ANSI C中任意长度数组的类型检查

您好，我仅限于stdio.h、stdlib.h和string.h，我需要请求用户输入-输入可以是1到6之间的任意数量的字符，但是前两个字符必须是大写字母，其余四个字符必须是0到9之间的数字

有效输入的示例：

• AB1
• AB1234
• AB
• A

无效输入的示例：

• AB12345（字符太多）
• 123（前两个字符不是大写字母）
• ABA（第二个字符后的字符不是数值）

以下是我迄今为止的尝试（请记住，我几乎没有使用C的经验，这个解决方案“惯用”的可能性几乎没有，我问这个问题的原因是为了让我能够学习）：

Flightcode是一个字符数组，定义为

Flightcode[7]

它位于另一个名为

flight

的结构中。我正在

fgets

首先将其放入

temp_数组[7]

中，然后

strcpy

将其放入flight->flightcode中，以便添加空终止符，我不知道更好的方法

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX_FLIGHTCODE_LEN 6
#define MAX_CITYCODE_LEN 3
#define MAX_NUM_FLIGHTS 50
#define DB_NAME "database"

typedef struct {
  int month;
  int day;
  int hour;
  int minute;
} date_time_t;

typedef struct {
  char flightcode[MAX_FLIGHTCODE_LEN + 1];
  date_time_t departure_dt;
  char arrival_city[MAX_CITYCODE_LEN + 1];
  date_time_t arrival_dt;
} flight_t;

date_time_t departure_dt;
date_time_t arrival_dt;

char * scanline(char *dest, int dest_len);



int main(){

char temp_string[100];
flight_t flight[MAX_NUM_FLIGHTS + 1];
int correct_code = 0;

printf("Enter flight code>\n");

scanline(temp_string, sizeof(flight->flightcode));
strcpy(flight->flightcode, temp_string);

while(correct_code == 0)
{
  for(int i = 0; flight->flightcode[i] != '\0' && correct_code == 0; i++)
  {
    while((i < 2 && (flight->flightcode[i] <= 64 || flight->flightcode[i] >= 91)) || (i > 1 && (flight->flightcode[i] < 48 || flight->flightcode[i] >= 58)))
    {
      printf("Invalid input.\n");

      scanline(temp_string, sizeof(flight->flightcode));
      strcpy(flight->flightcode, temp_string);
    }
    if((i < 2 && (flight->flightcode[i] > 64 || flight->flightcode[i] < 91)) || (i > 1 && (flight->flightcode[i] >= 48 || flight->flightcode[i] < 58)))
    {
      correct_code = 1;
    }
  }
}

}

char * scanline(char *dest, int dest_len){
  int i, ch;
  i = 0;
  for (ch = getchar();
       ch != '\n' && ch != EOF && i < dest_len -1; ch = getchar())
      dest[i++] = ch;
  dest[i] = '\0';

  while (ch != '\n' && ch != EOF)
    ch = getchar();

  return (dest);
}

#包括
#包括
#包括
#定义最大飞行代码长度6
#定义最大城市代码长度3
#定义最大飞行次数50
#定义数据库名称“数据库”
类型定义结构{
整月；
国际日；
整小时；
整数分钟；
}日期时间；
类型定义结构{
char flightcode[MAX_flightcode_LEN+1]；
日期时间出发日期；
字符到达城市[最大城市代码+1]；
到达日期时间；
}飞行;；
日期时间出发日期；
到达日期时间；
char*扫描线（char*dest，int dest_len）；
int main（）{
字符临时字符串[100]；
飞行时间[最大飞行次数+1]；
int correct_code=0；
printf（“输入航班代码>\n”）；
扫描线（临时字符串，sizeof（航班->航班代码））；
strcpy（航班->航班代码，临时字符串）；
while（正确的_代码==0）
{
对于（int i=0；flight->flightcode[i]！='\0'&&correct_code==0；i++）
{
而（（i<2&&（flight->flightcode[i]>=91））| |（i>1&&（flight->flightcode[i]<48| | flightcode[i]>=58）））
{
printf（“无效输入。\n”）；
扫描线（临时字符串，sizeof（航班->航班代码））；
strcpy（航班->航班代码，临时字符串）；
}
如果（（i<2&&（航班->航班代码[i]>64||航班->航班代码[i]<91））|（i>1&&（航班->航班代码[i]>=48||航班->航班代码[i]<58）））
{
正确的_代码=1；
}
}
}
}
字符*扫描线（字符*目的地，内部目的地）{
int i，ch；
i=0；
for（ch=getchar（）；
ch！='\n'&&ch！=EOF&&i

