointer to current location in string
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**
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** Returns: char * - Pointer to previous character in string.
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**
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** Globals: none
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**
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** N.b., if puch <= psz, AnsiPrev() will return psz.
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**
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** This function is implemented in a very slow fashion because we do not wish
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** to trust that the given string is necessarily DBCS "safe," i.e., contains
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** only single-byte characters and valid DBCS characters. So we start from
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** the beginning of the string and work our way forward.
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*/
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unsigned char far *AnsiPrev(unsigned char far *psz, unsigned char far *puch)
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{
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unsigned char far *puchPrevious;
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do
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{
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puchPrevious = psz;
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psz = AnsiNext(psz);
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} while (*psz != '\0' && psz < puch);
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return(puchPrevious);
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}
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