void main()
{
ostream stream();
stream << "hey" << 1 << 1L;
int size = stream.size();
char* buffer = stream.getBytes();
}
c++ datastream
Author
Hey
I looking for something like c++ streams for reding int, long, etc into a buffer and then getting the size of it and the whole buffer.
Something like this would be the usage:
My c++ stream knowledge is not so good, are there something in there that will help me with this or do I have to write my own stream, overriding streambuf etc.
thanks
Lizard
#include <sstream>#include <string>int main() // void main is not legal standard C++{ std::ostringstream stream; stream << "hey" << 1 << 1L; std::size_t size = stream.str().size(); std::string string = stream.str(); // buffer is only valid while string is valid and unchanged char const * buffer = string.c_str();}Enigma
Author
Yes I have tried stringstreams but I think that is not really what I'm looking for, but do correct me if I'm wrong. The thing is that I'm not looking to get a string as output, I'm looking to get a byte array to send over a network, i.e using this for serilazing.
So in the exaple I want the byte array returned to contain first tre bytes for the letters "h", "e", and "y" and then four bytes for the integer 1, and then four (both long and int is 4 bytes in c++, isn't it) bytes for the long value 1L.
I have tried things like the one Enigma describes above and things like:
but thanks for fast answers
Lizard
So in the exaple I want the byte array returned to contain first tre bytes for the letters "h", "e", and "y" and then four bytes for the integer 1, and then four (both long and int is 4 bytes in c++, isn't it) bytes for the long value 1L.
I have tried things like the one Enigma describes above and things like:
#include <iostream>#include <sstream>using namespace std;void main(){ stringstream stream; int i = 1; stream << i; stream.seekg(0, ios::end); int length = stream.tellg(); // length will be 1, expected 4 char* buffer = new char[length]; // char array will be the ascii code for '1' expected was the int value 1 stream.read(buffer, length); return;}but thanks for fast answers
Lizard
The insertion and extraction operators on C++ stream types are for formatted I/O. You use the read() or write() member functions to perform binary I/O. If you want to use operator<< or operator>> for binary I/O then you'll need to write wrappers or your own stream class.
On the other hand, if you did want formatted I/O, you should be aware that you can easily get a const char* alias to the std::string's storage (note constness; you will need to make some kind of copy if you have to change the data) by its .c_str() member function.
Quote:Original post by LizardCPP...both long and int is 4 bytes in c++, isn't it...
Lizard
Oh please note: the size of int and long is not always the same and has nothing to do with the language you are programming in.
A long will always be 4 bytes, but the size of an int depends on the Operating System (OS) you are working on. If you use Windows XP 32-bit edition for an example, then yes, int will be 4 bytes, but on the 64-bit edition it will be 8 bytes.
Regards,
Xeile
Quote:Original post by Xeile
A long will always be 4 bytes, but the size of an int depends on the Operating System (OS) you are working on.
Nope. The size of long and int are dependent on the compiler, not the operating system. Also, a long must always be the same size or larger than an int.
Quote:
If you use Windows XP 32-bit edition for an example, then yes, int will be 4 bytes, but on the 64-bit edition it will be 8 bytes.
For most compilers targeting 64 bit x86 architectures ints are still 4 bytes.
Microsoft has already posted that int will stay a 4-byte variable in 64-bit and you will need to use the long long type or use the _int64 types if you want an 8-byte. Now this is just how Microsoft is handling it in Visual Studio.
Quote:Original post by XeileQuote:Original post by LizardCPP...both long and int is 4 bytes in c++, isn't it...
Lizard
Oh please note: the size of int and long is not always the same and has nothing to do with the language you are programming in.
What are you talking about? It has plenty to do with the language you are programming in.
In C++, a long is at least as big as an int, but the size of neither is exactly guaranteed.
In Java, a long is signed, 8 bytes. an int is signed, 4 bytes. Full stop.
In Python, an int is an object that wraps a number that has a 4-byte range (roughly equivalent to java.lang.Integer). A long is an object that represents an arbitrary integral number (roughly equivalent to BigInteger in whatever package it's in).
Quote:A long will always be 4 bytes, but the size of an int depends on the Operating System (OS) you are working on. If you use Windows XP 32-bit edition for an example, then yes, int will be 4 bytes, but on the 64-bit edition it will be 8 bytes.
That's even worse. On a 64-bit platform, int may be 8 bytes. Or 4. Or 23. Similarly long. Similarly on a 32-bit platform, for either. The idea of an int being the "native" integer size is really only a suggestion.
But it is *not* OK on that 64-bit system for long to be 4 bytes while int is 8.
And anyway, platform != OS.
This topic is closed to new replies.
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