c语言实现解析转义字符串

发表于 | 分类于 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
static const unsigned char firstByteMark[7] = { 0x00, 0x00, 0xC0, 0xE0, 0xF0, 0xF8, 0xFC };
static const char *parse_string(const char *str)
{
	const char *ptr=str+1;char *ptr2;char *out;int len=0;unsigned uc,uc2;
	if (*str!='\"') {return 0;}	/* not a string! */
	
	while (*ptr!='\"' && *ptr && ++len) if (*ptr++ == '\\') ptr++;	/* Skip escaped quotes. */
	
	out=(char*)malloc(len+1);	/* This is how long we need for the string, roughly. */
	if (!out) return 0;
	
	ptr=str+1;ptr2=out;
	while (*ptr!='\"' && *ptr)
	{
		if (*ptr!='\\') *ptr2++=*ptr++;
		else
		{
			ptr++;
			switch (*ptr)
			{
				case 'b': *ptr2++='\b';	break;
				case 'f': *ptr2++='\f';	break;
				case 'n': *ptr2++='\n';	break;
				case 'r': *ptr2++='\r';	break;
				case 't': *ptr2++='\t';	break;
				case 'u':	 /* transcode utf16 to utf8. */
					sscanf(ptr+1,"%4x",&uc);ptr+=4;	/* get the unicode char. */

					if ((uc>=0xDC00 && uc<=0xDFFF) || uc==0)	break;	/* check for invalid.	*/

					if (uc>=0xD800 && uc<=0xDBFF)	/* UTF16 surrogate pairs.	*/
					{
						if (ptr[1]!='\\' || ptr[2]!='u')	break;	/* missing second-half of surrogate.	*/
						sscanf(ptr+3,"%4x",&uc2);ptr+=6;
						if (uc2<0xDC00 || uc2>0xDFFF)		break;	/* invalid second-half of surrogate.	*/
						uc=0x10000 + (((uc&0x3FF)<<10) | (uc2&0x3FF));
					}

					len=4;if (uc<0x80) len=1;else if (uc<0x800) len=2;else if (uc<0x10000) len=3; ptr2+=len;
					
					switch (len) {
						case 4: *--ptr2 =((uc | 0x80) & 0xBF); uc >>= 6;
						case 3: *--ptr2 =((uc | 0x80) & 0xBF); uc >>= 6;
						case 2: *--ptr2 =((uc | 0x80) & 0xBF); uc >>= 6;
						case 1: *--ptr2 =(uc | firstByteMark[len]);
					}
					ptr2+=len;
					break;
				default:  *ptr2++=*ptr; break;
			}
			ptr++;
		}
	}
	*ptr2=0;
	if (*ptr=='\"') ptr++;
	return out;
}
int main(void) {
    printf("%s\r\n","hh\r\nh");
    return 0;
}