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.TH Ns_DString 3aolserver 4.0 AOLserver "AOLserver Library Procedures"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
Ns_DStringAppend, Ns_DStringAppendArg, Ns_DStringAppendElement, Ns_DStringExport, Ns_DStringFree, Ns_DStringInit, Ns_DStringLength, Ns_DStringNAppend, Ns_DStringPop, Ns_DStringPrintf, Ns_DStringPush, Ns_DStringSetLength, Ns_DStringTrunc, Ns_DStringValue, Ns_DStringVarAppend \- library procedures
.SH SYNOPSIS
.nf
\fB#include "ns.h"\fR
.sp
char *
\fBNs_DStringAppend\fR(\fINs_DString *dsPtr, char *string\fR)
.sp
char *
\fBNs_DStringAppendArg\fR(\fINs_DString *dsPtr, char *string\fR)
.sp
char *
\fBNs_DStringAppendElement\fR(\fINs_DString *dsPtr, char *string\fR)
.sp
char *
\fBNs_DStringExport\fR(\fINs_DString *dsPtr\fR)
.sp
void
\fBNs_DStringFree\fR(\fINs_DString *dsPtr\fR)
.sp
void
\fBNs_DStringInit\fR(\fINs_DString *dsPtr\fR)
.sp
int
\fBNs_DStringLength\fR(\fINs_DString *dsPtr\fR)
.sp
char *
\fBNs_DStringNAppend\fR(\fINs_DString *dsPtr, char *string, int length\fR)
.sp
Ns_DString *
\fBNs_DStringPop\fR(\fIvoid\fR)
.sp
char *
\fBNs_DStringPrintf\fR(\fINs_DString *dsPtr, char *fmt,...\fR)
.sp
void
\fBNs_DStringPush\fR(\fINs_DString *dsPtr\fR)
.sp
void
\fBNs_DStringSetLength\fR(\fINs_DString *dsPtr, int length\fR)
.sp
void
\fBNs_DStringTrunc\fR(\fINs_DString *dsPtr, int length\fR)
.sp
char *
\fBNs_DStringValue\fR(\fINs_DString *dsPtr\fR)
.sp
char *
\fBNs_DStringVarAppend\fR(\fINs_DString *dsPtr, ...\fR)
.BE

.SH DESCRIPTION
.PP
These functions create, manipulate and destroy
Ns_DStrings. Ns_DStrings are structures that store strings and
information about the string length. These dynamic strings grow as
need to fit the strings placed in them or appended to them. If the
Ns_DString plus the appended string are larger than the size of
original string within the Ns_DString, for example, the Ns_DString
will be automatically extended by allocating more memory to it.
.PP
Many functions return string pointers that point directly to the
string within an Ns_DString structure. You must not free these
returned string pointers with Ns_Free or any other freeing function,
but must instead use Ns_DStringFree to free memory associated with the
Ns_DString.
.TP
\fBNs_DStringAppend\fR(\fIdsPtr, string\fR)

Append the specified string plus a terminating null character to the
end of the Ns_DString. Returns the string associated with the
current Ns_DString.

The Ns_DString ds of the following code would contain "foo\0" and
have a length of 3:

.CS
Ns_DString ds;
Ns_DStringInit(&ds);
Ns_DStringAppend(&ds, "foo");
/* do something with the dstring */
printf("%s\n", ds.string);
/* finished with dstring */
Ns_DStringFree(&ds);

.CE
.TP
\fBNs_DStringAppendArg\fR(\fIdsPtr, string\fR)

Append the specified argument plus a terminating null character to the
end of the Ns_DString. It is useful for making strings like
"foo\0bar\0baz\0". The string pointer associated with the current
Ns_DString is returned.
.TP
\fBNs_DStringAppendElement\fR(\fIdsPtr, string\fR)

Append a list element to the current value of a dynamic string. The
string argument is reformatted as a list element and added to the
current value of the Ns_DString.  The return value is a pointer to the
dynamic string's new value.
.TP
\fBNs_DStringExport\fR(\fIdsPtr\fR)

Returns the current Ns_DString string and leaves the Ns_DString in the
initialized state. In this case, the string returned needs to be freed
eventually with \fBNs_Free\fR because the string pointer returned is
not a part of the Ns_DString any longer.

.CS
Ns_DString ds;
char *stringdest;
Ns_DStringInit(&ds);
Ns_DStringAppend(&ds, "foo");
stringdest = Ns_DStringExport(&ds);
/* do something with .stringdest. */
Ns_Free(stringdest);
.CE
.TP
\fBNs_DStringFree\fR(\fIdsPtr\fR)

Free any allocated memory used by an Ns_DString.
.TP
\fBNs_DStringInit\fR(\fIdsPtr\fR)

Initialize an Ns_DString. Before using an Ns_DString, you must
initialize it with Ns_DStringInit. Storage for an Ns_DString is often
on the stack in the calling function. The example below shows a
typical usage.

.CS
int MyFunctions(int a, int b)
{
    Ns_DString ds;
    Ns_DStringInit(&ds);
    /*
     * ds is now initialized and ready to
     * pass to another function
     */
    ...
}
.CE
.TP
\fBNs_DStringLength\fR(\fIdsPtr\fR)

Return the current length of the string value that is contained within
an Ns_DString.

