防止值輸入零作爲第一個數字

Question

我有這樣的代碼，解碼從命令

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); 
     } 
    } 

這在小鍵盤數字鍵入的數字計數數和在一個盒子裏寫的數字輸入字符，例如

 |5|4|2|0| 

欲防止第一計數位爲0（或只接受1至9號）和第二，第三，...數字從0接受號 - 9

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

感謝

OK，通過增加功能解決：

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

你可以像這樣，而不是使用ISDIGIT執行檢查（）。

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

從「0」到「9」中的人物總是在用C相鄰順序，因此這張支票你需要什麼。