Cpl::Persistent::IndexedEntryReader Class Reference

This abstract class defines interface for reading/retrieve 'entries' from a a collection of entries (i.e. More...

Detailed Description

This abstract class defines interface for reading/retrieve 'entries' from a a collection of entries (i.e.

read an entry from a IndexedEntryRecord).

From a logical perspective, 'entries' are stored in a Ring Buffer. The Ring Buffer can be 'traversed' from the either end (i.e. oldest to newest, or newest to oldest).

Each entry that is stored has an 'index' value associated with it. This 'index' is used to uniquely identify each entry (even across overwritten entries) and it is used to identify the relative age between the entries.

NOTE: ALL entries (for a given IndexEntryRecord) must be the same fixed length.

NOTE: This interface/class is NOT THREAD SAFE and should only be 'used' from the Record Server's thread.

#include <IndexedEntryReader.h>

Classes
struct	EntryMarker_T
	This structure define an 'marker' that identifies an entry's location in persistent media. More...

Public Member Functions
virtual bool	getLatest (Payload &dst, EntryMarker_T &entryMarker) noexcept=0
	This method reads/retrieves the latest entry (from the list of Indexed Entries) stored in the persistent media.
virtual bool	getNext (uint64_t newerThan, const EntryMarker_T beginHereMarker, Payload &dst, EntryMarker_T &entryMarker) noexcept=0
	This method walks the entire 'list of entries' and returns the next newer entry as specified by the 'newerThan' value.
virtual bool	getPrevious (uint64_t olderThan, const EntryMarker_T beginHereMarker, Payload &dst, EntryMarker_T &entryMarker) noexcept=0
	This method is similar to getNext(), except that it returns the next oldest entry.
virtual bool	getByBufferIndex (size_t bufferIndex, Payload &dst, EntryMarker_T &entryMarker) noexcept=0
	This method can be used to read an entry by its 'buffer index'.
virtual size_t	getMaxIndex () const noexcept=0
	This method returns the maximum allowed 'bufferIndex' when calling getByIndex().
virtual	~IndexedEntryReader ()
	Virtual destructor.

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Class Documentation

Cpl::Persistent::IndexedEntryReader::EntryMarker_T

struct Cpl::Persistent::IndexedEntryReader::EntryMarker_T

This structure define an 'marker' that identifies an entry's location in persistent media.

Class Members
uint64_t	indexValue	The index/timestamp value for the entry (Note: This is NOT the 'Buffer Index' used by the getByBufferIndex() call)
size_t	mediaOffset	Offset, within a RegionMedia to the start of the Entry.

Constructor & Destructor Documentation

~IndexedEntryReader()

virtual Cpl::Persistent::IndexedEntryReader::~IndexedEntryReader ( )

inlinevirtual

Virtual destructor.

Member Function Documentation

getByBufferIndex()

virtual bool Cpl::Persistent::IndexedEntryReader::getByBufferIndex ( size_t  bufferIndex, Payload &  dst, EntryMarker_T &  entryMarker  )

pure virtualnoexcept

This method can be used to read an entry by its 'buffer index'.

The buffer index is a zero based index.

Returns true if the entry at 'bufferIndex' is a valid entry; else false is returned. Note: if 'bufferIndex' is out of range, false is returned.

NOTE: 'dst' is ALWAYS updated EVEN if no valid entry was 'found', basically 'dst' is used as a work buffer when traversing the list.

getLatest()

virtual bool Cpl::Persistent::IndexedEntryReader::getLatest ( Payload &  dst, EntryMarker_T &  entryMarker  )

pure virtualnoexcept

This method reads/retrieves the latest entry (from the list of Indexed Entries) stored in the persistent media.

The method is synchronous in that the method does not return until the entry has been 'read' from the persistent media.

Returns true if the latest entry is valid and has been read into 'dst'; else false is returned.

NOTE: When getLatest() returns false, this means there are NO entries stored.

NOTE: 'dst' is ALWAYS updated EVEN if no entry was 'found', basically 'dst' is used as a work buffer when traversing the list.

getMaxIndex()

virtual size_t Cpl::Persistent::IndexedEntryReader::getMaxIndex ( ) const

pure virtualnoexcept

This method returns the maximum allowed 'bufferIndex' when calling getByIndex().

getNext()

virtual bool Cpl::Persistent::IndexedEntryReader::getNext ( uint64_t  newerThan, const EntryMarker_T  beginHereMarker, Payload &  dst, EntryMarker_T &  entryMarker  )

pure virtualnoexcept

This method walks the entire 'list of entries' and returns the next newer entry as specified by the 'newerThan' value.

The traversal starts with the 'beginHereMarker' The method is synchronous in that the method does not return until the entry has been 'read' from the persistent media.

Returns true if the 'next' entry was found and has been read into 'dst'; else false is returned.

NOTE: 'dst' is ALWAYS updated EVEN if no entry was 'found', basically 'dst' is used as a work buffer when traversing the list.

getPrevious()

virtual bool Cpl::Persistent::IndexedEntryReader::getPrevious ( uint64_t  olderThan, const EntryMarker_T  beginHereMarker, Payload &  dst, EntryMarker_T &  entryMarker  )

pure virtualnoexcept

This method is similar to getNext(), except that it returns the next oldest entry.

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

• Cpl/Persistent/IndexedEntryReader.h