C語言對字符串進行轉義excape操作

/*
 @brief 對于url中的一些特殊字符會被轉義以利傳輸,


并且， 歸檔服務器上, php寫入cookie中的值可能存在特殊字符， 需要轉換
*參考: http://www.blooberry.com/indexdot/html/topics/urlencoding.htm
http://www.december.com/html/spec/esccodes.html
@param[in,out] data 需要處理的數據， 處理完后， 這個數據會被修改為期待的數據
@param[in] data_len data中的實際數據長度
/
int escape_url_character(char data, int data_len)
{
/ 下面只列出來了一些加密用到的字符， 而沒有列出所有的字符, 主要是空格, /, +, = /
char *transfer_table[][2] = { {"+", "2B"}, {"[","5B"},{"]","5D"},{"`","60"},{";","3B"},{"/","2F"},{"?","3F"},{":","3A"},{"@","40"},{"=","3D"},{"&","26"},{"$","24"},{" ","20"},{"<","3C"},{">","3E"},{"#","23"},{"%","25"},{"{","7B"},{"}","7D"},{"|","7C"},{"\","5C"},{"^","5E"},{"~","7E"}, {NULL, NULL} };
int i = 0, j;
char *buf = calloc(data_len + 1, sizeof(char));
while( i < data_len ){
if( '%' != data[i]){

strncat(buf, data+i, 1);
i++;
continue;

}
/ 查表 /
j = 0;
while( NULL != transfer_table[j][1] ){

if( 0 == strncasecmp(data+i+1, transfer_table[j][1], 2 )){
    strncat(buf, transfer_table[j][0], 1);
    i += 3;
    break;
}
j++;

}
/ 對于表中不存在的字符不作處理, 但輸出一條日志 /
if( NULL == transfer_table[j][1] ){

strncat(buf, data+i, 1);
printf("escape_url_character: unhandled sequence: %s\n", data+i);
i++;

}
}
memset(data, 0, data_len);
strcpy(data, buf);
free(buf);
return 0;
}</pre>