How to declare a pointerto an array of bytes

[Dave]

I am trying to call VerQueryValue from a C# program. VerQueryValue takes as
one of its parameters a pointer to a pointer to an array of bytes, which it
uses to return a pointer to the required array. Now, I can call it like this:
byte* lpBuffer;
int length;
string subBlock = @"\StringFileIn fo\" + langCodePage +
@"\FileDescript ion";
result = VerQueryValue(b uffer, subBlock, &lpBuffer, &length);
but then I don't have a byte[] to pass to an ASCIEncoding object to decode.
What I really want to do is declare
byte[]* lplpBuffer
and then pass that to VerQueryValue, but C# apparently won't allow that.
(Oddly enough if I declare
byte[] lpBuffer;
I get an error "cannot convert from byte[]* to byte**", which is peculiar if
it doesn't recognise byte[]* as a type anyway)
Can anyone shed any light?
--
Dave

[Willy Denoyette [MVP]]

"Dave" <Da**@discussio ns.microsoft.co m> wrote in message
news:E9******** *************** ***********@mic rosoft.com...

I am trying to call VerQueryValue from a C# program. VerQueryValue takes as
one of its parameters a pointer to a pointer to an array of bytes, which
it
uses to return a pointer to the required array. Now, I can call it like
this:
byte* lpBuffer;
int length;
string subBlock = @"\StringFileIn fo\" + langCodePage +
@"\FileDescript ion";
result = VerQueryValue(b uffer, subBlock, &lpBuffer, &length);
but then I don't have a byte[] to pass to an ASCIEncoding object to
decode.
What I really want to do is declare
byte[]* lplpBuffer
and then pass that to VerQueryValue, but C# apparently won't allow that.
(Oddly enough if I declare
byte[] lpBuffer;
I get an error "cannot convert from byte[]* to byte**", which is peculiar
if
it doesn't recognise byte[]* as a type anyway)
Can anyone shed any light?
--
Dave

No need to use pointers, pass the byte[] by reference:

byte[] lpBuffer;
VerQueryValue(. ..., ref lpBuffer,...);

Willy.

[Dave]

'Fraid not! That gives "cannot convert from 'ref byte[]' to 'byte**'
--
Dave
"Willy Denoyette [MVP]" wrote:

"Dave" <Da**@discussio ns.microsoft.co m> wrote in message
news:E9******** *************** ***********@mic rosoft.com...

I am trying to call VerQueryValue from a C# program. VerQueryValue takes as
one of its parameters a pointer to a pointer to an array of bytes, which
it
uses to return a pointer to the required array. Now, I can call it like
this:
byte* lpBuffer;
int length;
string subBlock = @"\StringFileIn fo\" + langCodePage +
@"\FileDescript ion";
result = VerQueryValue(b uffer, subBlock, &lpBuffer, &length);
but then I don't have a byte[] to pass to an ASCIEncoding object to
decode.
What I really want to do is declare
byte[]* lplpBuffer
and then pass that to VerQueryValue, but C# apparently won't allow that.
(Oddly enough if I declare
byte[] lpBuffer;
I get an error "cannot convert from byte[]* to byte**", which is peculiar
if
it doesn't recognise byte[]* as a type anyway)
Can anyone shed any light?
--
Dave

No need to use pointers, pass the byte[] by reference:

byte[] lpBuffer;
VerQueryValue(. ..., ref lpBuffer,...);

Willy.

[David Browne]

"Dave" <Da**@discussio ns.microsoft.co m> wrote in message
news:1F******** *************** ***********@mic rosoft.com...

'Fraid not! That gives "cannot convert from 'ref byte[]' to 'byte**'
--

How do you have the function declared?

David

[Willy Denoyette [MVP]]

..
"Dave" <Da**@discussio ns.microsoft.co m> wrote in message
news:1F******** *************** ***********@mic rosoft.com...

'Fraid not! That gives "cannot convert from 'ref byte[]' to 'byte**'
--
Dave
"Willy Denoyette [MVP]" wrote:

Please show us your VerQueryValue function declaration as declared in C,
describe the function semantics, who's allocating the buffers C# or the
unmanaged function, why the double redirection?

Willy.

