TChilkatCache Delphi ActiveX Reference Documentation

TChilkatCache

Importing the Chilkat ActiveX into Delphi

Important: Whenever upgrading to a new version of Chilkat, make sure to re-imported ActiveX DLL into Delphi to regenerate the files described below.

Two things are required to use an ActiveX in Delphi:

  1. The ActiveX DLL needs to be registered via regsvr32 on the system where the Delphi application runs. See How To Register ActiveX DLLs for detailed information.
  2. The ActiveX component needs to be "imported". Use the Delphi Import Component Wizard to import the Chilkat type library. This creates the following files: Chilkat_v9_5_0_TLB.pas and Chilkat_v9_5_0_TLB.dcr. The Chilkat_v9_5_0_TLB.pas should be added to your project.

To import the Chilkat type library, do the following:

  1. In the Delphi RAD Studio, select the menu item "Component" --> "Import a Type Library".
  2. Find "Chilkat ActiveX v9.5.0" in the list and select it. This will only appear in the list if the ChilkatAx-9.5.0-win32.dll (or ChilkatAx-9.5.0-x64.dll) has been registered w/ regsvr32.
  3. Check the "Generate Component Wrappers" checkbox.
  4. Select a directory where the unit files (.pas and .dcr) will be generated.
  5. Select "Create Unit" and then "Finish".
  6. Add the .pas to your Delphi project.

To use a Chilkat ActiveX object in your Delphi code, add "Chilkat_v9_5_0_TLB" to the "uses" statement. For example:

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_v9_5_0_TLB;

Object Creation

var
obj: TChilkatCache;
...
begin
obj := TChilkatCache.Create(Self);
...
// When finished, free the object instance.
obj.Free();

Properties

property DebugLogFilePath: WideString

If set to a file path, causes each Chilkat method or property call to automatically append it's LastErrorText to the specified log file. The information is appended such that if a hang or crash occurs, it is possible to see the context in which the problem occurred, as well as a history of all Chilkat calls up to the point of the problem. The VerboseLogging property can be set to provide more detailed information.

This property is typically used for debugging the rare cases where a Chilkat method call hangs or generates an exception that halts program execution (i.e. crashes). A hang or crash should generally never happen. The typical causes of a hang are:

  1. a timeout related property was set to 0 to explicitly indicate that an infinite timeout is desired,
  2. the hang is actually a hang within an event callback (i.e. it is a hang within the application code), or
  3. there is an internal problem (bug) in the Chilkat code that causes the hang.

property LastBinaryResult: OleVariant readonly

Introduced in version 9.5.0.52

The binary data returned by the last (binary data returning) method called. Only available if Chilkat.Global.KeepBinaryResult is set to 1. This provides a means for obtaining large varbinary results in the SQL Server environment (where limitations exist in getting large amounts of data returned by method calls, but where temp tables can be used for binary properties).

property LastErrorHtml: WideString readonly

Provides information in HTML format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

property LastErrorText: WideString readonly

Provides information in plain-text format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

Concept of LastErrorText

LastErrorText Standard Information

property LastErrorXml: WideString readonly

Provides information in XML format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

property LastEtagFetched: WideString readonly

The ETag of the last item fetched from cache.

property LastExpirationFetched: TDateTime readonly

This property is deprecated. It will be removed in a future version.

Expiration date/time of the last item fetched from cache.

property LastExpirationFetchedStr: WideString readonly

Expiration date/time of the last item fetched from cache in RFC822 string format.

property LastHitExpired: Integer readonly

1 if the LastExpirationFetched is before the current date/time. Otherwise 0.

property LastKeyFetched: WideString readonly

The key of the last item fetched from cache. (For web pages, the key is typically the canonicalized URL. Otherwise, the key is a unique identifer used to access the cached item.)

property LastMethodSuccess: Integer

Introduced in version 9.5.0.52

Indicate whether the last method call succeeded or failed. A value of 1 indicates success, a value of 0 indicates failure. This property is automatically set for method calls. It is not modified by property accesses. The property is automatically set to indicate success for the following types of method calls:

  • Any method that returns a string.
  • Any method returning a Chilkat object, binary bytes, or a date/time.
  • Any method returning a standard boolean status value where success = 1 and failure = 0.
  • Any method returning an integer where failure is defined by a return value less than zero.

