Function open_command_file

v2/engine/execnt.c:1097–1150

 */

static FILE * open_command_file( int const slot )
{
    string * const command_file = cmdtab[ slot ].command_file;

    /* If the temporary command file name has not already been prepared for this
     * slot number, prepare a new one containing a '##' place holder that will
     * be changed later and needs to be located at a fixed distance from the
     * end.
     */
    if ( !command_file->value )
    {
        DWORD const procID = GetCurrentProcessId();
        string const * const tmpdir = path_tmpdir();
        string_new( command_file );
        string_reserve( command_file, tmpdir->size + 64 );
        command_file->size = sprintf( command_file->value,
            "%s\\jam%d-%02d-##.bat", tmpdir->value, procID, slot );
    }

    /* For some reason opening a command file can fail intermittently. But doing
     * some retries works. Most likely this is due to a previously existing file
     * of the same name that happens to still be opened by an active virus
     * scanner. Originally pointed out and fixed by Bronek Kozicki.
     *
     * We first try to open several differently named files to avoid having to
     * wait idly if not absolutely necessary. Our temporary command file names
     * contain a fixed position place holder we use for generating different
     * file names.
     */
    {
        char * const index1 = command_file->value + command_file->size - 6;
        char * const index2 = index1 + 1;
        int waits_remaining;
        assert( command_file->value < index1 );
        assert( index2 + 1 < command_file->value + command_file->size );
        assert( index2[ 1 ] == '.' );
        for ( waits_remaining = 3; ; --waits_remaining )
        {
            int index;
            for ( index = 0; index != 20; ++index )
            {
                FILE * f;
                *index1 = '0' + index / 10;
                *index2 = '0' + index % 10;
                f = fopen( command_file->value, "w" );
                if ( f ) return f;
            }
            if ( !waits_remaining ) break;
            Sleep( 250 );
        }
    }

    return 0;
}


/*