[Ivan Wong]

You need to declare the function like the following:
[DllImport("What Ever.dll")]
public unsafe static extern void VerQueryValue (byte** buffer);

In the method you need to put the following:

//allocate memory on the heap
byte* dataArray = (byte*)Marshal. AllocCoTaskMem( 20);
byte** dataArrayArray = &dataArray;

//call the unmanaged function you import from dll file
VerQueryValue(d ataArrayArray);

//do what every you want here, before free the memory

//free the memory
Marshal.FreeCoT askMem((IntPtr) dataArray);
hope it helps,
Ivan Wong

"Dave" wrote:

I am trying to call VerQueryValue from a C# program. VerQueryValue takes as
one of its parameters a pointer to a pointer to an array of bytes, which it
uses to return a pointer to the required array. Now, I can call it like this:
byte* lpBuffer;
int length;
string subBlock = @"\StringFileIn fo\" + langCodePage +
@"\FileDescript ion";
result = VerQueryValue(b uffer, subBlock, &lpBuffer, &length);
but then I don't have a byte[] to pass to an ASCIEncoding object to decode.
What I really want to do is declare
byte[]* lplpBuffer
and then pass that to VerQueryValue, but C# apparently won't allow that.
(Oddly enough if I declare
byte[] lpBuffer;
I get an error "cannot convert from byte[]* to byte**", which is peculiar if
it doesn't recognise byte[]* as a type anyway)
Can anyone shed any light?
--
Dave

[Dave]

Hi guys, thanks for helping on this.
I have just found an MSDN tutorial at
http://msdn.microsoft.com/library/de...detutorial.asp
which explains how to do this. I can't say I fully understand how it gets
around the all the convolutions of pointers to pointers etc, but I've used it
and it works. Thanks to you all for looking at it. Hopefully this thread will
help someone else.
--
Dave
"Willy Denoyette [MVP]" wrote:

..
"Dave" <Da**@discussio ns.microsoft.co m> wrote in message
news:1F******** *************** ***********@mic rosoft.com...

'Fraid not! That gives "cannot convert from 'ref byte[]' to 'byte**'
--
Dave
"Willy Denoyette [MVP]" wrote:

Please show us your VerQueryValue function declaration as declared in C,
describe the function semantics, who's allocating the buffers C# or the
unmanaged function, why the double redirection?

Willy.

[Willy Denoyette [MVP]]

Dave, the samples in the tutorial illustrates you how to use unsafe
constructs, but as I said before YOU don't need unsafe constructs to achieve
the same if you don't want to. Use unsafe only when you realy need to (IMO
never in C#).

Here is the same sample not using unsafe constructs:

...
public class Win32Imports
{
[DllImport("vers ion.dll")]
public static extern bool GetFileVersionI nfo (string sFileName,
int handle, int size, byte[] infoBuffer);
[DllImport("vers ion.dll")]
public static extern int GetFileVersionI nfoSize (string sFileName,
out int handle);
[DllImport("vers ion.dll")]
public static extern bool VerQueryValue (byte[] pBlock,
string pSubBlock, out string pValue, out uint len);

[DllImport("vers ion.dll")]
public static extern bool VerQueryValue (byte[] pBlock,
string pSubBlock, out IntPtr pValue, out uint len);
}

public class C
{
public static int Main ()
{
try
{
int handle = 0;
// Figure out how much version info there is:
int size =
Win32Imports.Ge tFileVersionInf oSize("printver sion.exe",
out handle);

if (size == 0) return -1;

byte[] buffer = new byte[size];

if (!Win32Imports. GetFileVersionI nfo("printversi on.exe",
handle, size, buffer))
{
Console.WriteLi ne("Failed to query file version
information.");
return 1;
}
IntPtr subBlock = IntPtr.Zero;
uint len = 0;
// Get the locale info from the version info:
if (!Win32Imports. VerQueryValue (buffer,
@"\VarFileInfo\ Translation", out subBlock, out len))
{
Console.WriteLi ne("Failed to query version
information.");
return 1;
}
int p = (int)subBlock;
int i1 = Marshal.ReadInt 16((IntPtr)p);
p+=2;
int i2 = Marshal.ReadInt 16((IntPtr)p);
string sb = String.Format(" {0:X4}{1:X4}",i 1, i2);
string spv = @"\StringFileIn fo\" + sb +
@"\ProductVersi on";

// Get the ProductVersion value for this program:
string versionInfo;

if (!Win32Imports. VerQueryValue (buffer, spv, out
versionInfo, out len))
{
Console.WriteLi ne("Failed to query version
information.");
return 1;
}

Console.WriteLi ne ("ProductVersio n == {0}", versionInfo);
}
catch (Exception e)
{
Console.WriteLi ne ("Caught unexpected exception " +
e.Message);
}

return 0;
}
}

Willy.

"Dave" <Da**@discussio ns.microsoft.co m> wrote in message
news:88******** *************** ***********@mic rosoft.com...

