NBS_GET_VALUE

Get a byte array from a slice of a primitive item associated with the specified identifier

Description:

Check that the ID is not NIL and that it pertains to a primitive item.

Check that the offset into the data is not negative.

Repeat

{

Read the modified count for this item.

Copy as many bytes as there is room for in the user’s buffer from the noticeboard starting

at the specified offset and return the actual number of bytes in the item.

Read the modified count for this item once more.

}

Until time out or the two modified counts are equal and even

(which means that the values were not updated whilst they were being read).

If CHECK_MODIFY is FALSE, the item’s modified count is not checked at all and a timeout cannot occur.

If the specified offset is greater than the current size of the item’s data, no error status will be returned and no data will be copied, but the returned number of bytes (ACTBYTES) will be less than the offset (OFFSET) and this case should always be checked for.

Invocation

(Int) = NBS_GET_VALUE (ID,OFFSET,MAXBYTES,BYTE_ARRAY,ACTBYTES,STATUS)

Arguments

ID = INTEGER (Given)
Identifier of the item from which thew value is to be got.
OFFSET = INTEGER (Given)
Byte offset into item data.
MAXBYTES = INTEGER (Given)
Size in bytes of the user’s buffer.
BYTE_ARRAY = BYTE(∗) (Returned)
User’s buffer into which bytes will be got.
ACTBYTES = INTEGER (Returned)
Actual number of values associated with the item. This may be greater than OFFSET + MAXBYTES but no more than MAXBYTES bytes will be copied into the user’s buffer.
STATUS = INTEGER (Given and returned)
The global status. Possible return values are,
NBS__NILID NIL ID

NBS__NOTPRIMITIVE Item is not primitive

NBS__BADOFFSET Negative offset specified

NBS__TIMEOUT Timeout awaiting valid data