10 OCI Programming in a Global Environment

This chapter contains information about OCI programming in a globalized environment. This chapter includes the following topics:

Using the OCI NLS Functions

Many OCI NLS functions accept one of the following handles:

  • The environment handle

  • The user session handle

The OCI environment handle is associated with the client NLS environment and initialized with the client NLS environment variables. This environment does not change when ALTER SESSION statements are issued to the server. The character set associated with the environment handle is the client character set.

The OCI session handle is associated with the server session environment. Its NLS settings change when the session environment is modified with an ALTER SESSION statement. The character set associated with the session handle is the database character set.

Note that the OCI session handle does not have any NLS settings associated with it until the first transaction begins in the session. SELECT statements do not begin a transaction.

See Also:

Oracle Call Interface Programmer's Guide for detailed information about the OCI NLS functions

Specifying Character Sets in OCI

Use the OCIEnvNlsCreate function to specify client-side database and national character sets when the OCI environment is created. This function enables users to set character set information dynamically in applications, independent of the NLS_LANG and NLS_NCHAR initialization parameter settings. In addition, one application can initialize several environment handles for different client environments in the same server environment.

Any Oracle character set ID except AL16UTF16 can be specified through the OCIEnvNlsCreate function to specify the encoding of metadata, SQL CHAR data, and SQL NCHAR data. Use OCI_UTF16ID in the OCIEnvNlsCreate function to specify UTF-16 data.

See Also:

Oracle Call Interface Programmer's Guide for more information about the OCIEnvNlsCreate function

Getting Locale Information in OCI

An Oracle locale consists of language, territory, and character set definitions. The locale determines conventions such as day and month names, as well as date, time, number, and currency formats. A globalized application complies with a user's locale setting and cultural conventions. For example, when the locale is set to German, users expect to see day and month names in German.

You can use the OCINlsGetInfo() function to retrieve the following locale information:

Days of the week (translated)
Abbreviated days of the week (translated)
Month names (translated)
Abbreviated month names (translated)
Yes/no (translated)
AM/PM (translated)
AD/BC (translated)
Numeric format
Debit/credit
Date format
Currency formats
Default language
Default territory
Default character set
Default linguistic sort
Default calendar

Table 10-1 summarizes OCI functions that return locale information.

Table 10-1 OCI Functions That Return Locale Information

Function Description

OCINlsGetInfo()

Returns locale information. See preceding text.

OCINlsCharSetNameTold()

Returns the Oracle character set ID for the specified Oracle character set name

OCINlsCharSetIdToName()

Returns the Oracle character set name from the specified character set ID

OCINlsNumericInfoGet()

Returns specified numeric information such as maximum character size

OCINlsEnvironmentVariableGet()

Returns the character set ID from NLS_LANG or the national character set ID from NLS_NCHAR


Mapping Locale Information Between Oracle and Other Standards

The OCINlsNameMap function maps Oracle character set names, language names, and territory names to and from Internet Assigned Numbers Authority (IANA) and International Organization for Standardization (ISO) names.

Manipulating Strings in OCI

Two types of data structures are supported for string manipulation:

  • Native character strings

  • Wide character strings

Native character strings are encoded in native Oracle character sets. Functions that operate on native character strings take the string as a whole unit with the length of the string calculated in bytes. Wide character (wchar) string functions provide more flexibility in string manipulation. They support character-based and string-based operations with the length of the string calculated in characters.

The wide character datatype is Oracle-specific and should not be confused with the wchar_t datatype defined by the ANSI/ISO C standard. The Oracle wide character datatype is always 4 bytes in all platforms, while the size of wchar_t depends on the implementation and the platform. The Oracle wide character datatype normalizes native characters so that they have a fixed width for easy processing. This guarantees no data loss for round-trip conversion between the Oracle wide character format and the native character format.

String manipulation includes the :

  • Conversion of strings between native character format and wide character format

  • Character classifications

  • Case conversion

  • Calculations of display length

  • General string manipulation, such as comparison, concatenation, and searching

Table 10-2 summarizes the OCI string manipulation functions.

Note:

The functions and descriptions in Table 10-2 that refer to multibyte strings apply to native character strings.

Table 10-2 OCI String Manipulation Functions

Function Description

OCIMultiByteToWideChar()

Converts an entire null-terminated string into the wchar format

OCIMultiByteInSizeToWideChar()

Converts part of a string into the wchar format

OCIWideCharToMultiByte()

Converts an entire null-terminated wide character string into a multibyte string

OCIWideCharInSizeToMultiByte()

Converts part of a wide character string into the multibyte format

OCIWideCharToLower()

Converts the wchar character specified by wc into the corresponding lowercase character if it exists in the specified locale. If no corresponding lowercase character exists, then it returns wc itself.

