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Version: 20 R6

Blob

The Blob class lets you create and manipulate blob objects (4D.Blob).

Summary

4D.Blob.new() : 4D.Blob
4D.Blob.new( blobScal : Blob ) : 4D.Blob
4D.Blob.new( blobObj : 4D.Blob ) : 4D.Blob

creates a new 4D.Blob object optionally encapsulating a copy of the data from another blob (scalar blob or 4D.Blob)
.size : Real
returns the size of a 4D.Blob, expressed in bytes.
.slice() : 4D.Blob
.slice( start : Real ) : 4D.Blob
.slice( start : Real; end : Real ) : 4D.Blob

creates and returns a 4D.Blob that references data from a subset of the blob on which it's called. The original blob is not altered.

4D.Blob.new()

History
ReleaseChanges
19 R2Added

4D.Blob.new() : 4D.Blob
4D.Blob.new( blobScal : Blob ) : 4D.Blob
4D.Blob.new( blobObj : 4D.Blob ) : 4D.Blob

ParameterTypeDescription
blobBlob or 4D.Blob->Blob to copy
Result4D.Blob<-New 4D.Blob

Description

4D.Blob.new creates a new 4D.Blob object optionally encapsulating a copy of the data from another blob (scalar blob or 4D.Blob).

If the blob parameter is omitted, the method returns an empty 4D.Blob.

.size

.size : Real

Description

The .size property returns the size of a 4D.Blob, expressed in bytes.

.slice()

History
ReleaseChanges
19 R2Added

.slice() : 4D.Blob
.slice( start : Real ) : 4D.Blob
.slice( start : Real; end : Real ) : 4D.Blob

ParameterTypeDescription
startReal->index of the first byte to include in the new 4D.Blob.
endReal->index of the first byte that will not be included in the new 4D.Blob
Result4D.Blob<-New 4D.Blob

Description

.slice() creates and returns a 4D.Blob that references data from a subset of the blob on which it's called. The original blob is not altered.

The start parameter is an index into the blob indicating the first byte to include in the new 4D.Blob. If you specify a negative value, 4D treats it as an offset from the end of the blob toward the beginning. For example, -10 would be the 10th from last byte in the blob. The default value is 0. If you specify a value for start that is larger than the size of the source blob, the returned 4D.Blob's size is 0, and it contains no data.

The end parameter is an index into the blob indicating the first byte that will not be included in the new 4D.Blob (i.e. the byte exactly at this index is not included). If you specify a negative value, 4D treats it as an offset from the end of the blob toward the beginning. For example, -10 would be the 10th from last byte in the blob. The default value is the size of the blob.

Example

var $myBlob : 4D.Blob

// Store text in a 4D.Blob
CONVERT FROM TEXT("Hello, World!"; "UTF-8"; $myBlob)
$is4DBlob:=OB Instance of($myBlob; 4D.Blob); //True

$myString:=Convert to text($myBlob; "UTF-8")
// $myString contains "Hello, World!"

// Create a new 4D.Blob from $myBlob
$myNewBlob:=$myBlob.slice(0; 5)

$myString:=Convert to text($myNewBlob; "UTF-8")
// $myString contains "Hello"