Re: [問題] decode url string

[purpose (purpose)]

: 若我沒有弄錯，這個解法還是需要用到stack，只是pop與push的規則很單純

按照前面 manlike 大提供方法，寫了一個沒用到 stack 版本，
不確定有沒有寫對，看看吧

※ 其中的 isValid() 函數，因為我不知道轉換規格，所以不是正確的


程式碼線上版：http://codepad.org/0yhjKaFf

#include <iostream>
#include <string>
using namespace std;

char toASCII(char c1, char c2) {
  int tmp = 16 * (c1-'0') + (c2-'0');
  return (char)tmp;   // mov al, byte ptr[tmp]
}

bool isValid(char c1, char c2) {
  if (c1 == '%' || c2 == '%')
    return false;
  else
     return true;
}

string deURL(const string &encURL) {
  string decURL = encURL;
  size_t index = encURL.size();

  while (index >= 2) {
    while (decURL[index-2] == '%') {
      char c1 = decURL[index-1], c2 = decURL[index];
      if (isValid(c1, c2) == false) break;

      char ch = toASCII(c1, c2);
      if (ch == '%') {
        decURL[index-1] = 0;
        string tmp = decURL.c_str();
        const char *suffixStr = decURL.c_str() + index + 1;
        if (suffixStr[0] != 0) {
          tmp.append(suffixStr);
          if (suffixStr[1] == 0) {
            index--;
          }
        } else {
          index = index - 2;
        }
        decURL = tmp;
        cout << decURL << "\n";
      } else {
        decURL[index-2] = ch;
        decURL[index-1] = 0;
        string tmp = decURL.c_str();
        const char *suffixStr = decURL.c_str() + index + 1;
        if (suffixStr[0] != 0) {
          tmp.append(suffixStr);
        }
        decURL = tmp;
        cout << decURL << "\n";
      }
    }
    index--;
  }
  return decURL;
}

int main() {
  const string encodedURL = "http:://www.xxx.com/arg?C=0x%25%34%31B%25%25%25";
  cout << encodedURL.size() << ", " << encodedURL << "\n";
  string decodedURL = deURL(encodedURL);
  cout << "decode result = "<< decodedURL << "\n";
  return 0;
}

執行結果：
--------------------------------------
47, http:://www.xxx.com/arg?C=0x%25%34%31B%25%25%25
http:://www.xxx.com/arg?C=0x%25%34%31B%25%25%
http:://www.xxx.com/arg?C=0x%25%34%31B%25%%
http:://www.xxx.com/arg?C=0x%25%34%31B%%%
http:://www.xxx.com/arg?C=0x%25%341B%%%
http:://www.xxx.com/arg?C=0x%2541B%%%
http:://www.xxx.com/arg?C=0x%41B%%%
http:://www.xxx.com/arg?C=0xAB%%%
decode result = http:://www.xxx.com/arg?C=0xAB%%%
--------------------------------------


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推 yauhh:原來如此,做得好