我正在实现sscanf，我有这样一个功能：
my_string.h
#ifndef SRC_MY_STRING_H_
#define SRC_MY_STRING_H_
#define my_size_t unsigned long
#define my_NULL (void *)0
#include <stdarg.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h> //sscanf
#include <stdbool.h> //sscanf
my_size_t my_strlen(const char *string);
char *my_strcpy(char *restrict dst, const char *restrict src);
char *my_strncpy(char *restrict dst, const char *restrict src, size_t n);
#endif // SRC_MY_STRING_H_
my_string.c
#include "my_string.h"
my_size_t my_strlen(const char *string) {
my_size_t len = 0;
while (*(string + len)) {
len++;
}
return len;
}
char *my_strcpy(char *restrict dst, const char *restrict src) {
char *res = dst;
while (*src) {
*dst = *src;
dst++;
src++;
}
*dst = 0;
return res;
}
char *my_strncpy(char *restrict dst, const char *restrict src, my_size_t n) {
char *res = dst;
while (*src && n--) {
*dst = *src;
dst++;
src++;
}
*dst = 0;
return res;
}
my_sscanf.c
#include "my_string.h"
/*sscanf implementation*/
/* for specifiers */
enum {
spec_c = 1 << 0,
spec_d = 1 << 1,
spec_i = 1 << 2,
spec_e = 1 << 3,
spec_E = 1 << 4,
spec_f = 1 << 5,
spec_g = 1 << 6,
spec_G = 1 << 7,
spec_o = 1 << 8,
spec_s = 1 << 9,
spec_u = 1 << 10,
spec_x = 1 << 11,
spec_X = 1 << 12,
spec_p = 1 << 13,
spec_n = 1 << 14,
spec_percent = 1 << 15
};
/* for systems */
enum {
OCT = 8,
DEC = 10,
HEX = 16
};
/* for shifts */
enum {
SHIFT = 48, /* code of 0 in ASCII */
SHIFT_HEX = 55, /* code of A - 10 in ASCII */
SHIFT_hex = 87 /* code of a - 10 in ASCII */
};
/* check white-space characters */
static _Bool is_whitespace(char ch) {
return (ch == ' ' || ch == '\t' || ch == '\n') ? true : false;
}
/* skip white-space chatacters */
static int skip_whitespaces(char **string) {
int count = 0;
while (is_whitespace(**string)) {
(*string)++;
count++;
}
return count;
}
/* skip the whole string */
static void skip_all(char **string) {
while (**string) {
(*string)++;
}
}
/* sets the format_buf pointer to the character after the % */
static void get_specifier(char **str_buf, char **format_buf, _Bool *outsider_ch) {
int white_count = skip_whitespaces(format_buf);
if (white_count) {
skip_whitespaces(str_buf);
}
while (**format_buf != '%') { /* skip all regular characters*/
if (**format_buf != **str_buf) {
*outsider_ch = true;
}
(*format_buf)++;
(*str_buf)++;
}
/* stoped at % */
++(*format_buf);
}
/* check character if it's a digit*/
static _Bool is_digit(char ch) {
return ((ch >= '0') && (ch <= '9')) ? true : false;
}
/* converts from string to number */
static long str_to_dec(char **string, int width, int sign) {
long res = **string - SHIFT; /* get the first digit */
int count = 1;
(*string)++;
while (is_digit(**string) && ((count < width) || (!width))) {
res = res * DEC + (**string - SHIFT);
(*string)++;
count++;
}
return res * sign;
}
/* check character if it's a length*/
static _Bool is_correct_length(char **format_buf) {
_Bool res = false;
char next_ch = *((*format_buf) + 1);
if (((**format_buf == 'l') || (**format_buf == 'L')) && (next_ch = 'f')) {
res = true;
}
return res;
}
/* set the specs in an integer number according to enum */
static int set_specs(char **format_buf, _Bool *ass_supress, int *width, int *length) {
int specs = 0;
while ((**format_buf) && !is_whitespace(**format_buf) && (!specs)) {
switch (**format_buf) {
case 'c':
specs |= spec_c;
break;
case 'd':
specs |= spec_d;
break;
case 'i':
specs |= spec_i;
break;
case 'e':
specs |= spec_e;
specs |= spec_E;
break;
case 'f':
specs |= spec_f;
break;
case 'g':
specs |= spec_g;
break;
case 'G':
specs |= spec_G;
break;
case 'o':
specs |= spec_o;
break;
case 's':
specs |= spec_s;
break;
case 'u':
specs |= spec_u;