首先，要意识到您的问题文本缺少一个问题。此外，你的问题标题毫无意义

无论如何，这是一个可能的，故意的非常丑陋的解决方案。方法：您希望执行X，因此您编写了执行X的代码。让我们从

scanline（）

开始：

我知道这很难看，但我相信澄清文件输入中涉及的三个步骤是有帮助的：读取、检查和使用。请注意，如果行达到所需的字符数（比容纳终止符的缓冲区大小小一个），则返回

true

然后您要检查是否：

scanline（）

成功

至少有一个字符

字符0介于“A”和“Z”之间

字符1位于“A”和“Z”之间

字符2介于“0”和“1”之间

字符3介于“0”和“1”之间

字符4介于“0”和“1”之间

字符5介于“0”和“1”之间

让我们为此编写代码：

int main(void) 
{
    flight_t flight;

    while (1) {
        printf("Enter flight code>\n");
        if (!scanline(flight.flightcode, sizeof(flight.flightcode))) {
            printf("Too many characters.\n");
            continue;
        }
        int i = 0;
        if (flight.flightcode[i] == 0) {
            printf("Empty input.\n");
            continue;
        }
        if (flight.flightcode[i] < 'A' || flight.flightcode[i] > 'Z') {
            printf("Character %d is not upper case.\n", i);
            continue;
        }
        i++;
        if (flight.flightcode[i] == 0)
            break;
        if (flight.flightcode[i] < 'A' || flight.flightcode[i] > 'Z') {
            printf("Character %d is not upper case.\n", i);
            continue;
        }
        i++;
        if (flight.flightcode[i] == 0)
            break;
        if (flight.flightcode[i] < '0' || flight.flightcode[i] > '9') {
            printf("Character %d is not a digit.\n", i);
            continue;
        }
        i++;
        if (flight.flightcode[i] == 0)
            break;
        if (flight.flightcode[i] < '0' || flight.flightcode[i] > '9') {
            printf("Character %d is not a digit.\n", i);
            continue;
        }
        i++;
        if (flight.flightcode[i] == 0)
            break;
        if (flight.flightcode[i] < '0' || flight.flightcode[i] > '9') {
            printf("Character %d is not a digit.\n", i);
            continue;
        }
        i++;
        if (flight.flightcode[i] == 0)
            break;
        if (flight.flightcode[i] < '0' || flight.flightcode[i] > '9') {
            printf("Character %d is not a digit.\n", i);
            continue;
        }
        i++;
        if (flight.flightcode[i] == 0)
            break;
    }
}

int main（无效）
{
飞行;；
而(1){
printf（“输入航班代码>\n”）；
如果（！scanline（flight.flightcode，sizeof（flight.flightcode）））{
printf（“字符太多。\n”）；
继续；
}
int i=0；
if（flight.flightcode[i]==0）{
printf（“空输入。\n”）；
继续；
}
if（flight.flightcode[i]<'A'| | flight.flightcode[i]>'Z'）{
printf（“字符%d不是大写。\n”，i）；
继续；
}
i++；
if（flight.flightcode[i]==0）
打破
if（flight.flightcode[i]<'A'| | flight.flightcode[i]>'Z'）{
printf（“字符%d不是大写。\n”，i）；
继续；
}
i++；
if（flight.flightcode[i]==0）
打破
if（flight.flightcode[i]<'0'| | flight.flightcode[i]>'9'）{
printf（“字符%d不是数字。\n”，i）；
继续；
}
i++；
if（flight.flightcode[i]==0）
打破
if（flight.flightcode[i]<'0'| | flight.flightcode[i]>'9'）{
printf（“字符%d不是数字。\n”，i）；
继续；
}
i++；
if（flight.flightcode[i]==0）
打破
if（flight.flightcode[i]<'0'| | flight.flightcode[i]>'9'）{
printf（“字符%d不是数字。\n”，i）；
继续；
}
i++；
if（flight.flightcode[i]==0）
打破
if（flight.flightcode[i]<'0'| | flight.flightcode[i]>'9'）{
printf（“字符%d不是数字。\n”，i）；
继续；
}
i++；
if（flight.flightcode[i]==0）
打破
}
}

