Using Win32 functions in Visual FoxPro Image Gallery
Code examples:
GDI+: copying to the Clipboard (a) image of active FoxPro window/form, (b) image file
Adding and deleting Scheduled Tasks using NetScheduleJob API functions
How to change display settings: screen resolution, screen refresh rate
Enumerating printer drivers installed
Capturing keyboard activity of another application with the Raw Input API (VFP9)
Using Video Capture: displaying on FoxPro form frames and previewing video obtained from a digital camera
Custom GDI+ class
How to retrieve information about a cache entry (Internet Explorer)
How to activate Windows Calculator
Custom HttpRequest class (WinHTTP)
How to convert a bitmap file to monochrome format (1 bpp)
Using FoxTray ActiveX control: System Tray Icon and menu attached to VFP form
How to display Windows On-Screen Keyboard
Enumerating raw input devices attached to the system (keyboard, mouse, human interface device)
Using EnumPrinters function to enumerate locally installed printers
Windows Shell Icons displayed and exported to ICO files (Vista)
Winsock: retrieving Web pages using sockets (HTTP, port 80)
How to set Creation Date/Time for a folder (WinNT)
Winsock: sending email messages (SMTP, port 25)
Mapping and disconnecting network drives
Setting the date and time that a file was created
Using WM_COPYDATA for interprocess communication (VFP9)
Custom HttpRequest class (WinINet)
How to create MD-5 and SHA-1 hash values from a string
How to assemble an array of strings and pass it to external function

User rating: 0/10 (0 votes)
Rate this code sample:
  • ~
More code examples    Listed functions    Add comment     W32 Constants      Translate this page Printer friendly version of this code sample
Versions:
click to open
Before you begin:
The PathFindOnPath function is anything but special. Whatever it does, can be accomplished by using FILE() and GETENV() FoxPro functions. Though it gives me a chance to demonstrate a technique of assembling an array of strings for being passed to external function.

More comments below the source code.
#DEFINE MAX_PATH 260

DECLARE INTEGER PathFindOnPath IN shlwapi;
    STRING @pszFile, STRING @ppszOtherDirs

LOCAL cFile, oPath1, oPath2, oPath3, cPathArray

* The first parameter is not just a file name to search;
* If the search is successful, this parameter is used 
* to return the fully qualified path name.
* 
* For that reason it must be long enough to accomodate
* a path of maximum length
cFile = PADR("wininet.dll", MAX_PATH, CHR(0))

* PChar class wraps GlobalAlloc and GlobalFree calls
oPath1 = CREATEOBJECT("PChar", "c:\dir1" + CHR(0))
oPath2 = CREATEOBJECT("PChar", "c:\dir2" + CHR(0))
oPath3 = CREATEOBJECT("PChar", "c:\documents\dir1" + CHR(0))

* the null-terminated array contains three memory addresses
* padded with zero bytes
cPathArray = num2dword(oPath1.GetAddr()) +;
    num2dword(oPath2.GetAddr()) +;
    num2dword(oPath3.GetAddr()) +;
    num2dword(0) + CHR(0)

IF PathFindOnPath(@cFile, @cPathArray) = 0
    ? "File not found..."
ELSE
    * at this point cFile contains the fully qualified path
    * padded to MAX_PATH length with zero bytes
    cFile = STRTRAN(cFile, CHR(0), "")
    ? cFile
ENDIF
* end of main

FUNCTION num2dword(lnValue)
#DEFINE m0  256
#DEFINE m1  65536
#DEFINE m2  16777216
    IF lnValue < 0
        lnValue = 0x100000000 + lnValue
    ENDIF
    LOCAL b0, b1, b2, b3
    b3 = Int(lnValue/m2)
    b2 = Int((lnValue - b3*m2)/m1)
    b1 = Int((lnValue - b3*m2 - b2*m1)/m0)
    b0 = Mod(lnValue, m0)
RETURN Chr(b0)+Chr(b1)+Chr(b2)+Chr(b3)

DEFINE CLASS PChar As Custom
PROTECTED hMem

PROCEDURE Init(lcString)
    THIS.hMem = 0
    THIS.setValue (lcString)

PROCEDURE Destroy
    THIS.ReleaseString

FUNCTION GetAddr  && returns a pointer to the string
RETURN THIS.hMem

FUNCTION GetValue && returns string value
    LOCAL lnSize, lcBuffer
    lnSize = THIS.getAllocSize()
    lcBuffer = SPACE(lnSize)

    IF THIS.hMem <> 0
        DECLARE RtlMoveMemory IN kernel32 As MemToStr;
            STRING @, INTEGER, INTEGER
        = MemToStr(@lcBuffer, THIS.hMem, lnSize)
    ENDIF
RETURN lcBuffer

