com.ibm.lpex.core.LpexNls
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SWT LPEX v3.0.0 | |||||||||||
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java.lang.Object
This class provides national language support (NLS) functions. These are mostly DBCS/MBCS-related functions, and may not work correctly for other character encodings. Some bidirectional support will also be added gradually, mainly for the editor's internal use. There is one instance of this class for each document view.
These NLS functions attempt to ease the handling by users of files originating on and/or targeted for a remote system, in a manner similar to their handling in that particular environment (e.g., iSeries members being edited with an iSeries editor): emulation of SO/SI control characters, awareness of the text's actual positions, columns, length, and sequence numbers (all byte-determined), etc.
The current implementation, while attempting to be generic, focuses on Windows as the workstation, and zSeries (S/390) and iSeries (AS/400) as the remote system. These remote systems use EBCDIC character encodings: a DBCS character uses two bytes, a DBCS string is delimited by SO/SI controls, certain character combinations (Arabic lam + alef) may translate into a single-byte character (visual lamalef code point). Also, for these systems each byte in the character encoding takes up one display column on the screen (1-byte SBCS character = 1 display column, 2-byte DBCS character = 2-column display width, the SO and SI control characters = 1 display column each).
For EUC character encodings (UNIX, AIX, Linux), LpexNls may not provide adequate emulation of their source edit environments. The byte-length of characters differs from their display-column width, so you may have to use native code (JNI), e.g., the *mb* C library functions, for display-width calculations (as only byte-length information is currently obtainable in Java); these calculations affect the (column-based) tabs expansion in LPEX.
Terminology used in here:
| Unicode | LPEX, like any Java program, uses Unicode for its internal representation of characters. More specifically, this is the UTF-16 encoding, which encodes the basic multilingual plane of Unicode version 1 directly, and uses surrogate pairs as the escape mechanism to encode the next 16 planes of Unicode version 3 |
| encoding | a Java-supported character encoding, e.g., "Cp1252" (Windows Latin-1) |
| native encoding | this is the default character encoding of the platform (host operating system) that LPEX runs on, according to the default locale. This is, usually, an ASCII character encoding on a workstation (Windows, Linux, OS/2, etc.); an EBCDIC character encoding on a mainframe/midi (S/390, AS/400, etc.). This encoding is normally determined from the "file.encoding" Java system property |
| file encoding | this is the character encoding of an LPEX document's
underlying file. The file encoding is normally the native
encoding, as files are usually stored in an encoding that is
same as the default encoding of the host operating system (for
example, on the Japanese Linux, files are typically stored in
EUC-JP).
In a heterogeneous platform environment, the encoding of the host operating system may be different from the encoding of a file we want to load into the editor. In such a case, one must explicitly specify the encoding of the file, or let the editor attempt to detect it (see LpexView.LpexView(String,String,boolean)); the editor will then perform the character code conversion on loading the file in, and similarly whan saving the document. Internet character encodings are not supported. For these encodings, the surrounding escape sequences are not currently handled in the code. Their processing should be in a manner quite similar to the handling of SO/SI controls in EBCDIC DBCS. An application using the LPEX text widget may also read and write files in any encoding on its own, and use the editor API, for example, to set the document text from a Reader and save it through a Writer. As an example, an Eclipse technology LpexAbstractTextEditor-based editor may extend the FileDocumentProvider to read and save local UTF-8 files, while the LPEX Editor plug-in loads and saves its contents, all in Unicode, from and to the Eclipse IDocument provided. |
| source encoding | the source file's character encoding: the file being edited may originate from and/or be targeted for a remote system (i.e., different from the platform that LPEX runs on). Setting the source encoding information in the editor allows LPEX to emulate features of the file's original editing environment (for example, display emulated SO/SI controls), correctly establish the sequence numbers in effect, calculate the length limit of text lines for save operations, etc. |
| DBCS | Asian character set/encoding that contains double-byte characters |
| MBCS | Asian character set/encoding that contains multi-byte characters |
| SO, SI | Shift-out and Shift-in control characters. Only EBCDIC DBCS encodings use SO/SI escape characters. Balanced SO/SI characters enclose sequences of DBCS character bytes. LPEX can display emulation SO/SI characters in order to present the user an image of the file similar to the one seen in its source natural habitat (e.g., an iSeries member being edited with an iSeries editor). |
Here is a scenario for editing a remote file with LPEX:
----------------------------- ---------------------------- | Windows XP workstation | | zSeries mainframe | | IBM Java 2 SDK 1.4.1 | | | | | | | | Native encoding: MS 932 | | Source encoding: CP 939 | | (PC DBCS) | | (EBCDIC DBCS + SO/SIs) | | | | | | | | 1.remote file XXX | | | 2.file-transfer | | | | utility: | | | | zSeries -> | | | | workstation | | | |<=================== | | 3.local file xxx | | | | | | | | 4.LPEX loads file | | | | from workstation: | | | | "MS932" -> Unicode | | | | | | | | [5.set sourceEncoding | | | | to "Cp939" for | | | | emulation purposes | | | | 6.set sourceCcsid | | | | 7.set sequenceNumbers] | | | | | | | | 8.LPEX handles | | | | the editing of | | | | document xxx | | | | (all in Unicode) | | | | | | | | 9.LPEX saves file | | | | to workstation: | | | | Unicode -> "MS932" | | | | | | | | 10.local file xxx' | | | | | 11.file-transfer | | | | utility: | | | | workstation -> | | | | zSeries | | | ===================>| | | | | 12.remote file XXX' | | | | | ----------------------------- ---------------------------- |
