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:
8b1a9953c4611296a827abf8c47804d7While the command $ md5sum <<< Hello gives the result:
09f7e02f1290be211da707a266f153b3Why 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" | md5sumTo 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 0000006To 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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