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例子:

"Something %d"        and "Something else %d"       // Compatible
"Something %d"        and "Something else %f"       // Not Compatible
"Something %d"        and "Something %d else %d"    // Not Compatible
"Something %d and %f" and "Something %2$f and %1$d" // Compatible

我认为应该有一些 C 函数,但我没有得到任何相关的搜索结果。我的意思是编译器正在检查格式字符串和参数是否匹配,因此已经编写了用于检查的代码。唯一的问题是我怎么称呼它。

我使用的是 Objective-C,所以如果有一个 Objective-C 特定的解决方案也可以。

4

2 回答 2

9

检查 2 个printf()格式字符串是否兼容是格式解析中的一项练习。

C 至少没有标准的运行时比较函数,例如:

int format_cmp(const char *f1, const char *f2); // Does not exist

"%d %f"和之类的格式"%i %e"显然是兼容的,因为它们都期望intfloat/double。注意:float被提升为doubleasshortsigned char被提升为int.

格式"%*.*f""%i %d %e"是兼容的,但并不明显:两者都需要int,intfloat/double.

格式"%hhd""%d"两者都期望一个int,即使第一个将signed char在打印之前将其值转换为。

格式不兼容"%d"_ 尽管许多系统会按预期运行。注意:通常会升级为."%u"charint

格式"%d""%ld"严格兼容。在 32 位系统上,有等价的,但不是一般的。当然可以更改代码以适应这一点。OTOH"%lf"并且由于to的通常参数提升而"%f" 兼容floatdouble

格式"%lu""%zu" 可能兼容,但这取决于 和 的unsigned long实现size_t。代码的添加可以允许这个或相关的等价。

修饰符和说明符的某些组合未定义为"%zp". 以下内容不允许此类深奥的组合 - 但会比较它们。

修饰符 like"$"是对标准 C 的扩展,在下文中未实现。

的兼容性测试printf()不同于scanf().

#include <ctype.h>
#include <limits.h>
#include <stdio.h>
#include <string.h>

typedef enum {
  type_none,
  type_int,
  type_unsigned,
  type_float,
  type_charpointer,
  type_voidpointer,
  type_intpointer,
  type_unknown,
  type_type_N = 0xFFFFFF
} type_type;

typedef struct {
  const char *format;
  int int_queue;
  type_type type;
} format_T;

static void format_init(format_T *state, const char *format);
static type_type format_get(format_T *state);
static void format_next(format_T *state);

void format_init(format_T *state, const char *format) {
  state->format = format;
  state->int_queue = 0;
  state->type = type_none;
  format_next(state);
}

type_type format_get(format_T *state) {
  if (state->int_queue > 0) {
    return type_int;
  }
  return state->type;
}

const char *seek_flag(const char *format) {
  while (strchr("-+ #0", *format) != NULL)
    format++;
  return format;
}

const char *seek_width(const char *format, int *int_queue) {
  *int_queue = 0;
  if (*format == '*') {
    format++;
    (*int_queue)++;
  } else {
    while (isdigit((unsigned char ) *format))
      format++;
  }
  if (*format == '.') {
    if (*format == '*') {
      format++;
      (*int_queue)++;
    } else {
      while (isdigit((unsigned char ) *format))
        format++;
    }
  }
  return format;
}

const char *seek_mod(const char *format, int *mod) {
  *mod = 0;
  if (format[0] == 'h' && format[1] == 'h') {
    format += 2;
  } else if (format[0] == 'l' && format[1] == 'l') {
    *mod = ('l' << CHAR_BIT) + 'l';
    format += 2;
  } else if (strchr("ljztL", *format)) {
    *mod = *format;
    format++;
  } else if (strchr("h", *format)) {
    format++;
  }
  return format;
}

const char *seek_specifier(const char *format, int mod, type_type *type) {
  if (strchr("di", *format)) {
    *type = type_int;
    format++;
  } else if (strchr("ouxX", *format)) {
    *type = type_unsigned;
    format++;
  } else if (strchr("fFeEgGaA", *format)) {
    if (mod == 'l') mod = 0;
    *type = type_float;
    format++;
  } else if (strchr("c", *format)) {
    *type = type_int;
    format++;
  } else if (strchr("s", *format)) {
    *type = type_charpointer;
    format++;
  } else if (strchr("p", *format)) {
    *type = type_voidpointer;
    format++;
  } else if (strchr("n", *format)) {
    *type = type_intpointer;
    format++;
  } else {
    *type = type_unknown;
    exit(1);
  }
  *type |= mod << CHAR_BIT; // Bring in modifier
  return format;
}

void format_next(format_T *state) {
  if (state->int_queue > 0) {
    state->int_queue--;
    return;
  }
  while (*state->format) {
    if (state->format[0] == '%') {
      state->format++;
      if (state->format[0] == '%') {
        state->format++;
        continue;
      }
      state->format = seek_flag(state->format);
      state->format = seek_width(state->format, &state->int_queue);
      int mod;
      state->format = seek_mod(state->format, &mod);
      state->format = seek_specifier(state->format, mod, &state->type);
      return;
    } else {
      state->format++;
    }
  }
  state->type = type_none;
}

// 0 Compatible
// 1 Not Compatible
// 2 Not Comparable
int format_cmp(const char *f1, const char *f2) {
  format_T state1;
  format_init(&state1, f1);
  format_T state2;
  format_init(&state2, f2);
  while (format_get(&state1) == format_get(&state2)) {
    if (format_get(&state1) == type_none)
      return 0;
    if (format_get(&state1) == type_unknown)
      return 2;
    format_next(&state1);
    format_next(&state2);
  }
  if (format_get(&state1) == type_unknown)
    return 2;
  if (format_get(&state2) == type_unknown)
    return 2;
  return 1;
}

注意:只进行了最少的测试。可以添加许多额外的考虑因素。

已知缺点:hh,h,l,ll,j,z,t带有 . 的修饰符nls,c.

