encoding.3

tcl是工具命令语言

'\"
'\" Copyright (c) 1997-1998 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\" 
'\" RCS: @(#) $Id: Encoding.3,v 1.11 2002/07/01 18:24:39 jenglish Exp $
'\" 
.so man.macros
.TH Tcl_GetEncoding 3 "8.1" Tcl "Tcl Library Procedures"
.BS
.SH NAME
Tcl_GetEncoding, Tcl_FreeEncoding, Tcl_ExternalToUtfDString, Tcl_ExternalToUtf, Tcl_UtfToExternalDString, Tcl_UtfToExternal, Tcl_WinTCharToUtf, Tcl_WinUtfToTChar, Tcl_GetEncodingName, Tcl_SetSystemEncoding, Tcl_GetEncodingNames, Tcl_CreateEncoding, Tcl_GetDefaultEncodingDir, Tcl_SetDefaultEncodingDir \- procedures for creating and using encodings.
.SH SYNOPSIS
.nf
\fB#include <tcl.h>\fR
.sp
Tcl_Encoding
\fBTcl_GetEncoding\fR(\fIinterp, name\fR)
.sp
void
\fBTcl_FreeEncoding\fR(\fIencoding\fR)
.sp
char *
\fBTcl_ExternalToUtfDString\fR(\fIencoding, src, srcLen, dstPtr\fR)
.sp
int
\fBTcl_ExternalToUtf\fR(\fIinterp, encoding, src, srcLen, flags, statePtr, dst, dstLen, srcReadPtr, dstWrotePtr, 
	dstCharsPtr\fR)
.sp
char * 
\fBTcl_UtfToExternalDString\fR(\fIencoding, src, srcLen, dstPtr\fR)
.sp
int
\fBTcl_UtfToExternal\fR(\fIinterp, encoding, src, srcLen, flags, statePtr, dst, dstLen, srcReadPtr, dstWrotePtr, 
	dstCharsPtr\fR)
.sp
char *
\fBTcl_WinTCharToUtf\fR(\fItsrc, srcLen, dstPtr\fR)
.sp
TCHAR *
\fBTcl_WinUtfToTChar\fR(\fIsrc, srcLen, dstPtr\fR)
.sp
CONST char *
\fBTcl_GetEncodingName\fR(\fIencoding\fR)
.sp
int
\fBTcl_SetSystemEncoding\fR(\fIinterp, name\fR)
.sp
void
\fBTcl_GetEncodingNames\fR(\fIinterp\fR)
.sp
Tcl_Encoding
\fBTcl_CreateEncoding\fR(\fItypePtr\fR)
.sp
CONST char *
\fBTcl_GetDefaultEncodingDir\fR(\fIvoid\fR)
.sp
void
\fBTcl_SetDefaultEncodingDir\fR(\fIpath\fR)


.SH ARGUMENTS
.AS Tcl_EncodingState *dstWrotePtr
.AP Tcl_Interp *interp in
Interpreter to use for error reporting, or NULL if no error reporting is
desired.
.AP "CONST char" *name in
Name of encoding to load.
.AP Tcl_Encoding encoding in
The encoding to query, free, or use for converting text.  If \fIencoding\fR is 
NULL, the current system encoding is used.
.AP "CONST char" *src in
For the \fBTcl_ExternalToUtf\fR functions, an array of bytes in the
specified encoding that are to be converted to UTF-8.  For the
\fBTcl_UtfToExternal\fR and \fBTcl_WinUtfToTChar\fR functions, an array of
UTF-8 characters to be converted to the specified encoding.  
.AP "CONST TCHAR" *tsrc in
An array of Windows TCHAR characters to convert to UTF-8.
.AP int srcLen in 
Length of \fIsrc\fR or \fItsrc\fR in bytes.  If the length is negative, the 
encoding-specific length of the string is used.
.AP Tcl_DString *dstPtr out
Pointer to an uninitialized or free \fBTcl_DString\fR in which the converted
result will be stored.
.AP int flags in
Various flag bits OR-ed together.  
TCL_ENCODING_START signifies that the
source buffer is the first block in a (potentially multi-block) input
stream, telling the conversion routine to reset to an initial state and
perform any initialization that needs to occur before the first byte is
converted.  TCL_ENCODING_END signifies that the source buffer is the last
block in a (potentially multi-block) input stream, telling the conversion
routine to perform any finalization that needs to occur after the last
byte is converted and then to reset to an initial state.