break;
case 'x':
specs |= spec_x;
break;
case 'X':
specs |= spec_X;
break;
case 'p':
specs |= spec_p;
break;
case 'n':
specs |= spec_n;
break;
case '%':
specs |= spec_percent;
break;
case '*':
*ass_supress = true;
break;
default:
if (is_digit(**format_buf) && (**format_buf > '0')) {
*width = str_to_dec(format_buf, 0, 1); /* get width */
(*format_buf)--;
} else if (is_correct_length(format_buf)) {
*length = **format_buf;
} else {
fprintf(stderr, "Incorrect specifier\n");
// TODO:handle an error
}
}
(*format_buf)++;
}
return specs;
}
/* puts string into another vararg*/
static void str_into_arg(va_list *argp, _Bool ass_supress, _Bool outsider_ch, /*int length,*/ int count, char *str_buf_start, int *ret) {
if (!ass_supress && !outsider_ch) {
char *dst_string = va_arg(*argp, char*); /* take argument address */
my_strncpy(dst_string, str_buf_start, count); /* put string into argument */
my_strncpy(dst_string + count, "\0", 1); /* cut extra garbage */
(*ret)++;
}
}
/* */
static int str_to_str(char **str_buf, int width/*, int length*/) {
int count = 0; /* number of characters */
while (**str_buf && !is_whitespace(**str_buf) && ((count < width) || !width)) {
(*str_buf)++; /* go to end of string */
count++;
}
return count;
}
/* put string from source string to another agrument of sscanf */
static void scan_string(char **str_buf, va_list *argp, _Bool ass_supress, _Bool outsider_ch, int width, int *ret) {
skip_whitespaces(str_buf);
char *str_buf_start = *str_buf; //save start of string
int count = str_to_str(str_buf, width); // number of characters
str_into_arg(argp, ass_supress, outsider_ch, count, str_buf_start, ret);
}
/* check specs if it's a e/E/f/g/G */
static _Bool is_efg(int specs) {
return ((specs & spec_e) || (specs & spec_E) || (specs & spec_f) || (specs & spec_g) || (specs & spec_G)) ? true : false;
}
/* puts floating point number into another vararg*/
static void fpnum_into_arg(va_list *argp, _Bool ass_supress, _Bool outsider_ch, int length, int specs, long double res, int *ret) {
if (!ass_supress && !outsider_ch) {
if (is_efg(specs) && (length == 'L')) {
long double *dst_num = va_arg(*argp, long double*); /* take argument address */
*dst_num = res;
} else if (is_efg(specs) && (length == 'l')) {
double *dst_num = va_arg(*argp, double*);
*dst_num = res;
} else {
float *dst_num = va_arg(*argp, float*);
*dst_num = res;
}
(*ret)++;
}
}
/* checks if the character if a sign or not */
static _Bool is_sign(char ch) {
return ((ch == '-') || (ch == '+')) ? true : false;
}
/* gets sign and checks that there is no double sign*/
static int sign_check(char **str_buf) {
int sign = 1;
char next_ch = *((*str_buf) + 1);
if ((is_sign(**str_buf)) && (is_sign(next_ch))) {
sign = 0;
skip_all(str_buf);
} else if (**str_buf == '-') {
sign = -1;
(*str_buf)++;
} else if (**str_buf == '+') {
(*str_buf)++;
}
return sign;
}
/* multiplies the res by a power of 10 from the exponent */
static long double get_exp(long double res, char **str_buf) {
(*str_buf)++; /* go to the next char, must be a '-' or '+' */
int sign = sign_check(str_buf);
int power10 = str_to_dec(str_buf, 0, 1);
(*str_buf)--;
res = res * pow(DEC, power10 * sign);
return res;
}
/* */
static void get_first_fpnum(char **str_buf, int sign, long double *res, int* power10) {
char next_ch = *((*str_buf) + 1);
if (is_digit(**str_buf)) {
*res = (**str_buf - SHIFT) * sign;
(*str_buf)++;
} else if ((**str_buf == '.') && (is_digit(next_ch))){
(*power10)++;
(*str_buf)++;
} else {
// TODO:hanlde error
}
}
/* */
static void str_to_fpnum(char **str_buf, int width, int sign, int *power10, long double *res) {
int count = 1; // number of characters (digits or .)
