Tcl_DStringTrunc
Tcl_DString(3) Tcl Library Procedures Tcl_DString(3)
______________________________________________________________________________
NAME
Tcl_DStringInit, Tcl_DStringAppend, Tcl_DStringAppendElement,
Tcl_DStringStartSublist, Tcl_DStringEndSublist, 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.
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 terminat-
ing character.
int newLength (in) New length for dynamic string, not
including null terminating charac-
ter.
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; anything
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 argument (it appends all of string) and it con-
verts the string to a proper list element before appending.
Tcl_DStringAppendElement adds a separator space before the new list
element unless the new list element 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_DStringAppendElement 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_DStringAppendElement for
each of the elements in the sublist, then call Tcl_DStringEndSublist to
end the sublist. 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 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 initial-
ize 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 trun-
cated to zero length, so Tcl_DStringFree will still need to be called.
Tcl_DStringTrunc changes the length of a dynamic string. This proce-
dure 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 reinitial-
izes 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 allocating 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)
