使用C ++计算字符串的MD5 [英] Calculate MD5 of a string in C++

问题描述

我有一个很好的例子，内存映射文件计算文件的MD5哈希值。

我想更改它来计算字符串的MD5哈希值。

例如：

（include #include< openssl / md5.h>

 无符号字符结果[MD5_DIGEST_LENGTH];如果你想运行一个文件， 
 boost :: iostreams :: mapped_file_source src（path）; 
 MD5（（unsigned char *）src.data（），src.size（），result）; 
 
 std :: ostringstream sout; 
 sout<< std :: hex<< std :: setfill（'0'）; 
 for（long long c：result）
 {
 sout<< std :: setw（2）<< 
} 
 return sout.str（）; 
  

我所做的更改是：

  std :: string str（Hello）; 
 unsigned char result [MD5_DIGEST_LENGTH]; 
 MD5（（unsigned char *）str.c_str（），str.size（），result）; 
 
 std :: ostringstream sout; 
 sout<< std :: hex<< std :: setfill（'0'）; 
 for（long long c：result）
 {
 sout<< std :: setw（2）<< 
} 
 return sout.str（）; 
  

但这会产生结果：

  8b1a9953c4611296a827abf8c47804d7 
  

命令 $ md5sum <<

$

pre>

为什么结果不一致？哪一个错了？

感谢。

---

所以我得到了正确答案。从终端调用 md5sum 的正确方法是：

  $ printf' ％s'Hello| md5sum 
  

避免包含新行。

$ b $

$

$ b $ m b

您可以看到bash <<< 操作符添加换行符：

  $ od -ta<<< Hello 
 0000000 H ello nl 
 0000006 
  

要避免这种情况，请使用 printf ：

  $ printf'％s'Hello | od -ta 
 0000000 H e l l o 
 0000005 
 $ printf'％s'您好| md5sum 
 8b1a9953c4611296a827abf8c47804d7  -  
  

I have a nice example of memory mapped files that calculates the MD5 hash of a file. That works fine with no problems.

I would like to change it to calculate the MD5 hash of a string.

So the example is:

(include #include <openssl/md5.h> to run this code, and also boost stuff if you want to run the one with the file)

unsigned char result[MD5_DIGEST_LENGTH];
boost::iostreams::mapped_file_source src(path);
MD5((unsigned char*)src.data(), src.size(), result);

std::ostringstream sout;
sout<<std::hex<<std::setfill('0');
for(long long c: result)
{
    sout<<std::setw(2)<<(long long)c;
}
return sout.str();

The change I made is:

std::string str("Hello");
unsigned char result[MD5_DIGEST_LENGTH];
MD5((unsigned char*)str.c_str(), str.size(), result);

std::ostringstream sout;
sout<<std::hex<<std::setfill('0');
for(long long c: result)
{
    sout<<std::setw(2)<<(long long)c;
}
return sout.str();

But this produces the result:

8b1a9953c4611296a827abf8c47804d7

While the command $ md5sum <<< Hello gives the result:

09f7e02f1290be211da707a266f153b3

Why don't the results agree? Which one is wrong?

Thanks.

---

EDIT:

So I got the right answer which is ticked down there. The correct way to call md5sum from terminal is:

$ printf '%s' "Hello" | md5sum

To avoid the new line being included.

解决方案

You are passing a final newline to the md5sum program, but not to your code.

You can see that the bash<<< operator adds a newline:

$ od -ta <<<Hello
0000000   H   e   l   l   o  nl
0000006

To avoid this, use printf:

$ printf '%s' Hello | od -ta
0000000   H   e   l   l   o
0000005
$ printf '%s' Hello | md5sum
8b1a9953c4611296a827abf8c47804d7  -

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