path: root/doc/Utf.3

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'\" Copyright (c) 1997 Sun Microsystems, Inc.
'\"
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.TH Utf 3 "8.1" Tcl "Tcl Library Procedures"
.so man.macros
.BS
.SH NAME
Tcl_UniChar, Tcl_UniCharToUtf, Tcl_UtfToUniChar, Tcl_UtfToChar16, Tcl_UtfToWChar, Tcl_UniCharToUtfDString, Tcl_UtfToUniCharDString, Tcl_Char16ToUtfDString, Tcl_UtfToWCharDString, Tcl_UtfToChar16DString, Tcl_WCharToUtfDString, Tcl_WCharLen, Tcl_Char16Len, Tcl_UniCharLen, Tcl_UniCharNcmp, Tcl_UniCharNcasecmp, Tcl_UniCharCaseMatch, Tcl_UtfNcmp, Tcl_UtfNcasecmp, Tcl_UtfCharComplete, Tcl_NumUtfChars, Tcl_UtfFindFirst, Tcl_UtfFindLast, Tcl_UtfNext, Tcl_UtfPrev, Tcl_UniCharAtIndex, Tcl_UtfAtIndex, Tcl_UtfBackslash \- routines for manipulating UTF-8 strings
.SH SYNOPSIS
.nf
\fB#include <tcl.h>\fR
.sp
typedef ... \fBTcl_UniChar\fR;
.sp
Tcl_Size
\fBTcl_UniCharToUtf\fR(\fIch, buf\fR)
.sp
Tcl_Size
\fBTcl_UtfToUniChar\fR(\fIsrc, chPtr\fR)
.sp
Tcl_Size
\fBTcl_UtfToChar16\fR(\fIsrc, uPtr\fR)
.sp
Tcl_Size
\fBTcl_UtfToWChar\fR(\fIsrc, wPtr\fR)
.sp
char *
\fBTcl_UniCharToUtfDString\fR(\fIuniStr, numUniChars, dsPtr\fR)
.sp
char *
\fBTcl_Char16ToUtfDString\fR(\fIutf16, numUtf16, dsPtr\fR)
.sp
char *
\fBTcl_WCharToUtfDString\fR(\fIwcharStr, numWChars, dsPtr\fR)
.sp
Tcl_UniChar *
\fBTcl_UtfToUniCharDString\fR(\fIsrc, numBytes, dsPtr\fR)
.sp
unsigned short *
\fBTcl_UtfToChar16DString\fR(\fIsrc, numBytes, dsPtr\fR)
.sp
wchar_t *
\fBTcl_UtfToWCharDString\fR(\fIsrc, numBytes, dsPtr\fR)
.sp
int
\fBTcl_Char16Len\fR(\fIutf16\fR)
.sp
int
\fBTcl_WCharLen\fR(\fIwcharStr\fR)
.sp
int
\fBTcl_UniCharLen\fR(\fIuniStr\fR)
.sp
int
\fBTcl_UniCharNcmp\fR(\fIucs, uct, uniLength\fR)
.sp
int
\fBTcl_UniCharNcasecmp\fR(\fIucs, uct, uniLength\fR)
.sp
int
\fBTcl_UniCharCaseMatch\fR(\fIuniStr, uniPattern, nocase\fR)
.sp
int
\fBTcl_UtfNcmp\fR(\fIcs, ct, length\fR)
.sp
int
\fBTcl_UtfNcasecmp\fR(\fIcs, ct, length\fR)
.sp
int
\fBTcl_UtfCharComplete\fR(\fIsrc, numBytes\fR)
.sp
int
\fBTcl_NumUtfChars\fR(\fIsrc, numBytes\fR)
.sp
const char *
\fBTcl_UtfFindFirst\fR(\fIsrc, ch\fR)
.sp
const char *
\fBTcl_UtfFindLast\fR(\fIsrc, ch\fR)
.sp
const char *
\fBTcl_UtfNext\fR(\fIsrc\fR)
.sp
const char *
\fBTcl_UtfPrev\fR(\fIsrc, start\fR)
.sp
int
\fBTcl_UniCharAtIndex\fR(\fIsrc, index\fR)
.sp
const char *
\fBTcl_UtfAtIndex\fR(\fIsrc, index\fR)
.sp
Tcl_Size
\fBTcl_UtfBackslash\fR(\fIsrc, readPtr, dst\fR)
.fi
.SH ARGUMENTS
.AS "const Tcl_UniChar" *uniPattern in/out
.AP char *buf out
Buffer in which the UTF-8 representation of the Tcl_UniChar is stored.  At most
4 bytes are stored in the buffer.
