casacore
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#include <SSMStringHandler.h>

Public Member Functions

 SSMStringHandler (SSMBase *aBase)
 Default constructor initializes last string bucket to -1.
 
 ~SSMStringHandler ()
 
 SSMStringHandler (const SSMStringHandler &)=delete
 Forbid copy constructor.
 
SSMStringHandleroperator= (const SSMStringHandler &)=delete
 Forbid assignment.
 
void setLastStringBucket (Int lastStringBucket)
 Set or get last string bucketnr.
 
Int lastStringBucket () const
 
void put (Int &bucketNr, Int &offset, Int &length, const String &string)
 Put a single string or an array of strings into a bucket.
 
void put (Int &bucketNr, Int &offset, Int &length, const Array< String > &string, Bool handleShape)
 
void putShape (Int &bucketNr, Int &offset, Int &length, const IPosition &aShape)
 Put a single string or an array of strings into a bucket.
 
void getShape (IPosition &aShape, Int bucket, Int &offset, Int length)
 Get the shape in the given bucket and offset.
 
void remove (Int bucketNr, Int offset, Int length)
 Remove data with the given length from a bucket.
 
void get (String &string, Int bucket, Int offset, Int length)
 Get a string or an array of strings.
 
void get (Array< String > &string, Int bucket, Int offset, Int length, Bool handleShape)
 
void flush ()
 Flush the currently used string bucket.
 
void init ()
 Initialize the StringHandler.
 
void resync ()
 Resynchronize (after a table lock was acquired).
 

Private Member Functions

void getBucket (uInt bucketNr, Bool isNew=False)
 Get the given bucket and make it current.
 
void getNewBucket (Bool doConcat)
 Get a new bucket and make it current.
 
void putData (Int length, const Char *data)
 Put the data with the given length at the end of the current bucket.
 
void getData (Int length, Char *data, Int &offset)
 Get the data with the given length from the curent bucket at the given offset.
 
void replace (Int bucketNr, Int offset, Int length, const String &string)
 Replace the current data with the new data.
 
void replace (Int bucketNr, Int offset, Int length, Int totalLength, const IPosition &aShape)
 
void replace (Int bucketNr, Int offset, Int length, Int totalLength, const Array< String > &string, Bool handleShape)
 
void replaceData (Int &offset, Int length, const Char *data)
 

Private Attributes

SSMBaseitsSSMPtr
 
Int itsCurrentBucket
 
Int itsLength
 
Int itsNDeleted
 
Int itsUsedLength
 
Int itsNextBucket
 
char * itsData
 
char * itsIntBuf
 
Bool isChanged
 
uInt itsIntSize
 
Int itsLastBucket
 
uInt itsStart
 

Detailed Description

Store strings in the Standard Storage Manager.

Intended use:

Internal

Review Status

Reviewed By:
UNKNOWN
Date Reviewed:
before2004/08/25
Test programs:
tSSMStringHandler

Prerequisite

Etymology

SSMStringHandler handles strings for the Standard Storage Manager.

Synopsis

Variable length strings cannot be stored in the data bucket. Only short (<8 characters) strings can be stored directly. Class SSMStringhandler is used by the SSM to store strings in so-called string buckets. A string bucket has the following layout:

  • The first Int is reserved to be used for the free bucket list.
  • itsUsedLength tells how many bytes have been used. Thus it tells the next free byte in the string part. In principle it always increases. Only if data are removed from the last part of the string part, it is decreased, thus the deleted part can be reused again.
  • itsNDeleted tells how many bytes of the string part are deleted (i.e. not used). Initially it is the length of the string part of the bucket (i.e. bucketsize minus 4 Ints). When a string is stored, its length is subtracted from itsNDeleted. When a string is removed, its length is added again. When the string part is deleted, the bucket is added to the free bucket list.
  • itsNextBucket tells the next bucket if the last entry in the bucket is continued in another bucket. Normally this field is -1 (meaning not continued), but long strings or string arrays might be continued in another bucket (and continued from there again).
  • The string part is a sequence of bytes containing the string data. When a value is to be stored, it will replace the current value if the new value is not longer. Otherwise the current value (if any) is deleted and the new value is appended to the end of the string part in the last bucket used.

