Encapsulate an environment block in a class

[delphidabbler]

I really don't like how messy the TPJEnvironmentVars.CreateBlock method is.

It would be much better to encapsulate the whole messy business in a separate class and provide a Memory property that points to the required block.

TPJEnvironmentVars.CreateBlock could then be overridden to accept this new object as a parameter if it was thought necessary to retain such a method. The old TPJEnvironmentVars.CreateBlock could then be deprecated.

[delphidabbler]

Issue #12 proposes additional (class?) methods for this class.

[delphidabbler]

Possible prototype:

type
  TPJEnvironmentBlock = class
  public
    constructor Create;
    destructor Destroy; override;
    procedure AddEnvVar(EV: TPJEnvironmentVar); overload;
    procedure AddEnvVar(Name, Value: string); overload;
    procedure AddEnvVars(EVS: TPJEnvironmentVarArray); overload;
    procedure AddEnvVars(SL: TStrings); overload;
    procedure Build;
    property IsUnicode: Boolean; default True; // read write
    property IncludeProcessEnvVars: Boolean; default True; // read write
    property IsDirty: Boolean; // read only
    property Memory: Pointer; // read only
    property Size: Cardinal;  // size in bytes - read only
  end;

Notes:

• Class can generate either an ANSI or Unicode environment block since both are supported even in Unicode Windows. IsUnicode property determines the type.
• ANSI blocks use the current default code page.
• There are several methods to add single or multiple environment variables.
• The IncludeProcessEnvVars property determines whether the current process' environment variables are included in the environment block.
• Once all environment variables have been added the Build method must be called to construct the environment block.
• The Memory property points to a block of memory containing the environment block. This is nil until Build is called.
• The Size property gives the size of the environment block pointed to by Memory. Size is 0 until Build is called. The size is in bytes, not characters.
• The IsDirty property is True if any changes have been made since Build was last called. In this case the environment block pointed to by Memory, and the Size property, are out of sync with the changes and Build must be called to recreate the block.
• For a ANSI block Size must not exceed 32,767 bytes. An exception will be raised when Build is called if this is the case.

[delphidabbler]

There are limits on environment block sizes according to Microsoft on older operating systems. Here's what they say:

Windows Server 2003 and Windows XP: The maximum size of the environment block for the process is 32,767 characters. Starting with Windows Vista and Windows Server 2008, there is no technical limitation on the size of the environment block.

I'm assuming this limit also applies to Windows 2000.

As noted in a previous comment, the 32,767 also applies to ANSI blocks.

I can think of 2 ways to handle this limitation. Either detect the OS and raise an exception if the block is too large, or expose a function, say IsLargeBlock that returns true if the block size is greater than 32,767. If the 2nd approach is used then it's up to the user to check the OS if necessary.