Hi,
I am trying to learn how to use the Ghostscript API following the Ghostscript vb.net code example in “parrot fashion”. I do not have sufficient technical knowledge to understand error messages or the implications.
I am picking up an error message during the code implementation. I suspect it is because the version of kernel32.dll on my computer is incompatible with the vb.net source code.
Any pointers where I can learn about PInvoke and stacks will be much appreciated.
Any help in pointing me in the right direction is appreciated.
HerbiNZ
New Zealand
------------------------------------------------------------------------
File: kernel32.dll
Name: Windows NT BASE API Client DLL
Version: 5.1.2600.2945
File version: (xpsp_sp2_gdr.060704-2349)
Error message:
PInvokeStackImbalance was detected
Message: A call to PInvoke function 'ghostscriptTest!ConsoleApplication1.gsapi::CopyMemory' has unbalanced the stack. This is likely because the managed PInvoke signature does not match the unmanaged target signature. Check that the calling convention and parameters of the PInvoke signature match the target unmanaged signature.
This happens when the subroutine copyMemory is called.
Software: Ghostscript 8.54
Downloaded file: gs854w32-gpl.exe
The .exe file and sample source code was supplied by Ghostscript at: http://www.cs.wisc.edu/~ghost/
'Copyright (c) 2002 Dan Mount and Ghostgum Software Pty Ltd
'
' Permission is hereby granted, free of charge, to any person obtaining
' a copy of this software and associated documentation files (the
' "Software"), to deal in the Software without restriction, including
' without limitation the rights to use, copy, modify, merge, publish,
' distribute, sublicense, and/or sell copies of the Software, and to
' permit persons to whom the Software is furnished to do so, subject to
' the following conditions:
'
' The above copyright notice and this permission notice shall be
' included in all copies or substantial portions of the Software.
'
' THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
' EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
' MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
' NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
' BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
' ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
' CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
' SOFTWARE.
' This is an example of how to call the Ghostscript DLL from
' Visual Basic.NET. There are two examples, one converts
' colorcir.ps to PDF, the other is like command line Ghostscript.
' The display device is not supported.
'
' This code is not compatible with VB6. There is another
' example which does work with VB6. Differences include:
' 1. VB.NET uses GCHandle to get pointer
' VB6 uses StrPtr/VarPtr
' 2. VB.NET Integer is 32bits, Long is 64bits
' VB6 Integer is 16bits, Long is 32bits
' 3. VB.NET uses IntPtr for pointers
' VB6 uses Long for pointers
' 4. VB.NET strings are always Unicode
' VB6 can create an ANSI string
' See the following URL for some VB6 / VB.NET details
' http://msdn.microsoft.com/library/default.asp url=/library/en-us/dnvb600/html/vb6tovbdotnet.asp
Imports System.Runtime.InteropServices
Module gsapi
Public Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (ByVal dest As IntPtr, ByVal source As IntPtr, ByVal bytes As Long)
'------------------------------------------------
'UDTs Start
'------------------------------------------------
<StructLayout(LayoutKind.Sequential)> Public Structure GS_Revision
Public strProduct As IntPtr
Public strCopyright As IntPtr
Public intRevision As Integer
Public intRevisionDate As Integer
End Structure
'------------------------------------------------
'UDTs End
'------------------------------------------------
'------------------------------------------------
'Callback Functions Start
'------------------------------------------------
'These are only required if you use gsapi_set_stdio
Public Delegate Function StdioCallBack(ByVal handle As IntPtr, ByVal strptr As IntPtr, ByVal count As Integer) As Integer
Public Function gsdll_stdin(ByVal intGSInstanceHandle As IntPtr, ByVal strz As IntPtr, ByVal intBytes As Integer) As Integer
' This is dumb code that reads one byte at a time
' Ghostscript doesn't mind this, it is just very slow
If intBytes = 0 Then
gsdll_stdin = 0
Else
Dim ich As Integer = Console.Read()
If ich = -1 Then
gsdll_stdin = 0 ' EOF
Else
Dim bch As Byte = ich
Dim gcByte As GCHandle = GCHandle.Alloc(bch, GCHandleType.Pinned)
Dim ptrByte As IntPtr = gcByte.AddrOfPinnedObject()
CopyMemory(strz, ptrByte, 1)
ptrByte = IntPtr.Zero
gcByte.Free()
gsdll_stdin = 1
End If
End If
End Function
Public Function gsdll_stdout(ByVal intGSInstanceHandle As IntPtr, ByVal strz As IntPtr, ByVal intBytes As Integer) As Integer
' If you can think of a more efficient method, please tell me!