    For a scalar string only its characters are stored. Its length (and bucketnr and offset in string bucket) are stored in the data bucket.
    A fixed length array is stored as an array of bytes. That byte array contains length-value pairs for each element of the array. The total length (and bucketnr and offset) are stored in the data bucket.
    A variable length array is stored as the shape, a flag, optionally followed by the string array as length-value pairs (as above). The shape consists of the nr of dimensions followed by the length of each dimension. The flag indicates if a string array is actually stored. It is not if only the shape of the array is set, but no data put yet.

SSMStringHandler keeps a copy of the current bucket in use to reduce the number of accesses to the bucket cache.

It also keeps the bucket number of the last bucket where data were added to. It tells which bucket to use when new data has to be stored.

Definition at line 118 of file SSMStringHandler.h.

Constructor & Destructor Documentation

◆ SSMStringHandler() [1/2]

casacore::SSMStringHandler::SSMStringHandler ( SSMBase * aBase)

Default constructor initializes last string bucket to -1.

◆ ~SSMStringHandler()

casacore::SSMStringHandler::~SSMStringHandler ( )

◆ SSMStringHandler() [2/2]

casacore::SSMStringHandler::SSMStringHandler ( const SSMStringHandler & )
delete

Forbid copy constructor.

Member Function Documentation

◆ flush()

void casacore::SSMStringHandler::flush ( )

Flush the currently used string bucket.

◆ get() [1/2]

void casacore::SSMStringHandler::get ( Array< String > & string,
Int bucket,
Int offset,
Int length,
Bool handleShape )

◆ get() [2/2]

void casacore::SSMStringHandler::get ( String & string,
Int bucket,
Int offset,
Int length )

Get a string or an array of strings.

The array must have the correct shape. handleShape will be True for variable shaped arrays indicating that the data are preceeded by the shape.

◆ getBucket()

void casacore::SSMStringHandler::getBucket ( uInt bucketNr,
Bool isNew = False )
private

Get the given bucket and make it current.

It first writes the current bucket if it has changed.
If isNew is True the bucket is new, so the Ints at its beginning do not have to be interpreted.

◆ getData()

void casacore::SSMStringHandler::getData ( Int length,
Char * data,
Int & offset )
private

Get the data with the given length from the curent bucket at the given offset.

If sets the offset to the byte after the data read. Continuation buckets are followed (and made current).

◆ getNewBucket()

void casacore::SSMStringHandler::getNewBucket ( Bool doConcat)
private

Get a new bucket and make it current.

If doConcat is True, the new bucket is a continuation, so itsNextBucket in the currently used bucket is filled with the new bucket number.

◆ getShape()

void casacore::SSMStringHandler::getShape ( IPosition & aShape,
Int bucket,
Int & offset,
Int length )

Get the shape in the given bucket and offset.

It sets the offset to the data right after the shape. The IPosition object is resized as needed.

◆ init()

void casacore::SSMStringHandler::init ( )

Initialize the StringHandler.

◆ lastStringBucket()

Int casacore::SSMStringHandler::lastStringBucket ( ) const
inline

Definition at line 254 of file SSMStringHandler.h.

References itsLastBucket.

Referenced by setLastStringBucket().

◆ operator=()

SSMStringHandler & casacore::SSMStringHandler::operator= ( const SSMStringHandler & )
delete

Forbid assignment.

◆ put() [1/2]

void casacore::SSMStringHandler::put ( Int & bucketNr,
Int & offset,
Int & length,
const Array< String > & string,
Bool handleShape )

◆ put() [2/2]

void casacore::SSMStringHandler::put ( Int & bucketNr,
Int & offset,
Int & length,
const String & string )

Put a single string or an array of strings into a bucket.