Notes:
| Method Summary | |
|---|---|
| String | addSourceSosi(String s)
Add emulation SO/SIs to a Java Unicode string originating from, or targeted for, an EBCDIC DBCS source character encoding. |
| String | addSourceSosi(String s,
char shiftOut,
char shiftIn)
Add emulation SO/SIs to a Java Unicode string originating from, or targeted for, an EBCDIC DBCS source character encoding. |
| boolean | displayingSosi()
Query whether the view is displaying emulation SO/SI controls. |
| static int | encodingCharIndex(String s,
int index,
String encoding)
Return the character index into the encoded string (i.e., as converted from the given Java Unicode string using the specified character encoding), which corresponds to the specified index into the string. |
| static int | encodingLength(char c,
String encoding)
Get the byte-length for a string consisting of one Java Unicode character converted to the specified character encoding. |
| static int | encodingLength(String s,
String encoding)
Get the byte-length of a Java Unicode string in the specified character encoding. |
| String | getFileEncoding()
Retrieve the character encoding of the document's underlying file. |
| static String | getNativeEncoding()
Retrieve the native (platform's default) character encoding. |
| String | getSourceEncoding()
Retrieve the source character encoding of the document. |
| static int | indexFromEncodingIndex(String s,
int index,
String encoding)
Return the index into a Java Unicode text string which corresponds to the specified index into its encoded string (i.e., as converted using the specified character encoding). |
| static boolean | isBidi()
Query whether the editor is running in a bidirectional environment which it can handle. |
| static boolean | isBidiEncoding(String encoding)
Determine whether a character encoding is bidirectional. |
| static boolean | isEucEncoding(String encoding)
Determine whether a character encoding is EUC (AIX MBCS). |
| static boolean | isMbcsEncoding(String encoding)
Determine whether a character encoding is DBCS/MBCS. |
| static boolean | isSosiEncoding(String encoding)
Determine whether a character encoding uses SO/SI control characters (is an EBCDIC DBCS character encoding). |
| boolean | isSourceMbcs()
Query whether the source character encoding of the document is DBCS/MBCS. |
| boolean | isSourceSosi()
Query whether the source character encoding of the document is EBCDIC DBCS. |
| static boolean | isValidEncoding(String encoding)
Validate a character encoding. |
| int | sourceLength(char c)
Get the byte-length for a string consisting of one Java Unicode character converted to the source character encoding. |
| int | sourceTruncate(String s,
int textLimit)
Truncate a Java Unicode string so that it fits within the specified number of bytes when converted to its source encoding. |
| int | sourceWidth(char c)
Get the display-column width for one Java Unicode character converted to the source character encoding. |
| boolean | usingSourceColumns()
Convenience method to query whether the view's document is effectively using source columns. |
| Methods inherited from class java.lang.Object |
|---|
| clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
| Method Detail |
public static boolean isValidEncoding(String encoding)
public static boolean isMbcsEncoding(String encoding)
public static boolean isEucEncoding(String encoding)
public static boolean isSosiEncoding(String encoding)
public static boolean isBidiEncoding(String encoding)
public static String getNativeEncoding()
public String getFileEncoding()
public String getSourceEncoding()
The source character encoding either defaults to the file character encoding (usually the platform's default encoding), or has been explicitly set with the set sourceEncoding command for files brought over from a remote system.
public boolean isSourceMbcs()
public boolean isSourceSosi()
public boolean usingSourceColumns()
In these cases document column positions, text lengths, etc., as normally calculated by the internal editor's Unicode text processing may differ from the underlying file's byte-oriented text processing in its source encoding.
public boolean displayingSosi()
public static int encodingLength(String s,
String encoding)
public static int encodingLength(char c,
String encoding)
public int sourceLength(char c)
public int sourceWidth(char c)
Currently, this method effectively calls encodingLength(c, sourceEncoding). This may not be appropriate for certain character encodings (such as EUC).
public static int encodingCharIndex(String s,
int index,
String encoding)
If the encoding is EBCDIC DBCS, the index returned is positioned away from a SO/SI control character.
public static int indexFromEncodingIndex(String s,
int index,
String encoding)
public int sourceTruncate(String s,
int textLimit)
public String addSourceSosi(String s)
The SO/SI characters added are those defined by the current.shiftOutCharacter and current.shiftInCharacter editor parameters in this view.
public String addSourceSosi(String s,
char shiftOut,
char shiftIn)
public static boolean isBidi()
Currently, only SWT LPEX running on MS Windows platforms (Arabic and Hebrew) provides adequate bidirectional functionality, making use of the underlying Eclipse technology support.
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SWT LPEX v3.0.0 | |||||||||||
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