Wed Aug 28 22:11:25 2019 UTC ()

Add RCS Id, sort sections.


(wiz)

diff -r1.1 -r1.2 src/share/man/man9/thmap.9

--- src/share/man/man9/thmap.9 2019/08/28 20:08:11	1.1
+++ src/share/man/man9/thmap.9 2019/08/28 22:11:25	1.2

 @@ -1,236 +1,237 @@
 .\" $NetBSD: thmap.9,v 1.2 2019/08/28 22:11:25 wiz Exp $
 .\"
 .\" Copyright (c) 2018 Mindaugas Rasiukevicius <rmind at noxt eu>
 .\" All rights reserved.
 .\"
 .\" Redistribution and use in source and binary forms, with or without
 .\" modification, are permitted provided that the following conditions
 .\" are met:
 .\" 1. Redistributions of source code must retain the above copyright
 .\"    notice, this list of conditions and the following disclaimer.
 .\" 2. Redistributions in binary form must reproduce the above copyright
 .\"    notice, this list of conditions and the following disclaimer in the
 .\"    documentation and/or other materials provided with the distribution.
 .\"
 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
 .Dd December 11, 2018
 .Dt THMAP 9
 .Os
 .Sh NAME
 .Nm thmap
 .Nd concurrent trie-hash map
 .Sh SYNOPSIS
 .In thmap.h
 .\" -----
 .Ft thmap_t *
 .Fn thmap_create "uintptr_t baseptr" "const thmap_ops_t *ops" "unsigned flags"
 .Ft void
 .Fn thmap_destroy "thmap_t *hmap"
 .Ft void *
 .Fn thmap_get "thmap_t *hmap" "const void *key" "size_t len"
 .Ft void *
 .Fn thmap_put "thmap_t *hmap" "const void *key" "size_t len" "void *val"
 .Ft void *
 .Fn thmap_del "thmap_t *hmap" "const void *key" "size_t len"
 .Ft void *
 .Fn thmap_stage_gc "thmap_t *hmap"
 .Ft void
 .Fn thmap_gc "thmap_t *hmap" "void *ref"
 .Ft void
 .Fn thmap_setroot "thmap_t *thmap" "uintptr_t root_offset"
 .Ft uintptr_t
 .Fn thmap_getroot "const thmap_t *thmap"
 .\" -----
 .Sh DESCRIPTION
 Concurrent trie-hash map \(em a general purpose associative array,
 combining the elements of hashing and radix trie.
 Highlights:
 .Pp
 .Bl -hyphen -compact
 .It
 Very competitive performance, with logarithmic time complexity on average.
 .It
 Lookups are lock-free and inserts/deletes are using fine-grained locking.
 .It
 Incremental growth of the data structure (no large resizing/rehashing).
 .It
 Optional support for use with shared memory, e.g. memory-mapped file.
 .El
 .Pp
 Delete operations (the key/data destruction) must be synchronized with
 the readers using some reclamation mechanism.
 .\" -----
 .Sh FUNCTIONS
 .Bl -tag -width thmap_create
 .It Fn thmap_create
 Construct a new trie-hash map.
 The optional
 .Fa ops
 parameter can
 used to set the custom allocate/free operations (see the description of
 .Vt thmap_ops_t
 below).
 In such case, the
 .Fa baseptr
 is the base (start) address of the address space mapping (it must be
 word-aligned).
 If
 .Fa ops
 is set to
 .Dv NULL ,
 then
 .Xr malloc 3
 and
 .Xr free 3
 will be used as the default operations and
 .Fa baseptr
 should be set to zero.
 Currently, the supported
 .Fa flags
 are:
 .Bl -tag -width THMAP_NOCOPY
 .It Dv THMAP_NOCOPY
 The keys on insert will not be copied and the given pointers to them will
 be expected to be valid and the values constant until the key is deleted;
 by default, the put operation will make a copy of the key.
 .It Dv THMAP_SETROOT
 Indicate that the root of the map will be manually set using the
 .Fn thmap_setroot
 routine;
 by default, the map is initialized and the root node is set on
 .Fn thmap_create .
 .El
 .\" ---
 .It Fn thmap_destroy
 Destroy the map, freeing the memory it uses.
 .\" ---
 .It Fn thmap_get
 Lookup the key (of a given length) and return the value associated with it.
 Return
 .Dv NULL
