BYTE array size
Chunekit Pong
BYTE const* pbBinary
I would like to know how many bytes in that byte array
but if I do - sizeof(* pbBinary); - then I got 1
but if I do - sizeof( pbBinary); - then I got 4
I am sure the array has hundreds of bytes
how can I do that?
======================
BYTE const* pbBinary = &bytes[0];
int size = sizeof( pbBinary);
Fred Zwarts
>I have a BYTE array -
> BYTE const* pbBinary
You don't have a BYTE array, you have a pointer to BYTE.
(What is a BYTE?)
>
> I would like to know how many bytes in that byte array
>
> but if I do - sizeof(* pbBinary); - then I got 1
> but if I do - sizeof( pbBinary); - then I got 4
>
> I am sure the array has hundreds of bytes
>
> how can I do that?
Without other information you can't.
mliptak
> I have a BYTE array -
> BYTE const* pbBinary
>
> I would like to know how many bytes in that byte array
>
> but if I do - sizeof(* pbBinary); - then I got 1
> but if I do - sizeof( pbBinary); - then I got 4
>
> I am sure the array has hundreds of bytes
>
pbBinary is just a pointer.. it does not store the information about
number of bytes/elements it points to
if you care about the size of an "array", use std::vector<> instead.
m.
Chunekit Pong
wrote:
The whole code is like this - the purpose is to convert binary file
into a Base64 string
=================
typedef unsigned char BYTE;
std::ifstream file1("c:/test2.png");
// read from test2.png into BYTE array
std::vector<BYTE> bytes(
(std::istreambuf_iterator<char>(file1))
, (std::istreambuf_iterator<char>())
);
if(bytes.empty())
; // no bytes have been read
BYTE const* pbBinary = &bytes[0];
int size = sizeof(pbBinary);
unsigned long ulEncLen = 0;
char *pEncOut = NULL;
BOOL fRet = ::CryptBinaryToString( pbBinary, size,
CRYPT_STRING_BASE64, pEncOut, &ulEncLen );
====================
BOOL WINAPI CryptBinaryToString(
__in const BYTE *pbBinary,
__in DWORD cbBinary,
__in DWORD dwFlags,
__out_opt LPTSTR pszString,
__inout DWORD *pcchString
);
Fred Zwarts
bytes.size () gives you the size of the vector.
Tonni Tielens
> The whole code is like this - the purpose is to convert binary file
You cannot get the size of an array, by doing sizeof on a pointer to
an external array. Only if the pointer is in fact declared as a
statically dimensioned array (eg. BYTE pbBinary[10]) you can get the
size of the array by doing sizeof(pbBinary). In your case you are in
the same scope, but still pbBinary is considered as a pointer to a
dynamically allocated or external array. Note that sizeof is
calculated compile time, and when you declare a pointer to an array,
the compiler CANNOT know what the size of the array will be to what
the pointer will point at runtime.
Rolf Magnus
> I have a BYTE array -
> BYTE const* pbBinary
>
> I would like to know how many bytes in that byte array
>
> but if I do - sizeof(* pbBinary); - then I got 1
Well, *pbBinary is a BYTE, so you get the size of a BYTE.
> but if I do - sizeof( pbBinary); - then I got 4
pbBinary is a pointer to const BYTE, so you get the size of a pointer to
const BYTE.
> I am sure the array has hundreds of bytes
>
> how can I do that?
You can't, unless the array contains some end marker that you can use to find
out.
James Kanze
> On Nov 20, 9:25 am, Chunekit Pong <worlman...@yahoo.com> wrote:
> > The whole code is like this - the purpose is to convert
> > binary file
> You cannot get the size of an array, by doing sizeof on a
> pointer to an external array.
I know what you mean, but you really should say that you can't
get the size of an array given a pointer to its first element.
(Pointers to arrays, i.e. BYTE (*p)[ 200 ], exist, and in such
cases, sizeof( *p ) would be useful. But they aren't very
idiomatic.)
> Only if the pointer is in fact declared as a statically
> dimensioned array (eg. BYTE pbBinary[10]) you can get the size
> of the array by doing sizeof(pbBinary).
If something is declared as an array, it's not a pointer.
--
James Kanze (GABI Software) email:james...@gmail.com
Conseils en informatique orientée objet/
Beratung in objektorientierter Datenverarbeitung
9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34
James Kanze
> I have a BYTE array -
> BYTE const* pbBinary
> I would like to know how many bytes in that byte array
> but if I do - sizeof(* pbBinary); - then I got 1
> but if I do - sizeof( pbBinary); - then I got 4
> I am sure the array has hundreds of bytes
Ask whoever created the array to tell you. Once the array has
been converted to a pointer to the first element, all
information concerning the size has been lost.
A better solution might be to use std::vector.
zr
> On Thu, 20 Nov 2008 08:46:12 +0100, "Fred Zwarts" <F.Zwa...@KVI.nl>
> wrote:
>
>
>
> >"Chunekit Pong" <worlman...@yahoo.com> wrote in messagenews:f54ai4l6o3hdj8k2j...@4ax.com...
The previous posters have explained the problem. A possible fix to
your program:
Instead of:
int size = sizeof(pbBinary);
Try:
int size = bytes.size();
Andre Kostur
Why bother to make pbBinary and size ?
>
> unsigned long ulEncLen = 0;
> char *pEncOut = NULL;
>
> BOOL fRet = ::CryptBinaryToString( pbBinary, size,
> CRYPT_STRING_BASE64, pEncOut, &ulEncLen );
Why not:
BOOL fRet = ::CryptBinaryToString(&bytes[0], bytes.size(),
CRYPT__STRING_BASE64, pEncOut, &ulEncLen);
?