OCIWideCharToUpper()

Converts the wchar character specified by wc into the corresponding uppercase character if it exists in the specified locale. If no corresponding uppercase character exists, then it returns wc itself.

OCIWideCharStrcmp()

Compares two wide character strings by binary, linguistic, or case-insensitive comparison method.

Note: The UNICODE_BINARY sort method cannot be used with OCIWideCharStrcmp() to perform a linguistic comparison of the supplied wide character arguments.

OCIWideCharStrncmp()

Similar to OCIWideCharStrcmp(). Compares two wide character strings by binary, linguistic, or case-insensitive comparison methods. At most len1 bytes form str1, and len2 bytes form str2.

Note: As with OCIWideCharStrcmp(), the UNICODE_BINARY sort method cannot be used with OOCIWideCharStrncmp() to perform a linguistic comparison of the supplied wide character arguments.

OCIWideCharStrcat()

Appends a copy of the string pointed to by wsrcstr. Then it returns the number of characters in the resulting string.

OCIWideCharStrncat()

Appends a copy of the string pointed to by wsrcstr. Then it returns the number of characters in the resulting string. At most n characters are appended.

OCIWideCharStrchr()

Searches for the first occurrence of wc in the string pointed to by wstr. Then it returns a pointer to the wchar if the search is successful.

OCIWideCharStrrchr()

Searches for the last occurrence of wc in the string pointed to by wstr

OCIWideCharStrcpy()

Copies the wchar string pointed to by wsrcstr into the array pointed to by wdststr. Then it returns the number of characters copied.

OCIWideCharStrncpy()

Copies the wchar string pointed to by wsrcstr into the array pointed to by wdststr. Then it returns the number of characters copied. At most n characters are copied from the array.

OCIWideCharStrlen()

Computes the number of characters in the wchar string pointed to by wstr and returns this number

OCIWideCharStrCaseConversion()

Converts the wide character string pointed to by wsrcstr into the case specified by a flag and copies the result into the array pointed to by wdststr

OCIWideCharDisplayLength()

Determines the number of column positions required for wc in display

OCIWideCharMultibyteLength()

Determines the number of bytes required for wc in multibyte encoding

OCIMultiByteStrcmp()

Compares two multibyte strings by binary, linguistic, or case-insensitive comparison methods

OCIMultiByteStrncmp()

Compares two multibyte strings by binary, linguistic, or case-insensitive comparison methods. At most len1 bytes form str1 and len2 bytes form str2.

OCIMultiByteStrcat()

Appends a copy of the multibyte string pointed to by srcstr

OCIMultiByteStrncat()

Appends a copy of the multibyte string pointed to by srcstr. At most n bytes from srcstr are appended to dststr.

OCIMultiByteStrcpy()

Copies the multibyte string pointed to by srcstr into an array pointed to by dststr. It returns the number of bytes copied.

OCIMultiByteStrncpy()

Copies the multibyte string pointed to by srcstr into an array pointed to by dststr. It returns the number of bytes copied. At most n bytes are copied from the array pointed to by srcstr to the array pointed to by dststr.

OCIMultiByteStrlen()

Returns the number of bytes in the multibyte string pointed to by str

OCIMultiByteStrnDisplayLength()

Returns the number of display positions occupied by the complete characters within the range of n bytes

OCIMultiByteStrCaseConversion()

Converts part of a string from one character set to another


Classifying Characters in OCI

Table 10-3 shows the OCI character classification functions.

Table 10-3 OCI Character Classification Functions

Function Description

OCIWideCharIsAlnum()

Tests whether the wide character is an alphabetic letter or decimal digit

OCIWideCharIsAlpha()

Tests whether the wide character is an alphabetic letter

OCIWideCharIsCntrl()

Tests whether the wide character is a control character

OCIWideCharIsDigit()

Tests whether the wide character is a decimal digit

OCIWideCharIsGraph()

Tests whether the wide character is a graph character

OCIWideCharIsLower()

Tests whether the wide character is a lowercase letter

OCIWideCharIsPrint()

Tests whether the wide character is a printable character

OCIWideCharIsPunct()

Tests whether the wide character is a punctuation character

OCIWideCharIsSpace()

Tests whether the wide character is a space character

OCIWideCharIsUpper()

Tests whether the wide character is an uppercase character

OCIWideCharIsXdigit()

Tests whether the wide character is a hexadecimal digit

OCIWideCharIsSingleByte()

Tests whether wc is a single-byte character when converted into multibyte


Converting Character Sets in OCI

Conversion between Oracle character sets and Unicode (16-bit, fixed-width Unicode encoding) is supported. Replacement characters are used if a character has no mapping from Unicode to the Oracle character set. Therefore, conversion back to the original character set is not always possible without data loss.