Hi guys, thanks for helping on this.
I have just found an MSDN tutorial at
http://msdn.microsoft.com/library/de...detutorial.asp
which explains how to do this. I can't say I fully understand how it gets
around the all the convolutions of pointers to pointers etc, but I've used
it
and it works. Thanks to you all for looking at it. Hopefully this thread
will
help someone else.
--
Dave
"Willy Denoyette [MVP]" wrote:

..
"Dave" <Da**@discussio ns.microsoft.co m> wrote in message
news:1F******** *************** ***********@mic rosoft.com...

> 'Fraid not! That gives "cannot convert from 'ref byte[]' to 'byte**'
> --
> Dave
>
>
> "Willy Denoyette [MVP]" wrote:
>

Please show us your VerQueryValue function declaration as declared in C,
describe the function semantics, who's allocating the buffers C# or the
unmanaged function, why the double redirection?

Willy.

[Dave]

Hi Willy.
yes, thanks for that. Once I got the code from the sample working I started
taking out the unsafe constructs and eventually lo and behold they were all
gone and it still worked. I'm an experienced C++ programmer but still new to
C#. Actually I'm quite impressed that it can make all those calls without
resorting to pointers.
--
Dave
"Willy Denoyette [MVP]" wrote:

Dave, the samples in the tutorial illustrates you how to use unsafe
constructs, but as I said before YOU don't need unsafe constructs to achieve
the same if you don't want to. Use unsafe only when you realy need to (IMO
never in C#).

Here is the same sample not using unsafe constructs:

...
public class Win32Imports
{
[DllImport("vers ion.dll")]
public static extern bool GetFileVersionI nfo (string sFileName,
int handle, int size, byte[] infoBuffer);
[DllImport("vers ion.dll")]
public static extern int GetFileVersionI nfoSize (string sFileName,
out int handle);
[DllImport("vers ion.dll")]
public static extern bool VerQueryValue (byte[] pBlock,
string pSubBlock, out string pValue, out uint len);

[DllImport("vers ion.dll")]
public static extern bool VerQueryValue (byte[] pBlock,
string pSubBlock, out IntPtr pValue, out uint len);
}

public class C
{
public static int Main ()
{
try
{
int handle = 0;
// Figure out how much version info there is:
int size =
Win32Imports.Ge tFileVersionInf oSize("printver sion.exe",
out handle);

if (size == 0) return -1;

byte[] buffer = new byte[size];

if (!Win32Imports. GetFileVersionI nfo("printversi on.exe",
handle, size, buffer))
{
Console.WriteLi ne("Failed to query file version
information.");
return 1;
}
IntPtr subBlock = IntPtr.Zero;
uint len = 0;
// Get the locale info from the version info:
if (!Win32Imports. VerQueryValue (buffer,
@"\VarFileInfo\ Translation", out subBlock, out len))
{
Console.WriteLi ne("Failed to query version
information.");
return 1;
}
int p = (int)subBlock;
int i1 = Marshal.ReadInt 16((IntPtr)p);
p+=2;
int i2 = Marshal.ReadInt 16((IntPtr)p);
string sb = String.Format(" {0:X4}{1:X4}",i 1, i2);
string spv = @"\StringFileIn fo\" + sb +
@"\ProductVersi on";

// Get the ProductVersion value for this program:
string versionInfo;

if (!Win32Imports. VerQueryValue (buffer, spv, out
versionInfo, out len))
{
Console.WriteLi ne("Failed to query version
information.");
return 1;
}

Console.WriteLi ne ("ProductVersio n == {0}", versionInfo);
}
catch (Exception e)
{
Console.WriteLi ne ("Caught unexpected exception " +
e.Message);
}

return 0;
}
}

Willy.

"Dave" <Da**@discussio ns.microsoft.co m> wrote in message
news:88******** *************** ***********@mic rosoft.com...

Hi guys, thanks for helping on this.
I have just found an MSDN tutorial at
http://msdn.microsoft.com/library/de...detutorial.asp
which explains how to do this. I can't say I fully understand how it gets
around the all the convolutions of pointers to pointers etc, but I've used
it
and it works. Thanks to you all for looking at it. Hopefully this thread
will
help someone else.
--
Dave
"Willy Denoyette [MVP]" wrote:

..
"Dave" <Da**@discussio ns.microsoft.co m> wrote in message
news:1F******** *************** ***********@mic rosoft.com...
> 'Fraid not! That gives "cannot convert from 'ref byte[]' to 'byte**'
> --
> Dave
>
>
> "Willy Denoyette [MVP]" wrote:
>

Please show us your VerQueryValue function declaration as declared in C,
describe the function semantics, who's allocating the buffers C# or the
unmanaged function, why the double redirection?

