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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 {
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(STRING_SIZE(numChars))
#define stringAlloc(numChars) \
(String *) ckalloc(STRING_SIZE(numChars))
#define stringRealloc(ptr, numChars) \
(String *) ckrealloc((ptr), STRING_SIZE(numChars))
#define stringAttemptRealloc(ptr, numChars) \
(String *) attemptckrealloc((ptr), 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:
*/
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