EvalContext Class Reference

#include <Expression.h>

List of all members.

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Detailed Description

Context for use in evaluating an expression.

Before evaluating an expression, create an EvalContext to describe the actual evaluation environment.

Currently, the only property of an EvalContext is a single input tuple (which must match the TupleDescription in the ExprContext specified when the expression was originally parsed).

Note that creating an EvalContext is (by design) expensive since an EvalContext contains an EStringPool; create only one EvalContext for many evaluation and use reset() to clear the context each time.

Public Member Functions
	EvalContext (unsigned int num_tuples=1, unsigned int pool_size=EStringPool::DEFAULT_INITIAL_SIZE)
	Constructor.
void	reset ()
	Resets the evaluation context.
void	setTuple (const void *tuple)
	Sets the input tuple.
void	setTuple (unsigned int index, const void *tuple)
	Sets an input tuple.
const char *	getTuple (unsigned int index=0) const
	Returns the input tuple.
char *	alloc (unsigned int size) const
	Allocates memory from the string pool.
EStringPool &	getPool () const
	Returns the string pool contained within this context.

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Constructor & Destructor Documentation

EvalContext::EvalContext (  unsigned int  num_tuples = 1, unsigned int  pool_size = EStringPool::DEFAULT_INITIAL_SIZE )

Constructor. Parameters: num_tuples  the number of tuples contained in the EvalContext pool_size  the initial size of the memory pool to use for string data

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Member Function Documentation

char* EvalContext::alloc (  unsigned int  size  )  const

Allocates memory from the string pool. This memory remains usable only until the context is reset.

EStringPool& EvalContext::getPool (   )  const

Returns the string pool contained within this context.

const char* EvalContext::getTuple (  unsigned int  index = 0  )  const

Returns the input tuple.

void EvalContext::reset (   )

Resets the evaluation context. Should be called after every evaluation. This resets the memory pool and hence invalidates any memory allocated with alloc.

void EvalContext::setTuple (  unsigned int  index, const void *  tuple )

Sets an input tuple.

void EvalContext::setTuple (  const void *  tuple  )

Sets the input tuple.

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The documentation for this class was generated from the following file:

• Expression.h

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