a_cmp.c

C标准库源代码

/***
*a_cmp.c - A version of CompareString.
*
*       Copyright (c) 1993-1997, Microsoft Corporation. All rights reserved.
*
*Purpose:
*       Use either CompareStringA or CompareStringW depending on which is
*       available
*
*******************************************************************************/

#include <cruntime.h>
#include <internal.h>
#include <dbgint.h>
#include <stdlib.h>
#include <setlocal.h>
#include <awint.h>
#include <dbgint.h>

#define USE_W   1
#define USE_A   2

/***
*int __cdecl strncnt - count characters in a string, up to n.
*
*Purpose:
*       Internal local support function. Counts characters in string before NULL.
*       If NULL not found in n chars, then return n.
*
*Entry:
*       const char *string   - start of string
*       int n                - byte count
*
*Exit:
*       returns number of bytes from start of string to
*       NULL (exclusive), up to n.
*
*Exceptions:
*
*******************************************************************************/

static int __cdecl strncnt (
        const char *string,
        int cnt
        )
{
        int n = cnt;
        char *cp = (char *)string;

        while (n-- && *cp)
            cp++;

        if (!*cp)
            return cp - string;
        return cnt;
}

/***
*int __cdecl __crtCompareStringA - Get type information about an ANSI string.
*
*Purpose:
*       Internal support function. Assumes info in ANSI string format. Tries
*       to use NLS API call CompareStringA if available and uses CompareStringW
*       if it must. If neither are available it fails and returns 0.
*
*Entry:
*       LCID    Locale      - locale context for the comparison.
*       DWORD   dwCmpFlags  - see NT\Chicago docs
*       LPCSTR  lpStringn   - multibyte string to be compared
*       int     cchCountn   - char (byte) count (NOT including NULL)
*                             (-1 if NULL terminated)
*       int     code_page   - for MB/WC conversion. If 0, use __lc_codepage
*
*Exit:
*       Success: 1 - if lpString1 <  lpString2
*                2 - if lpString1 == lpString2
*                3 - if lpString1 >  lpString2
*       Failure: 0
*
*Exceptions:
*
*******************************************************************************/

int __cdecl __crtCompareStringA(
        LCID     Locale,
        DWORD    dwCmpFlags,
        LPCSTR   lpString1,
        int      cchCount1,
        LPCSTR   lpString2,
        int      cchCount2,
        int      code_page
        )
{
        static int f_use = 0;

        /*
         * Look for unstubbed 'preferred' flavor. Otherwise use available flavor.
         * Must actually call the function to ensure it's not a stub.
         * (Always try wide version first so WinNT can process codepage correctly.)
         */

        if (0 == f_use)
        {
            if (0 != CompareStringW(0, 0, L"\0", 1, L"\0", 1))
                f_use = USE_W;

            else if (0 != CompareStringA(0, 0, "\0", 1, "\0", 1))
                f_use = USE_A;

            else
                return 0;
        }

        /*
         * CompareString will compare past NULL. Must find NULL if in string
         * before cchCountn chars.
         */

        if (cchCount1 > 0)
            cchCount1 = strncnt(lpString1, cchCount1);
        if (cchCount2 > 0)
            cchCount2 = strncnt(lpString2, cchCount2);

        /* Use "A" version */

        if (USE_A == f_use)
        {
            return CompareStringA( Locale,
                                   dwCmpFlags,
                                   lpString1,
                                   cchCount1,
                                   lpString2,
                                   cchCount2 );
        }

        /* Use "W" version */

        if (USE_W == f_use)
        {
            int buff_size1;
            int buff_size2;
            wchar_t *wbuffer1;
            wchar_t *wbuffer2;

            /*
             * Use __lc_codepage for conversion if code_page not specified
             */

            if (0 == code_page)
                code_page = __lc_codepage;

            /*
             * Special case: at least one count is zero
             */

            if (!cchCount1 || !cchCount2)
            {
                unsigned char *cp;  // char pointer
                CPINFO lpCPInfo;    // struct for use with GetCPInfo

