~~Title: Blob ~~
<pageheader/>

A **Blob** object represents a chunk of binary data. Scripting languages like //VBScript// and //JScript// have no built-in support for binary data - this object can be used to allocate a chunk of memory and manipulate it in a similar way to low-level languages like C. You can use **Blob** objects in conjunction with the **[[file|File]]** object to read or write binary data from or to disk files.

**Blob** objects are convertible to and from two types of ActiveX arrays - a //SAFEARRAY// of type //VT_UI1// (known as an **array**) and a //SAFEARRAY// of type //VT_VARIANT//, with each variant holding a //VT_UI1// (known as a **VB array**). You can initialize a **Blob** with either of these two types of array (either when creating it via the **DOpusFactory.Blob** method or with the **Blob.CopyFrom** method), and you can also convert a **Blob** back to an array with the **ToArray** and **ToVBArray** methods. Support for these array types is dependent on the scripting language.



You can read and write individual bytes within the **Blob** by indexing the byte offset starting from 0. For example, //my_blob(5) = 128// would set the value of the sixth byte in the blob to 128.


<commandtable columns="3" id="cmdtable_1">
$$ Property Name
$$ Return Type
$$ Description
$$ size
$$ //object://**[[filesize|FileSize]]** 
$$ Returns a **[[filesize|FileSize]]** object representing the size of this **Blob** in bytes.
</commandtable>


<commandtable columns="4" id="cmdtable_2">
$$ Method Name
$$ **Arguments**
$$ Return Type
$$ Description
$$ Compare
$$ <Blob:source>\\
<int:to>\\
<int:from>\\
<int:size>
$$ //int//
$$ Compares the contents of this **Blob** against another **Blob** (or array). By default the entire contents of the two blobs are compared. The optional parameters that let you configure the operation are:

to - specifies the byte offset within this **Blob** to compare against. Defaults to 0.\\
from - specifies the byte offset within the source **Blob** to compare with. Defaults to 0.\\
size - specifies the number of bytes to compare. Defaults to the full size of the source **Blob**.

The return value is **0** if the two blobs are the same. A value of **-1** indicates this blob is less than the other blob, and **1** indicates this blob is greater than the other blob.
$$ CopyFrom
$$ <Blob:source>\\
<int:to>\\
<int:from>\\
<int:size>

//or//\\
 \\
<string>\\
<type>
$$ //none//
$$ Copies data from the source **Blob** (or array) into this **Blob**. By default the entire contents of the source **Blob** will be copied over the top of this one. The optional parameters that let you configure the operation are:

to - specifies the byte offset within this **Blob** to copy to. Defaults to 0.\\
from - specifies the byte offset within the source **Blob** to copy from. Defaults to 0.\\
size - specifies the number of bytes to copy. Defaults to the full size of the source **Blob**.

As well as copying from another **Blob**, you can use this method to initialise a **Blob** from a string. By default the **Blob** will be set to the Unicode form of the string; if you pass **"utf8"** as the second parameter it will initialise the **Blob** with the UTF8-encoded form of the string.

If this **Blob** is not currently large enough to contain the copied data it will be resized automatically.\\
$$ Find
$$ <Blob:search>\\
<int:from>\\
<int:size>
$$ //object://**[[filesize|FileSize]]** 
$$ Searches the contents of this **Blob** for the data contained in another **Blob** (or array). By default the entire contents of this **Blob** are searched. The optional **from** parameter lets you specify the starting position for the search, and the optional **size** parameter lets you specify the length of data in this Blob to search through.\\
The return value is -1 if the search data were not found, otherwise the offset from the start of the **Blob** data is returned.
$$ Free
$$ //none//
$$ //none//
$$ Frees the memory associated with this **Blob** and resets its size to 0.
$$ Init
$$ //none//
$$ //none//
$$ Initialises the contents of the **Blob** (every byte within the blob will be set to 0). Equivalent to //Set(0)//.
$$ Resize
$$ <int:size>
$$ //none//
$$ Resizes the **Blob** to the specified number of bytes.
$$ Reverse
$$ //none//
$$ //none//
$$ Reverses the contents of the **Blob**.
$$ Set
$$ <byte:value>\\
<int:to>\\
<int:size>
$$ //none//
$$ Sets the contents of the **Blob** to the specified byte value (every byte within the blob will be set to that value). By default the whole **Blob** will be affected. The option //to// parameter lets you specify a byte offset to start at, and the optional //size// parameter lets you control the number of bytes affected.
$$ ToArray
$$ <int:from>\\
<int:size>
$$ SAFEARRAY of\\
VT_UI1
$$ Converts the contents of this **Blob** to a //SAFEARRAY// of type //VT_UI1//. By default the entire contents of the **Blob** will be copied to the array. The optional parameters that let you configure the operation are:\\
from - specifies the byte offset within the source **Blob** to copy from. Defaults to 0.\\
size - specifies the number of bytes to copy. Defaults to the full size of the source **Blob**.
$$ ToVBArray
$$ <int:from>\\
<int:size>
$$ SAFEARRAY of\\
VT_VARIANT
$$ Converts the contents of this **Blob** to a //SAFEARRAY// of type //VT_VARIANT//. Each variant in the array contains a //VT_UI1//. By default the entire contents of the **Blob** will be copied to the array. The optional parameters that let you configure the operation are:

from - specifies the byte offset within the source **Blob** to copy from. Defaults to 0.\\
size - specifies the number of bytes to copy. Defaults to the full size of the source **Blob**.
</commandtable>