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C++: pointer to byte array


deepzero

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Hi,

For some reason i cant get a pointer to the first element of a byte array, which is driving me mad. :verymad:

COnsider this:

BYTE  searchpattern[] = {0x6d, 0x70, 0x6f, 0x72, 0x74};
cout << "deref: " << &searchpattern[0];

Isnt this supposed to dereference the first element of the array?

Instead it prints the whole array.

or
/>http://msdn.microsoft.com/en-us/library/hbswzcs5%28VS.80%29.aspx

BYTE* pbArr = &searchpattern[0];
cout << "asdf: " << pbArr;

same thing... :unsure:

or

BYTE* pbArr = &searchpattern[0];
cout << &pbArr;

This prints a pointer to 1 dword before the actual array... :ermm::kick:

any help would be appreciated, chances are good i`m missing something obvious... :rolleyes:

Edited by deepzero
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Assuming A is some sort of array (note that in most contexts, type* blah and type blah[] act the same concerning usual array indirections), we got the following similarities:

// address of first element:
&a[0]// address of array variable itself:
a
&a// first element itself (indirection):
a[0]
*a// second element:
a[1]
*(a + 1)
Edited by metr0
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This works now:

cout  << &searchpattern << endl;

I am 100% sure i tried this, though. :wacko:

Anyways, thanks a lot! :)

edit:

why cant i store the result in a dword variable?

DWORD tmp = &searchpattern;

wont compile:

error C2440: '=': 'BYTE (*)[5]' cant be converted to 'DWORD'.
Edited by deepzero
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why cant i store the result in a dword variable?

Consider the following:


typedef struct _bytetodword {
BYTE byte1;
BYTE byte2;
BYTE byte3;
BYTE byte4;
} bytetodword;
bytetodword btodw;BYTE searchpattern[] = {0x6d, 0x70, 0x6f, 0x72, 0x74}btodw.byte1 = (byte)&searchpattern[0];
btodw.byte2 = (byte)&searchpattern[1];
btodw.byte3 = (byte)&searchpattern[2];
btodw.byte4 = (byte)&searchpattern[3];DWORD tmp = &btodw;
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I know you cant store 5 bytes in a DWORD, but i was under the impression that i stored the address of the 5-bytes-array in that DWORD.

cout << &searchpattern;

outputs, on my machine: 0012FF6C which is the address of the array.

I am now trying to store that address in a DWORD, which should be possible. :ermm:

ie, i was hoping that after executing DWORD tmp = &searchpattern; the dword tmp would hold the address of the array, 0012ff6c.

:help

edit:

I got it!!! :woot:

Will post what exactly i wanted to do & did later. :)

Edited by deepzero
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DWORD WhyOEver = (DWORD)&searchpattern;

Is that what you want? For pointer safety regarding a future x64-compliant version, try considering ULONG_PTR instead.

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BYTE searchpattern[] = {0x6d, 0x70, 0x6f, 0x72, 0x74};
cout << "deref: " << &searchpattern[0];

Can't output bytes directly, you need to format them as text


BYTE searchpattern[] = {0x6d, 0x70, 0x6f, 0x72, 0x74};
CHAR tempstring[32];sprintf( tempstring, "%08X", &searchpattern[0] );
cout << "address of byte: " << tempstring;sprintf( tempstring, "%02X", searchpattern[0] );
cout << "deref: " << tempstring;

HR,

Ghandi

Edited by ghandi
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  • 2 months later...

why cant i store the result in a dword variable?

DWORD tmp = &searchpattern;

you can

DWORD tmp = *(DWORD*)&searchpattern[0];

if you want to search a byte array for dword

//eax= ??

DWORD tmp = *(DWORD*)&searchpattern[eax*4];

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I just wanted to add one thing:

This

cout << "deref: " << &searchpattern[0];

is the same thing as

cout << "deref: " << searchpattern;

As the address of the first element is the same thing as the char* searchpattern itself. Also in almost all cases of working with output a simple cast would help you greatly. For instance (int) if you want it to interpret your address as a number and escape characters to change the base \h for hex \d for decimal, etc.

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