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BYTE array size

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

how can I do that?

======================

BYTE const* pbBinary = &bytes[0];
int size = sizeof( pbBinary);
Nov 20 '08 #1
10 22472
"Chunekit Pong" <wo********@yahoo.comwrote in message news:f5********************************@4ax.com...
>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.
Nov 20 '08 #2
On Nov 20, 8:27*am, Chunekit Pong <worlman...@yahoo.comwrote:
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.
Nov 20 '08 #3
On Thu, 20 Nov 2008 08:46:12 +0100, "Fred Zwarts" <F.******@KVI.nl>
wrote:
>"Chunekit Pong" <wo********@yahoo.comwrote in message news:f5********************************@4ax.com...
>>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.
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<BYTEbytes(
(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
);
Nov 20 '08 #4
"Chunekit Pong" <wo********@yahoo.comwrote in message news:ok********************************@4ax.com...
On Thu, 20 Nov 2008 08:46:12 +0100, "Fred Zwarts" <F.******@KVI.nl>
wrote:
>>"Chunekit Pong" <wo********@yahoo.comwrote in message news:f5********************************@4ax.com...
>>>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.
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<BYTEbytes(
(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);
bytes.size () gives you the size of the vector.
Nov 20 '08 #5
On Nov 20, 9:25*am, Chunekit Pong <worlman...@yahoo.comwrote:
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.
Nov 20 '08 #6
Chunekit Pong wrote:
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.

Nov 20 '08 #7
On Nov 20, 12:47 pm, Tonni Tielens <tonnitiel...@gmail.comwrote:
On Nov 20, 9:25 am, Chunekit Pong <worlman...@yahoo.comwrote:
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:ja*********@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
Nov 20 '08 #8
On Nov 20, 8:27 am, Chunekit Pong <worlman...@yahoo.comwrote:
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.

--
James Kanze (GABI Software) email:ja*********@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
Nov 20 '08 #9
zr
On Nov 20, 10:25*am, Chunekit Pong <worlman...@yahoo.comwrote:
On Thu, 20 Nov 2008 08:46:12 +0100, "Fred Zwarts" <F.Zwa...@KVI.nl>
wrote:
"Chunekit Pong" <worlman...@yahoo.comwrote in messagenews:f5********************************@4ax .com...
>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.

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<BYTEbytes(
* * * * * * * * * * * * (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
);
The previous posters have explained the problem. A possible fix to
your program:

Instead of:
int size = sizeof(pbBinary);
Try:
int size = bytes.size();
Nov 20 '08 #10
Chunekit Pong <wo********@yahoo.comwrote in
news:ok********************************@4ax.com:
On Thu, 20 Nov 2008 08:46:12 +0100, "Fred Zwarts" <F.******@KVI.nl>
wrote:
>>"Chunekit Pong" <wo********@yahoo.comwrote in message
news:f5********************************@4ax.com. ..
>>>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.

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<BYTEbytes(
(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);
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);

?
Nov 20 '08 #11

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