I want an std::string object (such as a name) to a uint8_t array in C++. The
function reinterpret_cast<const uint8_t*> rejects my string. And since I'm coding using NS-3, some warnings are being interpreted as errors.
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3Show your code. What do you mean by "string object"? std::string or a pointer to a char.selbie– selbie2011-10-05 16:27:07 +00:00Commented Oct 5, 2011 at 16:27
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3 Answers
If you want a pointer to the string's data:
reinterpret_cast<const uint8_t*>(&myString[0])
If you want a copy of the string's data:
std::vector<uint8_t> myVector(myString.begin(), myString.end());
uint8_t *p = &myVector[0];
13 Comments
fbrereto
reinterpret_cast<const uint8_t*>(myString.c_str()) would work though (assuming myString is a std::string).
rubenvb
+1: The
std::vector is great stuff. Creates a simple copy without memcpy or other C style stuff that likes to pop up in answers to these kinds of questions.
David Rodríguez - dribeas
@awoodland: While in C++03 it might not be null terminated, in C++11 the standard requires null termination of the buffer.
Mooing Duck
@Rob: I was told C++03 did not require it. However, I see it in C++11 at least. §21.4.1 / 5
...for any basic_string object s, the identity &*(s.begin() + n) == &*s.begin() + n shall hold for all values of n such that 0 <= n < s.size().rubenvb
David: I know it does that under the hood, it just hides the fragile and unnecessary details away so the code is a lot more readable and bugs for such operations become non-existant.
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String objects have a .c_str() member function that returns a const char*. This pointer can be cast to a const uint8_t*:
std::string name("sth");
const uint8_t* p = reinterpret_cast<const uint8_t*>(name.c_str());
Note that this pointer will only be valid as long as the original string object isn't modified or destroyed.
1 Comment
Carlo
Is there a way to do it backwards? For example, I would like to cast the uint8_t array to a c_str. Is that possible?
If you need an actual array (not a pointer, as other answers have suggested; the difference is explained very nicely in this answer), you need to use std::copy from <algorithm>:
std::string str = "foo";
uint8_t arr[32];
std::copy(str.begin(), str.end(), std::begin(arr));