If its length does not exceed the given length, it reuses the currently used space (given by bucketnr and offset). Otherwise it adds the data to the last string bucket. It fills the offset and bucketnr where the data are stored and the length occupied in the buckets. An array of strings is flattened first (a la SSMColumn::writeString).
If handleShape is True (for variable shaped arrays), the shape will be put first.

◆ putData()

void casacore::SSMStringHandler::putData ( Int length,
const Char * data )
private

Put the data with the given length at the end of the current bucket.

If they do not fit, they are continued in a new bucket.

◆ putShape()

void casacore::SSMStringHandler::putShape ( Int & bucketNr,
Int & offset,
Int & length,
const IPosition & aShape )

Put a single string or an array of strings into a bucket.

If its length does not exceed the given length, it reuses the currently used space (given by bucketnr and offset). Otherwise it adds the data to the last string bucket. It fills the offset and bucketnr where stored and the length occupied in the buckets.

◆ remove()

void casacore::SSMStringHandler::remove ( Int bucketNr,
Int offset,
Int length )

Remove data with the given length from a bucket.

If the data are continued in next bucket(s), they will be removed there as well.

◆ replace() [1/3]

void casacore::SSMStringHandler::replace ( Int bucketNr,
Int offset,
Int length,
const String & string )
private

Replace the current data with the new data.

It is used by put after having assured that the new length does not exceed the current one. It follows continuation buckets as needed.

◆ replace() [2/3]

void casacore::SSMStringHandler::replace ( Int bucketNr,
Int offset,
Int length,
Int totalLength,
const Array< String > & string,
Bool handleShape )
private

◆ replace() [3/3]

void casacore::SSMStringHandler::replace ( Int bucketNr,
Int offset,
Int length,
Int totalLength,
const IPosition & aShape )
private

◆ replaceData()

void casacore::SSMStringHandler::replaceData ( Int & offset,
Int length,
const Char * data )
private

◆ resync()

void casacore::SSMStringHandler::resync ( )

Resynchronize (after a table lock was acquired).

It clears the itsCurrentBucket variable to assure that buckets are reread.

◆ setLastStringBucket()

void casacore::SSMStringHandler::setLastStringBucket ( Int lastStringBucket)
inline

Set or get last string bucketnr.

Setting is needed when an existing table is opened.

Definition at line 249 of file SSMStringHandler.h.

References itsLastBucket, and lastStringBucket().

Member Data Documentation

◆ isChanged

Bool casacore::SSMStringHandler::isChanged
private

Definition at line 242 of file SSMStringHandler.h.

◆ itsCurrentBucket

Int casacore::SSMStringHandler::itsCurrentBucket
private

Definition at line 235 of file SSMStringHandler.h.

◆ itsData

char* casacore::SSMStringHandler::itsData
private

Definition at line 240 of file SSMStringHandler.h.

◆ itsIntBuf

char* casacore::SSMStringHandler::itsIntBuf
private

Definition at line 241 of file SSMStringHandler.h.

◆ itsIntSize

uInt casacore::SSMStringHandler::itsIntSize
private

Definition at line 243 of file SSMStringHandler.h.

◆ itsLastBucket

Int casacore::SSMStringHandler::itsLastBucket
private

Definition at line 244 of file SSMStringHandler.h.

Referenced by lastStringBucket(), and setLastStringBucket().

◆ itsLength

Int casacore::SSMStringHandler::itsLength
private

Definition at line 236 of file SSMStringHandler.h.

◆ itsNDeleted

Int casacore::SSMStringHandler::itsNDeleted
private

Definition at line 237 of file SSMStringHandler.h.

◆ itsNextBucket

Int casacore::SSMStringHandler::itsNextBucket
private

Definition at line 239 of file SSMStringHandler.h.

◆ itsSSMPtr

SSMBase* casacore::SSMStringHandler::itsSSMPtr
private

Definition at line 234 of file SSMStringHandler.h.

◆ itsStart

uInt casacore::SSMStringHandler::itsStart
private

Definition at line 245 of file SSMStringHandler.h.

◆ itsUsedLength

Int casacore::SSMStringHandler::itsUsedLength
private

Definition at line 238 of file SSMStringHandler.h.


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