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designing a FileSystem ! :)

FxMazter · 2004-06-10T20:16:47

Hello everyone! This is the first time I''m trying to make a FileSystem. And I''ll spitt it out... I got no clue about where to start :/ I''ve been thinking about some stuff: 1. It has to replaceable, so I can change a filesystem... 2. I want to have a structure that let''s adding new filetypes along with the engine, such as bmp files or pak files. 3. It should be easy to use. So with those things in mind I started up thinking about the design: 1. Working with interfaces, will make it easy to change the FileSystem implementation. class IFile; //IFileOperations is an interface for IO write/read functions //for easily changing Platform class IFileOperations; //IFileCreator will create the correct IFile for a specific //filetype, like .bmp or .pak etc... class IFileCreator; class IFileSystem { public: virtual IFile* OpenFile(const char* sPathName) = 0; virtual void SetIODrivers(IFileOperations* pIODriver) = 0; virtual void RegisterFileType(const char* pFileEnding, IFileCreator* pCreator) = 0; //... What more would be useful ... // ? }; That will enable changing IO drivers for Win or Unix etc... And also adding new FileTypes. Now before looking on the IFile, we need some sort of pathfinding system that will check directorys, look for files etc...: class IPath { public: IPath(const char* sPathName) { //... } //Is needed for Finding Directorys in differend Platforms static void setFileOperations(IFileOperations* pFileOperations) { m_pFileOperations = pFileOperations; } virtual bool addPath(IPath newPath) = 0; virtual bool addFile(IFile* pFile) = 0; virtual bool addFile(IPath path, IFile* pFile) = 0; virtual bool contains(IPath findPath) = 0; virtual bool contains(IFile* pFile) = 0; virtual IPath* getPath(const char* sPathName) = 0; virtual IFile* getFile(const char* sFileName) = 0; virtual const char* getPathName() = 0; private: private static IFileOperations* m_pFileOperations; }; Now IPath implementations should give enougth operations to easily iterate through the filesystem looking for files or directorys. For eg: class CDirecotry : public IPath { //... }; Ok, lets look at the IFile: //BaseClass for headers of different filetypes... //All IFileHeader''s will have default data as: //1. FileTypeId, eg. BMP_HEADER, JPG_HEADER, PAK_HEADER class IFileHeader; class IFile { public: virtual void Save() = 0; virtual void ReadFileHeader(IFileHeader* pHeader) = 0; virtual IFileHeader* getFileHeader() = 0; virtual IPath* getPath() = 0; virtual void* getFileData() = 0; //... what more could be useful ?? }; OK, I think this should work just fine for a quite ok filesystem. But I''m having trouble with the Save() / ReadFileHeader(IFileHeader* pHeader) stuff. It works just fine if the given IFile is "real" file in a Directory. Then I can just write the file to disk, overwriting the old one. But what if the given IFile is not "real", such as if it''s in a .PAK file? Then I can''t just write it to disk, since it''s actually the .PAK file that should write the data. So then it should redirect the Save call to the .PAK file! But, the thing is that .PAK files are just an IPath like this: class IPakFile : public IFile, public IPath { //... } That way at startup I can just open all PAK files and create a TREE system with IPath''s. And later when searching for a file the PAK files will work just as an IPath, that is just as a Directory... But How is a single IFile supposed to know if it should Save(), that is write the data directly to disk or REDIRECT the call to a specific PAK file? I mean, the IFile does not know that it comes from a IPakFile. All it knows is that it comes from a specific IPath, which could be a CDirecotry or a IPakFile. I have been thinking of redirecting ALL calls from the IFile to the parent IPath, where the IFile is contained. And then the IPath could redirect the call to it''s parent IPath etc... Until the call arrives at a IPath that is actually an CDirectory, which will write the file to disk, or the call could arrive at an IPakFile, which will write the file to ITSELF! First off, Big thanks for just reading this long post I would really appreciate some ideas on how to do this in some other way, and I would especially appreciate some info on how the IFileOperation''s should look like. - I was thinking about something like WriteFile(...), FindFile(...), CreateDir(...), CreateFile(...). But I''m not sure how those functions should look to make it possible to implement in different Platforms. Thank you!

General and Gameplay Programming Programming

Started by FxMazter June 07, 2004 07:51 AM

10 comments, last by FxMazter 19 years, 10 months ago

OOCCO

100

June 09, 2004 08:15 AM

Creating a PAK file format

"The Holocaust was an obscene period in our nation's history. I mean in this century's history. But we all lived in this century. I didn't live in this century."...Governor George W. Bush, 9/15/95

Mayrel

348

June 10, 2004 08:16 PM

quote:Original post by xorjesus
Wow, fantastic explanation Willem, thank you :] The original author states that he may someday use this code in a resume. I program in the same way all the time using abstract classes, and oop hierarchy. Will I have a better looking resume if I start turning all abstract systems into interfaces? Such as -> class Entity {method()=0;} to class IEntity {method()=0;}?

Surely you''re not serious?

Sticking ''I'' in front of your class names will not improve your resume. What''s going to make your resume look good is well-designed programs that work.

CoV

designing a FileSystem ! :)

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designing a FileSystem ! :)

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