Converting a unsigned char * to const char *

[hamishd]

Is this possible? Sorry if this question isn't relevant here.

actually, I'm really trying to convert a unsigned char * to an int

 

[Jim Langston]

Is this possible? Sorry if this question isn't relevant here.

actually, I'm really trying to convert a unsigned char * to an int

Are you trying to convert the value of the pointer, or where the pointer is
pointing to?

Either way, reinterpret_cast is what you want.
reinterpret_cast<int>( Foo );

 

[=?ISO-8859-1?Q?Erik_Wikstr=F6m?=]

Are you trying to convert the value of the pointer, or where the pointer is
pointing to?

Either way, reinterpret_cast is what you want.
reinterpret_cast<int>( Foo );

reinterpret_cast should not be needed it it's a unsigned char -> int
conversion the OP is trying to do, both are integer types so a normal
assignment should do, right?

 

[Barry]

Are you trying to convert the value of the pointer, or where the pointer is
pointing to?

Either way, reinterpret_cast is what you want.
reinterpret_cast<int>( Foo );

I think reinpterpret_cast does *NOT* work with constness
maybe static_cast and const_cast together will work

 

[Barry]

I think reinpterpret_cast does *NOT* work with constness
maybe static_cast and const_cast together will work

sorry, the title from the OP is misleading

 

[Barry]

reinterpret_cast should not be needed it it's a unsigned char -> int
conversion the OP is trying to do, both are integer types so a normal
assignment should do, right?

you can assign unsigned char* to int

I think reinterpret_cast is fine here

 

[Ian Collins]

Is this possible? Sorry if this question isn't relevant here.

actually, I'm really trying to convert a unsigned char * to an int

There isn't a portable way to do this, on many systems a char* is bigger
than an int.

 

[hamishd]

Are you trying to convert the value of the pointer, or where the pointer is
pointing to?

Either way, reinterpret_cast is what you want.
reinterpret_cast<int>( Foo );

Below is exactly what I'm doing. I want to read a value from the
registry. Let's say the registry value is "453".

unsigned char ikey[256];
ULONG ilen = 256;
HKEY ihKey;

RegQueryValueEx(ihKey, "Value", 0, NULL, ikey, &ilen);

But now ikey is not an int, i want an int of value 453.

int RegistryVal = reinterpret_cast<int>(ikey);

This does not work.
The reason i asked about converting to a constr char * is that I
wanted to use atoi()

 

[Ian Collins]

Are you trying to convert the value of the pointer, or where the pointer is
pointing to?

Either way, reinterpret_cast is what you want.
reinterpret_cast<int>( Foo );

Below is exactly what I'm doing. I want to read a value from the
registry. Let's say the registry value is "453".

unsigned char ikey[256];
ULONG ilen = 256;
HKEY ihKey;

RegQueryValueEx(ihKey, "Value", 0, NULL, ikey, &ilen);

But now ikey is not an int, i want an int of value 453.

What does RegQueryValueEx do to the ikey parameter?

int RegistryVal = reinterpret_cast<int>(ikey);

This does not work.

Why should it?

The reason i asked about converting to a constr char * is that I
wanted to use atoi()

Why not just use static_cast<char*>(ikey)?

 

[BobR]

There isn't a portable way to do this, on many systems a char* is bigger
than an int.

unsigned char *uc( 0 );
int int16bit( reinterpret_cast<int>(uc) & 0xFF );

But it wouldn't be logical. <G>

 

[Jim Langston]

Are you trying to convert the value of the pointer, or where the pointer
is
pointing to?

Either way, reinterpret_cast is what you want.
reinterpret_cast<int>( Foo );

Below is exactly what I'm doing. I want to read a value from the
registry. Let's say the registry value is "453".

unsigned char ikey[256];
ULONG ilen = 256;
HKEY ihKey;

RegQueryValueEx(ihKey, "Value", 0, NULL, ikey, &ilen);

But now ikey is not an int, i want an int of value 453.

int RegistryVal = reinterpret_cast<int>(ikey);

This does not work.
The reason i asked about converting to a constr char * is that I
wanted to use atoi()

Oh. You want to convert "453" to an int. I would use stringstream, which
is an alternative to atoi

std::stringstream convert;
convert << ikey;
int Value;
convert >> value;

std::string convert( ikey );
int Value;
convert >> Value;

may also work. Not sure if stringstream has a constructor taking a char*

 

[BobR]

Are you trying to convert the value of the pointer, or where the pointer is
pointing to?
Either way, reinterpret_cast is what you want.
reinterpret_cast<int>( Foo );

Below is exactly what I'm doing. I want to read a value from the
registry. Let's say the registry value is "453".

unsigned char ikey[256];
ULONG ilen = 256;
HKEY ihKey;
RegQueryValueEx(ihKey, "Value", 0, NULL, ikey, &ilen);

But now ikey is not an int, i want an int of value 453.

int RegistryVal = reinterpret_cast<int>(ikey);
This does not work.

The reason i asked about converting to a constr char * is that I
wanted to use atoi()

Why?

#include <iostream>
#include <sstream>

{ // main() or ?
unsigned char ikey[256] = "453\0";
std::stringstream sis;
sis << ikey;
int number;
sis >> number;
std::cout<<"number = "<<number<<std::endl;
}
// out: number = 453

 

[BobR]

Below is exactly what I'm doing. I want to read a value from the
registry. Let's say the registry value is "453".

unsigned char ikey[256];
ULONG ilen = 256;
HKEY ihKey;
RegQueryValueEx(ihKey, "Value", 0, NULL, ikey, &ilen);
But now ikey is not an int, i want an int of value 453.
int RegistryVal = reinterpret_cast<int>(ikey);
This does not work.
The reason i asked about converting to a constr char * is that I
wanted to use atoi()

Oh. You want to convert "453" to an int. I would use stringstream, which
is an alternative to atoi

std::stringstream convert;
convert << ikey;
int Value;
convert >> value;

// > std::string convert( ikey );

std::string Sconvert( ikey );
std::stringstream convert( Sconvert );

int Value;
convert >> Value;

may also work. Not sure if stringstream has a constructor taking a char*

It does for 'char*', but not for 'unsigned char*' (not on my old MinGW).

// -------
char const scc[] = "453\0";
std::istringstream is( scc ); // no problem
// -------
unsigned char const scc[] = "453\0";
std::istringstream is( scc );
// error: invalid conversion from `const unsigned char*' to `
// const char*'
// error: initializing argument 1 of std::basic_string...
(again, the casts got real ugly! <G>).
// -------