The example: http://www.koopman.me/dbtable/
I got the concept of the class, DbTable, from a book called PHP5 Professional. The idea is we have a class, this abstract class, that allows us to quickly make a new class out of any database table. Database tables make good objects. We often make them names of objects, like Shopper or Product. It makes sense to create classes that represent these objects, and to have a clean, consistent way to manipulate the data in the table. It also abstracts the database layer from application logic. If you just looked at example.phps, you’d have no idea if the database was flat file, MySQL, postgreSQL, or if it was even a database at all. Abstraction is a good thing, and one of the principles of object oriented programming.
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Deduplication is a term that refers to the practice of storing files by breaking up into chunks (or slices), getting a unique hash for each chunk, then storing the chunks and keeping metadata that explains how to reassemble the file later. This is useful in backup strategy, because you don’t have to back up the same file chunk twice. This is very useful when backing up multiple systems that contain the same, or similar files. Imagine that I backup files on one system, including common operating system files, and other common files. When I go to back them up on another machine, I don’t have to upload the file chunks on the second system, instead I’m merely storing the metadata about the file and how to reassemble it. Another good use is with files that grow. When I back it up a second time, rather than storing the same information, I only upload the new parts. A third use is taking snapshot backups of the same directory. If I take a full snapshot backup of a directory, the second time I take a snapshot of that same directory, I only upload the deltas. In other words, say I take a snapshot every day of a particular directory – instead of storing a full copy of mostly redundant data, I only save the new file chunks. The snapshot is a point in time map explaining which files existed and which chunks to use to reassemble each file.
The concept: Take each File -> break up into 5 MB chunks -> create a unique md4 hash of each chunk -> compare each hash to hashes already stored -> upload chunks that do not yet exist in the storage area -> save metadata so you can re-assemble the files later.
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If you haven’t heard of Amazon S3, check it out here. It’s remote storage for your files, at $0.15 per GB per month. You sign up for an account for free, then pay at the end of each month for the GB and data transfer you used. It’s nice and cheap, and I find it better than an FTP account to backup files, for a couple reasons. 1) It’s cheap, pay only for what you use. 2) Interface is all HTTP REST making it easier to interface with in code. 3) It’s cheap 4) You can make select files public readable and available via an HTTP address 5) There is a Firefox extension, S3 Organizer, that looks like an FTP client, you can move files back and forth from your desktop. 6) It’s all the hype right now 7) It’s cheap remote backup.
The HTTP REST interface is easy to use with PHP. I made a few command line utils with PHP:
s3ls <path> – lists file details in S3 account that are prefixed with <path>
s3put <file> – stores file in S3 account in the same dir it’s in on your server
s3get <file> – retrieves file from S3 account – can use absolute path, else it assumes current working directory
s3syncdir <dir> – removes files from S3 that no longer exist on server, then uploads any missing or modified files to S3
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s3put.php:
Note: This file requires:
pear install Crypt_HMAC
pear install HTTP_Request
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PostPosted: Sat Sep 10, 2005 6:00 pm Post subject: Reply with quote
Imagine that you are supposed to type in an email address into a form. You would typically type an email address that may be stored in your address book from a MySQL database. There are too many emails in your address book to pre-populate into a list on the page. Instead you want to start typing and have addresses that match what you’ve typed so far appear in a drop down. We will fetch the emails to populate the drop down from the server, on the fly, in the background.
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I’m just getting the code in the post for now… hopefully I’ll have time to come back and document it for you. I am excluding my config.php on purpose, you’ll need to define you’re own constants in there.
<?php
require_once(“config.php”);
require_once(“nusoap.php”);
/*
* This function takes an $email address and returns an array of email addresses
* that are the given email address’s recent contacts from their address book.
*
* @param string $email (the email address of the user)
* @param string $token (a password that is used for authentication for use of this function, it is NOT the email users password.)
*/
function getAutocompleteContacts( $email, $num, $token ) {
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Available from the PEAR website, http://pear.php.net/package/Net_IPv4, the Net_IPv4 package is pretty cool. Check this out:
<?php
require_once(“IPv4.php”);
$ip = $argv[1];
$netmask = $argv[2];
$ip_calc = new Net_IPv4();
$ip_calc->ip = $ip;
$ip_calc->netmask = $netmask;
$ip_calc->calculate();
$ip_calc->min = $ip_calc->network;
$ip_calc->max = $ip_calc->broadcast;
$ip_calc->min_long = $ip_calc->ip2double($ip_calc->network);
$ip_calc->max_long = $ip_calc->ip2double($ip_calc->broadcast);
$ip_calc->gateway = long2ip($ip_calc->max_long-1);
print_r($ip_calc);
?>
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Pre-req:
+ Must have php5 with –enable-sockets
What is a magic packet?
It’s a udp packet sent through the broadcast address to all servers on the network (ie, all servers serviced by the broadcast address). It’s called magic, because the format of the message is so strange. A mac address looks like this, 00:30:1B:BA:FA:47, it’s a series of 6 hexidecimal numbers. The magic packet message is a 6 char header, then the mac address, converted to a character sequence, repeated 16 times.
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