' We need to convert from a byte buffer to a string
' First we create a byte array of the appropriate size
Dim aByte(intBytes) As Byte
' Then we get the address of the byte array
Dim gcByte As GCHandle = GCHandle.Alloc(aByte, GCHandleType.Pinned)
Dim ptrByte As IntPtr = gcByte.AddrOfPinnedObject()
' Then we copy the buffer to the byte array
CopyMemory(ptrByte, strz, intBytes)
' Release the address locking
ptrByte = IntPtr.Zero
gcByte.Free()
' Then we copy the byte array to a string, character by character
Dim str As String = ""
Dim i As Integer
For i = 0 To intBytes - 1
str = str + Chr(aByte(i))
Next
' Finally we output the message
Console.Write(str)
gsdll_stdout = intBytes
End Function
Public Function gsdll_stderr(ByVal intGSInstanceHandle As IntPtr, ByVal strz As IntPtr, ByVal intBytes As Integer) As Integer
gsdll_stderr = gsdll_stdout(intGSInstanceHandle, strz, intBytes)
End Function
'------------------------------------------------
'Callback Functions End
'------------------------------------------------
'------------------------------------------------
'API Calls Start
'------------------------------------------------
'Win32 API
'GhostScript API
' Public Declare Function gsapi_revision Lib "gsdll32.dll" (ByVal pGSRevisionInfo As IntPtr, ByVal intLen As Integer) As Integer
Public Declare Function gsapi_revision Lib "gsdll32.dll" (ByRef pGSRevisionInfo As GS_Revision, ByVal intLen As Integer) As Integer
Public Declare Function gsapi_new_instance Lib "gsdll32.dll" (ByRef lngGSInstance As IntPtr, ByVal lngCallerHandle As IntPtr) As Integer
Public Declare Function gsapi_set_stdio Lib "gsdll32.dll" (ByVal lngGSInstance As IntPtr, ByVal gsdll_stdin As StdioCallBack, ByVal gsdll_stdout As StdioCallBack, ByVal gsdll_stderr As StdioCallBack) As Integer
Public Declare Sub gsapi_delete_instance Lib "gsdll32.dll" (ByVal lngGSInstance As IntPtr)
Public Declare Function gsapi_init_with_args Lib "gsdll32.dll" (ByVal lngGSInstance As IntPtr, ByVal lngArgumentCount As Integer, ByVal lngArguments As IntPtr) As Integer
Public Declare Function gsapi_run_file Lib "gsdll32.dll" (ByVal lngGSInstance As IntPtr, ByVal strFileName As String, ByVal intErrors As Integer, ByVal intExitCode As Integer) As Integer
Public Declare Function gsapi_exit Lib "gsdll32.dll" (ByVal lngGSInstance As IntPtr) As Integer
'------------------------------------------------
'API Calls End
'------------------------------------------------
'------------------------------------------------
'User Defined Functions Start
'------------------------------------------------
Public Function StringToAnsiZ(ByVal str As String) As Byte()
' Convert a Unicode string to a null terminated Ansi string for Ghostscript.
