NameHash Class Reference

A file-based Hash table for strings. More...

#include <NameHash.h>

Classes
class	Entry
	One entry in the NameHash. More...
class	Iterator
	Iterator over names in the hash. More...

Public Member Functions
	NameHash (FileAllocator &fa, FileOffset anchor)
	Constructor. More...
void	init (uint32_t ht_size=1009)
	Create a new hash table of given size. More...
void	reattach ()
	Attach to existing hash table Exceptions GenericException on error. More...
bool	insert (const stdString &name, const stdString &ID_txt, FileOffset ID)
	Insert name w/ ID. More...
Entry *	find (const stdString &name)
	Locate name and obtain its ID. More...
Iterator *	iterator ()
	Start iterating over all entries (in table's order). More...
void	showStats (FILE *f)
	Generate info on table fill ratio and list length.

Static Public Attributes
static const uint32_t	anchor_size = 8
	anchor size

Friends
class	PrivateIterator

Detailed Description

A file-based Hash table for strings.

Beginning at the 'anchor' position in the file, NameHash deposits the start offset of the hash table and the number of table entries.

Each hash table entry is a file offset that points to the beginnig of the NameHash::Entry list for that hash value.

One NameHash entry on the disk is stored like this:

*      long next
*      long ID
*      short length of name
*      short length of ID_txt
*      char  name[]   // Stored without the delimiting'\0' !!
*      char  ID_txt[] // Stored without the '\0' !!
*  

ID_txt might be "", but the name can never be empty.

Constructor & Destructor Documentation

NameHash::NameHash	(	FileAllocator &	fa,
		FileOffset	anchor
	)

Constructor.

Parameters

fa,:	The File allocator
anchor,:	The NameHash will deposit its root pointer there. Caller needs to assert that there are anchor_size bytes available at that location in the file.

Member Function Documentation

Entry* NameHash::find

(

const stdString &

name

)

Locate name and obtain its ID.

Returns

Returns NameInfo or 0 if nothing found. Receiver must delete.

Exceptions

GenericException

on internal error.

void NameHash::init

(

uint32_t

ht_size = 1009

)

Create a new hash table of given size.

Parameters

ht_size

determines the hash table size and should be prime.

Exceptions

GenericException

on error.

bool NameHash::insert	(	const stdString &	name,
		const stdString &	ID_txt,
		FileOffset	ID
	)

Insert name w/ ID.

Returns

True if a new entry was generated, false if an existing entry for that name was updated with possibly new information.

Exceptions

GenericException

on error.

Iterator* NameHash::iterator

(

)

Start iterating over all entries (in table's order).

Returns

Returns iterator. Might not be 'valid'. Caller must delete.

Exceptions

GenericException

on error.

void NameHash::reattach

(

)

Attach to existing hash table

Exceptions

GenericException

on error.

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

• /home/malitsky/projects/epics-archiver/sourceforge/trunk/ea4-cpp/include/common/storage/NameHash.h