Blob Basics
The final East type to cover is the blob. A blob is just bytes of data, and Elara uses blobs to represent computer files. These might contain data in text, CSV or Excel formats. Or they might contain docker images for usage in Elara's custom task executor. Blobs add an extra layer of flexibility to the Elara platform.
Blob values and type
The East type for blobs is BlobType.
The EDK accepts standard JavaScript Uint8Array objects as values for BlobType.
You may also use a NodeJS Buffer, which is a subclass of Uint8Array.
| East type | Example value (JavaScript) | East object notation |
|---|---|---|
BlobType | new Uint8Array() | 0x |
BlobType | new Uint8Array([1, 1, 3, 7]) | 0x01030307 |
While you can use NodeJS functionality to load files and include blob values in your solution template (for example inside expressions), it is preferable to upload large files to writeable BlobType streams seperately.
Basic operations on blobs
You can get the number of bytes in a blob with Size.
You can also convert between East's built-in strings and UTF-8 encoded binary data (which includes ASCII).
| East function | Description | Example usage | Result |
|---|---|---|---|
Size | Get the number of bytes in a blob | Size(new Uint8Array[97, 98, 99]) | 3 |
Utf8Encode | Convert a string to a blob using UTF-8 encoding | Utf8Encode("abc") | 0x616263 |
Utf8Decode | Convert a blob to a string assuming UTF-8 encoding | Utf8Decode(new Uint8Array[97, 98, 99]) | "abc" |
East is not designed for the direct manipulation of binary data, and does not have utilities for the deep inspection or encoding/decoding of custom binary formats. Blobs are a primitive type – they are atomic values as far as East is concerned.
Equality and ordering
Two blobs are equal if they contain exactly the same bytes.
Ordering of blobs is defined lexically. The first bytes are compared, then the second, until the end is reached. If one blob is the "prefix" of another, then it is lesser.
Representation
Blobs are represented in East's canonical JSON representation as JSON arrays containing numbers between 0 and 255, for the value of each byte.
They are printed by Print as 0x followed by the hexadecimal representation of the data.
(Take care not to accidentally Print a large blob, as the resulting string could be huge.)
Next steps
Continue to the next tutorial to understand how to convert between blobs and strings using East and Elara.