.AP int ch in
The Unicode character to be converted or examined.
.AP Tcl_UniChar *chPtr out
Filled with the Tcl_UniChar represented by the head of the UTF-8 string.
.AP unsigned short *uPtr out
Filled with the utf-16 represented by the head of the UTF-8 string.
.AP wchar_t *wPtr out
Filled with the wchar_t represented by the head of the UTF-8 string.
.AP "const char" *src in
Pointer to a UTF-8 string.
.AP "const char" *cs in
Pointer to a UTF-8 string.
.AP "const char" *ct in
Pointer to a UTF-8 string.
.AP "const Tcl_UniChar" *uniStr in
A sequence of \fBTcl_UniChar\fR units with null-termination optional
depending on function.
.AP "const Tcl_UniChar" *ucs in
A null-terminated sequence of \fBTcl_UniChar\fR.
.AP "const Tcl_UniChar" *uct in
A null-terminated sequence of \fBTcl_UniChar\fR.
.AP "const Tcl_UniChar" *uniPattern in
A null-terminated sequence of \fBTcl_UniChar\fR.
.AP "const unsigned short" *utf16 in
A sequence of UTF-16 units with null-termination optional
depending on function.
.AP "const wchar_t" *wcharStr in
A sequence of \fBwchar_t\fR units with null-termination optional
depending on function.
.AP int numBytes in
The length of the UTF-8 input in bytes.  If
negative, the length includes all bytes until the first null byte.
.AP int numUtf16 in
The length of the input in UTF-16 units.
If negative, the length includes all bytes until the first null.
.AP int numUniChars in
The length of the input in Tcl_UniChar units.
If negative, the length includes all bytes until the first null.
.AP int numWChars in
The length of the input in wchar_t units.
If negative, the length includes all bytes until the first null.
.AP "Tcl_DString" *dsPtr in/out
A pointer to a previously initialized \fBTcl_DString\fR.
.AP "const char" *start in
Pointer to the beginning of a UTF-8 string.
.AP Tcl_Size index in
The index of a character (not byte) in the UTF-8 string.
.AP int *readPtr out
If non-NULL, filled with the number of bytes in the backslash sequence,
including the backslash character.
.AP char *dst out
Buffer in which the bytes represented by the backslash sequence are stored.
At most 4 bytes are stored in the buffer.
.AP int nocase in
Specifies whether the match should be done case-sensitive (0) or
case-insensitive (1).
.BE

.SH DESCRIPTION
.PP
These routines convert between UTF-8 strings and Unicode/Utf-16 characters.
A UTF-8 character is a Unicode character represented as a varying-length
sequence of up to \fB4\fR bytes.  A multibyte UTF-8 sequence
consists of a lead byte followed by some number of trail bytes.
.PP
\fBTCL_UTF_MAX\fR is the maximum number of bytes that \fBTcl_UtfToUniChar\fR
can consume in a single call.
.PP
\fBTcl_UniCharToUtf\fR stores the character \fIch\fR as a UTF-8 string
in starting at \fIbuf\fR.  The return value is the number of bytes stored
in \fIbuf\fR. The character \fIch\fR can be or'ed with the value TCL_COMBINE
to enable special behavior, compatible with Tcl 8.x. Then, if ch is a high
surrogate (range U+D800 - U+DBFF), the return value will be 1 and a single
byte in the range 0xF0 - 0xF4 will be stored. If \fIch\fR is a low surrogate
(range U+DC00 - U+DFFF), an attempt is made to combine the result with
the earlier produced bytes, resulting in a 4-byte UTF-8 byte sequence.
.PP
\fBTcl_UtfToUniChar\fR reads one UTF-8 character starting at \fIsrc\fR
and stores it as a Tcl_UniChar in \fI*chPtr\fR.  The return value is the
number of bytes read from \fIsrc\fR.  The caller must ensure that the
source buffer is long enough such that this routine does not run off the
end and dereference non-existent or random memory; if the source buffer
is known to be null-terminated, this will not happen.  If the input is
a byte in the range 0x80 - 0x9F, \fBTcl_UtfToUniChar\fR assumes the
cp1252 encoding, stores the corresponding Tcl_UniChar in \fI*chPtr\fR
and returns 1. If the input is otherwise
not in proper UTF-8 format, \fBTcl_UtfToUniChar\fR will store the first
byte of \fIsrc\fR in \fI*chPtr\fR as a Tcl_UniChar between 0x00A0 and
0x00FF and return 1.