[编辑]

OP 关于安全问题的评论。这改变了职位的性质以及从平等到安全的比较。我想其中一个模式 (A) 将是参考模式,下一个 (B) 将是测试。测试将是“B 至少和 A 一样安全吗?”。示例A = "%.20s"B1 = "%.19s", B2 = "%.20s", B3 = "%.21s"B1并且B2两者都通过了安全测试,因为它们没有提取更多 20 charB3是一个问题,因为它通过了 20 的参考限制char。此外,任何非宽度合格的%s %[ %c都是一个安全问题 - 在参考或测试模式中。这个答案的代码没有解决这个问题。

如前所述,代码尚未处理带有"%n".

[2018年编辑]

关于“格式"%d""%u"不兼容。”:这是一般要打印的值。对于[0..INT_MAX]范围内的值,任何一种格式都可以按照 C11dr §6.5.2.2 6 工作。

于 2015-05-12T20:44:50.680 回答
-1

我对您想要什么的理解是,您基本上需要一种可以查看两个字符串并检测它们是否具有相同类型的值的方法。或者那些很长的东西......如果是这样,那么试试这个(或类似的东西):

-(int)checkCompatible:(NSString *)string_1 :(NSString *)string_2 {

    // Separate the string into single elements.
    NSArray *stringArray_1 = [string_1 componentsSeparatedByString:@" "];
    NSArray *stringArray_2 = [string_2 componentsSeparatedByString:@" "];

    // Store only the numbers for comparison in a new array.
    NSMutableArray *numbers_1 = [[NSMutableArray alloc] init];
    NSMutableArray *numbers_2 = [[NSMutableArray alloc] init];

    // Make sure the for loop below, runs for the appropriate
    // number of cycles depending on which array is bigger.
    int loopMax = 0;

    if ([stringArray_1 count] > [stringArray_2 count]) {
        loopMax = (int)[stringArray_1 count];
    } 

    else {
        loopMax = (int)[stringArray_2 count];
    }

    // Now go through the stringArray's and store only the 
    // numbers in the mutable array's. This will be used 
    // during the comparison stage.
    for (int loop = 0; loop < loopMax; loop++) {

        NSCharacterSet *notDigits = [[NSCharacterSet decimalDigitCharacterSet] invertedSet];

        if (loop < [stringArray_1 count]) {

            if ([[stringArray_1 objectAtindex:loop] rangeOfCharacterFromSet:notDigits].location == NSNotFound) {
                // String consists only of the digits 0 through 9.
                [numbers_1 addObject:[stringArray_1 objectAtindex:loop]];
            }
        }

        if (loop < [stringArray_2 count]) {

            if ([[stringArray_2 objectAtindex:loop] rangeOfCharacterFromSet:notDigits].location == NSNotFound) {
                // String consists only of the digits 0 through 9.
                [numbers_2 addObject:[stringArray_2 objectAtindex:loop]];
            }
        }
    }

    // Now look through the mutable array's
    // and perform the type comparison,.

    if ([numbers_1 count] != [numbers_2 count]) {

        // One of the two strings has more numbers 
        // than the other, so they are NOT compatible.
        return 1;
    }

    else {

        // Both string have the same number of  numbers
        // numbers so lets go through them to make 
        // sure the  numbers are of the same type.
        for (int loop = 0; loop < [numbers_1 count]; loop++) {

            // Check to see if the number in the current array index
            // is a float or an integer. All the numbers in the array have
            // to be the SAME type, in order for the strings to be compatible.
            BOOL check_float_1 = [[NSScanner scannerWithString:[numbers_1 objectAtindex:loop]] scanFloat:nil];
            BOOL check_int_1 = [[NSScanner scannerWithString:[numbers_1 objectAtindex:loop]] scanInt:nil];
            BOOL check_float_2 = [[NSScanner scannerWithString:[numbers_2 objectAtindex:loop]] scanFloat:nil];
            BOOL check_int_2 = [[NSScanner scannerWithString:[numbers_2 objectAtindex:loop]] scanInt:nil];

            if (check_float_1 == YES) {

                if (check_float_2 == NO) {
                    return 1;
                }
            }

            else if (check_int_1 == YES) {

                if (check_int_2 == NO) {
                    return 1;
                }
            }

            else {
                // Error of some sort......
                return 1;
            }
        }

        // All the numbers in the strings are of the same
        // type (otherwise we would NOT have reached
        // this point). Therefore the strings are compatible.
        return 0;
      }
}
于 2015-05-07T09:24:07.940 回答