TCL_ENCODING_STOPONERROR signifies that the conversion routine should
return immediately upon reading a source character that doesn't exist in
the target encoding; otherwise a default fallback character will
automatically be substituted.  
.AP Tcl_EncodingState *statePtr in/out
Used when converting a (generally long or indefinite length) byte stream
in a piece by piece fashion.  The conversion routine stores its current
state in \fI*statePtr\fR after \fIsrc\fR (the buffer containing the
current piece) has been converted; that state information must be passed
back when converting the next piece of the stream so the conversion
routine knows what state it was in when it left off at the end of the
last piece.  May be NULL, in which case the value specified for \fIflags\fR 
is ignored and the source buffer is assumed to contain the complete string to
convert.
.AP char *dst out
Buffer in which the converted result will be stored.  No more than
\fIdstLen\fR bytes will be stored in \fIdst\fR.
.AP int dstLen in
The maximum length of the output buffer \fIdst\fR in bytes.
.AP int *srcReadPtr out
Filled with the number of bytes from \fIsrc\fR that were actually
converted.  This may be less than the original source length if there was
a problem converting some source characters.  May be NULL.
.AP int *dstWrotePtr out
Filled with the number of bytes that were actually stored in the output
buffer as a result of the conversion.  May be NULL.
.AP int *dstCharsPtr out
Filled with the number of characters that correspond to the number of bytes
stored in the output buffer.  May be NULL.
.AP Tcl_EncodingType *typePtr in
Structure that defines a new type of encoding.  
.AP "CONST char" *path in
A path to the location of the encoding file.  
.BE
.SH INTRODUCTION
.PP
These routines convert between Tcl's internal character representation,
UTF-8, and character representations used by various operating systems or
file systems, such as Unicode, ASCII, or Shift-JIS.  When operating on
strings, such as such as obtaining the names of files or displaying
characters using international fonts, the strings must be translated into
one or possibly multiple formats that the various system calls can use.  For
instance, on a Japanese Unix workstation, a user might obtain a filename
represented in the EUC-JP file encoding and then translate the characters to
the jisx0208 font encoding in order to display the filename in a Tk widget.
The purpose of the encoding package is to help bridge the translation gap.
UTF-8 provides an intermediate staging ground for all the various
encodings.  In the example above, text would be translated into UTF-8 from
whatever file encoding the operating system is using.  Then it would be
translated from UTF-8 into whatever font encoding the display routines
require.
.PP
Some basic encodings are compiled into Tcl.  Others can be defined by the
user or dynamically loaded from encoding files in a
platform-independent manner.
.SH DESCRIPTION
.PP
\fBTcl_GetEncoding\fR finds an encoding given its \fIname\fR.  The name may
refer to a builtin Tcl encoding, a user-defined encoding registered by
calling \fBTcl_CreateEncoding\fR, or a dynamically-loadable encoding
file.  The return value is a token that represents the encoding and can be
used in subsequent calls to procedures such as \fBTcl_GetEncodingName\fR,
\fBTcl_FreeEncoding\fR, and \fBTcl_UtfToExternal\fR.  If the name did not
refer to any known or loadable encoding, NULL is returned and an error
message is returned in \fIinterp\fR.
.PP
The encoding package maintains a database of all encodings currently in use.
The first time \fIname\fR is seen, \fBTcl_GetEncoding\fR returns an
encoding with a reference count of 1.  If the same \fIname\fR is requested
further times, then the reference count for that encoding is incremented
without the overhead of allocating a new encoding and all its associated
data structures.  
.PP
When an \fIencoding\fR is no longer needed, \fBTcl_FreeEncoding\fR
should be called to release it.  When an \fIencoding\fR is no longer in use
anywhere (i.e., it has been freed as many times as it has been gotten)
\fBTcl_FreeEncoding\fR will release all storage the encoding was using
and delete it from the database. 
.PP
\fBTcl_ExternalToUtfDString\fR converts a source buffer \fIsrc\fR from the
specified \fIencoding\fR into UTF-8.  The converted bytes are stored in 
\fIdstPtr\fR, which is then NULL terminated.  The caller should eventually
call \fBTcl_DStringFree\fR to free any information stored in \fIdstPtr\fR.
When converting, if any of the characters in the source buffer cannot be
represented in the target encoding, a default fallback character will be
used.  The return value is a pointer to the value stored in the DString.
.PP
\fBTcl_ExternalToUtf\fR converts a source buffer \fIsrc\fR from the specified
\fIencoding\fR into UTF-8.  Up to \fIsrcLen\fR bytes are converted from the
source buffer and up to \fIdstLen\fR converted bytes are stored in \fIdst\fR.
