Tcl_DString(3) Tcl (7.4) Tcl_DString(3)
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NAME
Tcl_DStringInit, Tcl_DStringAppend,
Tcl_DStringAppendElement, Tcl_DStringStartSublist,
Tcl_DStringEndSublist, Tcl_DStringLength, Tcl_DStringValue,
Tcl_DStringSetLength, 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_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 terminating
character.
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Tcl_DString(3) Tcl (7.4) Tcl_DString(3)
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.
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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 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 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
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Tcl_DString(3) Tcl (7.4) Tcl_DString(3)
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 contents 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_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 interp->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
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