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Tcl_UtfAtIndex

Utf(3)                      Tcl Library Procedures                      Utf(3)



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NAME
       Tcl_UniChar,   Tcl_UniCharToUtf,  Tcl_UtfToUniChar,  Tcl_UniCharToUtfD-
       String,   Tcl_UtfToUniCharDString,   Tcl_UniCharLen,   Tcl_UniCharNcmp,
       Tcl_UtfCharComplete,  Tcl_NumUtfChars,  Tcl_UtfFindFirst,  Tcl_UtfFind-
       Last,  Tcl_UtfNext,  Tcl_UtfPrev,  Tcl_UniCharAtIndex,  Tcl_UtfAtIndex,
       Tcl_UtfBackslash - routines for manipulating UTF-8 strings.

SYNOPSIS
       #include <tcl.h>

       typedef ... Tcl_UniChar;

       int
       Tcl_UniCharToUtf(ch, buf)

       int
       Tcl_UtfToUniChar(src, chPtr)

       char *
       Tcl_UniCharToUtfDString(uniStr, numChars, dstPtr)

       Tcl_UniChar *
       Tcl_UtfToUniCharDString(src, len, dstPtr)

       int
       Tcl_UniCharLen(uniStr)

       int
       Tcl_UniCharNcmp(uniStr, uniStr, num)

       int
       Tcl_UtfNcmp(src, src, num)

       int
       Tcl_UtfNcasecmp(src, src, num)

       int
       Tcl_UtfCharComplete(src, len)

       int
       Tcl_NumUtfChars(src, len)

       char *
       Tcl_UtfFindFirst(src, ch)

       char *
       Tcl_UtfFindLast(src, ch)

       char *
       Tcl_UtfNext(src)

       char *
       Tcl_UtfPrev(src, start)

       Tcl_UniChar
       Tcl_UniCharAtIndex(src, index)

       char *
       Tcl_UtfAtIndex(src, index)

       int
       Tcl_UtfBackslash(src, readPtr, dst)

ARGUMENTS
       char                *buf       (out)     Buffer in which the UTF-8 rep-
                                                resentation of the Tcl_UniChar
                                                is     stored.      At    most
                                                TCL_UTF_MAX bytes  are  stored
                                                in the buffer.

       int                 ch         (in)      The  Tcl_UniChar  to  be  con-
                                                verted or examined.

       Tcl_UniChar         *chPtr     (out)     Filled  with  the  Tcl_UniChar
                                                represented by the head of the
                                                UTF-8 string.

       CONST char          *src       (in)      Pointer to a UTF-8 string.

       CONST Tcl_UniChar   *uniStr    (in)      A   NULL-terminated    Unicode
                                                string.

       int                 len        (in)      The length of the UTF-8 string
                                                in bytes  (not  UTF-8  charac-
                                                ters).  If negative, all bytes
                                                up to the first null byte  are
                                                used.

       int                 numChars   (in)      The   length  of  the  Unicode
                                                string in characters.  Must be
                                                greater than or equal to 0.

       Tcl_DString         *dstPtr    (in/out)  A pointer to a previously-ini-
                                                tialized Tcl_DString.

       unsigned long       num        (in)      The number  of  characters  to
                                                compare.

       CONST char          *start     (in)      Pointer  to the beginning of a
                                                UTF-8 string.

       int                 index      (in)      The index of a character  (not
                                                byte) in the UTF-8 string.

       int                 *readPtr   (out)     If  non-NULL,  filled with the
                                                number of bytes in  the  back-
                                                slash  sequence, including the
                                                backslash character.

       char                *dst       (out)     Buffer in which the bytes rep-
                                                resented   by   the  backslash
                                                sequence are stored.  At  most
                                                TCL_UTF_MAX  bytes  are stored
                                                in the buffer.
_________________________________________________________________


DESCRIPTION
       These routines convert  between  UTF-8  strings  and  Tcl_UniChars.   A
       Tcl_UniChar  is  a Unicode character represented as an unsigned, fixed-
       size quantity.  A UTF-8 character is a Unicode character represented as
       a  varying-length  sequence  of  up  to TCL_UTF_MAX bytes.  A multibyte
       UTF-8 sequence consists of a lead byte followed by some number of trail
       bytes.

       TCL_UTF_MAX  is  the maximum number of bytes that it takes to represent
       one Unicode character in the UTF-8 representation.

       Tcl_UniCharToUtf stores the Tcl_UniChar ch as a UTF-8 string in  start-
       ing at buf.  The return value is the number of bytes stored in buf.

       Tcl_UtfToUniChar  reads  one UTF-8 character starting at src and stores
       it as a Tcl_UniChar in *chPtr.  The return value is the number of bytes
       read  from src..  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 not in proper  UTF-8
       format,  Tcl_UtfToUniChar will store the first byte of src in *chPtr as
       a Tcl_UniChar between 0x0000 and 0x00ff and return 1.