' The result is stored in a byte array. Later you will need to convert
' this byte array to a pointer with GCHandle.Alloc(XXXX, GCHandleType.Pinned)
' and GSHandle.AddrOfPinnedObject()
Dim intElementCount As Integer
Dim intCounter As Integer
Dim aAnsi() As Byte
Dim bChar As Byte
intElementCount = Len(str)
ReDim aAnsi(intElementCount + 1)
For intCounter = 0 To intElementCount - 1
bChar = Asc(Mid(str, intCounter + 1, 1))
aAnsi(intCounter) = bChar
Next intCounter
aAnsi(intElementCount) = 0
StringToAnsiZ = aAnsi
End Function
Public Function AnsiZtoString(ByVal strz As IntPtr) As String
' We need to convert from a byte buffer to a string
Dim byteCh(1) As Byte
Dim bOK As Boolean = True
Dim gcbyteCh As GCHandle = GCHandle.Alloc(byteCh, GCHandleType.Pinned)
Dim ptrByte As IntPtr = gcbyteCh.AddrOfPinnedObject()
Dim j As Integer = 0
Dim str As String = ""
While bOK
' This is how to do pointer arithmetic!
Dim sPtr As New IntPtr(strz.ToInt64() + j)
CopyMemory(ptrByte, sPtr, 1)
If byteCh(0) = 0 Then
bOK = False
Else
str = str + Chr(byteCh(0))
End If
j = j + 1
End While
AnsiZtoString = str
End Function
Public Function CheckRevision(ByVal intRevision As Integer) As Boolean
' Check revision number of Ghostscript
Dim intReturn As Integer
Dim udtGSRevInfo As GS_Revision
Dim gcRevision As GCHandle
gcRevision = GCHandle.Alloc(udtGSRevInfo, GCHandleType.Pinned)
intReturn = gsapi_revision(udtGSRevInfo, 16)
Console.WriteLine("Revision = " & udtGSRevInfo.intRevision)
Console.WriteLine("RevisionDate = " & udtGSRevInfo.intRevisionDate)
Console.WriteLine("Product = " & AnsiZtoString(udtGSRevInfo.strProduct))
Console.WriteLine("Copyright = " & AnsiZtoString(udtGSRevInfo.strCopyright))
If udtGSRevInfo.intRevision = intRevision Then
CheckRevision = True
Else
CheckRevision = False
End If
gcRevision.Free()
End Function
Public Function CallGS(ByVal astrGSArgs() As String) As Boolean
Dim intReturn As Integer
Dim intGSInstanceHandle As IntPtr
Dim aAnsiArgs() As Object
Dim aPtrArgs() As IntPtr
Dim aGCHandle() As GCHandle
Dim intCounter As Integer
Dim intElementCount As Integer
' Dim iTemp As Integer
Dim callerHandle As IntPtr
Dim gchandleArgs As GCHandle
Dim intptrArgs As IntPtr
' Print out the revision details.
' If we want to insist on a particular version of Ghostscript
' we should check the return value of CheckRevision().
CheckRevision(704)
' Load Ghostscript and get the instance handle
intReturn = gsapi_new_instance(intGSInstanceHandle, callerHandle)
If (intReturn < 0) Then
Return (False)
End If
' Capture stdio
Dim stdinCallback As StdioCallBack
stdinCallback = AddressOf gsdll_stdin
Dim stdoutCallback As StdioCallBack
stdoutCallback = AddressOf gsdll_stdout
Dim stderrCallback As StdioCallBack
stderrCallback = AddressOf gsdll_stderr
intReturn = gsapi_set_stdio(intGSInstanceHandle, stdinCallback, stdoutCallback, stderrCallback)
If (intReturn >= 0) Then
' Convert the Unicode strings to null terminated ANSI byte arrays
' then get pointers to the byte arrays.
