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.\" ========================================================================
.\"
.IX Title "tst 3"
.TH tst 3 "2008-04-06" "INN 2.4.5" "InterNetNews Documentation"
.SH "NAME"
tst \- ternary search trie functions
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
\&\fB#include <inn/tst.h>\fR
.PP
\&\fBstruct tst;\fR
.PP
\&\fBstruct tst *tst_init(int \fR\fInode_line_width\fR\fB);\fR
.PP
\&\fBvoid tst_cleanup(struct tst *\fR\fItst\fR\fB);\fR
.PP
\&\fBint tst_insert(struct tst *\fR\fItst\fR\fB, const unsigned char *\fR\fIkey\fR\fB, void *\fR\fIdata\fR\fB, int \fR\fIoption\fR\fB, void **\fR\fIexist_ptr\fR\fB);\fR
.PP
\&\fBvoid *tst_search(struct tst *\fR\fItst\fR\fB, const unsigned char *\fR\fIkey\fR\fB);\fR
.PP
\&\fBvoid *tst_delete(struct tst *\fR\fItst\fR\fB, const unsigned char *\fR\fIkey\fR\fB);\fR
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fBtst_init\fR allocates memory for members of \fIstruct tst\fR, and
allocates the first \fInode_line_width\fR nodes. A \s-1NULL\s0 pointer is
returned by \fBtst_init\fR if any part of the memory allocation fails. On
success, a pointer to a \fIstruct tst\fR is returned.
.PP
The value for \fInode_line_width\fR must be chosen very carefully. One
node is required for every character in the tree. If you choose a
value that is too small, your application will spend too much time
calling \fImalloc\fR\|(3) and your node space will be too spread out. Too large
a value is just a waste of space.
.PP
\&\fBtst_cleanup\fR frees all memory allocated to nodes, internal structures,
as well as \fItst\fR itself.
.PP
\&\fBtst_insert\fR inserts the string \fIkey\fR into the tree. Behavior when a
duplicate key is inserted is controlled by \fIoption\fR. If \fIkey\fR is
already in the tree then \fB\s-1TST_DUPLICATE_KEY\s0\fR is returned, and the
data pointer for the existing key is placed in \fIexist_ptr\fR.  If
\&\fIoption\fR is set to \fB\s-1TST_REPLACE\s0\fR then the existing data pointer for
the existing key is replaced by \fIdata\fR.  Note that the old data
pointer will still be placed in \fIexist_ptr\fR.
.PP
If a duplicate key is encountered and \fIoption\fR is not set to
\&\fB\s-1TST_REPLACE\s0\fR then \fB\s-1TST_DUPLICATE_KEY\s0\fR is returned. If \fIkey\fR is
zero length then \fB\s-1TST_NULL_KEY\s0\fR is returned. A successful insert or
replace returns \fB\s-1TST_OK\s0\fR. A return value of \fB\s-1TST_ERROR\s0\fR indicates
that a memory allocation error occurred while trying to grow the node
free.
.PP
Note that the \fIdata\fR argument must never be \fB\s-1NULL\s0\fR. If it is, then
calls to \fBtst_search\fR will fail for a key that exists because the
data value was set to \fB\s-1NULL\s0\fR, which is what \fBtst_search\fR returns. If
you just want a simple existence tree, use the \fBtst\fR pointer as the
data pointer.
.PP
\&\fBtst_search\fR finds the string \fIkey\fR in the tree if it exists and
returns the data pointer associated with that key.
.PP
If \fIkey\fR is not found then \fB\s-1NULL\s0\fR is returned, otherwise the data pointer
associated with \fIkey\fR is returned.
.PP
\&\fBtst_delete\fR deletes the string \fIkey\fR from the tree if it exists and
returns the data pointer assocaited with that key.
.PP
If \fIkey\fR is not found then \fB\s-1NULL\s0\fR is returned, otherwise the data
pointer associated with \fIkey\fR is returned.
.SH "HISTORY"
.IX Header "HISTORY"
Converted to \s-1POD\s0 from Peter A. Friend's ternary search trie
documentation by Alex Kiernan <alex.kiernan@thus.net> for InterNetNews
2.4.0.
.PP
$Id: tst.3 7880 2008-06-16 20:37:13Z iulius $