C language implementation of URL encode and URL decode

Problems encountered in the project and Java communication, after reading the SessionKey, once again sent to the other side, always appear the session error prompt. The following information is then consulted:Java.net.URLEncode Coding and UrlDecode decoding problems

When a form in a Web page is submitted using the Post method, the type of data content is application/x-www-form-urlencoded, which is:
1. The characters "a"-"Z", "a"-"Z", "0"-"9", ".", "-", "*", and "_" are not encoded;
3. Convert non-textual content into "%xy" form, XY is a two-bit 16 binary value;
4. Place the & symbol between each name=value pair.
2. Convert the space to a plus sign (+);

Look at the following example: Open a Web page to fetch his sessionkey and then look at the values of the SessionKey used by other connection requests to compare:
  Reply When you log in to the website:   "SessionKey": "8ikbgdraqqzbasq5mrq+uxp6sba="
When you use the session to access other content on the site: sessionkey=8ikbgdraqqzbasq5mrq%2buxp6sba%3d

#include <stdlib.h> #include <string.h> #include <ctype.h> #include <sys/types.h> #include " Url.h "static unsigned char hexchars[] =" 0123456789ABCDEF ", Static int php_htoi (char *s) {int Value;int c;c = ((Unsigned cha R *) s) [0];if (Isupper (c)) C = ToLower (c); value = (c >= ' 0 ' && C <= ' 9 '? C-' 0 ': C-' a ' +) * 16;c = ((u nsigned char *) s) [1];if (Isupper (c)) C = ToLower (c); value + = c >= ' 0 ' && C <= ' 9 '? C-' 0 ': C-' a ' + 10;return (value);} Char *php_url_encode (char const *s, int len, int *new_length) {Register unsigned char c;unsigned char *to, *start;unsigned Char Const *from, *end;from = (unsigned char *) S;end = (unsigned char *) s + len;start = to = (unsigned char *) calloc (1, 3*len+1) while (from < end) {c = *from++;if (c = = ") {*to++ = ' + ';} else if ((C < ' 0 ' && c! = '-' &&am P c! = '. ') || (C < ' A ' && C > ' 9 ') | | (C > ' Z ' && C < ' a ' && c! = ' _ ') | | (C > ' z ')) {to[0] = '% '; to[1] = Hexchars[c >> 4];to[2] = hexchars[c & 15];to + + 3;} else {*to++ = c;}} *to = 0;if (new_length) {*new_length = To-start;} Return (char *) start; int Php_url_decode (char *str, int len) {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);d ata + = 2;len-= 2;} else {*dest = *data;} data++;d est++;} *dest = '/0 '; return dest-str;}

Reference: http://blog.csdn.net/langeldep/article/details/6264058

C language implementation of URL encode and URL decode