       Tcl_UniCharToUtfDString converts the given  Unicode  string  to  UTF-8,
       storing  the  result in a previously-initialized Tcl_DString.  You must
       specify the length of the given Unicode string.  The return value is  a
       pointer to the UTF-8 representation of the Unicode string.  Storage for
       the return value is appended to the end of the Tcl_DString.

       Tcl_UtfToUniCharDString coverts the  given  UTF-8  string  to  Unicode,
       storing  the result in the previously-initialized Tcl_DString.  you may
       either specify the length of the given UTF-8 string or "-1",  in  which
       case  Tcl_UtfToUniCharDString uses strlen to calculate the length.  The
       return value is a pointer to the Unicode representation  of  the  UTF-8
       string.   Storage  for  the  return value is appended to the end of the
       Tcl_DString.  The Unicode string is  terminated  with  a  Unicode  NULL
       character.

       Tcl_UniCharLen  corresponds  to  strlen  for  Unicode  characters.   It
       accepts a NULL-terminated Unicode string and returns the number of Uni-
       code characters (not bytes) in that string.

       Tcl_UniCharNcmp  corresponds  to  strncmp  for  Unicode characters.  It
       accepts two NULL-terminated Unicode strings and the number  of  charac-
       ters  to compare.  (Both strings are assumed to be at least len charac-
       ters long.)  Tcl_UniCharNcmp 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.

       Tcl_UtfNcmp  corresponds  to  strncmp 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  len  characters long.)
       Tcl_UtfNcmp 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.

       Tcl_UtfNcasecmp  corresponds  to  strncasecmp for UTF-8 strings.  It is
       similar to Tcl_UtfNcmp except comparisons ignore  differences  in  case
       when comparing upper, lower or title case characters.

       Tcl_UtfCharComplete  returns 1 if the source UTF-8 string src of length
       len bytes is long enough to be decoded by Tcl_UtfToUniChar, or 0 other-
       wise.   This function does not guarantee that the UTF-8 string is prop-
       erly formed.  This routine is used by procedures that are operating  on
       a  byte at a time and need to know if a full Tcl_UniChar has been seen.

       Tcl_NumUtfChars corresponds to strlen for UTF-8  strings.   It  returns
       the  number  of  Tcl_UniChars  that are represented by the UTF-8 string
       src.  The length of the source string is len bytes.  If the  length  is
       negative, all bytes up to the first NULL byte are used.

       Tcl_UtfFindFirst corresponds to strchr for UTF-8 strings.  It returns a
       pointer to the first occurance of  the  Tcl_UniChar  ch  in  the  NULL-
       terminated UTF-8 string src.  The NULL terminator is considered part of
       the UTF-8 string.

       Tcl_UtfFindLast corresponds to strrchr for UTF-8 strings.  It returns a
       pointer  to the last occurance of the Tcl_UniChar ch in the NULL termi-
       nated UTF-8 string src.  The NULL terminator is considered part of  the
       UTF-8 string.

       Given  src,  a  pointer to some location in a UTF-8 string, Tcl_UtfNext
       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.

       Given src, a pointer to some location in a  UTF-8  string,  Tcl_UtfPrev
       returns  a pointer to the previous UTF-8 character in the string.  This
       function will not back up to a position before start, the start of  the
       UTF-8  string.   If  src was already at start, the return value will be
       start.

       Tcl_UniCharAtIndex corresponds to a C string array dereference  or  the
       Pascal  Ord()  function.  It returns the Tcl_UniChar represented at the
       specified character (not byte) index in  the  UTF-8  string  src.   The
       source  string  must  contain  at  least index characters.  Behavior is
       undefined if a negative index is given.

       Tcl_UtfAtIndex returns a pointer to the specified character (not  byte)
       index in the UTF-8 string src.  The source string must contain at least
       index characters.  This is  equivalent  to  calling  Tcl_UtfNext  index
       times.   If a negative index is given, the return pointer points to the
       first character in the source string.

       Tcl_UtfBackslash is a utility procedure used by several of the Tcl com-
       mands.   It  parses a backslash sequence and stores the properly formed
       UTF-8 character represented by the backslash  sequence  in  the  output
       buffer  dst.   At  most  TCL_UTF_MAX  bytes  are  stored in the buffer.
       Tcl_UtfBackslash modifies *readPtr 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.

       See the Tcl  manual  entry  for  information  on  the  valid  backslash
       sequences.   All of the sequences described in the Tcl manual entry are
       supported by Tcl_UtfBackslash.


KEYWORDS
       utf, unicode, backslash



Tcl                                   8.1                               Utf(3)