.PP
\fBTcl_UniCharToUtfDString\fR converts the input in the form of a
sequence of \fBTcl_UniChar\fR code points to UTF-8, appending the result to the
previously initialized output \fBTcl_DString\fR. The return value is a pointer
to the UTF-8 representation of the \fBappended\fR string.
.PP
\fBTcl_UtfToUniCharDString\fR converts the input in the form of
a UTF-8 encoded string to a \fBTcl_UniChar\fR sequence
appending the result in the previously initialized \fBTcl_DString\fR.
The return value is a pointer to the appended result which is also
terminated with a \fBTcl_UniChar\fR null character.
.PP
\fBTcl_WCharToUtfDString\fR and \fBTcl_UtfToWCharDString\fR are similar to
\fBTcl_UniCharToUtfDString\fR and \fBTcl_UtfToUniCharDString\fR except they
operate on sequences of \fBwchar_t\fR instead of \fBTcl_UniChar\fR.
.PP
\fBTcl_Char16ToUtfDString\fR and \fBTcl_UtfToChar16DString\fR are similar to
\fBTcl_UniCharToUtfDString\fR and \fBTcl_UtfToUniCharDString\fR except they
operate on sequences of \fBUTF-16\fR units instead of \fBTcl_UniChar\fR.
.PP
\fBTcl_Char16Len\fR corresponds to \fBstrlen\fR for UTF-16
characters.  It accepts a null-terminated UTF-16 sequence and returns
the number of UTF-16 units until the null.
.PP
\fBTcl_WCharLen\fR corresponds to \fBstrlen\fR for wchar_t
characters.  It accepts a null-terminated \fBwchar_t\fR sequence and returns
the number of \fBwchar_t\fR units until the null.
.PP
\fBTcl_UniCharLen\fR corresponds to \fBstrlen\fR for Unicode
characters.  It accepts a null-terminated Unicode string and returns
the number of Unicode characters (not bytes) in that string.
.PP
\fBTcl_UniCharNcmp\fR and \fBTcl_UniCharNcasecmp\fR correspond to
\fBstrncmp\fR and \fBstrncasecmp\fR, respectively, for Unicode characters.
They accept two null-terminated Unicode strings and the number of characters
to compare.  Both strings are assumed to be at least \fIuniLength\fR characters
long. \fBTcl_UniCharNcmp\fR  compares the two strings character-by-character
according to the Unicode character ordering.  It returns an integer greater
than, equal to, or less than 0 if the first string is greater than, equal
to, or less than the second string respectively.  \fBTcl_UniCharNcasecmp\fR
is the Unicode case insensitive version.
.PP
\fBTcl_UniCharCaseMatch\fR is the Unicode equivalent to
\fBTcl_StringCaseMatch\fR.  It accepts a null-terminated Unicode string,
a Unicode pattern, and a boolean value specifying whether the match should
be case sensitive and returns whether the string matches the pattern.
.PP
\fBTcl_UtfNcmp\fR corresponds to \fBstrncmp\fR for UTF-8 strings. It
accepts two null-terminated UTF-8 strings and the number of characters
to compare.  (Both strings are assumed to be at least \fIlength\fR
characters long.)  \fBTcl_UtfNcmp\fR compares the two strings
character-by-character according to the Unicode character ordering.
It returns an integer greater than, equal to, or less than 0 if the
first string is greater than, equal to, or less than the second string
respectively.
.PP
\fBTcl_UtfNcasecmp\fR corresponds to \fBstrncasecmp\fR for UTF-8
strings.  It is similar to \fBTcl_UtfNcmp\fR except comparisons ignore
differences in case when comparing upper, lower or title case
characters.
.PP
\fBTcl_UtfCharComplete\fR returns 1 if the source UTF-8 string \fIsrc\fR
of \fInumBytes\fR bytes is long enough to be decoded by
\fBTcl_UtfToUniChar\fR/\fBTcl_UtfNext\fR, or 0 otherwise.  This function
does not guarantee that the UTF-8 string is properly formed.  This routine
is used by procedures that are operating on a byte at a time and need to
know if a full Unicode character has been seen.