Note: Methods that do not fit the above requirements will always set this property equal to 1. For example, a method that returns no value (such as a "void" in C++) will technically always succeed.

property LastStringResult: WideString readonly

Introduced in version 9.5.0.52

The string return value of the last (string returning) method called. Only available if Chilkat.Global.KeepStringResult is set to 1. This provides a means for obtaining large string results in the SQL Server environment (where limitations exist in getting long strings returned by method calls, but where temp tables can be used for string properties).

Long Strings Returned by ActiveX Methods in SQL Server

property LastStringResultLen: Integer readonly

Introduced in version 9.5.0.53

The length, in characters, of the string contained in the LastStringResult property.

property Level: Integer

The number of directory levels in the cache. Possible values are:

0: All cache files are in a single directory (the cache root).

1: Cache files are located in 256 sub-directories numbered 0 .. 255 directly under the cache root.

2: There are two levels of sub-directories under the cache root. The 1st level has 256 sub-directories numbered 0 .. 255 directly under the cache root. The 2nd level allows for up to 256 sub-directories (0..255) under each level-1 directory. Cache files are stored in the leaf directories.

property NumRoots: Integer readonly

The number of root directories composing the cache. A typical multi-root cache would place each root on a separate hard drive.

property VerboseLogging: Integer

If set to 1, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is 0. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.

property Version: WideString readonly

Version of the component/library, such as "9.5.0.63"

Methods

procedure AddRoot(path: WideString);

Must be called once for each cache root. For example, if the cache is spread across D:\cacheRoot, E:\cacheRoot, and F:\cacheRoot, an application would setup the cache object by calling AddRoot three times -- once with "D:\cacheRoot", once with "E:\cacheRoot", and once with "F:\cacheRoot".

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function DeleteAll(): Integer;

Deletes all items in the cache. This method completely clears the cache. All files in the cache are deleted. (If the cache is multi-level, existing sub-directories are not deleted.)

Returns the number of items (i.e. cache files) deleted.

function DeleteAllExpired(): Integer;

Deletes all expired items from the cache.

Returns the number of items (i.e. cache files) deleted.

function DeleteFromCache(key: WideString): Integer;

Deletes a single item from the disk cache. Returns 0 if the item exists in cache but could not be deleted. Otherwise returns 1.

Returns 1 for success, 0 for failure.

function DeleteOlder(dateTime: TDateTime): Integer;

This method is deprecated. It will be removed in a future version.

Deletes all items older than a specified date/time.

Returns the number of items (i.e. cache files) deleted. Returns -1 on error.

function DeleteOlderDt(dateTime: TCkDateTime): Integer;

The same as DeleteOlder, except the dateTime is passed as a CkDateTime.

function DeleteOlderStr(dateTimeStr: WideString): Integer;

The same as DeleteOlder, except the dateTimeStr is passed as a date/time in RFC822 format.

function FetchFromCache(key: WideString): OleVariant;

Fetches an item from cache.

The key may be any length and may include any characters. It should uniquely identify the cached item. (No two items in the cache should have the same key.)

Returns a zero-length byte array (as an OleVariant) on failure.
An empty array will have a VarArrayHighBound of -1 meaning 0 elements.

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function FetchText(key: WideString): WideString;

Fetches a text item from the cache and returns it's text content.

The key may be any length and may include any characters. It should uniquely identify the cached item. (No two items in the cache should have the same key.)

Returns a zero-length WideString on failure

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function GetEtag(key: WideString): WideString;

Returns the eTag for an item in the cache.

Returns a zero-length WideString on failure

function GetExpiration(key: WideString): TDateTime;

This method is deprecated. It will be removed in a future version.