.CS
Ns_DString ds;
Ns_DStringInit(&ds);
Ns_DStringAppend(&ds, "<html></html>");
printf("len=%d\n", Ns_DStringLength(&ds));
/* finished with dstring */
Ns_DStringFree(&ds); 
.CE
.TP
\fBNs_DStringNAppend\fR(\fIdsPtr, string, length\fR)

Append n-characters of string to Ns_DString dsPtr. The function appends
a string up to the specified number of characters, plus a terminating
null character. Unlike the Tcl_DStringAppend function, which only
works with string data, the AOLserver Ns_DStringNAppend function can
append binary data.  Returns the string associated with the current
Ns_DString.

.CS
The resulting Ns_DString in this example, ds would
contain "foo\0" and have a length of 3:

Ns_DString ds;
Ns_DStringInit(&ds);
Ns_DStringNAppend(&ds, "fooasdf", 3);
printf("%s\n", ds.string);
Ns_DStringFree(&ds); /* finished with dstring */

If you need a null-terminated list of null-terminated
strings, such as "foo\0bar\0\0", you would add one to
the length of the appended strings to get the extra
terminating null character. For example:

Ns_DString ds;
Ns_DStringInit(&ds);
Ns_DStringNAppend(&ds, "foo", 4);
Ns_DStringNAppend(&ds, "bar", 4);
.CE
.TP
\fBNs_DStringPop\fR(\fIvoid\fR)

Pop an Ns_DString from the per-thread cache, allocating the space for
the Ns_DString if necessary.  This will initialize Thread Local
Storage (TLS) and configure parameters on first use. TLS is a means of
storing data associated with a particular thread within the thread's
context, so that it is always available to that thread. A pointer to
the initialized Ns_DString is returned.
.TP
\fBNs_DStringPrintf\fR(\fIdsPtr, fmt, ...\fR)

Append a formatted string to an Ns_DString. The Ns_DStringPrintf
function appends a string that has been created by calling the sprintf
function with the given format and optional arguments. This function
currently uses a fixed length buffer of 1024 characters to sprintf()
the data before appending to the Ns_DString.

.CS
Ns_DString ds;

Ns_DStringInit(&ds);
Ns_DStringPrintf(&ds, "/path%d", getpid());
/* do something with dstring */
printf ("%s\n", ds.string);
/* finished with dstring */
Ns_DStringFree(&ds);
.CE
.TP
\fBNs_DStringPush\fR(\fIdsPtr\fR)

Push an Ns_DString onto the per-thread cache. The Ns_DString will be
free'd if the maximum number of entries or the maximum size parameters
have been exceeded. The contents held by the Ns_DString are destroyed.

This is a performance function. Creating Ns_DStrings is a more expensive
operation than cleaning out an already-existing Ns_DString and storing
it for later use by the same thread.
.TP
\fBNs_DStringSetLength\fR(\fIdsPtr, length\fR)

The length of dsPtr is changed to length and a null byte is
stored at that position in the string.  If length is larger
than the space allocated for dsPtr, then a panic occurs.
.TP
\fBNs_DStringTrunc\fR(\fIdsPtr, length\fR)

Truncate an Ns_DString. The Ns_DStringTrunc function truncates an
Ns_DString to the given length. Unlike Ns_DStringFree, which truncates
the Ns_DString to length 0 and frees any memory that may have been
allocated on the heap, Ns_DStringTrunc allows you to truncate the
string to any length. It maintains any memory allocated on the
heap. This function is useful in a loop where the Ns_DString is likely
to overflow the static space each time through. Using Ns_DStringTrunc
instead of Ns_DStringFree will avoid having the Ns_DString call malloc
to obtain the addition space in each iteration. You will need to call
Ns_DStringFree eventually to free any space that may have been
allocated for the Ns_DString.

.CS
Ns_DString ds;
int i;
Ns_DStringInit(&ds);

for (i=0; i < 50; i++) {
    Ns_DStringPrintf(&ds, "%s%d", "aBigString", i);
    /* do something with the dstring constructed above */
    Ns_DStringTrunc(&ds, 0);
}
.CE
.TP
\fBNs_DStringValue\fR(\fIdsPtr\fR)

Return the current value of an Ns_DString. The Ns_DStringValue macro
returns a pointer to the current value of an Ns_DString.  This may be
a pointer to the Ns_DString.s static space or to a string allocated on
the heap if the static space has overflowed. It is not safe to use the
value returned by this macro after an intervening call to
Ns_DStringAppend because the Ns_DString string could overflow to or
move within the heap.

.CS
Ns_DString ds;
Ns_DStringInit(&ds);
Ns_DStringAppend(&ds, "foo");
/* do something with the dstring */
printf ("%s\n", Ns_DStringValue(&ds));
Ns_DStringFree(&ds);
.CE
.TP
\fBNs_DStringVarAppend\fR(\fIdsPtr, ...\fR)

Append a variable number of strings to an Ns_DString. The
Ns_DStringVarAppend function appends a variable number of strings to
an Ns_DString. The list must end with NULL.

.CS
Ns_DString ds;
Ns_DStringInit(&ds);
Ns_DStringVarAppend(&ds, "foo", "bar", NULL);
/* do something with the dstring */
printf ("%s\n", ds.string);
Ns_DStringFree(&ds);
.CE
.SH "SEE ALSO"
nsd(1), info(n)

.SH KEYWORDS