Table 10-4 summarizes the OCI character set conversion functions.

Table 10-4 OCI Character Set Conversion Functions

Function Description

OCICharSetToUnicode()

Converts a multibyte string pointed to by src to Unicode into the array pointed to by dst

OCIUnicodeToCharSet()

Converts a Unicode string pointed to by src to multibyte into the array pointed to by dst

OCINlsCharSetConvert()

Converts a string from one character set to another

OCICharSetConversionIsReplacementUsed()

Indicates whether replacement characters were used for characters that could not be converted in the last invocation of OCINlsCharSetConvert() or OCIUnicodeToCharSet()


OCI Messaging Functions

The user message API provides a simple interface for cartridge developers to retrieve their own messages as well as Oracle messages.

Table 10-5 summarizes the OCI messaging functions.

Table 10-5 OCI Messaging Functions

Function Description

OCIMessageOpen()

Opens a message handle in a language pointed to by hndl

OCIMessageGet()

Retrieves a message with message number identified by msgno. If the buffer is not zero, then the function copies the message into the buffer specified by msgbuf.

OCIMessageClose()

Closes a message handle pointed to by msgh and frees any memory associated with this handle


lmsgen Utility

Purpose

The lmsgen utility converts text-based message files (.msg) into binary format (.msb) so that Oracle messages and OCI messages provided by the user can be returned to OCI functions in the desired language.

Messages used by the server are stored in binary-format files that are placed in the $ORACLE_HOME/product_name/mesg directory, or the equivalent for your operating system. Multiple versions of these files can exist, one for each supported language, using the following filename convention:

<product_id><language_abbrev>.msb

For example, the file containing the server messages in French is called oraf.msb, because ORA is the product ID (<product_id>) and F is the language abbreviation (<language_abbrev>) for French. The value for product_name is rdbms, so it is in the $ORACLE_HOME/rdbms/mesg directory.

Syntax

LMSGEN text_file product facility [language] [-i indir] [-o outdir]


text_file is a message text file.
product is the name of the product.
facility is the name of the facility.
language is the optional message language corresponding to the language specified in the NLS_LANG parameter. The language parameter is required if the message file is not tagged properly with language.
indir is the optional directory to specify the text file location.
outdir is the optional directory to specify the output file location.

The output (.msb) file will be generated under the $ORACLE_HOME/product/mesg/ directory.

Text Message Files

Text message files must follow these guidelines:

  • Lines that start with / and // are treated as internal comments and are ignored.

  • To tag the message file with a specific language, include a line similar to the following:

    #   CHARACTER_SET_NAME= Japanese_Japan.JA16EUC

  • Each message contains three fields:

     message_number, warning_level, message_text

The message number must be unique within a message file.
The warning level is not currently used. Use 0.
The message text cannot be longer than 511 bytes.

The following example shows an Oracle message text file:

/ Copyright (c) 2006 by Oracle.  All rights reserved.
/ This is a test us7ascii message file
# CHARACTER_SET_NAME= american_america.us7ascii
/
00000, 00000, "Export terminated unsuccessfully\n"
00003, 00000, "no storage definition found for segment(%lu, %lu)"

Example: Creating a Binary Message File from a Text Message File

The following table contains sample values for the lmsgen parameters:

Parameter Value
product myapp
facility imp
language AMERICAN
text_file impus.msg

One of the lines in the text message file is the following:

00128,2, "Duplicate entry %s found in %s"

The lmsgen utility converts the text message file (impus.msg) into binary format, resulting in a file called impus.msb. The directory $ORACLE_HOME/myapp/mesg must already exist.

% lmsgen impus.msg myapp imp AMERICAN

The following output results:

Generating message file impus.msg -->
$ORACLE_HOME/myapp/mesg/impus.msb

NLS Binary Message File Generation Utility: Version 10.2.0.1.0 - Production

Copyright (c) Oracle 1979, 2006.  All rights reserved.

CORE 10.2.0.1.0       Production