Willy.

[Willy Denoyette [MVP]]

Dave,

All pointer stuff is taken care of by the interop layer in the CLR
(PInvoke), but rest assured they still exist, be it under the covers.

Willy.

"Dave" <Da**@discussio ns.microsoft.co m> wrote in message
news:19******** *************** ***********@mic rosoft.com...

Hi Willy.
yes, thanks for that. Once I got the code from the sample working I
started
taking out the unsafe constructs and eventually lo and behold they were
all
gone and it still worked. I'm an experienced C++ programmer but still new
to
C#. Actually I'm quite impressed that it can make all those calls without
resorting to pointers.
--
Dave
"Willy Denoyette [MVP]" wrote:

Dave, the samples in the tutorial illustrates you how to use unsafe
constructs, but as I said before YOU don't need unsafe constructs to
achieve
the same if you don't want to. Use unsafe only when you realy need to
(IMO
never in C#).

Here is the same sample not using unsafe constructs:

...
public class Win32Imports
{
[DllImport("vers ion.dll")]
public static extern bool GetFileVersionI nfo (string sFileName,
int handle, int size, byte[] infoBuffer);
[DllImport("vers ion.dll")]
public static extern int GetFileVersionI nfoSize (string sFileName,
out int handle);
[DllImport("vers ion.dll")]
public static extern bool VerQueryValue (byte[] pBlock,
string pSubBlock, out string pValue, out uint len);

[DllImport("vers ion.dll")]
public static extern bool VerQueryValue (byte[] pBlock,
string pSubBlock, out IntPtr pValue, out uint len);
}

public class C
{
public static int Main ()
{
try
{
int handle = 0;
// Figure out how much version info there is:
int size =

Win32Imports.Ge tFileVersionInf oSize("printver sion.exe",
out handle);

if (size == 0) return -1;

byte[] buffer = new byte[size];

if
(!Win32Imports. GetFileVersionI nfo("printversi on.exe",
handle, size, buffer))
{
Console.WriteLi ne("Failed to query file version
information.");
return 1;
}
IntPtr subBlock = IntPtr.Zero;
uint len = 0;
// Get the locale info from the version info:
if (!Win32Imports. VerQueryValue (buffer,
@"\VarFileInfo\ Translation", out subBlock, out len))
{
Console.WriteLi ne("Failed to query version
information.");
return 1;
}
int p = (int)subBlock;
int i1 = Marshal.ReadInt 16((IntPtr)p);
p+=2;
int i2 = Marshal.ReadInt 16((IntPtr)p);
string sb = String.Format(" {0:X4}{1:X4}",i 1, i2);
string spv = @"\StringFileIn fo\" + sb +
@"\ProductVersi on";

// Get the ProductVersion value for this program:
string versionInfo;

if (!Win32Imports. VerQueryValue (buffer, spv, out
versionInfo, out len))
{
Console.WriteLi ne("Failed to query version
information.");
return 1;
}

Console.WriteLi ne ("ProductVersio n == {0}",
versionInfo);
}
catch (Exception e)
{
Console.WriteLi ne ("Caught unexpected exception " +
e.Message);
}

return 0;
}
}

Willy.

"Dave" <Da**@discussio ns.microsoft.co m> wrote in message
news:88******** *************** ***********@mic rosoft.com...

> Hi guys, thanks for helping on this.
> I have just found an MSDN tutorial at
> http://msdn.microsoft.com/library/de...detutorial.asp
> which explains how to do this. I can't say I fully understand how it
> gets
> around the all the convolutions of pointers to pointers etc, but I've
> used
> it
> and it works. Thanks to you all for looking at it. Hopefully this
> thread
> will
> help someone else.
> --
> Dave
>
>
> "Willy Denoyette [MVP]" wrote:
>
>>
>> ..
>> "Dave" <Da**@discussio ns.microsoft.co m> wrote in message
>> news:1F******** *************** ***********@mic rosoft.com...
>> > 'Fraid not! That gives "cannot convert from 'ref byte[]' to 'byte**'
>> > --
>> > Dave
>> >
>> >
>> > "Willy Denoyette [MVP]" wrote:
>> >
>>
>> Please show us your VerQueryValue function declaration as declared in
>> C,
>> describe the function semantics, who's allocating the buffers C# or
>> the
>> unmanaged function, why the double redirection?
>>
>> Willy.
>>
>>
>>
>>