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diff --git a/generic/tclStringRep.h b/generic/tclStringRep.h
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+/*
+ * tclStringRep.h --
+ *
+ *	This file contains the definition of the Unicode string internal
+ *	representation and macros to access it.
+ *
+ *	A Unicode string is an internationalized string. Conceptually, a
+ *	Unicode string is an array of 16-bit quantities organized as a
+ *	sequence of properly formed UTF-8 characters. There is a one-to-one
+ *	map between Unicode and UTF characters. Because Unicode characters
+ *	have a fixed width, operations such as indexing operate on Unicode
+ *	data. The String object is optimized for the case where each UTF char
+ *	in a string is only one byte. In this case, we store the value of
+ *	numChars, but we don't store the Unicode data (unless Tcl_GetUnicode
+ *	is explicitly called).
+ *
+ *	The String object type stores one or both formats. The default
+ *	behavior is to store UTF. Once Unicode is calculated by a function, it
+ *	is stored in the internal rep for future access (without an additional
+ *	O(n) cost).
+ *
+ *	To allow many appends to be done to an object without constantly
+ *	reallocating the space for the string or Unicode representation, we
+ *	allocate double the space for the string or Unicode and use the
+ *	internal representation to keep track of how much space is used vs.
+ *	allocated.
+ *
+ * Copyright (c) 1995-1997 Sun Microsystems, Inc.
+ * Copyright (c) 1999 by Scriptics Corporation.
+ *
+ * See the file "license.terms" for information on usage and redistribution of
+ * this file, and for a DISCLAIMER OF ALL WARRANTIES.
+ */
+
+/*
+ * The following structure is the internal rep for a String object. It keeps
+ * track of how much memory has been used and how much has been allocated for
+ * the Unicode and UTF string to enable growing and shrinking of the UTF and
+ * Unicode reps of the String object with fewer mallocs. To optimize string
+ * length and indexing operations, this structure also stores the number of
+ * characters (same of UTF and Unicode!) once that value has been computed.
+ *
+ * Under normal configurations, what Tcl calls "Unicode" is actually UTF-16
+ * restricted to the Basic Multilingual Plane (i.e. U+00000 to U+0FFFF). This
+ * can be officially modified by altering the definition of Tcl_UniChar in
+ * tcl.h, but do not do that unless you are sure what you're doing!
+ */
+
+typedef struct String {
+    int numChars;		/* The number of chars in the string. -1 means
+				 * this value has not been calculated. >= 0
+				 * means that there is a valid Unicode rep, or
+				 * that the number of UTF bytes == the number
+				 * of chars. */
+    int allocated;		/* The amount of space actually allocated for
+				 * the UTF string (minus 1 byte for the
+				 * termination char). */
+    int maxChars;		/* Max number of chars that can fit in the
+				 * space allocated for the unicode array. */
+    int hasUnicode;		/* Boolean determining whether the string has
+				 * a Unicode representation. */
+    Tcl_UniChar unicode[1];	/* The array of Unicode chars. The actual size
+				 * of this field depends on the 'maxChars'
+				 * field above. */
+} String;
+
+#define STRING_MAXCHARS \
+    (int)(((size_t)UINT_MAX - sizeof(String))/sizeof(Tcl_UniChar))
+#define STRING_SIZE(numChars) \
+    (sizeof(String) + ((numChars) * sizeof(Tcl_UniChar)))
+#define stringCheckLimits(numChars) \
+    do {								\
+	if ((numChars) < 0 || (numChars) > STRING_MAXCHARS) {		\
+	    Tcl_Panic("max length for a Tcl unicode value (%d chars) exceeded", \
+		      STRING_MAXCHARS);					\
+	}								\
+    } while (0)
+#define stringAttemptAlloc(numChars) \
+    (String *) attemptckalloc((unsigned) STRING_SIZE(numChars))
+#define stringAlloc(numChars) \
+    (String *) ckalloc((unsigned) STRING_SIZE(numChars))
+#define stringRealloc(ptr, numChars) \
+    (String *) ckrealloc((ptr), (unsigned) STRING_SIZE(numChars))
+#define stringAttemptRealloc(ptr, numChars) \
+    (String *) attemptckrealloc((ptr), (unsigned) STRING_SIZE(numChars))
+#define GET_STRING(objPtr) \
+    ((String *) (objPtr)->internalRep.twoPtrValue.ptr1)
+#define SET_STRING(objPtr, stringPtr) \
+    ((objPtr)->internalRep.twoPtrValue.ptr1 = (void *) (stringPtr))
+
+/*
+ * Local Variables:
+ * mode: c
+ * c-basic-offset: 4
+ * fill-column: 78
+ * End:
+ */