一些评论：

在代码中，您可以在第一个字符正常后将

correct_code

设置为1。如果要循环使用这些字符，必须检查是否有错误并退出循环

当您有特定的字符文本可用时，不要使用ASCII码

我建议您采用我的解决方案，作为练习，修复它，以便能够与套利合作

int main(void) 
{
    flight_t flight;

    while (1) {
        printf("Enter flight code>\n");
        if (!scanline(flight.flightcode, sizeof(flight.flightcode))) {
            printf("Too many characters.\n");
            continue;
        }
        int i = 0;
        if (flight.flightcode[i] == 0) {
            printf("Empty input.\n");
            continue;
        }
        if (flight.flightcode[i] < 'A' || flight.flightcode[i] > 'Z') {
            printf("Character %d is not upper case.\n", i);
            continue;
        }
        i++;
        if (flight.flightcode[i] == 0)
            break;
        if (flight.flightcode[i] < 'A' || flight.flightcode[i] > 'Z') {
            printf("Character %d is not upper case.\n", i);
            continue;
        }
        i++;
        if (flight.flightcode[i] == 0)
            break;
        if (flight.flightcode[i] < '0' || flight.flightcode[i] > '9') {
            printf("Character %d is not a digit.\n", i);
            continue;
        }
        i++;
        if (flight.flightcode[i] == 0)
            break;
        if (flight.flightcode[i] < '0' || flight.flightcode[i] > '9') {
            printf("Character %d is not a digit.\n", i);
            continue;
        }
        i++;
        if (flight.flightcode[i] == 0)
            break;
        if (flight.flightcode[i] < '0' || flight.flightcode[i] > '9') {
            printf("Character %d is not a digit.\n", i);
            continue;
        }
        i++;
        if (flight.flightcode[i] == 0)
            break;
        if (flight.flightcode[i] < '0' || flight.flightcode[i] > '9') {
            printf("Character %d is not a digit.\n", i);
            continue;
        }
        i++;
        if (flight.flightcode[i] == 0)
            break;
    }
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX_FLIGHTCODE_LEN 6
#define MAX_CITYCODE_LEN 3
#define MAX_NUM_FLIGHTS 50
#define DB_NAME "database"

typedef struct {
  int month;
  int day;
  int hour;
  int minute;
} date_time_t;

typedef struct {
  char flightcode[MAX_FLIGHTCODE_LEN + 1];
  date_time_t departure_dt;
  char arrival_city[MAX_CITYCODE_LEN + 1];
  date_time_t arrival_dt;
} flight_t;

date_time_t departure_dt;
date_time_t arrival_dt;


int main(void){

  char temp_string[100];
  flight_t flight[MAX_NUM_FLIGHTS + 1];
  int correct_code;
  size_t len;
  int i;

  do
  {
    /* we first assume the code is correct and set this to 0 on any error */
    correct_code = 1;
    printf("Enter flight code>\n");

    if(fgets(temp_string, sizeof(temp_string), stdin) == NULL)
    {
        if(feof(stdin)) fprintf(stderr, "no input (EOF)\n");
        else perror("fgets");
        correct_code = 0;
        temp_string[0] = '\0';
    }

    if(correct_code)
    {
      len = strlen(temp_string);

      /* cut off newline
       * Use a loop to handle CR and LF just in case Windows might leave more than one character */
      while((len > 0) &&
            ((temp_string[len - 1] == '\n') ||
             (temp_string[len - 1] == '\r')))
      {
        len--;
        temp_string[len] == '\0';
      }

      if(len > MAX_FLIGHTCODE_LEN)
      {
        correct_code = 0;
        fprintf(stderr, "Input must not be longer than %d characters.\n", MAX_FLIGHTCODE_LEN);
      }

      if(len == 0)
      {
        correct_code = 0;
        fprintf(stderr, "Empty input.\n");
      }
    }

    /* check first two letters */
    for(i = 0; (i < 2) && (i < len) && correct_code; i++)
    {
      /* you could use function isupper when you make sure the locale is set to "C" */
      if((temp_string[i] < 'A') || (temp_string[i] > 'Z'))
      {
        correct_code = 0;
        fprintf(stderr, "first two characters must be uppercase letters. Found '%c' at position %d\n", temp_string[i], i);
      }
    }

    /* check digits starting from 3rd character */
    for(i = 2; (i < MAX_FLIGHTCODE_LEN) && (i < len) && correct_code; i++)
    {
      /* you could use function isdigit here */
      if((temp_string[i] < '0') || (temp_string[i] > '9'))
      {
        correct_code = 0;
        fprintf(stderr, "Third to last characters must be digits. Found '%c' at position %d\n", temp_string[i], i);
      }
    }

    if(correct_code)
    {
      /* we already checked that length is not more than MAX_FLIGHTCODE_LEN, so we don't need strncpy to avoid buffer overflow */
      strcpy(flight->flightcode, temp_string);
      printf("Valid code: %s\n", flight->flightcode);
    }
    else
    {
      fprintf(stderr, "Invalid code.\n");
    }
  } while(!correct_code);

  return 0;

