从 C++ 中的 std::string 获取字节
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Get bytes from std::string in C++
提问by Vic
I'm working in a C++ unmanaged project.
我在一个 C++ 非托管项目中工作。
I need to know how can I take a string like this "some data to encrypt" and get a byte[] array which I'm gonna use as the source for Encrypt.
我需要知道如何获取像“一些要加密的数据”这样的字符串并获得一个 byte[] 数组，我将使用它作为 Encrypt 的源。
In C# I do
在 C# 中我做
for (int i = 0; i < text.Length; i++)
buffer[i] = (byte)text[i];
What I need to know is how to do the same but using unmanaged C++.
我需要知道的是如何使用非托管 C++ 做同样的事情。
Thanks!
谢谢！
回答by Johannes Schaub - litb
If you just need read-only access, then c_str()will do it:
如果您只需要只读访问权限，则c_str()可以这样做：
char const *c = myString.c_str();
If you need read/write access, then you can copy the string into a vector. vectors manage dynamic memory for you. You don't have to mess with allocation/deallocation then:
如果您需要读/写访问，那么您可以将字符串复制到向量中。向量为您管理动态内存。你不必搞乱分配/解除分配然后：
std::vector<char> bytes(myString.begin(), myString.end());
bytes.push_back('unsigned char buffer[mystring.length()];
memcpy(buffer, mystring.data(), mystring.length());
');
char *c = &bytes[0];
回答by Christopher Smith
std::string::datawould seem to be sufficient and most efficient. If you want to have non-const memory to manipulate (strange for encryption) you can copy the data to a buffer using memcpy:
std::string::data似乎是足够和最有效的。如果您想操作非常量内存（加密很奇怪），您可以使用memcpy将数据复制到缓冲区：
std::copy(mystring.begin(), mystring.end(), buffer);
STL fanboys would encourage you to use std::copyinstead:
STL 粉丝会鼓励你使用std::copy来代替：
encrypt(const void *ptr, size_t bufferSize);
but there really isn't much of an upside to this. If you need null termination use std::string::c_str()and the various string duplication techniques others have provided, but I'd generally avoid that and just query for the length. Particularly with cryptography you just know somebody is going to try to break it by shoving nulls in to it, and using std::string::data()discourages you from lazily making assumptions about the underlying bits in the string.
但这确实没有太大的好处。如果您需要使用空终止std::string::c_str()以及其他人提供的各种字符串复制技术，但我通常会避免这种情况，只需查询length. 特别是对于密码学，你只知道有人会试图通过将空值推入其中来破坏它，并且使用会std::string::data()阻止你懒惰地对字符串中的底层位做出假设。
回答by Vic
Normally, encryption functions take
通常，加密函数需要
encrypt(strng.c_str(), strng.length());
as arguments. You can pass c_str and length directly:
作为论据。您可以直接传递 c_str 和 length：
length = str.copy( buffer, str.size() );
This way, extra space is allocated or wasted.
这样，额外的空间被分配或浪费。
回答by Nick Haddad
From a std::string you can use the c_ptr() method if you want to get at the char_t buffer pointer.
如果要获取 char_t 缓冲区指针，可以从 std::string 使用 c_ptr() 方法。
It looks like you just want copy the characters of the string into a new buffer. I would simply use the std::string::copyfunction:
看起来您只想将字符串的字符复制到新缓冲区中。我会简单地使用std::string::copy函数：
encrypt(str.data(),str.size());
回答by Martin York
If you just need to read the data.
如果你只需要读取数据。
std::vector<byte> source(str.begin(),str.end());
encrypt(&source[0],source.size());
If you need a read/write copy of the data put it into a vector. (Don;t dynamically allocate space that's the job of vector).
如果您需要数据的读/写副本，请将其放入向量中。（不要动态分配空间，这是矢量的工作）。
strcpy(buffer, text.c_str());
Of course we are all assuming that byte is a char!!!
当然，我们都假设 byte 是一个字符！！！
回答by Mark
If this is just plain vanilla C, then:
如果这只是普通的香草 C，那么：
encrypt(text.c_str())
Assuming that buffer is allocated and large enough to hold the contents of 'text', which is the assumption in your original code.
假设缓冲区已分配并且足够大以容纳“文本”的内容，这是原始代码中的假设。
If encrypt() takes a 'const char *' then you can use
如果 encrypt() 使用 'const char *' 那么你可以使用
string str = "some text;
byte[] bytes = System.Text.Encoding.ASCII.GetBytes(str);
and you do not need to copy the string.
并且您不需要复制字符串。
回答by Hippiehunter
I dont think you want to use the c# code you have there. They provide System.Text.Encoding.ASCII(also UTF-*)
我认为您不想使用那里的 c# 代码。他们提供 System.Text.Encoding.ASCII（也是 UTF-*）
##代码##your problems stem from ignoring the encoding in c# not your c++ code
您的问题源于忽略 c# 中的编码而不是您的 c++ 代码
