EDOBE XDOM PMML Manuel d'utilisateur télécharger pdf (Page 88)

1. Request input and output data rows.

The

execute() method must call CNKBufReader::setRequestRows to

request access to its input data, and call

CNKBufWriter::setRequestRows to allocate space for its output data.

It is important to note that a

CNKProc cannot assume that any other

parts of the pipeline are being processed in parallel. Therefore, if

CNKBufReader::setRequestRows has been called to request access to

a certain number of rows, and these rows are not yet ready (according

CNKBufReader::isReady()), then the execute() method must

simply return, waiting until it is called again later to see if the data is

ready. An execute method should never enter a wait loop, waiting for

some event to occur in some other part of the pipeline.

When a

CNKBuf is initialized via CNKBUF::init(), the row requests for

all its readers or writers are initialized to zero, so initially

CNKBufReader::isReady() and CNKBufWriter::isReady() will always

return true (non-zero) for all of the inputs and outputs of a

CNKProc.

When

execute() is called the first time, with zero rows available on

its inputs and outputs, it will need to call

setRequestRows to request

the appropriate number of input and output rows.

In many situations, this processing can be done by calling

CNKProc::executeRequestRows(). This utility method calls

setRequestRows on all of the inputs (requesting getNumRows() rows)

and outputs (requesting

getOutputNumRows() rows). Then, it calls

isReady() on all of the inputs and outputs, to check whether the

requests are satisfied. If all of the inputs and outputs are ready,

executeRequestRows returns the minimum number of rows available

on any of the inputs or outputs. This may be less than

getNumRows()

if one of the inputs has encountered an

EOF. If any of the inputs or

outputs is not ready, then this method returns

-1. If

executeRequestRows() returns less than zero, the execute method

should simply return, to wait for the input and output row requests to

be satisfied.

2. Process data.

The

execute() method must actually perform the data processing,

reading data from its inputs with methods such as

CNKBufReader::getDouble, and writing the resulting data to its

outputs with methods such as

CNKBufWriter::setDouble.

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EDOBE XDOM PMML Manuel d'utilisateur Page 88

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