Cpl::Json::ObjectDetector Class Reference

This helper class is used to determine when an entire Json object has been read from an input source. More...

Detailed Description

This helper class is used to determine when an entire Json object has been read from an input source.

This class does not read or store the incoming data - it simply inspect the provide data (one byte at time) and declares a JSON object when it see as match trailing '}' for the leading '{'

Usage:

Cpl::Io::File::Input fd("bob.txt");
ObjectDetector       detector;
 
while( fd.eof() == false )
{
    uint8_t buffer[256];
    int     bytesRead;
    if ( fd.read( buffer, sizeof(buffer), bytesRead ) )
    {
        size_t startPosition;
        size_t endPosition;
 
        if ( detector.scan( buffer, bytesRead, startPosition, endPosition ) )
        {
            // JSON object found.  
            // The initial '{' is at  'startPosition'
            // The final/closing '}' is at 'endPosition'
            // DO Something...
        }
    }
}

#include <ObjectDetector.h>

Public Member Functions
bool	scan (const void *inputStream, size_t numBytesToScan, size_t &startOffset, size_t &endOffset)
	Inspect 'numBytes' and returns true if a complete JSON object was found.
void	reset ()
	Resets the detector to being looking for a new JSON object.

Protected Types
enum	State_T {   eNOT_STARTED , ePLAIN , eQUOTED , eESCAPED ,   eFOUND }
	Detector state. More...

Protected Attributes
size_t	m_offset
	Current offset.
size_t	m_startOffset
	Offset of the initial '{'.
size_t	m_braceCount
	Number of '{' encountered.
State_T	m_state
	Quoted key/value state.

Member Enumeration Documentation

State_T

enum Cpl::Json::ObjectDetector::State_T

protected

Detector state.

Member Function Documentation

reset()

void Cpl::Json::ObjectDetector::reset

(

)

Resets the detector to being looking for a new JSON object.

scan()

bool Cpl::Json::ObjectDetector::scan	(	const void *	inputStream,
		size_t	numBytesToScan,
		size_t &	startOffset,
		size_t &	endOffset
	)

Inspect 'numBytes' and returns true if a complete JSON object was found.

The pointers 'startOffset' and 'endOffset' return the byte offset to the start and end of the found JSON object. The offset is based on the number of number consumed since the object was created or reset() was called.

NOTE: The class does NOT VALIDATE the JSON syntax. It ONLY finds starting and trailing curly braces. It assumes the JSON syntax and quoted character escaping semantics when searching for the trailing curly brace.

The method will ALWAYS return true if called after detecting a JSON object and set 'startOffset' and 'endOffset' to zero. Use the reset() method to restart/reuse the detector instance.

Member Data Documentation

m_braceCount

size_t Cpl::Json::ObjectDetector::m_braceCount

protected

Number of '{' encountered.

m_offset

size_t Cpl::Json::ObjectDetector::m_offset

protected

Current offset.

m_startOffset

size_t Cpl::Json::ObjectDetector::m_startOffset

protected

Offset of the initial '{'.

m_state

State_T Cpl::Json::ObjectDetector::m_state

protected

Quoted key/value state.

---

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

• Cpl/Json/ObjectDetector.h