C language implementation of URL encode and URL decode

Reprinted from: http://blog.csdn.net/langeldep/article/details/6264058

The code for this article has been modified from PHP code, leaving only 2 functions.

int Php_url_decode (char *str, int len);
Char *php_url_encode (char const *s, int len, int *new_length);

URL encoding does the following:

Character "a"-"Z" , "A"-"Z" , "0"-"9" "." , "-" , "*" "_"   are not coded to maintain the original value;

The space "" is converted to the plus sign "+".

Each of the other bytes is represented as a 3-character string in the "%xy" format , encoded as UTF-8.

#include <stdio.h>#include<stdlib.h>#include<string.h>#include<ctype.h>#include<sys/types.h>StaticUnsignedCharHexchars[] ="0123456789ABCDEF";Static intPhp_htoi (Char*1) {    intvalue; intC; C= ((unsignedChar*) s) [0]; if(Isupper (c)) C=ToLower (c); Value= (c >='0'&& C <='9'? C'0'C'a'+Ten) * -; C= ((unsignedChar*) s) [1]; if(Isupper (c)) C=ToLower (c); Value+ = C >='0'&& C <='9'? C'0'C'a'+Ten; return(value);}Char*php_url_encode (Char Const*s,intLenint*new_length) {Register unsignedCharC; unsignedChar*to, *start; unsignedChar Const* from, *end;  from= (unsignedChar*) s; End= (unsignedChar*) s +Len; Start= to = (unsignedChar*)calloc(1,3*len+1);  while( from<end) {C= * from++; if(c = =' ')         {            *to++ ='+'; }         Else if(C <'0'&& C! ='-'&& C! ='.') ||(c<'A'&& C >'9') ||(c>'Z'&& C <'a'&& C! ='_') ||(c>'Z') ) {to[0] ='%'; to[1] = Hexchars[c >>4]; to[2] = hexchars[c & the]; to+=3; }        Else         {            *to++ =C; }    }    *to =0; if(new_length) {*new_length = to-start; }    return(Char*) Start;intPhp_url_decode (Char*STR,intLen) {    Char*dest =str; Char*data =str;  while(len--)     {        if(*data = ='+')         {            *dest =' '; }        Else if(*data = ='%'&& Len >=2&& Isxdigit ((int) * (Data +1)) && Isxdigit ((int) * (Data +2)))         {            *dest = (Char) Php_htoi (Data +1); Data+=2; Len-=2; }         Else         {            *dest = *data; } Data++; Dest++; }    *dest =' /'; returnDest-str;}intMainintargcChar**argv) {    Char*str ="Hello, world! ",*New_str; intLen =0, New_len =0, Old_len =0; Len=strlen (str); New_str= Php_url_encode (str,len,&New_len); printf ("new string:%s,new length:%d\n", New_str,new_len); Old_len=Php_url_decode (New_str,new_len); printf ("Old string:%s,old length:%d\n", New_str,old_len); return 0;}

PS: Check a lot of information to understand the principle of urldecode, so simple, hehe

C language implementation of URL encode and URL decode