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Oracle® C++ Call Interface Programmer's Guide
10g Release 1 (10.1)

Part Number B10778-01
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Clob Class

The Clob class defines the common properties of objects of type CLOB. A Clob is a large character object stored as a column value in a row of a database table. A Clob object contains a logical pointer to a CLOB, not the CLOB itself.

Methods of the Clob class enable you to perform specific tasks related to Clob objects, including methods for getting the length of a SQL CLOB, for materializing a CLOB on the client, and for extracting a part of the CLOB.

The only methods valid on a NULL CLOB object are setName(), isNull(), and operator=() .

Methods in the ResultSet and Statement classes, such as getClob() and setClob(), enable you to access an SQL CLOB value.

An uninitialized CLOB object can be initialized by:


See Also:


Table 10-8 Summary of Clob Methods

Method Summary
Clob()
Clob class constructor.
append()
Append a Clob at the end of the current Clob.
close()
Close a previously opened Clob.
closeStream()
Close the Stream object obtained from the current Clob.
copy()
Copy all or a portion of a Clob or BFILE into the current Clob.
getCharSetForm()
Return the character set form of the Clob.
getCharSetId()
Return the character set ID of the Clob.
getChunkSize()
Return the chunk size of the Clob.
getStream()
Return data from the CLOB as a Stream object.
isInitialized()
Test whether the Clob object is initialized.
isNull()
Test whether the Clob object is atomically NULL.
isOpen()
Test whether the Clob is open.
length()
Return the number of characters in the current CLOB.
open()
Open the CLOB with read or read/write access.
operator=()
Assign a CLOB locator to the current Clob object.
operator==()
Test whether two Clob objects are equal.
operator!=()
Test whether two Clob objects are not equal.
read()
Read a portion of the CLOB into a buffer.
setCharSetId()
Sets the character set ID associated with the Clob.
setCharSetIdUString()
Sets the character set ID associated with the Clob; used when the environment character set is UTF16.
setCharSetForm()
Sets the character set form associated with the Clob.
setEmpty()
Set the Clob object to empty.
setEmpty()
Set the Clob object to empty and initialize the connection pointer to the passed parameter.
setNull()
Set the Clob object to atomically NULL.
trim()
Truncate the Clob to a specified length.
write()
Write a buffer into an unopened CLOB.
writeChunk()
Write a buffer into an open CLOB.


Clob()

Clob class constructor.

Syntax Description
Clob();
Creates a NULL Clob object.
Clob(
   const Connection *connectionp);
Create an uninitialized Clob object.
Clob(
   const Clob *srcClob);
Create a copy of a Clob object.

Parameter Description
connectionp
Connection pointer
srcClob
The source Clob object


append()

Appends a CLOB to the end of the current CLOB.


Syntax
void append(
   const Clob &srcClob);
Parameter Description
srcClob
The CLOB to be appended to the current CLOB.


close()

Closes a CLOB.


Syntax
void close();


closeStream()

Closes the Stream object obtained from the CLOB.


Syntax
void closeStream(
   Stream *stream);
Parameter Description
stream
The Stream object to be closed.


copy()

Copies a part or all of a BFILE or CLOB into the current CLOB.

Syntax Description
void copy(
   const Bfile &srcBfile,
   unsigned int numBytes,
   unsigned int dstOffset = 1,
   unsigned int srcOffset = 1);
Copies a BFILE into the current CLOB.
void copy(
   const Blob &srcClob,
   unsigned int numBytes,
   unsigned int dstOffset = 1,
   unsigned int srcOffset = 1);
Copies a CLOB into the current CLOB.

Parameter Description
srcBfile
The BFILE from which the data is to be copied.
srcClob
The CLOB from which the data is to be copied.
numBytes
The number of characters to be copied from the source BFILE or CLOB. Valid values are numbers greater than 0.
dstOffset
The starting position at which data is to be is at 0.

The starting position at which to begin writing data into the current CLOB Valid values are numbers greater than or equal to 1 written in the destination buffer; the position of the first byte.

srcOffset
The starting position at which to begin reading data from the source BFILE or CLOB. Valid values are numbers greater than or equal to 1.


getCharSetForm()

Returns the character set form of the CLOB.


Syntax
CharSetForm getCharSetForm() const;


getCharSetId()

Returns the character set ID of the CLOB, in string form.


