Long URLs are mapped to a short representation and available via a shorter URL. Sample use cases:
- message length restricted forums (IRC, IM, etc.)
- ASCII representation of complicated URLs for technical reasons
- easily hand-writable URLs with low error rate on subsequent input.
Made from proof-of-concept and "would be fun to do some web programming in Python" perspectives, and that is where it will most probably stay. I run it locally for personal use only at the moment.
No styling has been done HTML-wise apart from semantic markup. It would be an easy task to add, though.
It is needed to set up
- the database structure
- the web server configuration
- the script configuration file to reflect above choices.
See shortweb.example.config in the base directory.
Default translation (short → long) table:
CREATE TABLE IF NOT EXISTS `translation_table` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`long_url` varchar(2048) COLLATE utf8_unicode_ci NOT NULL,
`last_accessed` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00'
ON UPDATE CURRENT_TIMESTAMP,
`created` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
`access_counter` int(10) unsigned NOT NULL DEFAULT '0',
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
Default base representation table:
CREATE TABLE IF NOT EXISTS `base_info` (
`base_chars` varchar(53) COLLATE utf8_unicode_ci NOT NULL,
PRIMARY KEY (`base_chars`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
INSERT INTO `base_info` (`base_chars`) VALUES
('abcdefghijkmnopqrstuvwxyzACDEFGHJKLMNPQRTUVWXYZ234679');
Note that varchar(53) corresponds to the number of characters in the base.
The chosen base decides which characters are available for URL shortening. Rules/guidelines:
- Make sure all characters are unique.
- Don't change base once the system is in place (this will destroy the short form mapping and invalidate previously generated URLs).
- Tabs, spaces and newlines are allowed for readability in code, but are stripped before use.
- Avoid
+/&?[]and other characters that get mangled or otherwise special treatment in HTTP transmission.+is also used as a "magic value" as a URL with a trailing+shows the corresponding link info instead of redirecting.
The more available characters, the shorter the URLs become in general. N allowed characters gives N^M different entries for M short ID characters.
#Enables <http://example.com/s/{shortid}> style links via mod_rewrite.
<Directory /var/www>
RewriteEngine on
RewriteRule ^s/?([^/]*)/?$ /short?short=$1 [L]
</Directory>
#Keep the CGI directory out of the web root for security reasons.
ScriptAlias /short "/path/to/the/script/shortweb.cgi"
<Directory /path/to/the/script>
Order allow,deny
allow from all
</Directory>
If you are not interested in these, just skip this section.
Create a configuration file shortweb.test.config in the base directory. It
has the same form as the regular configuration file. Here is a sample to
illustrate some points:
[DB]
host = localhost
user = short
passwd = password
db = short
# Do the testing in a separate table. Not "really" needed, but good form in
# case tests fail. Just copy the standard table to the one specified below.
data_table_name = test_translation_table
# Define a short form that is not supposed to have a corresponding
# translation entry. The one below won't be assigned in my base until I
# have 10^17 entries, so it's quite safe.
base_id_with_no_corresponding_db_entry = bananarama
# These two values are inserted into the table beforehand to test that
# the modules return correct results.
long_url = http://farside.ph.utexas.edu/teaching/jk1/lectures/node50.html
# `c` in my base corresponds to `id`=2 in the test table.
base_id = c
[Web]
base_url = http://example.com/s/
title = Test suite title
One of the tests in swlib.dbinteraction uses a stored procedure in MySQL to
restore AUTO_INCREMENT on the test table after adding and removing test
entries. It can be commented or implemented in SQL in the test code via a
commented example, or the stored procedure can be added, also with instructions
in the file itself.
The project lives at https://github.com/dandersson/shortweb.