while (((count < width) || !width) && **str_buf && !is_whitespace(**str_buf) && (is_digit(**str_buf) || (**str_buf == '.') || (**str_buf == 'e') || (**str_buf == 'E'))) {
if (is_digit(**str_buf) && (!(*power10))) {
*res = (*res) * DEC + (**str_buf - SHIFT) * sign;
} else if (is_digit(**str_buf) && (*power10)) {
*res = (*res) + ((long double)(**str_buf - SHIFT) / pow(DEC, (*power10)++)) * sign;
} else if ((**str_buf == '.') && (!(*power10))) {
(*power10)++;
} else if ((**str_buf == 'e') || (**str_buf == 'E')) {
*res = get_exp(*res, str_buf);
} else {
//TODO: handle error
break;
}
(*str_buf)++;
count++;
}
}
/* put floating-point number from source string to another agrument of sscanf */
static void scan_efg(char **str_buf, va_list *argp, _Bool ass_supress, _Bool outsider_ch, int width, int length, int specs, int *ret) {
skip_whitespaces(str_buf);
int sign = sign_check(str_buf);
long double res = 0;
int power10 = 0; /* for power of 10 */
get_first_fpnum(str_buf, sign, &res, &power10);
str_to_fpnum(str_buf, width, sign, &power10, &res);
fpnum_into_arg(argp, ass_supress, outsider_ch, length, specs, res, ret);
}
/* check if the character is a hexadecimal symbol */
static _Bool is_hex(char ch) {
return ((is_digit(ch)) || ((ch >= 'A') && (ch <= 'F')) || ((ch >= 'a') && (ch <= 'f'))) ? true : false;
}
/* check if the character is a octal symbol */
static _Bool is_oct(char ch) {
return ((ch >= '0') && (ch <= '7')) ? true : false;
}
/* check for a prefix and skipping it if it exists */
static int prefix_check(char **str_buf, int specs) {
int prefix = DEC; // for decimal
char next_ch = *((*str_buf) + 1);
char next_next_ch = *((*str_buf) + 2);
if ((specs & spec_x) || (specs & spec_X) || (specs & spec_p) || (specs & spec_i)) { /* for hexadecimal */
if ((**str_buf == '0') && ((next_ch == 'x') || (next_ch == 'X')) && is_hex(next_next_ch)) {
prefix = HEX;
(*str_buf) += 2;
}
}
if ((specs & spec_o) || (specs & spec_i)) { /* for octal */
if ((**str_buf == '0') && is_oct(next_ch)) {
prefix = OCT;
(*str_buf)++;
}
}
return prefix;
}
/* puts integer number into another vararg*/
static void inum_into_arg(va_list *argp, _Bool ass_supress, _Bool outsider_ch, int length, int specs, long res, int *ret) {
if (!ass_supress && !outsider_ch) {
if (is_efg(specs) && (length == 'l')) {
long *dst_num = va_arg(*argp, long*); /* take argument address */
*dst_num = res;
} else if (is_efg(specs) && (length == 'h')) {
short *dst_num = va_arg(*argp, short*);
*dst_num = (short)res;
} else {
int *dst_num = va_arg(*argp, int*);
*dst_num = (int)res;
}
(*ret)++;
}
}
/* puts pointer into another vararg*/
static void pointer_into_arg(va_list *argp, _Bool ass_supress, _Bool outsider_ch, unsigned long res, int *ret) {
if (!ass_supress && !outsider_ch) {
void **dst_pointer;
dst_pointer = va_arg(*argp, void**);
*dst_pointer = (void*)res;
(*ret)++;
}
}
/* converts hex characters to numbers */
static short hex_to_num(char hex) {
short num = 0;