Syntax
string getCharSetId() const;


getChunkSize()

Returns the chunk size of the CLOB. When creating a table that contains a CLOB, the user can specify the chunking factor, which can be a multiple of Oracle blocks. This corresponds to the chunk size used by the LOB data layer when accessing and modifying the CLOB.


Syntax
unsigned int getChunkSize() const;


getStream()

Returns a Stream object from the CLOB. If a stream is already open, it is disallowed to open another stream on CLOB object, so the user must always close the stream before performing any Clob object operations. The client's character set id and form will be used by default, unless they are explicitly set through setCharSetId() and setEmpty() calls.


Syntax
Stream* getStream(
   unsigned int offset = 1,
   unsigned int amount = 0);
Parameter Description
offset
The starting position at which to begin reading data from the CLOB. If offset is not specified, the data is written from the beginning of the CLOB. Valid values are numbers greater than or equal to 1.
amount
The total number of consecutive characters to be read. If amount is 0, the data will be read from the offset value until the end of the CLOB.


isInitialized()

Tests whether the Clob object is initialized. If the Clob object is initialized, TRUE is returned; otherwise, FALSE is returned.


Syntax
bool isInitialized() const;


isNull()

Tests whether the Clob object is atomically NULL. If the Clob object is atomically NULL, TRUE is returned; otherwise, FALSE is returned.


Syntax
bool isNull() const;


isOpen()

Tests whether the CLOB is open. If the CLOB is open, TRUE is returned; otherwise, FALSE is returned.


Syntax
bool isOpen() const;


length()

Returns the number of characters in the CLOB.


Syntax
unsigned int length() const;


open()

Opens the CLOB in read/write or read-only mode.


Syntax
void open(
   LObOpenMode mode = OCCI_LOB_READWRITE);
Parameter Description
mode
The mode the CLOB is to be opened in. Valid values are:
  • OCCI_LOB_READWRITE

  • OCCI_LOB_READONLY



operator=()

Assigns a CLOB to the current CLOB. The source CLOB gets copied to the destination CLOB only when the destination CLOB gets stored in the table.


Syntax
Clob& operator=(
   const Clob &srcClob);
Parameter Description
srcClob
The Clob from which the data must be copied.


operator==()

Compares two Clob objects for equality. Two Clob objects are equal if they both refer to the same CLOB. Two NULL Clob objects are not considered equal. If the Blob objects are equal, then TRUE is returned; otherwise, FALSE is returned.


Syntax
bool operator==(
   const Clob &srcClob) const;
Parameter Description
srcClob
The Clob object to be compared with the current Clob object.


operator!=()

Compares two Clob objects for inequality. Two Clob objects are equal if they both refer to the same CLOB. Two NULL Clob objects are not considered equal. If the Clob objects are not equal, then TRUE is returned; otherwise, FALSE is returned.


Syntax
bool operator!=(
   const Clob &srcClob) const;
Parameter Description
srcClob
The Clob object to be compared with the current Clob object.


read()

Reads a part or all of the CLOB into a buffer.

Returns the actual number of characters read for fixed-width charactersets, such as UTF16, or the number of bytes read for multibyte charactersets, including UTF8.

The client's character set id and form will be used by default, unless they are explicitly set through setCharSetId(), setCharSetIdUString() and setCharSetForm() calls.

Syntax Description
unsigned int read(
   unsigned int amt,
   unsigned char *buffer,
   unsigned int bufsize,
   unsigned int offset=1) const;
Reads a part or all of the CLOB into a buffer.
unsigned int read(
   unsigned int amt,
   unsigned utext *buffer,
   unsigned int bufsize,
   unsigned int offset=1) const;
Reads a part or all of the CLOB into a buffer; globalization enabled. Should be called after setting character set to OCCIUTF16 using setCharSetId() method.


Note:

For the second version of the method, the return value represents either the number of characters read for fixed-width charactersets (UTF16), or the number of bytes read for multibyte charactersets (including UTF8).

Parameter Description
amt
The number of bytes to be read. from the CLOB.
buffer
The buffer that the CLOB data is to be read into.
buffsize
The size of the buffer. Valid values are numbers greater than or equal to amt.
offset
The starting position at which to begin reading data from the CLOB. If offset is not specified, the data is written from the beginning of the CLOB. Valid values are numbers greater than or equal to 1.


setCharSetId()

Sets the Character set Id associated with Clob. The charset id set will be used for read/write and getStream() operations. If no value is set explicitly, the default client's character set id is used. List of character sets supported is given in Globalization Support Guide Appendix A.


