You can compress or decompress a Blob in OCL with SysSingleton.oclsingleton.Deflate when you need to transport compressed binary data, for example a SAML token in a URL.

Prerequisite

Set Eco.ExternalLateBound=true before calling this operation. The operation is accessed through SysSingleton.oclsingleton.

Operation

Deflate(bytes:Blob; inflate:Boolean):Blob

The bytes argument is the binary data to process. The inflate argument selects the direction:

Value	Result
false	Compress the input Blob.
true	Decompress (inflate) the input Blob.

The operation corresponds to the .NET DeflateStream functionality.

Compress text for URL transport

When your source is clear text, first convert it to a UTF-8 Base64 string and then to a Blob. Compress that Blob, convert the compressed result back to Base64, and URL-encode the Base64 value.

The following expression prepares XML for URL transport:

let compressedbase64=SysSingleton.oclsingleton.Deflate(xml.Replace('\r\n', ' ').Replace('\n', ' ').StringToBase64.Base64ToBlob,false).BlobToBase64 in
(
  SysSingleton.oclsingleton.UrlEncode(compressedbase64,false)
)

In this example:

1. Replace removes line breaks from xml by replacing them with spaces.
2. StringToBase64 produces a Base64 representation of the text, and Base64ToBlob creates the Blob required by Deflate.
3. Deflate(..., false) compresses the Blob.
4. BlobToBase64 makes the compressed binary result representable as text.
5. UrlEncode encodes that text so it can travel as a URL value.

Use the matching reverse sequence at the receiving end: URL-decode the value when applicable, convert the Base64 text to a Blob, call Deflate with true, and then convert the resulting Blob as required by the receiving code.

Decompress a Blob

Pass true as the second argument to inflate a previously compressed Blob. This example first decrypts a value, then inflates the decrypted Blob, and finally returns the result as Base64:

vAnswer:=SysSingleton.oclsingleton.Deflate(vCert.RSADecrypt(  vAnswer.Base64ToBlob),true).blobtobase64

Here, vAnswer.Base64ToBlob converts the incoming Base64 value to binary data. The example assumes that vCert.RSADecrypt(...) returns the compressed Blob expected by Deflate. The final BlobToBase64 converts the inflated binary result to Base64.

Choose the correct conversion

Use the conversion that matches the data you have and the data the next operation expects:

Situation	Conversion pattern
You have clear text and need a Blob for Deflate	'My text'.StringToBase64.Base64ToBlob
You have a compressed Blob and need text-safe representation	compressedBlob.BlobToBase64
You will put Base64 text in a URL	Apply SysSingleton.oclsingleton.UrlEncode(base64Value,false).

For details on text and Base64 conversion, see Documentation:OCLOperators StringToBase64. If you need to explicitly convert between strings and byte arrays, see Documentation:Encoding.

See also

• Documentation:SysSingleton.UrlEncode
• Documentation:OCLOperators StringToBase64
• Documentation:Encoding
• Documentation:Attribute.Eco.BlobType