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