Returns the expire date/time for an item in the cache.

function GetExpirationDt(key: WideString): TCkDateTime;

Returns the expiration date/time for an item in the cache as a CkDateTime object.

Returns nil on failure

function GetExpirationStr(url: WideString): WideString;

Returns the expiration date/time for an item in the cache in RFC822 string format.

Returns a zero-length WideString on failure

function GetFilename(key: WideString): WideString;

Returns the absolute file path of the cache file associated with the key.

Returns a zero-length WideString on failure

function GetRoot(index: Integer): WideString;

Returns the directory path of the Nth cache root. (Indexing begins at 0.)

Returns a zero-length WideString on failure

function IsCached(key: WideString): Integer;

Returns 1 if the item is found in the cache, otherwise returns 0.

function SaveText(key: WideString; expireDateTime: TDateTime; eTag: WideString; itemTextData: WideString): Integer;

This method is deprecated. It will be removed in a future version.

Inserts or replaces an text item in the cache. The eTag is optional and may be set to a zero-length string. Applications may use it as a place to save additional information about the cached item. The key may be any length and may include any characters. It should uniquely identify the cached item. (No two items in the cache should have the same key.)

Returns 1 for success, 0 for failure.

function SaveTextDt(key: WideString; expireDateTime: TCkDateTime; eTag: WideString; itemTextData: WideString): Integer;

The same as SaveText, except the expire date/time is passed as a CkDateTime object.

Returns 1 for success, 0 for failure.

function SaveTextNoExpire(key: WideString; eTag: WideString; itemTextData: WideString): Integer;

Inserts or replaces an text item in the cache with no expiration date/time. The eTag is optional and may be set to a zero-length string. Applications may use it as a place to save additional information about the cached item.

Returns 1 for success, 0 for failure.

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function SaveTextStr(key: WideString; expireDateTime: WideString; eTag: WideString; itemTextData: WideString): Integer;

The same as SaveText, except the expire date/time is passed as a string in RFC822 format.

Returns 1 for success, 0 for failure.

function SaveToCache(key: WideString; expireDateTime: TDateTime; eTag: WideString; itemData: OleVariant): Integer;

This method is deprecated. It will be removed in a future version.

Inserts or replaces an item in the cache. The eTag is optional and may be set to a zero-length string. Applications may use it as a place to save additional information about the cached item. (The Chilkat HTTP component, when caching a page, writes the eTag (entity-tag) from the HTTP response header to this field.)

The key may be any length and may include any characters. It should uniquely identify the cached item. (No two items in the cache should have the same key.)

Returns 1 for success, 0 for failure.

function SaveToCacheDt(key: WideString; expireDateTime: TCkDateTime; eTag: WideString; itemData: OleVariant): Integer;

The same as SaveToCache, except the expire date/time is passed as a CkDateTime object.

Returns 1 for success, 0 for failure.

function SaveToCacheNoExpire(key: WideString; eTag: WideString; itemData: OleVariant): Integer;

Inserts or replaces an item in the cache. The cached item will have no expiration. The eTag is optional and may be set to a zero-length string. Applications may use it as a place to save additional information about the cached item.

Returns 1 for success, 0 for failure.

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function SaveToCacheStr(key: WideString; expireDateTime: WideString; eTag: WideString; itemData: OleVariant): Integer;

The same as SaveToCache, except the expire date/time is passed in RFC822 string format.

Returns 1 for success, 0 for failure.

function UpdateExpiration(key: WideString; expireDateTime: TDateTime): Integer;

This method is deprecated. It will be removed in a future version.

Updates the expire date/time for a cached item.

Returns 1 for success, 0 for failure.

function UpdateExpirationDt(key: WideString; expireDateTime: TCkDateTime): Integer;

The same as UpdateExpiration, except the expireDateTime is passed as a CkDateTime.

Returns 1 for success, 0 for failure.

function UpdateExpirationStr(key: WideString; expireDateTime: WideString): Integer;

The same as UpdateExpiration, except the expireDateTime is passed in RFC822 string format.

Returns 1 for success, 0 for failure.