Question

我有这个代码解码来自命令的输入字符

    if( arg && isdigit( arg[ 0 ] ) {

        /* Decode the input char from commands.  */
        if( cmd->digit_counter == 0 ) memset( cmd->next_chan_buffer, 0, 5 );
        cmd->next_chan_buffer[ cmd->digit_counter ] = arg[ 0 ];
        cmd->digit_counter++;
        cmd->frame_counter = cmd->delay;

        /**
         * Send an enter command if we type more digits than there are stations.
         */
        if( cmd->digit_counter > 0 && (station_get_max_position( cmd->station ) < 10) ) {
            commands_handle( cmd, ENTER, 0 );
        } else if( cmd->digit_counter > 1 && (station_get_max_position( cmd->station ) < 100) ) {
            commands_handle( cmd, ENTER, 0 );
        } else if( cmd->digit_counter > 2 ) {
            commands_handle( cmd, ENTER, 0 );
        }
    }

此键盘数字中输入的计数位数和方框中的写入数字，例如

      |5|4|2|0|

我想防止第一个计数数字为0（或接受数字仅为1到9）和第二个，第三个......数字接受0到9之间的数字

digits count           1            2        3        4
          -------------------------------------------------
          | only digits 1 to 9 | 0 to 9 | 0 to 9 | 0 to 9 |
          -------------------------------------------------

由于

好的，通过添加功能解决：

int first_digit( int num ) 
{
        while(num >= 10) {
            num = ( num - ( num % 10 ) ) / 10;
        }
        return num;
}

if( arg && isdigit( arg[ 0 ] ) {

        /* Decode the input char from commands.  */
        if( cmd->digit_counter == 0 ) memset( cmd->next_buffer, 0, 5 );
        cmd->next_buffer[ cmd->digit_counter ] = arg[ 0 ];
        if( first_digit( atoi( cmd->next_chan_buffer ) ) != 0 ) {
            cmd->digit_counter++;
            cmd->frame_counter = cmd->delay;
        }
}

Answer 1

您可以执行此类检查，而不是使用isdigit（）。

if( arg && arg[0] >= '1' && arg[0] <= '9' ) { // only accept '1' through '9'

从'0'到'9'的字符在C中始终是相邻的顺序，因此这项检查可以满足您的需要。

防止键入零作为值的第一个数字

1 个答案: