Please have a look at the followng header file
#pragma once
class MissileLauncher
{
public:
MissileLauncher(void);
private:
byte abc[3];
};
This generated the error
Error 1 error C2143: syntax error : missing ';' before '*'
I tried to do it in this way
byte *abc;
but it also failed, same error. However, I noticed I can call other built in tyes arrays in this way for an example, an int array. Why this is happening to byte array? How to solve this? I would like to assign the values in cpp file. Any ideas?
This question is related to
c++
arrays
visual-studio-2010
byte
Try
class MissileLauncher
{
public:
MissileLauncher(void);
private:
unsigned char abc[3];
};
or
using byte = unsigned char;
class MissileLauncher
{
public:
MissileLauncher(void);
private:
byte abc[3];
};
**Note: In older compilers (non-C++11) replace the using
line with typedef unsigned char byte;
If you want exactly one byte, uint8_t defined in cstdint would be the most expressive.
Byte is not a standard type in C or C++. Try char, which is usually and at least 8 bits long.
Byte is not a standard data type in C/C++ but it can still be used the way i suppose you want it. Here is how: Recall that a byte is an eight bit memory size which can represent any of the integers between -128 and 127, inclusive. (There are 256 integers in that range; eight bits can represent 256 -- two raised to the power eight -- different values.). Also recall that a char in C/C++ is one byte (eight bits). So, all you need to do to have a byte data type in C/C++ is to put this code at the top of your source file: #define byte char So you can now declare byte abc[3];
Maybe you can leverage the std::bitset
type available in C++11. It can be used to represent a fixed sequence of N
bits, which can be manipulated by conventional logic.
#include<iostream>
#include<bitset>
class MissileLauncher {
public:
MissileLauncher() {}
void show_bits() const {
std::cout<<m_abc[2]<<", "<<m_abc[1]<<", "<<m_abc[0]<<std::endl;
}
bool toggle_a() {
// toggles (i.e., flips) the value of `a` bit and returns the
// resulting logical value
m_abc[0].flip();
return m_abc[0];
}
bool toggle_c() {
// toggles (i.e., flips) the value of `c` bit and returns the
// resulting logical value
m_abc[2].flip();
return m_abc[2];
}
bool matches(const std::bitset<3>& mask) {
// tests whether all the bits specified in `mask` are turned on in
// this instance's bitfield
return ((m_abc & mask) == mask);
}
private:
std::bitset<3> m_abc;
};
typedef std::bitset<3> Mask;
int main() {
MissileLauncher ml;
// notice that the bitset can be "built" from a string - this masks
// can be made available as constants to test whether certain bits
// or bit combinations are "on" or "off"
Mask has_a("001"); // the zeroth bit
Mask has_b("010"); // the first bit
Mask has_c("100"); // the second bit
Mask has_a_and_c("101"); // zeroth and second bits
Mask has_all_on("111"); // all on!
Mask has_all_off("000"); // all off!
// I can even create masks using standard logic (in this case I use
// the or "|" operator)
Mask has_a_and_b = has_a | has_b;
std::cout<<"This should be 011: "<<has_a_and_b<<std::endl;
// print "true" and "false" instead of "1" and "0"
std::cout<<std::boolalpha;
std::cout<<"Bits, as created"<<std::endl;
ml.show_bits();
std::cout<<"is a turned on? "<<ml.matches(has_a)<<std::endl;
std::cout<<"I will toggle a"<<std::endl;
ml.toggle_a();
std::cout<<"Resulting bits:"<<std::endl;
ml.show_bits();
std::cout<<"is a turned on now? "<<ml.matches(has_a)<<std::endl;
std::cout<<"are both a and c on? "<<ml.matches(has_a_and_c)<<std::endl;
std::cout<<"Toggle c"<<std::endl;
ml.toggle_c();
std::cout<<"Resulting bits:"<<std::endl;
ml.show_bits();
std::cout<<"are both a and c on now? "<<ml.matches(has_a_and_c)<<std::endl;
std::cout<<"but, are all bits on? "<<ml.matches(has_all_on)<<std::endl;
return 0;
}
Compiling using gcc 4.7.2
g++ example.cpp -std=c++11
I get:
This should be 011: 011
Bits, as created
false, false, false
is a turned on? false
I will toggle a
Resulting bits:
false, false, true
is a turned on now? true
are both a and c on? false
Toggle c
Resulting bits:
true, false, true
are both a and c on now? true
but, are all bits on? false
Byte is not a standard type in C/C++, so it is represented by char
.
An advantage of this is that you can treat a basic_string
as a byte array allowing for safe storage and function passing. This will help you avoid the memory leaks and segmentation faults you might encounter when using the various forms of char[]
and char*
.
For example, this creates a string as a byte array of null values:
typedef basic_string<unsigned char> u_string;
u_string bytes = u_string(16,'\0');
This allows for standard bitwise operations with other char
values, including those stored in other string
variables. For example, to XOR the char
values of another u_string
across bytes
:
u_string otherBytes = "some more chars, which are just bytes";
for(int i = 0; i < otherBytes.length(); i++)
bytes[i%16] ^= (int)otherBytes[i];
You could use Qt which, in case you don't know, is C++ with a bunch of additional libraries and classes and whatnot. Qt has a very convenient QByteArray class which I'm quite sure would suit your needs.
Source: Stackoverflow.com