EDOBE XDOM PMML Bedienungsanleitung PDF herunterladen (Seite 73)

To avoid this problem, the CNKBuf must have at least as many rows as

the largest possible

CNKBufWriter::setRequestRows value plus the

largest possible

CNKBufReader::setRequestRows value (from the

multiple readers).

In order to determine whether this is true, it is necessary to know the

maximum number of rows a given

CNKProc will request from its input

or output.

CNKProc maintains two properties, the maximum number

of rows that will be requested from any of its inputs (accessed with

CNKProc::getNumRows), and the maximum number of rows spaces

that will be requested from any of its outputs (accessed with

CNKProc::getOutputNumRows).

The

getMinRowsToAvoidDeadlock and isDeadlockPossible methods

are used to check whether the

CNKBuf has enough rows to avoid this

deadlock.

getMinRowsToAvoidDeadlock() returns the minimum

number of rows that would be necessary to avoid deadlock.

isDeadlockPossible() returns true (non-zero) if this value is less than

CNKBuf::getNumRows().

isDeadlockPossible() is called from CNKBuf::init(), to check

whether a deadlock is possible. If it is, the error string is set for the

CNKBuf.

CNKBackingFileB

uf Methods

CNKBackingFileBuf is a subclass of CNKBuf that implements a data

buffer with an associated "backing file" on disk. Whereas

CNKMemoryBuf only supports procs that sequentially read their input

data,

CNKBackingFileBuf can be used with procs that need to scan

through their input data multiple times, or access it in random order.

CNKBackingFileBuf can be used in two ways,

1. as a file writer, or

2. as a file reader.

In the first case, the backing file is initially empty, the

CNKBackingFileBuf has a single buf writer, and zero or more

sequential buf readers. As the pipeline executes, the buf writer writes

data to the

CNKBackingFileBuf, which writes it to the backing file, and

also passes it to any sequential readers. In the second case, the

backing file is an existing data file, the

CNKBackingFileBuf has no buf

writer, and it has exactly one buf reader. As the pipeline executes, the

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