In all cases, \fI*srcReadPtr\fR is filled with the number of bytes that were
successfully converted from \fIsrc\fR and \fI*dstWrotePtr\fR is filled with
the corresponding number of bytes that were stored in \fIdst\fR.  The return
value is one of the following:
.RS
.IP \fBTCL_OK\fR 29
All bytes of \fIsrc\fR were converted.
.IP \fBTCL_CONVERT_NOSPACE\fR 29
The destination buffer was not large enough for all of the converted data; as
many characters as could fit were converted though.
.IP \fBTCL_CONVERT_MULTIBYTE\fR 29
The last fews bytes in the source buffer were the beginning of a multibyte
sequence, but more bytes were needed to complete this sequence.  A
subsequent call to the conversion routine should pass a buffer containing
the unconverted bytes that remained in \fIsrc\fR plus some further bytes
from the source stream to properly convert the formerly split-up multibyte
sequence.  
.IP \fBTCL_CONVERT_SYNTAX\fR 29
The source buffer contained an invalid character sequence.  This may occur
if the input stream has been damaged or if the input encoding method was
misidentified.
.IP \fBTCL_CONVERT_UNKNOWN\fR 29
The source buffer contained a character that could not be represented in
the target encoding and TCL_ENCODING_STOPONERROR was specified.  
.RE
.LP
\fBTcl_UtfToExternalDString\fR converts a source buffer \fIsrc\fR from UTF-8 
into the specified \fIencoding\fR.  The converted bytes are stored in
\fIdstPtr\fR, which is then terminated with the appropriate encoding-specific
NULL.  The caller should eventually call \fBTcl_DStringFree\fR to free any
information stored in \fIdstPtr\fR.  When converting, if any of the
characters in the source buffer cannot be represented in the target
encoding, a default fallback character will be used.  The return value is
a pointer to the value stored in the DString.
.PP
\fBTcl_UtfToExternal\fR converts a source buffer \fIsrc\fR from UTF-8 into
the specified \fIencoding\fR.  Up to \fIsrcLen\fR bytes are converted from
the source buffer and up to \fIdstLen\fR converted bytes are stored in
\fIdst\fR.  In all cases, \fI*srcReadPtr\fR is filled with the number of
bytes that were successfully converted from \fIsrc\fR and \fI*dstWrotePtr\fR
is filled with the corresponding number of bytes that were stored in
\fIdst\fR.  The return values are the same as the return values for
\fBTcl_ExternalToUtf\fR.
.PP
\fBTcl_WinUtfToTChar\fR and \fBTcl_WinTCharToUtf\fR are
Windows-only convenience
functions for converting between UTF-8 and Windows strings.  On Windows 95
(as with the Macintosh and Unix operating systems),
all strings exchanged between Tcl and the operating system are "char"
based.  On Windows NT, some strings exchanged between Tcl and the
operating system are "char" oriented while others are in Unicode.  By
convention, in Windows a TCHAR is a character in the ANSI code page
on Windows 95 and a Unicode character on Windows NT.
.PP
If you planned to use the same "char" based interfaces on both Windows
95 and Windows NT, you could use \fBTcl_UtfToExternal\fR and
\fBTcl_ExternalToUtf\fR (or their \fBTcl_DString\fR equivalents) with an
encoding of NULL (the current system encoding).  On the other hand,
if you planned to use the Unicode interface when running on Windows NT
and the "char" interfaces when running on Windows 95, you would have
to perform the following type of test over and over in your program
(as represented in pseudo-code):
.CS
if (running NT) {
    encoding <- Tcl_GetEncoding("unicode");
    nativeBuffer <- Tcl_UtfToExternal(encoding, utfBuffer);
    Tcl_FreeEncoding(encoding);
} else {
    nativeBuffer <- Tcl_UtfToExternal(NULL, utfBuffer);
.CE
\fBTcl_WinUtfToTChar\fR and \fBTcl_WinTCharToUtf\fR automatically
handle this test and use the proper encoding based on the current
operating system.  \fBTcl_WinUtfToTChar\fR returns a pointer to
a TCHAR string, and \fBTcl_WinTCharToUtf\fR expects a TCHAR string
pointer as the \fIsrc\fR string.  Otherwise, these functions
behave identically to \fBTcl_UtfToExternalDString\fR and
\fBTcl_ExternalToUtfDString\fR.