}

#define TRUE 1
#define FALSE 0

inline int isupper(int c) {
    return c >= 'A' && c <= 'Z';  // only for ASCII and derived
}
inline int isdigit(char c) {
    return c >= '0' && c <= '9';    // guarantee per standard
}
inline int isblank(int c) {
    return c == ' ' || c == '\t';
}
inline int isspace(int c) {
    static const char spaces[] = " \t\r\n\v";
    for(const char *s=spaces; *s != '\0'; s++) {
        if (c == *s) return TRUE;
    }
    return FALSE;
}

char *get_string(char *buffer, int maxupper, int maxdigit, FILE *fd) {
    char buf[16];      // any size >=2 will fit
    char *cur = buffer;
    int state = 0, uppersize=0, digitsize=0;
    for (;;) {         // allow lines longer than buf
        if (NULL == fgets(buf, sizeof(buf), fd)) {
            *cur = '\0';           // EOF: do not forget the terminating NULL
            return state >= 1 ? buffer : NULL;   // must have at least 1 char
        }
        for (char *b=buf; *b!='\0'; b++) {
            switch(state) {
                case 0:   // spaces before first uppercase
                    if (isblank(*b)) break;
                    state++;
                case 1:   // first uppercase
                    if (! isupper(*b)) {
                        state = 5;    // must read up to \n
                        break;
                    }
                    state++;
                case 2:   // process uppercase chars
                    if (! isupper(*b)) {
                        if (uppersize > 0) state++;
                        else  {
                            state = 5;    // must read up to \n
                            break;
                        }
                    }
                    else {
                        if (uppersize >= maxupper)  {
                            state = 5;    // must read up to \n
                            break;
                        }
                        *cur++ = *b;
                        uppersize++;
                        break;
                    }
                case 3:   // process digit chars
                    if (! isdigit(*b)) {
                        state++;
                    }
                    else {
                        if (digitsize >= maxdigit)  {
                            state = 5;    // must read up to \n
                            break;
                        }
                        *cur++ = *b;
                        digitsize++;
                        break;
                    }
                case 4:    // allow spaces after last digit
                    if ('\n' == *b) {
                        *cur = '\0';
                        return buffer;
                    }
                    if (! isspace(*b)) state++
                    break;
                case 5:    // on error clean end of line
                    if ('\n' == *b) return NULL;
            }
        }
    }
}

...
printf("Enter flight code>\n");
if (NULL == get_string(flight->flightcode, 2, 4, stdin)) {
    // process the error
    ...
}
...

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX_FLIGHTCODE_LEN 6
#define MAX_CITYCODE_LEN 3
#define MAX_NUM_FLIGHTS 50
#define DB_NAME "database"

typedef struct {
    int month;
    int day;
    int hour;
    int minute;
} date_time_t;

typedef struct {
    char flightcode[MAX_FLIGHTCODE_LEN + 1];
    date_time_t departure_dt;
    char arrival_city[MAX_CITYCODE_LEN + 1];
    date_time_t arrival_dt;
} flight_t;

date_time_t departure_dt;
date_time_t arrival_dt;

char * scanline(char *dest, int dest_len);

int main(){
    int head = 0, leading = 0, tail = 0;
    int correct_code = 0;
    int result = 0;
    char temp_string[100];
    char upper[3] = "";
    char digits[5] = "";
    flight_t flight[MAX_NUM_FLIGHTS + 1];
    do {
        printf("Enter flight code>\n");

        scanline(temp_string, sizeof(temp_string));
        if ( 0 < ( result = sscanf ( temp_string, "%n%2[A-Z]%n%4[0-9]%n", &head, upper, &leading, digits, &tail))) {
            if ( 1 == result && 0 == temp_string[leading]) {
                correct_code = 1;
                break;
            }
            if ( 2 == result && 2 == leading - head && 7 > tail - head && 0 == temp_string[tail]) {
                correct_code = 1;
            }
            else {
                printf ( "invalid input\n");
            }
        }
        else {
            printf ( "invalid input\n");
        }
    } while(correct_code == 0);
    printf ( "Input is: %s\n", temp_string);
    strcpy(flight->flightcode, temp_string);
    return 0;
}

char * scanline(char *dest, int dest_len){
    int i, ch;
    i = 0;
    for (ch = getchar(); ch != '\n' && ch != EOF && i < dest_len -1; ch = getchar()) {
        dest[i++] = ch;
    }
    dest[i] = '\0';

    while (ch != '\n' && ch != EOF) {
        ch = getchar();
    }

    return dest;
}