#include <stdlib.h>
#include <dos.h>
#include <errno.h>
#include <process.h>
#include <string.h>
#include <dir.h>
#include <io.h>

struct __execblock {
    unsigned short  envseg;
    void far *      cmdtail;
    void far *      fcb1;
    void far *      fcb2;
};

int __cdecl __dosexec( char *name, void *blk );

unsigned char __dogetrt( void );
#pragma aux __dogetrt = \
    "mov ah, 0x4D"      \
    "int 0x21"          \
    value [al]          \
    modify [ax];

static const char *__searchexe( const char *path )
{
    static char exename[ _MAX_PATH ];

    if( access( path, 0 ) == 0 ) return( __retsfn( path ) );

    if( strchr( path + strlen( path ) - 4, '.' ) != NULL ) 
        return( path ); /* Check for explicit ext */

    strcpy( exename, path );
    strcat( exename, ".COM" );

    if( access( exename, 0 ) == 0 ) return( __retsfn( exename ) );

    strcpy( exename, path );
    strcat( exename, ".EXE" );

    if( access( exename, 0 ) == 0 ) return( __retsfn( exename ) );
    
    strcpy( exename, path );
    strcat( exename, ".BAT" );

    if( access( exename, 0 ) == 0 ) return( __retsfn( exename ) );

    return( __retsfn( path ) );
}

int spawnve( int mode, char *path, char **argv, char **envp )
{
    struct __execblock exb;
    struct fcb tmpfcb, tmpfcb2;
    char buf[ 128 ], cmdline[ 126 ];
    char *p, *c, *name;
    int len = 0, retval, i, isbat = 0;

    if( mode == P_NOWAIT ) {
        errno = ENOEXEC;
        return( -1 );
    }

    if( strstr( ( name = ( char * )__searchexe( path ) ), ".BAT" ) != NULL ) {
        strcpy( cmdline, "/c " );
        strcat( cmdline, name );
        isbat = 1;
        if( ( p = getenv( "COMSPEC" ) ) == NULL ) {
            errno = ENOENT;
            return( -1 );
        }
    }
    for( i = 1; *argv[ i ]; i++ ) {
        if( ( len = strlen( cmdline ) ) != 0 ) strcat( cmdline, " " );
        if( ( len += strlen( argv[ i ] ) + 1 ) > 126 ) {
            errno = E2BIG;
            return( -1 );
        }
        if( ( c = strchr( argv[ i ], ' ' ) ) != NULL ) strcat( cmdline, "\"" );
        strcat( cmdline, argv[ i ] );
        if( c != NULL ) strcat( cmdline, "\"" );
    }

    buf[ 0 ] = len;
    strcpy( &buf[ 1 ], cmdline );
    strcpy( &buf[ buf[ 0 ] + 1 ], "\xd" );

    exb.envseg = FP_SEG( envp );
    exb.cmdtail = ( void far * )MK_FP( FP_SEG( buf ), FP_OFF( buf ) );
    if( ( p = parsfnm( cmdline, &tmpfcb, 1 ) ) != NULL )
        parsfnm( p, &tmpfcb2, 1 );
    exb.fcb1 = ( void far * )&tmpfcb;
    exb.fcb2 = ( void far * )&tmpfcb2;

    if( ( retval = __dosexec( ( isbat ) ? p : name, &exb ) ) < 0 ) {
        errno = - retval;
        return( -1 );
    }

    retval = __dogetrt();

    if( mode == P_OVERLAY ) exit( retval );

    return( retval );
}