FUNCTION GetAllocSize  && returns allocated memory size (string length)
    DECLARE INTEGER GlobalSize IN kernel32 INTEGER hMem
RETURN Iif(THIS.hMem=0, 0, GlobalSize(THIS.hMem))

PROCEDURE SetValue (lcString) && assigns new string value
#DEFINE GMEM_FIXED   0 
    THIS.ReleaseString

    DECLARE INTEGER GlobalAlloc IN kernel32 INTEGER, INTEGER
    DECLARE RtlMoveMemory IN kernel32 As StrToMem;
        INTEGER, STRING @, INTEGER

    LOCAL lnSize
    lcString = lcString + Chr(0)
    lnSize = Len(lcString)
    THIS.hMem = GlobalAlloc(GMEM_FIXED, lnSize)
    IF THIS.hMem <> 0
        = StrToMem(THIS.hMem, @lcString, lnSize)
    ENDIF

PROCEDURE ReleaseString  && releases allocated memory
    IF THIS.hMem <> 0
        DECLARE INTEGER GlobalFree IN kernel32 INTEGER
        = GlobalFree (THIS.hMem)
        THIS.hMem = 0
    ENDIF
ENDDEFINE  && pchar



User rating: 0/10 (0 votes)
Rate this code sample:
  • ~
2847 bytes  
Created: 2005-04-27 19:35:53  
Modified: 2005-04-28 09:32:16  
Visits in 7 days: 39  
Listed functions:
GlobalAlloc
GlobalFree
GlobalSize
PathFindOnPath
Printer friendly API declarations
My comment:
The second parameter of the PathFindOnPath is a memory address of null-terminated array of pointers to strings. Members of such array must be 4-byte numbers, format called UINT or DWORD. Each array member is an address of allocated in memory string that contains a directory name.

In this code sample, I want to make this function search for the file in three directories:
c:\dir1
c:\dir2
c:\documents\dir1



As the first step, I use the GlobalAlloc to allocate each directory name in memory. Three GlobalAlloc calls return three memory addresses.

To become a null-terminated array, these memory addresses must be put one after another to a memory buffer and padded by some null characters. As I said, each address must occupy four bytes.

So far these numbers are in FoxPro numeric format. This is something similar to managed objects in .Net. Technically I can not say how many bytes each numeric value takes and where exactly it resides in memory.

Somehow I need to convert them to 4-byte DWORDs. Three addresses, as three directories are searched, and five zero bytes, produce the total length of 17 bytes. I use num2dword() function to convert each number to 4-character string, which is the binary character representation of the DWORD format. In VFP9 you probably can use BINTOC() for this conversion.

So now I have created the binary character representation for the array -- a string 17 characters long. I could use the GlobalAlloc again to allocate this string in memory and obtain its address.

But more elegant solution is declaring this parameter as STRING @ -- a reference to a string, cPathArray in the code above. That makes the FoxPro to take care about all memory operations: memory allocation, passing the pointer to the PathFindOnPath and releasing the memory in the end.

PChar class hides certain complexity of memory API calls. In particular, it calls the GlobalFree, whenever a PChar instance is destroyed or re-allocated, preventing memory leaks.
Word Index links for this example:
Translate this page:
  Spanish    Portuguese    German    French    Italian  
FreeTranslation.com offers instant, free translations of text or web pages.
User Contributed Notes:
There are no notes on this subject.


Copyright 2001-2014 News2News, Inc. Before reproducing or distributing any data from this site please ask for an approval from its owner. Unless otherwise specified, this page is for your personal and non-commercial use. The information on this page is presented AS IS, meaning that you may use it at your own risk. Microsoft Visual FoxPro and Windows are trade marks of Microsoft Corp. All other trademarks are the property of their respective owners. 

Privacy policy
Credits: PHP (4.4.9), an HTML-embedded scripting language, MySQL (5.1.68), the Open Source standard SQL database, AceHTML Freeware Version 4, freeware HTML Editor of choice.   Hosted by Korax Online Inc.
Last Topics Visited (23.22.194.120)
1 sec.Function: 'sendto'
Function group: 'Windows Sockets 2 (Winsock)'
3 sec.Function: 'CeDeleteFile'
Function group: 'Remote Application Programming (RAPI)'
5 sec.Solution: 'ContextMenu ActiveX Control'
46 sec.Example: 'Displaying printer-properties Property Sheet for the specified printer'
6.7 hrs.Function: 'GdipDrawImageRectRectI'
3 day(s)Function: 'JetCreateDatabase'
Function group: 'Extensible Storage Engine (ESE, Jet Blue)'
 Example: 'Subclassing CommandButton control to create BackColor property'
 Function: 'waveOutSetVolume'
 Function: 'MAPISendDocuments'
Function group: 'Simple MAPI'
 Function: 'NetScheduleJobDel'
Function group: 'Network Management'
Google
Advertise here!