Using Advanced Installer DLL with Delphi

ONLINECAST

2 min read

·

02-09-2024

15

0

Share

Using Advanced Installer DLLs with Delphi: A Practical Guide

Delphi developers often need to interact with external libraries to enhance their applications. One such library is the Advanced Installer DLL, which provides powerful features for managing licensing and other installation-related aspects. This article will guide you through using the Advanced Installer DLL in your Delphi applications, focusing on the GetPropertyValue function, a key component for accessing license information.

Understanding the GetPropertyValue Function

The GetPropertyValue function is a vital part of the Advanced Installer DLL, allowing you to retrieve specific license properties. It takes three parameters:

1. propertyName: A string representing the name of the licensing property you want to retrieve.
2. result: A pointer to a WideString variable where the retrieved property value will be stored.
3. resultLen: A pointer to a DWORD variable that holds the size of the buffer pointed to by result. This parameter is crucial for managing memory allocation and preventing access violations.

Common Error Handling: ERROR_MORE_DATA (234)

The GetPropertyValue function returns an integer value indicating success or failure. One common error code is ERROR_MORE_DATA (234), which signals that the provided buffer is too small to hold the entire value and terminating null character.

Delphi Implementation with Error Handling

function GetPropertyValue(propertyName : LPCWSTR; Result : PLPWSTR; ResultLen : PDWORD64):Int32; stdcall; external DLLDirectory;

procedure TForm3.btn2Click(Sender: TObject);
Var
  asReturn : PWideString;
  intSize : DWORD64;
  TestValue : LPCWSTR;
  theint : Integer;
begin
  TestValue := LPCWSTR('TrialName');
  // Allocate memory for the result buffer
  GetMem(asReturn, 256); // Allocate 256 bytes for the result buffer
  intSize := 256; // Set the buffer size

  theint := GetPropertyValue(TestValue, asReturn, @intSize);

  // Handle the return value and potential buffer resizing
  if theint = 234 then begin
    // The buffer was too small. Allocate more memory and try again.
    GetMem(asReturn, intSize); // Resize the buffer to the required size
    theint := GetPropertyValue(TestValue, asReturn, @intSize);
  end;

  // Process the retrieved property value
  if theint = 0 then begin 
    // Property value retrieved successfully
    ShowMessage(PWideChar(asReturn)^); // Display the retrieved value
  end else begin
    // Handle other error scenarios
    ShowMessage('Error retrieving property value: ' + theint.ToString);
  end;

  // Release allocated memory
  FreeMem(asReturn);
end;

Explanation:

1. Memory Allocation: The code allocates initial memory for the asReturn buffer using GetMem. The initial size (256 bytes) should be enough for most cases.
2. Error Handling: After the first call to GetPropertyValue, the code checks for ERROR_MORE_DATA. If detected, it dynamically resizes the buffer using GetMem to the required size (provided in intSize) and calls GetPropertyValue again.
3. Value Processing: The code then handles the returned value. If theint is 0, the property value is retrieved successfully and can be displayed. Other error scenarios can be addressed accordingly.
4. Memory Release: Finally, the code releases the allocated memory using FreeMem to prevent memory leaks.

Additional Notes:

• Advanced Installer Documentation: Refer to the Advanced Installer documentation for a complete list of available properties and their specific usage.
• Error Handling: It's crucial to implement robust error handling to ensure your application functions correctly in all scenarios.
• Memory Management: Always release allocated memory after use to prevent memory leaks and improve application stability.

By following this guide and understanding the important aspects of the GetPropertyValue function, you can effectively integrate the Advanced Installer DLL into your Delphi applications to manage licensing information and enhance your application's functionality.