.PP
\fBTcl_NumUtfChars\fR corresponds to \fBstrlen\fR for UTF-8 strings.  It
returns the number of Tcl_UniChars that are represented by the UTF-8 string
\fIsrc\fR.  The length of the source string is \fIlength\fR bytes.  If the
length is negative, all bytes up to the first null byte are used.
.PP
\fBTcl_UtfFindFirst\fR corresponds to \fBstrchr\fR for UTF-8 strings.  It
returns a pointer to the first occurrence of the Unicode character \fIch\fR
in the null-terminated UTF-8 string \fIsrc\fR.  The null terminator is
considered part of the UTF-8 string.
.PP
\fBTcl_UtfFindLast\fR corresponds to \fBstrrchr\fR for UTF-8 strings.  It
returns a pointer to the last occurrence of the Unicode character \fIch\fR
in the null-terminated UTF-8 string \fIsrc\fR.  The null terminator is
considered part of the UTF-8 string.
.PP
Given \fIsrc\fR, a pointer to some location in a UTF-8 string,
\fBTcl_UtfNext\fR returns a pointer to the next UTF-8 character in the
string.  The caller must not ask for the next character after the last
character in the string if the string is not terminated by a null
character. \fBTcl_UtfCharComplete\fR can be used in that case to
make sure enough bytes are available before calling \fBTcl_UtfNext\fR.
.PP
\fBTcl_UtfPrev\fR is used to step backward through but not beyond the
UTF-8 string that begins at \fIstart\fR.  If the UTF-8 string is made
up entirely of complete and well-formed characters, and \fIsrc\fR points
to the lead byte of one of those characters (or to the location one byte
past the end of the string), then repeated calls of \fBTcl_UtfPrev\fR will
return pointers to the lead bytes of each character in the string, one
character at a time, terminating when it returns \fIstart\fR.
.PP
When the conditions of completeness and well-formedness may not be satisfied,
a more precise description of the function of \fBTcl_UtfPrev\fR is necessary.
It always returns a pointer greater than or equal to \fIstart\fR; that is,
always a pointer to a location in the string. It always returns a pointer to
a byte that begins a character when scanning for characters beginning
from \fIstart\fR. When \fIsrc\fR is greater than \fIstart\fR, it
always returns a pointer less than \fIsrc\fR and greater than or
equal to (\fIsrc\fR - 4).  The character that begins
at the returned pointer is the first one that either includes the
byte \fIsrc[-1]\fR, or might include it if the right trail bytes are
present at \fIsrc\fR and greater. \fBTcl_UtfPrev\fR never reads the
byte \fIsrc[0]\fR nor the byte \fIstart[-1]\fR nor the byte
\fIsrc[-5]\fR.
.PP
\fBTcl_UniCharAtIndex\fR corresponds to a C string array dereference or the
Pascal Ord() function.  It returns the Unicode character represented at the
specified character (not byte) \fIindex\fR in the UTF-8 string
\fIsrc\fR.  The source string must contain at least \fIindex\fR
characters.  If \fIindex\fR is negative it returns -1.
.PP
\fBTcl_UtfAtIndex\fR returns a pointer to the specified character (not
byte) \fIindex\fR in the UTF-8 string \fIsrc\fR.  The source string must
contain at least \fIindex\fR characters.  This is equivalent to calling
\fBTcl_UtfToUniChar\fR \fIindex\fR times.  If \fIindex\fR is negative,
the return pointer points to the first character in the source string.
.PP
\fBTcl_UtfBackslash\fR is a utility procedure used by several of the Tcl
commands.  It parses a backslash sequence and stores the properly formed
UTF-8 character represented by the backslash sequence in the output
buffer \fIdst\fR.  At most 4 bytes are stored in the buffer.
\fBTcl_UtfBackslash\fR modifies \fI*readPtr\fR to contain the number
of bytes in the backslash sequence, including the backslash character.
The return value is the number of bytes stored in the output buffer.
.PP
See the \fBTcl\fR manual entry for information on the valid backslash
sequences.  All of the sequences described in the Tcl manual entry are
supported by \fBTcl_UtfBackslash\fR.

.SH KEYWORDS
utf, unicode, backslash