Eri*_*k B 39 c compatibility printf objective-c format-string
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功能,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它的代码.唯一的问题是我怎么称呼它.
我正在使用Objective-C,所以如果有一个Objective-C特定的解决方案也没关系.
检查2 printf()格式字符串是否兼容是格式解析的练习.
C,至少没有标准的运行时比较功能,例如:
int format_cmp(const char *f1, const char *f2); // Does not exist
类似的格式"%d %f"和"%i %e"显然是兼容的,因为它们都期望int和float/double.注:float被提升到double作为short和signed char被晋升为int.
格式"%*.*f"和"%i %d %e"兼容,但并不明显:两者都期望一个int,int和float/double.
格式"%hhd"和"%d"两者都期望int,即使第一个将signed char在打印之前将其值转换为值.
格式"%d"和"%u"是不兼容的.即使许多系统都表现得像希望的那样.注意:通常char会推广到int.
格式"%d"和"%ld"是不严格的兼容.在32位系统上有相同的,但不是一般的.当然可以改变代码以适应这种情况.OTOH "%lf"和"%f" 是兼容的,由于通常的参数提升float至double.
格式"%lu"和"zu" 可以兼容,但这取决于执行unsigned long和size_t.对代码的添加可以允许这种或相关的等价.
修饰符和说明符的某些组合未定义为"zp".以下不会禁止这种深奥的组合 - 但会比较它们.
修饰符"$"是标准C的扩展,并未在下面实现.
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.可以添加许多其他考虑因素.
已知的缺点:用hh,h,l,ll,j,z,t改性剂n. l与s,c.
[编辑]
OP对安全问题的评论.这改变了帖子的性质以及从平等和安全性的比较.我想,其中一个模式(A)将是一个参考模式,下一个(B)将是测试.测试将是"B至少和A一样安全吗？".实施例A = "%.20s"和B1 = "%.19s",B2 = "%.20s",B3 = "%.21s". B1并且B2都通过了安全测试,因为他们没有提取更多的20 char. B3它是一个问题,因为它通过参考限制20 char.此外,任何非宽度限定的%s %[ %c都是安全问题 - 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,代码尚未处理修饰符"%n".
[2018编辑]
关于"格式"%d"并且"%u"不兼容.":这是用于一般打印的值.对于[0..INT_MAX]范围内的值,根据C11dr§6.5.2.26,任一格式都可以工作.
小智 -1
我对你想要的理解是，你基本上想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。或者一些很长的东西......如果是这样，那么尝试这个（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;
}
}