 if the key is not found (see the
 .Sx CAVEATS
 section).
 .\" ---
 .It Fn thmap_put
 Insert the key with an arbitrary value.
 If the key is already present, return the already existing associated value
 without changing it.
 Otherwise, on a successful insert, return the given value.
 Just compare the result against
 .Fa val
 to test whether the insert was successful.
 .\" ---
 .It Fn thmap_del
 Remove the given key.
 If the key was present, return the associated value;
 otherwise return
 .Dv NULL .
 The memory associated with the entry is not released immediately, because
 in the concurrent environment (e.g., multi-threaded application) the caller
 may need to ensure it is safe to do so.
 It is managed using the
 .Fn thmap_stage_gc
 and
 .Fn thmap_gc
 routines.
 .\" ---
 .It Fn thmap_stage_gc
 Stage the currently pending entries (the memory not yet released after
 the deletion) for reclamation (G/C).
 This operation should be called
 .Em before
 the synchronization barrier.
 .Pp
 Returns a reference which must be passed to
 .Fn thmap_gc .
 Not calling the G/C function for the returned reference would result in
 a memory leak.
 .\" ---
 .It Fn thmap_gc
 Reclaim (G/C) the staged entries i.e. release any memory associated
 with the deleted keys.
 The reference must be the value returned by the call to
 .Fn thmap_stage_gc .
 .Pp
 This function must be called
 .Em after
 the synchronization barrier which guarantees that there are no active
 readers referencing the staged entries.
 .\" ---
 .El
 .Pp
 If the map is created using the
 .Fa THMAP_SETROOT
 flag, then the following functions are applicable:
 .\" ---
 .Bl -tag -width thmap_setroot
 .It Fn thmap_setroot
 Set the root node.
 The address must be relative to the base address, as if allocated by the
 .Fn thmap_ops_t::alloc
 routine.
 Return 0 on success and \-1 on failure (if already set).
 .It Fn thmap_getroot
 Get the root node address.
 The returned address will be relative to the base address.
 .El
 .\" ---
 .Pp
 Members of
 .Vt thmap_ops_t
 are
 .Bd -literal
         uintptr_t (*alloc)(size_t len);
         void      (*free)(uintptr_t addr, size_t len);
 .Ed
 .\" -----
 .Sh CAVEATS
 The implementation uses pointer tagging and atomic operations.
 This requires the base address and the allocations to provide at least word
 alignment.
 .Pp
 While the
 .Dv NULL
 values may be inserted,
 .Fn thmap_get
 and
 .Fn thmap_del
 cannot indicate whether the key was not found or a key with a
 .Dv NULL
 value was found.
 If the caller needs to indicate an "empty" value, it can use a
 special pointer value, such as
 .Li (void *)(uintptr_t)0x1 .
 .\" -----
 .Sh EXAMPLES
 Simple case backed by
 .Xr malloc 3 ,
 which could be used in multi-threaded environment:
 .Bd -literal
 	thmap_t *kvmap;
 	struct obj *obj;
 	kvmap = thmap_create(0, NULL);
 	assert(kvmap != NULL);
 	...
 	obj = obj_create();
 	thmap_put(kvmap, "test", sizeof("test") - 1, obj);
 	...
 	obj = thmap_get(kvmap, "test", sizeof("test") - 1);
 	...
 	thmap_destroy(kvmap);
 .Ed
 .\" -----
 .Sh AUTHORS
 .An Mindaugas Rasiukevicius Aq Mt rmind@noxt.eu
 .Sh CAVEATS
 The implementation uses pointer tagging and atomic operations.
 This requires the base address and the allocations to provide at least word
 alignment.
 .Pp
 While the
 .Dv NULL
 values may be inserted,
 .Fn thmap_get
 and
 .Fn thmap_del
 cannot indicate whether the key was not found or a key with a
 .Dv NULL
 value was found.
 If the caller needs to indicate an "empty" value, it can use a
 special pointer value, such as
 .Li (void *)(uintptr_t)0x1 .
 .\" -----