I got a text at 8:00am:
"Hey, can you jump on a conference call?"
Groggy and disoriented, I blearily type the conference line and enter my
passcode, followed by the pound or hash sign. At the tone, I would be the 6th
person to enter the conference. Tone.
"The app is down, and trading has stopped."
Continue reading Mojolicious Triumphs Over Legacy Code...
Originally posted on blogs.perl.org -- Managing SQL Data with
Every week, I work with about a dozen SQL databases. Some are Sybase, some
MySQL, some SQLite. Some have different versions in dev, staging, and
production. All of them need data extracted, transformed, and loaded.
DBI is the clear choice for dealing with SQL databases in Perl, but there are a
dozen lines of Perl code in between me and the operation that I want. Sure,
I've got modules and web applications and ad-hoc commands and scripts that
perform certain individual tasks on my databases, but sometimes those things
don't quite do what I need right now, and I just want something that will let
me execute whatever SQL I can come up with.
Yertl (ETL::Yertl) is a shell-based ETL
framework. It's under development (as is all software), but included already is
a small utility called ysql to make dealing
with SQL databases easy.
Continue reading Managing SQL Data with Yertl...
Boilerplate is everything I hate about programming:
- Doing the same thing more than once
- Leaving clutter in every file
- Making it harder to change things in the future
- Eventually blindly copying without understanding (cargo-cult programming)
In an effort to reduce some of my boilerplate, I wrote
Import::Base, a module to collect and
import useful bundles of modules, removing the need for long lists of
Continue reading Manage Boilerplate with Import::Base...
... or "Ask Not To Whom The Pointer Points, It Points To Thee."
TL;DR: A pointer is not a reference. A pointer knows nothing about the data
being pointed to. Returning multiple values requires actual work.
Everything went wrong when I wanted a string with a
NUL character inside it.
C strings are not Perl scalars, they don't know how long they are. So to mark
the end of a string, C uses the
strcpy function will
copy to your destination until the first
\0 from your source. When you want to
have a string with a
\0 inside of it that does not mark the end of the string,
you need to know exactly how long the string is. This is not difficult to do,
but you also have to return that length from the function that creates your
C functions do not have more than one return value.
(char* buffer, int bufferSize) = get_string_with_nuls();
// You thought it could be that easy?
So in order for your function to result in more than one value, you have to
pass in references to be used to fill in with actual values.
int bufferSize = get_string_with_nuls( buffer );
// C programmers will already know what I did wrong here
Thinking like a Perl programmer, I thought I could just pass in the pointer to
the function and the function could fill it with data. Two problems:
- I passed in the pointer itself, not a reference to the pointer:
- I did not initialize the pointer to anything.
A more correct way would be:
char* buffer = malloc( 128 * sizeof( char ) );
int bufferSize = get_string_with_nuls( &buffer );
But this suffers from another problem: I have to know beforehand how big my
string is going to be and allocate that much memory beforehand.
The way I ended up succeeding was:
char* buffer = get_string_with_nuls( &bufferSize );
get_string_with_nuls can handle the
malloc with exactly the correct
size and give it to me. I don't have to guess at a size beforehand.
Of course, a struct could do this better, or since I'm actually in C++, an
object. I'll be planning a new API as soon as I confirm this one actually
works and has proper tests (written in Perl, of course).