if (is_digit(hex)) {
num = hex - SHIFT;
} else if ((hex >= 'A') && (hex <= 'F')) {
num = hex - SHIFT_HEX;
} else {
num = hex - SHIFT_hex;
}
return num;
}
/* convert from string to hexadecimal integer */
static long str_to_hex(char **str_buf, int width, int sign) {
int count = 0; // number of hexadecimal characters
char *hex_start = *str_buf;
while (((count < width) || !width) && **str_buf && !is_whitespace(**str_buf) && is_hex(**str_buf)) {
(*str_buf)++;
count++;
}
long res = 0;
char *hex_finish = --(*str_buf); // on last hex
int power16 = 0;
for (char *hex_cur = hex_finish; hex_cur >= hex_start; hex_cur--) {
res += hex_to_num(*hex_cur) * pow(HEX, power16++);
}
res *= sign;
*str_buf = hex_finish + 1;
return res;
}
/* put hexadecimal integer from source string to another agrument of sscanf */
static void scan_hex(char **str_buf, va_list *argp, _Bool ass_supress, _Bool outsider_ch, int width, int length, int specs, int *ret) {
skip_whitespaces(str_buf);
int sign = sign_check(str_buf); /* get sign or check for double sign */
prefix_check(str_buf, specs); /* skip 0x/0X prefix */
long res = str_to_hex(str_buf, width, sign); /* convert from string to hex int*/;
inum_into_arg(argp, ass_supress, outsider_ch, length, specs, res, ret);
}
/* convert from string to octal integer */
static long str_to_oct(char **str_buf, int width, int sign) {
int count = 0; /* number of octal characters */
char *oct_start = *str_buf;
while (((count < width) || !width) && **str_buf && !is_whitespace(**str_buf) && is_oct(**str_buf)) {
(*str_buf)++;
count++;
}
long res = 0;
char *oct_finish = --(*str_buf); // on last oct
int power8 = 0;
for (char *oct_cur = oct_finish; oct_cur >= oct_start; oct_cur--) {
res += hex_to_num(*oct_cur) * pow(OCT, power8++);
}
res *= sign;
*str_buf = oct_finish + 1;
return res;
}
/* put octal integer from source string to another agrument of sscanf */
static void scan_oct(char **str_buf, va_list *argp, _Bool ass_supress, _Bool outsider_ch, int width, int length, int specs, int *ret) {
skip_whitespaces(str_buf);
int sign = sign_check(str_buf); /* get sign or check for double sign */
prefix_check(str_buf, specs); /* skip 0 prefix */
long res = str_to_oct(str_buf, width, sign); /* convert from string to octal int*/
inum_into_arg(argp, ass_supress, outsider_ch, length, specs, res, ret); /* write down into another arg*/
}
/* put pointer from source string to another agrument of sscanf */
static void scan_pointer(char **str_buf, va_list *argp, _Bool ass_supress, _Bool outsider_ch, int width, int specs, int *ret) {
skip_whitespaces(str_buf);
prefix_check(str_buf, specs);
int count = 0; /* number of hexadecimal characters */
char *hex_start = *str_buf;
while (((count < width) || !width) && **str_buf && !is_whitespace(**str_buf) && (is_digit(**str_buf) || is_hex(**str_buf))) {
(*str_buf)++;
count++;
}
unsigned long res = 0;
char *hex_finish = --(*str_buf); // on last hex
int power16 = 0;
