Tcl_DString(3) Tcl Library Procedures Tcl_DString(3)
____________________________________________________________________________________________________________
NAME
Tcl_DStringInit, Tcl_DStringAppend, Tcl_DStringAppendElement, Tcl_DStringStartSublist, Tcl_DStrin-gEndSublist, Tcl_DStringEndSublist,
gEndSublist, Tcl_DStringLength, Tcl_DStringValue, Tcl_DStringSetLength, Tcl_DStringTrunc,
Tcl_DStringFree, Tcl_DStringResult, Tcl_DStringGetResult - manipulate dynamic strings
SYNOPSIS
#include <tcl.h>
Tcl_DStringInit(dsPtr)
char *
Tcl_DStringAppend(dsPtr, string, length)
char *
Tcl_DStringAppendElement(dsPtr, string)
Tcl_DStringStartSublist(dsPtr)
Tcl_DStringEndSublist(dsPtr)
int
Tcl_DStringLength(dsPtr)
char *
Tcl_DStringValue(dsPtr)
Tcl_DStringSetLength(dsPtr, newLength)
Tcl_DStringTrunc(dsPtr, newLength)
Tcl_DStringFree(dsPtr)
Tcl_DStringResult(interp, dsPtr)
Tcl_DStringGetResult(interp, dsPtr)
ARGUMENTS
Tcl_DString *dsPtr (in/out) Pointer to structure that is used to manage a dynamic string.
CONST char *string (in) Pointer to characters to add to dynamic string.
int length (in) Number of characters from string to add to dynamic string. If
-1, add all characters up to null terminating character.
int newLength (in) New length for dynamic string, not including null terminating
character.
Tcl_Interp *interp (in/out) Interpreter whose result is to be set from or moved to the
dynamic string.
____________________________________________________________________________________________________________
DESCRIPTION
Dynamic strings provide a mechanism for building up arbitrarily long strings by gradually appending
information. If the dynamic string is short then there will be no memory allocation overhead; as
the string gets larger, additional space will be allocated as needed.
Tcl_DStringInit initializes a dynamic string to zero length. The Tcl_DString structure must have
been allocated by the caller. No assumptions are made about the current state of the structure; any-thing anything
thing already in it is discarded. If the structure has been used previously, Tcl_DStringFree should
be called first to free up any memory allocated for the old string.
Tcl_DStringAppend adds new information to a dynamic string, allocating more memory for the string if
needed. If length is less than zero then everything in string is appended to the dynamic string;
otherwise length specifies the number of bytes to append. Tcl_DStringAppend returns a pointer to the
characters of the new string. The string can also be retrieved from the string field of the
Tcl_DString structure.
Tcl_DStringAppendElement is similar to Tcl_DStringAppend except that it doesn't take a length argu-ment argument
ment (it appends all of string) and it converts the string to a proper list element before appending.
Tcl_DStringAppendElement adds a separator space before the new list element unless the new list ele-ment element
ment is the first in a list or sub-list (i.e. either the current string is empty, or it contains the
single character ``{'', or the last two characters of the current string are `` {''). Tcl_DStringAp-pendElement Tcl_DStringAppendElement
pendElement returns a pointer to the characters of the new string.
Tcl_DStringStartSublist and Tcl_DStringEndSublist can be used to create nested lists. To append a
list element that is itself a sublist, first call Tcl_DStringStartSublist, then call Tcl_DStringAp-pendElement Tcl_DStringAppendElement
pendElement for each of the elements in the sublist, then call Tcl_DStringEndSublist to end the sub-list. sublist.
list. Tcl_DStringStartSublist appends a space character if needed, followed by an open brace;
Tcl_DStringEndSublist appends a close brace. Lists can be nested to any depth.
Tcl_DStringLength is a macro that returns the current length of a dynamic string (not including the
terminating null character). Tcl_DStringValue is a macro that returns a pointer to the current con-tents contents
tents of a dynamic string.
Tcl_DStringSetLength changes the length of a dynamic string. If newLength is less than the string's
current length, then the string is truncated. If newLength is greater than the string's current
length, then the string will become longer and new space will be allocated for the string if needed.
However, Tcl_DStringSetLength will not initialize the new space except to provide a terminating null
character; it is up to the caller to fill in the new space. Tcl_DStringSetLength does not free up
the string's storage space even if the string is truncated to zero length, so Tcl_DStringFree will
still need to be called.
Tcl_DStringTrunc changes the length of a dynamic string. This procedure is now deprecated.
Tcl_DStringSetLength should be used instead.
Tcl_DStringFree should be called when you're finished using the string. It frees up any memory that
was allocated for the string and reinitializes the string's value to an empty string.
Tcl_DStringResult sets the result of interp to the value of the dynamic string given by dsPtr. It
does this by moving a pointer from dsPtr to the interpreter's result. This saves the cost of allo-cating allocating
cating new memory and copying the string. Tcl_DStringResult also reinitializes the dynamic string to
an empty string.
Tcl_DStringGetResult does the opposite of Tcl_DStringResult. It sets the value of dsPtr to the
result of interp and it clears interp's result. If possible it does this by moving a pointer rather
than by copying the string.
KEYWORDS
append, dynamic string, free, result
Tcl 7.4 Tcl_DString(3)
|