erminating NUL byte.  Since it does not need
 *				an extra byte for a terminating NUL, it fills
 *				all dstLen bytes with encoded UTF-8 content if
 *				needed.  If clear, a byte is reserved in the
 *				dst space for NUL termination, and a
 *				terminating NUL is appended.
 * TCL_ENCODING_CHAR_LIMIT -	If set and dstCharsPtr is not NULL, then
 *				Tcl_ExternalToUtf takes the initial value of
 *				*dstCharsPtr as a limit of the maximum number
 *				of chars to produce in the encoded UTF-8
 *				content.  Otherwise, the number of chars
 *				produced is controlled only by other limiting
 *				factors.
 */

#define TCL_ENCODING_START		0x01
#define TCL_ENCODING_END		0x02
#define TCL_ENCODING_STOPONERROR	0x04
#define TCL_ENCODING_NO_TERMINATE	0x08
#define TCL_ENCODING_CHAR_LIMIT		0x10

/*
 * The following definitions are the error codes returned by the conversion
 * routines:
 *
 * TCL_OK -			All characters were converted.
 * TCL_CONVERT_NOSPACE -	The output buffer would not have been large
 *				enough for all of the converted data; as many
 *				characters as could fit were converted though.
 * TCL_CONVERT_MULTIBYTE -	The last few bytes in the source string 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 the beginning of this
 *				unconverted sequence plus additional bytes
 *				from the source stream to properly convert the
 *				formerly split-up multibyte sequence.
 * TCL_CONVERT_SYNTAX -		The source stream contained an invalid
 *				character sequence. This may occur if the
 *				input stream has been damaged or if the input
 *				encoding method was misidentified. This error
 *				is reported only if TCL_ENCODING_STOPONERROR
 *				was specified.
 * TCL_CONVERT_UNKNOWN -	The source string contained a character that
 *				could not be represented in the target
 *				encoding. This error is reported only if
 *				TCL_ENCODING_STOPONERROR was specified.
 */

#define TCL_CONVERT_MULTIBYTE	(-1)
#define TCL_CONVERT_SYNTAX	(-2)
#define TCL_CONVERT_UNKNOWN	(-3)
#define TCL_CONVERT_NOSPACE	(-4)

/*
 * The maximum number of bytes that are necessary to represent a single
 * Unicode character in UTF-8. The valid values should be 3, 4 or 6
 * (or perhaps 1 if we want to support a non-unicode enabled core). If 3 or
 * 4, then Tcl_UniChar must be 2-bytes in size (UCS-2) (the default). If 6,
 * then Tcl_UniChar must be 4-bytes in size (UCS-4). At this time UCS-2 mode
 * is the default and recommended mode. UCS-4 is experimental and not
 * recommended. It works for the core, but most extensions expect UCS-2.
 */

#ifndef TCL_UTF_MAX
#define TCL_UTF_MAX		3
#endif

/*
 * This represents a Unicode character. Any changes to this should also be
 * reflected in regcustom.h.
 */

#if TCL_UTF_MAX > 4
    /*
     * unsigned int isn't 100% accurate as it should be a strict 4-byte value.
     * The size of this value must be reflected correctly in regcustom.h.
     * XXX: Tcl is currently UCS-2 and planning UTF-16 for the Unicode
     * XXX: string rep that Tcl_UniChar represents.  Changing the size
     * XXX: of Tcl_UniChar is /not/ supported.
     */
typedef unsigned int Tcl_UniChar;
#else
typedef unsigned short Tcl_UniChar;
#endif