for (char *hex_cur = hex_finish; hex_cur >= hex_start; hex_cur--) {
res += hex_to_num(*hex_cur) * pow(HEX, power16++);
}
*str_buf = hex_finish + 1;
// TODO: str_to_pointer into separate function
pointer_into_arg(argp, ass_supress, outsider_ch, res, ret);
}
/* */
static void count_chars(char **str_buf, const char* const *str_start, va_list *argp, _Bool ass_supress, _Bool outsider_ch, int length, int specs, int *ret) {
int amount = *str_buf - *str_start;
inum_into_arg(argp, ass_supress, outsider_ch, length, specs, amount, ret);
}
/* put signed decimal/octal/hexadecimal integer from source string to another agrument of sscanf */
static void scan_doh(char **str_buf, va_list *argp, _Bool ass_supress, _Bool outsider_ch, int width, int length, int specs, int *ret) {
skip_whitespaces(str_buf);
if (**str_buf) {
int sign = sign_check(str_buf); /* get sign or check for double sign */
int prefix = prefix_check(str_buf, specs);
long res = 0;
switch (prefix) {
case DEC:
res = str_to_dec(str_buf, width, sign);
break;
case OCT:
res = str_to_oct(str_buf, width, sign);
break;
case HEX:
res = str_to_hex(str_buf, width, sign);
break;
}
inum_into_arg(argp, ass_supress, outsider_ch, length, specs, res, ret);
} else {
*ret = EOF;
}
}
/* scan processing*/
static void scan_proc(char **str_buf, const char* const *str_start, int specs, va_list *argp, _Bool ass_supress, _Bool outsider_ch, int width, int length, int *ret) {
if (specs & spec_s) { /* scan strings */
scan_string(str_buf, argp, ass_supress, outsider_ch, width, ret);
}
if (is_efg(specs)) { /* scan decimal numbers with floating point or scientific notation */
scan_efg(str_buf, argp, ass_supress, outsider_ch, width, length, specs, ret);
}
if ((specs & spec_x) || (specs & spec_X)) { /* scan hexadecimal integers */
scan_hex(str_buf, argp, ass_supress, outsider_ch, width, length, specs, ret);
}
if (specs & spec_o) { /* scan octal integers */
scan_oct(str_buf, argp, ass_supress, outsider_ch, width, length, specs, ret);
}
if (specs & spec_p) { /* scan pointer */
scan_pointer(str_buf, argp, ass_supress, outsider_ch, width, specs, ret);
}
if (specs & spec_n) { /* count characters read before n */
count_chars(str_buf, str_start, argp, ass_supress, outsider_ch, width, specs, ret);
}
if ((specs & spec_i) || (specs & spec_d)) { /* scan signed integer: dec/oct/hex */
scan_doh(str_buf, argp, ass_supress, outsider_ch, width, length, specs, ret);
}
}
int my_sscanf(const char *str, const char *format, ...) {
char *str_buf = (char*)malloc(my_strlen(str) * sizeof(char));
char *format_buf = (char*)malloc(my_strlen(format) * sizeof(char));
const char * const str_start = str_buf; /* save start of string for %n and free() */
const char * const format_start = format_buf; /* save start of string for free() */
my_strcpy(str_buf, str);
my_strcpy(format_buf, format);
va_list argp;
va_start(argp, format);
_Bool outsider_ch = false; /* for outsider characters in the format string*/
int ret = 0;
