Reads a chunk of bytes from the BLOB accessible through this into blob.
| this |
a BlobOp |
| blob |
a Blob to read data to |
| offset |
offset to read from the start of the blob (starts at 0) |
| size |
maximum number of bytes to read. |
|
the number of bytes actually read. In case of error, -1 is returned and the provider should have added an error to the connection. |