处理从和到十六进制的转换 [英] Handling of conversions from and to hex

问题描述

我想要构建一个函数来轻松地将包含十六进制代码的字符串（例如0ae34e）转换为包含等效ascii值的字符串，反之亦然。
我是否需要将Hex字符串分成两对值并将它们再次联系在一起，或者是否有一种方便的方法来实现这一点？

谢谢 p>

解决方案

基于 binascii_unhexlify（） 功能：

  #include< cctype> //是* 
 
 int to_int（int c）{
 if（not isxdigit（c））return -1; //错误：找到非十六进制数字
 if（isdigit（c））return c  - '0'; 
 if（isupper（c））c = tolower（c）; 
返回c  - 'a'+ 10; 
} 
 
模板< class InputIterator，class OutputIterator> int 
 unhexlify（InputIterator first，InputIterator last，OutputIterator ascii）{
 while（first！= last）{
 int top = to_int（* first ++）; 
 int bot = to_int（* first ++）; 
 if（top == -1 or bot == -1）
 return -1; //错误
 * ascii ++ =（top <= 4）+ bot; 
} 
返回0; 
} 
  

Example

  #include< iostream> 
 
 int main（）{
 char hex [] =7B5a7D; 
 size_t len = sizeof（hex） -  1; // strlen 
 char ascii [len / 2 + 1]; 
 ascii [len / 2] ='\0'; 
 
 if（unhexlify（hex，hex + len，ascii）<0）return 1; //错误
 std :: cout<<十六进制<<  - ><< ascii<<的std :: ENDL; 
 
  

输出

  7B5a7D  - > {z} 
  

源代码中的评论有趣引用：

当我读数十个编程或解码
格式的程序（documentation？hihi :-)时，我制定了Jansen的
观察：

以ASCII格式编码二进制数据的程序以
这样的风格编写，它们尽可能不可读。使用的设备包括
不必要的全局变量，将重要的表埋入不相关的
源文件中，将函数放入包含文件中，使用
表达式描述变量名称用于不同目的，调用
空子例程和其他人。

我试图打破这个传统，但我猜想
确实使性能不是最优的。哦，太糟糕了......

CWI的Jack Jansen，1995年7月。

I want to build a function to easily convert a string containing hex code (eg. "0ae34e") into a string containing the equivalent ascii values and vice versa. Do I have to cut the Hex string in pairs of 2 values and gue them together again or is there a convenient way to do that?

thanks

解决方案

Based on binascii_unhexlify() function from Python:

#include <cctype> // is*

int to_int(int c) {
  if (not isxdigit(c)) return -1; // error: non-hexadecimal digit found
  if (isdigit(c)) return c - '0';
  if (isupper(c)) c = tolower(c);
  return c - 'a' + 10;
}

template<class InputIterator, class OutputIterator> int
unhexlify(InputIterator first, InputIterator last, OutputIterator ascii) {
  while (first != last) {
    int top = to_int(*first++);
    int bot = to_int(*first++);
    if (top == -1 or bot == -1)
      return -1; // error
    *ascii++ = (top << 4) + bot;
  }
  return 0;
}

Example

#include <iostream>

int main() {
  char hex[] = "7B5a7D";
  size_t len = sizeof(hex) - 1; // strlen
  char ascii[len/2+1];
  ascii[len/2] = '\0';

  if (unhexlify(hex, hex+len, ascii) < 0) return 1; // error
  std::cout << hex << " -> " << ascii << std::endl;
}

Output

7B5a7D -> {Z}

An interesting quote from the comments in the source code:

While I was reading dozens of programs that encode or decode the formats here (documentation? hihi:-) I have formulated Jansen's Observation:

Programs that encode binary data in ASCII are written in such a style that they are as unreadable as possible. Devices used include unnecessary global variables, burying important tables in unrelated sourcefiles, putting functions in include files, using seemingly-descriptive variable names for different purposes, calls to empty subroutines and a host of others.

I have attempted to break with this tradition, but I guess that that does make the performance sub-optimal. Oh well, too bad...

Jack Jansen, CWI, July 1995.

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