if (!(*str_buf) && *format_buf) {
ret = EOF;
}
while (*str_buf && *format_buf) {
get_specifier(&str_buf, &format_buf, &outsider_ch); /* set format_buf to the start of specifier*/
_Bool ass_supress = false; /* supress assignment (*) */
int width = 0, length = 0;
int specs = set_specs(&format_buf, &ass_supress, &width, &length); /* fill the specs number */
scan_proc(&str_buf, &str_start, specs, &argp, ass_supress, outsider_ch, width, length, &ret);
}
va_end(argp);
free((void*)str_start);
free((void*)format_start); // free(): invalid pointer Aborted (core dumped)
return ret;
}
my_sscanf.c 的驱动
#include <stdio.h>
int my_sscanf(const char *str, const char *format, ...);
int main(void) {
int a1 = 0, a2 = 0, a3 = 0, a4 = 0;
int b1 = 0, b2 = 0, b3 = 0, b4 = 0;
const char *src = "5555621 0666 0x777 0X888";
const char *format = "%8i %10i %i %i";
int res = 0, test_res = 0;
puts("===sscanf===");
res = sscanf(src, format, &a1, &a2, &a3, &a4);
printf("a1 - a2: %d %d %d %d\n", a1, a2, a3, a4);
printf("res: %d\n", res);
puts("===s21_sscanf===");
test_res = s21_sscanf(src, format, &b1, &b2, &b3, &b4);
printf("b1 - b2: %d %d %d %d\n", b1, b2, b3, b4);
printf("test_res: %d\n", test_res);
return 0;
}
当我使用格式字符串
"%8i %10i %i %i""5555621 0666 0x777 0X888"free(): invalid pointer Aborted (core dumped)mallocfree特别为此，我将地址保存在
format_startstr_startProgram received signal SIGABRT, Aborted.
__pthread_kill_implementation (no_tid=0, signo=6, threadid=140737350555456) at ./nptl/pthread_kill.c:44
44 ./nptl/pthread_kill.c: No such file or directory.
(gdb) backtrace
#0 __pthread_kill_implementation (no_tid=0, signo=6, threadid=140737350555456)
at ./nptl/pthread_kill.c:44
#1 __pthread_kill_internal (signo=6, threadid=140737350555456) at ./nptl/pthread_kill.c:78
#2 __GI___pthread_kill (threadid=140737350555456, signo=signo@entry=6) at ./nptl/pthread_kill.c:89
#3 0x00007ffff7cda476 in __GI_raise (sig=sig@entry=6) at ../sysdeps/posix/raise.c:26
#4 0x00007ffff7cc07f3 in __GI_abort () at ./stdlib/abort.c:79
#5 0x00007ffff7d216f6 in __libc_message (action=action@entry=do_abort,
fmt=fmt@entry=0x7ffff7e73b8c "%s\n") at ../sysdeps/posix/libc_fatal.c:155
#6 0x00007ffff7d38d7c in malloc_printerr (str=str@entry=0x7ffff7e71764 "free(): invalid pointer")
at ./malloc/malloc.c:5664
#7 0x00007ffff7d3aac4 in _int_free (av=<optimized out>, p=<optimized out>, have_lock=0)
at ./malloc/malloc.c:4439
#8 0x00007ffff7d3d4d3 in __GI___libc_free (mem=<optimized out>) at ./malloc/malloc.c:3391
#9 0x0000555555557128 in my_sscanf (str=0x555555558238 "5555621 0666 0x777 0X888",
format=0x555555558251 "%8i %10i %i %i") at my_sscanf.c:546
#10 0x0000555555557273 in main () at sscanf_driver.c:27
(gdb) frame 9
#9 0x0000555555557128 in my_sscanf (str=0x555555558238 "5555621 0666 0x777 0X888",
format=0x555555558251 "%8i %10i %i %i") at my_sscanf.c:546
warning: Source file is more recent than executable.
546 free((void*)format_start);
此外，使用格式字符串的其他值，一切正常，没有错误！你能告诉我是什么原因造成的吗？我该如何解决？谢谢