Simple Web Indexing System for Humans: C++ version
SWISH++ is a Unix-based file indexing and searching engine
(typically used to index and search files on web sites). It
was based on SWISH-E although SWISH++ is a complete rewrite.
SWISH++ was developed to circumvent my difficulties with using
the SWISH-E package.
SWISH++ has been ported to compile and run under Microsoft
Windows by Robert J. Lebowitz <firstname.lastname@example.org> and
Christoph Conrad <email@example.com>.
1. Lightning-fast indexing
SWISH++ attains its speed chiefly by doing two things:
using good algorithms and data structures and by doing fast
A. SWISH++ uses the C++ Standard Template Library's map
class that is typically implemented either as a
red-black or AVL tree for which the worst-case
running time is O(lg n).
B. SWISH++ uses the mmap(2) Unix system call to read
files instead of using standard I/O. If you are
unfamiliar with mmap, it "maps" a file into memory
using the same virtual memory management mechanism
the operating system itself uses. When the first
character of a file is read, a page fault occurs and
the operating system maps a page of the file into
memory. It is impossible to get faster access.
Additionally, because the file is in memory, the
characters in it are accessed via pointers using
simple pointer arithmetic rather than through
library function calls and input buffers.
Other factors contributing to SWISH++'s speed are that it
does very little explicit dynamic memory allocation, uses
function inlining, and makes very few function calls in
2. Indexes META elements, ALT, and other attributes
For HTML or XHTML files, SWISH++ indexes words in META
element CONTENT attributes and associates them with the
NAME attributes. Meta names can later be queried against
search author = hawking
SWISH++ also indexes the words in ALT attributes (for the
AREA, IMG, and INPUT elements), STANDBY attributes (for the
OBJECT element), SUMMARY attributes (for the TABLE
element), and TITLE attributes (for any HTML or XHTML
3. Selectively not index text within HTML or XHTML elements
Text within HTML or XHTML elements belonging to specified
classes can be not indexed. This is most useful not to
index text in common page headers, footers, and pop-up
4. Intelligently index mail and news files
SWISH++ indexes words in headers and associates them with
the name of the headers as meta names that can later be
queried against specifically, e.g.:
search subject = big-bang
Similarly, words in vCard fields are associated with the
names of the fields as meta names that can also later be
queried against, e.g.:
search title = professor
search org = SLAC
Additionally, plain and enriched text, and HTML in any one
of ASCII, ISO-8859-1, UTF-7, or UTF-8 character sets in any
one of 7-bit, 8-bit, quoted-printable, or base-64 encodings
is decoded and converted on-the-fly thus properly indexing
encoded bodies and attachments.
Lastly, attachments having other MIME types can be filtered
on-the-fly before being indexed, e.g., convert Microsoft
Word or PDF attachments to plain text.
5. Index Unix manual page files
SWISH++ indexes words in sections and associates them with
the name of the section as meta names that can later be
queried against specifically, e.g.:
search description = environment
search author = lucas
SWISH++ can therefore be used as a much better apropos(1)
6. Index LaTeX and RTF documents
SWISH++ can ignore LaTeX and RTF markup. Additionally, for LaTeX
documents, SWISH++ sets the document title to the content of the
7. Index ID3 tags of MP3 files
SWISH++ indexes words in ID3 tags of MP3 files and
associates them with the name of the fields as meta names
than can later be queried against specifically, e.g.:
search artist = roxette
search title = dangerous
All ID3 tag versions through 2.4 are supported.
Additionally, text fields in any one of ASCII, ISO-8859-1,
UTF-8, or UTF-16 character sets are supported.
8. Index non-text files such as Microsoft Office documents
A separate text-extraction utility "extract" is included to
assist in indexing non-text files. It is a essentially a
more sophisticated version of the Unix strings(1) command,
but employs the same word-determination heuristics used for
9. Apply filters to files on-the-fly prior to indexing
Based on filename patterns, files can be filtered before
being indexed, e.g.: compressed files uncompressed, PDF
files converted to plain text, etc.
10. Modular indexing architecture
New indexing modules can be written to index other file
formats directly (without filters).
11. Index new files incrementally
New files can be indexed and added to an existing index
12. Index remote web sites
A separate utility "httpindex" is included that interfaces
SWISH++ to the wget(1) command enabling remote web sites to
be indexed. This is useful to be able to search all the
servers in your local area network simultaneously.
13. Handles large collections of files
SWISH++ automatically splits and merges partial indices for
large collections of files as it goes thereby not bringing
your machine to its knees by exhausting physical memory and
causing it to swap like mad.
14. Lightning-fast searching
The same mmap(2) technique used for indexing is used again
for searching. The generated index file is written to disk
such that it can be mmap'ed back into memory and binary
searched immediately, with no parsing of the data, also in
O(lg n) time.
15. Optional word stemming (suffix stripping)
SWISH++ allows stemming to be performed at the time of
searches, not at the time of index generation. This allows
users to decide whether to perform stemming or not.
16. Ability to run as a search server
SWISH++'s search engine can run in the background as a
multi-threaded daemon process to function as a search
server accepting query requests and returning results via a
Unix domain or TCP socket or both. For search-intensive
applications, such as a search engine on a heavily used web
site, this can yield a large performance improvement since
the start-up cost (fork(2), exec(2), and initialization) is
paid only once.
17. Easy-to-parse results format
SWISH++ outputs its search results in the form:
rank path_name file_size file_title
By placing the file_title, which may contain spaces, last,
you can easily parse it, e.g., in Perl:
($rank,$path,$size,$title) = split( / /, $_, 4 );
18. XML results format
Alternatively, SWISH++ can output search results in XML for
increased interoperability with other XML applications.
19. Generously commented source code
The source code is clearly written with lots of comments
including references to other works in case you want to
modify it under the terms of the GNU general public
The following is a list of the features SWISH++ does not have
that SWISH-E does. I wrote SWISH++ to solve my immediate
indexing problems; therefore, I implemented only those features
useful to me. If others can also benefit from the work, great.
I may implement other features as time permits.
1. Indexing and searching based on HTML tags
SWISH++ has no equivalent means for searching within
specific HTML tags (the SWISH-E -t option). I didn't have a
need for this feature.
2. Document properties
This functionality can be achieved by using the extract_meta()
function in the included WWW Perl module.
3. Crash and burn on files
SWISH++ will not crash while indexing any file. Period. If
it does, there's a bug and I'll fix it.
Copyright (C) 1998-2002 by Paul J. Lucas <firstname.lastname@example.org>
SWISH++ is available under the GNU General Public License.
This file last updated: May 13, 2002