Game Development Reference
In-Depth Information
See also
F
Decompressing iles from the .zip archives
Enumerating iles in the .zip archives
To incorporate the contents of a
.zip
ile seamlessly into our ilesystem, we need to read
the archive contents and be able to access each ile individually. Since we are developing our
own ile I/O library, we use the
iIStream
interface to access
.zip
iles. The NDK provides
a way to read the
.apk
assets from your C++ application (see
usr/include/android/
asset_manager.h
in your NDK folder). However, it is only available on Android 2.3, and will
make debugging of ile access in your game more complex on a desktop computer without
an emulator. To make our native code portable to previous Android versions and other mobile
operating systems, we will craft our own assets reader.
Android applications are distributed as
.apk
packages, which are basically
just renamed
.zip
archives, containing a special folder structure and
metadata inside them.
Getting ready
We use the
zlib
library and the
MiniZIP
project to access the content of a
.zip
archive.
The most recent versions can be downloaded from
http://www.winimage.com/
zLibDll/minizip.html
.
How to do it...
1.
The
zlib
library is designed to be extensible. It does not assume every developer
uses only the
fopen()
calls or the
std::ifstream
interface. To read the data from
our own containers with the
iIStream
interface, we cast the
iIStream
instances
to the
void*
pointers and write a set of routines that are passed to
zlib
. These
routines resemble the standard
fopen()
-like interface and essentially only redirect
the
zlib
to our
iIStream
classes:
static voidpf ZCALLBACK zip_fopen( voidpf opaque,
const void* filename, int mode )
{
( ( iIStream* )opaque )->Seek( 0 );
return opaque;
}