                /* both strings zero */
                if (cchCount1 == cchCount2)
                    return 2;

                /* string 1 greater */
                if (cchCount2 > 1)
                    return 1;

                /* string 2 greater */
                if (cchCount1 > 1)
                    return 3;

                /*
                 * one has zero count, the other has a count of one
                 * - if the one count is a naked lead byte, the strings are equal
                 * - otherwise it is a single character and they are unequal
                 */

                if (GetCPInfo(code_page, &lpCPInfo) == FALSE)
                    return 0;

                _ASSERTE(cchCount1==0 && cchCount2==1 || cchCount1==1 && cchCount2==0);

                /* string 1 has count of 1 */
                if (cchCount1 > 0)
                {
                    if (lpCPInfo.MaxCharSize < 2)
                        return 3;

                    for ( cp = (unsigned char *)lpCPInfo.LeadByte ;
                          cp[0] && cp[1] ;
                          cp += 2 )
                        if ( (*(unsigned char *)lpString1 >= cp[0]) &&
                             (*(unsigned char *)lpString1 <= cp[1]) )
                            return 2;

                    return 3;
                }

                /* string 2 has count of 1 */
                if (cchCount2 > 0)
                {
                    if (lpCPInfo.MaxCharSize < 2)
                    return 1;

                    for ( cp = (unsigned char *)lpCPInfo.LeadByte ;
                          cp[0] && cp[1] ;
                          cp += 2 )
                        if ( (*(unsigned char *)lpString2 >= cp[0]) &&
                             (*(unsigned char *)lpString2 <= cp[1]) )
                            return 2;

                    return 1;
                }
            }

            /*
             * Convert strings and return the requested information.
             */

            /* find out how big a buffer we need (includes NULL if any) */
            if ( 0 == (buff_size1 = MultiByteToWideChar( code_page,
                                                         MB_PRECOMPOSED |
                                                            MB_ERR_INVALID_CHARS,
                                                         lpString1,
                                                         cchCount1,
                                                         NULL,
                                                         0 )) )
                return 0;

            /* allocate enough space for chars */
            __try {
                wbuffer1 = (wchar_t *)_alloca( buff_size1 * sizeof(wchar_t) );
            }
            __except( EXCEPTION_EXECUTE_HANDLER ) {
                wbuffer1 = NULL;
            }

            if ( wbuffer1 == NULL )
                return 0;

            /* do the conversion */
            if ( 0 == MultiByteToWideChar( code_page,
                                           MB_PRECOMPOSED,
                                           lpString1,
                                           cchCount1,
                                           wbuffer1,
                                           buff_size1 ) )
                return 0;

            /* find out how big a buffer we need (includes NULL if any) */
            if ( 0 == (buff_size2 = MultiByteToWideChar( code_page,
                                                         MB_PRECOMPOSED |
                                                            MB_ERR_INVALID_CHARS,
                                                         lpString2,
                                                         cchCount2,
                                                         NULL,
                                                         0 )) )
                return 0;

            /* allocate enough space for chars */
            __try {
                wbuffer2 = (wchar_t *)_alloca( buff_size2 * sizeof(wchar_t) );
            }
            __except( EXCEPTION_EXECUTE_HANDLER ) {
                wbuffer2 = NULL;
            }

            if ( wbuffer2 == NULL )
                return 0;

            /* do the conversion */
            if ( 0 == MultiByteToWideChar( code_page,
                                           MB_PRECOMPOSED,
                                           lpString2,
                                           cchCount2,
                                           wbuffer2,
                                           buff_size2 ) )
                return 0;

            return CompareStringW( Locale,
                                   dwCmpFlags,
                                   wbuffer1,
                                   buff_size1,
                                   wbuffer2,
                                   buff_size2 );
        }
        else   /* f_use is neither USE_A nor USE_W */
            return 0;
}