intElementCount = UBound(astrGSArgs)
ReDim aAnsiArgs(intElementCount)
ReDim aPtrArgs(intElementCount)
ReDim aGCHandle(intElementCount)
For intCounter = 0 To intElementCount
aAnsiArgs(intCounter) = StringToAnsiZ(astrGSArgs(intCounter))
aGCHandle(intCounter) = GCHandle.Alloc(aAnsiArgs(intCounter), GCHandleType.Pinned)
aPtrArgs(intCounter) = aGCHandle(intCounter).AddrOfPinnedObject()
Next
gchandleArgs = GCHandle.Alloc(aPtrArgs, GCHandleType.Pinned)
intptrArgs = gchandleArgs.AddrOfPinnedObject()
callerHandle = IntPtr.Zero
intReturn = gsapi_init_with_args(intGSInstanceHandle, intElementCount + 1, intptrArgs)
' Release the pinned memory
For intCounter = 0 To intElementCount
aGCHandle(intCounter).Free()
Next
gchandleArgs.Free()
' Stop the Ghostscript interpreter
gsapi_exit(intGSInstanceHandle)
End If
' release the Ghostscript instance handle
gsapi_delete_instance(intGSInstanceHandle)
If (intReturn >= 0) Then
CallGS = True
Else
CallGS = False
End If
End Function
Private Function ConvertFile() As Boolean
Dim astrArgs(10) As String
astrArgs(0) = "ps2pdf" 'The First Parameter is Ignored
astrArgs(1) = "-dNOPAUSE"
astrArgs(2) = "-dBATCH"
astrArgs(3) = "-dSAFER"
astrArgs(4) = "-r300"
astrArgs(5) = "-sDEVICE=pdfwrite"
astrArgs(6) = "-sOutputFile=d:\temp\out.pdf"
astrArgs(7) = "-c"
astrArgs(8) = ".setpdfwrite"
astrArgs(9) = "-f"
astrArgs(10) = "d:\temp\colorcir.ps"
Return CallGS(astrArgs)
End Function
Private Function InteractiveGS() As Boolean
Dim astrArgs(2) As String
astrArgs(0) = "gs" 'The First Parameter is Ignored
astrArgs(1) = "-c"
astrArgs(2) = "systemdict /start get exec"
Return CallGS(astrArgs)
End Function
Sub Main()
ConvertFile()
'InteractiveGS()
MsgBox("Done")
End Sub
'------------------------------------------------
'User Defined Functions End
'------------------------------------------------
End Module
PInvoke unbalanced the stack kernel32.dll
P R W
Thank you, Max
I found the article very useful.
Regards
Herman
shohaib
Hello HerziNZ,
Could you tell me what code changes you've made to make this work
I'm facing the same problem.
Many thanks
Michel Pikard
mario.muja
Brendan,
I agree that the unbalanced stack warnings/exceptions are a worthwhile enhancement in the 2.0 framework.
I have made the changes and the code works.
Let the developer who upgrades to the 2.0 framework beware!
Thank you for the help.
Herman
Auckland, New Zealand
Chris.Stewart
Hi,
Check following article:
http://www.codeproject.com/vb/net/CopyMemory_in_Net.asp
Max
Chris Lively
The unbalanced stack warnings/exceptions are one of my favorite features in the new 2.0 framework as it makes it much much harder for you to send the wrong data (or wrong size of data) to unmanaged code.
An example of what you are seeing would be when VB.NET thinks it’s going to call a method whose first argument is 32-bits wide, but in fact is only 16-bits wide and if you are really unlucky, this kind of issue could cause you much pain and suffering.
From the looks of it you are having a problem with calling MoveMemory in VB.NET which correlates to RtlMoveMemory in Kernel32.dll and a quick hop onto pinvoke.net suggests the following signature for the method:
Declare Auto Sub MoveMemory Lib "Kernel32.dll" _
Alias "RtlMoveMemory" (ByRef dest As IntPtr, ByRef src As IntPtr, ByVal size As Integer)
While the one you are using very close so let’s try replacing yours with the one from above and see if that doesn’t fix your problem. At the very least I expect that the change from yours specifying of a long for the third argument now being an Integer might fix a few things.
It's also worth noting that from the looks of it that code is a port from VB6 code where a Long integer was 32-bits, but where in VB.NET a Long is 64-bits.