[英]C++: How to encode a std::string into base64 without losing NUL character
I am working on getting someone else's code up and running. 我正在努力启动并运行其他人的代码 。 The code is written in C++.
该代码用C ++编写。 The part that is failing is when it converts a std::string to base64:
失败的部分是将std :: string转换为base64时:
std::string tmp = "\0";
tmp.append(strUserName);
tmp.append("\0");
tmp.append(strPassword);
tmp = base64_encode(tmp.c_str(), tmp.length());
where base64 is: 其中base64是:
std::string base64_encode(char const* bytes_to_encode, unsigned int in_len) {
std::string ret;
int i = 0;
int j = 0;
unsigned char char_array_3[3];
unsigned char char_array_4[4];
while (in_len--) {
char_array_3[i++] = *(bytes_to_encode++);
if (i == 3) {
char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
char_array_4[3] = char_array_3[2] & 0x3f;
for(i = 0; (i <4) ; i++)
ret += base64_chars[char_array_4[i]];
i = 0;
}
}
if (i)
{
for(j = i; j < 3; j++)
char_array_3[j] = '\0';
char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
char_array_4[3] = char_array_3[2] & 0x3f;
for (j = 0; (j < i + 1); j++)
ret += base64_chars[char_array_4[j]];
while((i++ < 3))
ret += '=';
}
return ret;
}
It uses the 'tmp' string to make a call to a server and it's imperative that the base64 string has the two NUL characters embedded within it (before strUserName and before strPassword). 它使用“ tmp”字符串来调用服务器,并且必须在base64字符串中嵌入两个NUL字符(在strUserName之前和strPassword之前)。 However, it seems that since the code is passing tmp as a c_str(), the NUL characters are being stripped.
但是,由于代码正在将tmp作为c_str()传递,因此NUL字符已被剥离。 Is there a good solution for this?
有一个好的解决方案吗? Thanks.
谢谢。
Update I guess I should add that the code includes " #include <asm/errno.h>
" which I googled for and didn't find compatibility for macOS so I just commented it out.. Not sure if that is making things not work but I doubt it. 更新,我想我应该补充一点,代码中包括“
#include <asm/errno.h>
”,我用它搜索了一下,但没有发现与macOS的兼容性,所以我只是将其注释掉了。但我对此表示怀疑。 Full disclosure. 全面披露。
std::string tmp = "\\0";
and tmp.append("\\0");
和
tmp.append("\\0");
don't add any '\\0'
characters to tmp
. 不要在
tmp
添加任何'\\0'
字符。 The versions of std::string::string
and std::string::append
that take a const char*
take a NUL-terminated C-style string, so they stop as soon as they see a NUL character. 带有
const char*
的std::string::string
和std::string::append
的版本采用NUL终止的C样式字符串,因此一旦看到NUL字符,它们就会停止。
To actually add a NUL character to your string, you'll need to use the constructor and append
methods that take a length along with a const char*
, or the versions that take a count and a char
: 要将NUL字符实际添加到字符串中,您需要使用构造函数并
append
带有const char*
长度的方法或带有count和char
的版本的方法:
std::string tmp("\0", 1);
tmp.append(strUserName);
tmp.append("\0", 1);
tmp.append(strPassword);
tmp = base64_encode(tmp.c_str(), tmp.length());
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