Syntax
void setCharSetId(
   const string &charset);
Parameter Description
charset
Oracle supported characterset name (WE8DEC, ZHT16BIG5), or "OCCIUTF16".


setCharSetIdUString()

Sets the Character set Id associated with Clob; used when the environment's charset is UTF16. The charset id set will be used for read/write and getStream() operations.


Syntax
void setCharSetIdUSString(
   const string &charset);
Parameter Description
charset
Oracle supported characterset name (WE8DEC, ZHT16BIG5), or "OCCIUTF16" in UString (UTF16 characterset).


setCharSetForm()

Sets the character set form associated with the CLOB. The charset form set will be used for read/write and getStream() operations. If no value is set explicitly, by default, OCCI_SQLCS_IMPLICIT will be used.


Syntax
void setCharSetForm(
   CharSetForm csfrm );
Parameter Description
csfrm
The char set form for Clob.


setEmpty()

Sets the Clob object to empty.


Syntax
void setEmpty();


setEmpty()

Sets the Clob object to empty and initializes the connection pointer to the passed parameter.


Syntax
void setEmpty(
   const Connection* connectionp);
Parameter Description
connectionp
The new connection pointer for the Clob object.


setNull()

Sets the Clob object to atomically NULL.


Syntax
void setNull();


trim()

Truncates the CLOB to the new length specified.


Syntax
void trim(
   unsigned int newlen);
Parameter Description
newlen
The new length of the CLOB. Valid values are numbers less than or equal to the current length of the CLOB.


write()

Writes data from a buffer into a CLOB.

This method implicitly opens the CLOB, copies the buffer into the CLOB, and implicitly closes the CLOB. If the CLOB is already open, use writeChunk() instead. The actual number of characters written is returned. The client's character set id and form will be used by default, unless they are explicitly set through setCharSetId() and setCharSetForm() calls.

Syntax Description
unsigned int write(
   unsigned int amt,
   unsigned char *buffer,
   unsigned int bufsize,
   unsigned int offset=1) const;
Writes data from a buffer into a CLOB.
unsigned int write(
   unsigned int amt,
   utext *buffer,
   unsigned int bufsize,
   unsigned int offset=1) const;
Writes data from a UTF16 buffer into a CLOB; globalization enabled. Should be called after setting character set to OCCIUTF16 using setCharSetIdUString() method.

Parameter Description
amt
The amount parameter represents:
  • number of characters written for fixed-width charactersets (UTF16)

  • number of bytes written for multibyte charactersets (including UTF8)

buffer
The buffer containing the data to be written to the CLOB.
buffsize
The size of the buffer containing the data to be written to the CLOB. Valid values are numbers greater than or equal to amt.
offset
The starting position at which to begin writing data into the CLOB. If offset is not specified, the data is written from the beginning of the CLOB. Valid values are numbers greater than or equal to 1.


writeChunk()

Writes data from a buffer into a previously opened CLOB.

The actual number of characters written is returned. The client's character set id and form will be used by default, unless they are explicitly set through setCharSetId() and setCharSetForm() calls.

Syntax Description
unsigned int writeChunk(
   unsigned int amt,
   unsigned char *buffer,
   unsigned int bufsize,
   unsigned int offset=1) const;
Writes data from a buffer into a previously opened CLOB.
unsigned int writeChunk(
   unsigned int amt,
   utext *buffer,
   unsigned int bufsize,
   unsigned int offset=1) const;
Writes data from a UTF16 buffer into a CLOB; globalization enabled. Should be called after setting character set to OCCIUTF16 using setCharSetIdUString() method.

Parameter Description
amt
The amount parameter represents
  • number of characters written for fixed-width charactersets (UTF16)

  • number of bytes written for multibyte charactersets (including UTF8)

buffer
The buffer containing the data to be written to the CLOB.
buffsize
The size of the buffer containing the data to be written to the CLOB. Valid values are numbers greater than or equal to amt.
offset
The starting position at which to begin writing data into the CLOB. If offset is not specified, the data is written from the beginning of the CLOB. Valid values are numbers greater than or equal to 1.