1Tcl_DString(3) Tcl Library Procedures Tcl_DString(3)
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8 Tcl_DStringInit, Tcl_DStringAppend, Tcl_DStringAppendElement,
9 Tcl_DStringStartSublist, Tcl_DStringEndSublist, Tcl_DStringLength,
10 Tcl_DStringValue, Tcl_DStringSetLength, Tcl_DStringTrunc,
11 Tcl_DStringFree, Tcl_DStringResult, Tcl_DStringGetResult - manipulate
12 dynamic strings
13
15 #include <tcl.h>
16 Tcl_DStringInit(dsPtr)
18 char *
20 Tcl_DStringAppend(dsPtr, bytes, length)
21 char *
23 Tcl_DStringAppendElement(dsPtr, element)
24 Tcl_DStringStartSublist(dsPtr)
26 Tcl_DStringEndSublist(dsPtr)
28 int
30 Tcl_DStringLength(dsPtr)
31 char *
33 Tcl_DStringValue(dsPtr)
34 Tcl_DStringSetLength(dsPtr, newLength)
36 Tcl_DStringTrunc(dsPtr, newLength)
38 Tcl_DStringFree(dsPtr)
40 Tcl_DStringResult(interp, dsPtr)
42 Tcl_DStringGetResult(interp, dsPtr)
44
46 Tcl_DString *dsPtr (in/out) Pointer to structure that is used
47 to manage a dynamic string.
48 const char *bytes (in) Pointer to characters to append to
50 dynamic string.
51 const char *element (in) Pointer to characters to append as
53 list element to dynamic string.
54 int length (in) Number of bytes from bytes to add
56 to dynamic string. If -1, add all
57 characters up to null terminating
58 character.
59 int newLength (in) New length for dynamic string, not
61 including null terminating charac‐
62 ter.
63 Tcl_Interp *interp (in/out) Interpreter whose result is to be
65 set from or moved to the dynamic
66 string.
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68
71 Dynamic strings provide a mechanism for building up arbitrarily long
72 strings by gradually appending information. If the dynamic string is
73 short then there will be no memory allocation overhead; as the string
74 gets larger, additional space will be allocated as needed.
75 Tcl_DStringInit initializes a dynamic string to zero length. The
77 Tcl_DString structure must have been allocated by the caller. No
78 assumptions are made about the current state of the structure; anything
79 already in it is discarded. If the structure has been used previously,
80 Tcl_DStringFree should be called first to free up any memory allocated
81 for the old string.
82 Tcl_DStringAppend adds new information to a dynamic string, allocating
84 more memory for the string if needed. If length is less than zero then
85 everything in bytes is appended to the dynamic string; otherwise
86 length specifies the number of bytes to append. Tcl_DStringAppend
87 returns a pointer to the characters of the new string. The string can
88 also be retrieved from the string field of the Tcl_DString structure.
89 Tcl_DStringAppendElement is similar to Tcl_DStringAppend except that it
91 does not take a length argument (it appends all of element) and it con‐
92 verts the string to a proper list element before appending.
93 Tcl_DStringAppendElement adds a separator space before the new list
94 element unless the new list element is the first in a list or sub-list
95 (i.e. either the current string is empty, or it contains the single
96 character “{”, or the last two characters of the current string are “
97 {”). Tcl_DStringAppendElement returns a pointer to the characters of
98 the new string.
99 Tcl_DStringStartSublist and Tcl_DStringEndSublist can be used to create
101 nested lists. To append a list element that is itself a sublist, first
102 call Tcl_DStringStartSublist, then call Tcl_DStringAppendElement for
103 each of the elements in the sublist, then call Tcl_DStringEndSublist to
104 end the sublist. Tcl_DStringStartSublist appends a space character if
105 needed, followed by an open brace; Tcl_DStringEndSublist appends a
106 close brace. Lists can be nested to any depth.
107 Tcl_DStringLength is a macro that returns the current length of a
109 dynamic string (not including the terminating null character).
110 Tcl_DStringValue is a macro that returns a pointer to the current con‐
111 tents of a dynamic string.
112 Tcl_DStringSetLength changes the length of a dynamic string. If
114 newLength is less than the string's current length, then the string is
115 truncated. If newLength is greater than the string's current length,
116 then the string will become longer and new space will be allocated for
117 the string if needed. However, Tcl_DStringSetLength will not initial‐
118 ize the new space except to provide a terminating null character; it
119 is up to the caller to fill in the new space. Tcl_DStringSetLength
120 does not free up the string's storage space even if the string is trun‐
121 cated to zero length, so Tcl_DStringFree will still need to be called.
122 Tcl_DStringTrunc changes the length of a dynamic string. This proce‐
124 dure is now deprecated. Tcl_DStringSetLength should be used instead.
125 Tcl_DStringFree should be called when you are finished using the
127 string. It frees up any memory that was allocated for the string and
128 reinitializes the string's value to an empty string.
129 Tcl_DStringResult sets the result of interp to the value of the dynamic
131 string given by dsPtr. It does this by moving a pointer from dsPtr to
132 the interpreter's result. This saves the cost of allocating new memory
133 and copying the string. Tcl_DStringResult also reinitializes the
134 dynamic string to an empty string.
135 Tcl_DStringGetResult does the opposite of Tcl_DStringResult. It sets
137 the value of dsPtr to the result of interp and it clears interp's
138 result. If possible it does this by moving a pointer rather than by
139 copying the string.
140
143 append, dynamic string, free, result
144Tcl 7.4 Tcl_DString(3)