I'm really kind of surprised I couldn't find an answer to this on Google. Especially since xml files lend themselves to being zipped since they are so verbose.
I'm implementing the sax reader from the msxml library in my VB6 program to read large multi-gigabyte xml files from a zip file. Unzipping these files to the hard drive and then reading them is not the way to go since unzipping to disk is not necessary and so slow. This is where my problem comes in.
I can use zlib to read chunks of data from the zip file and process those chunks, but I don't see any way in the SAXXMLReader to process chunks. I've read that the parse method accepts IStream, but I haven't been able to find any method using Google to get an IStream from a zip file.
Can anyone here please provide me an answer to this problem or a pointer in the right direction? Thank you so much for your time.
The idea of getting a stream from the zip file is certainly how I'd deal with this in Java.
I'm not a .Net developer, so it's hard for me to certify this, but it sort of looks like SharpZipLib may have what you're looking for.
Related
I am trying to parse very large gzip compressed (10+GB) file in python3. Instead of creating the parse tree, instead I used embedded actions based on the suggestions in this answer.
However, looking at the FileStream code it wants to read the entire file and then parse it. This will not work for big files.
So, this is a two part question.
Can ANTLR4 use a file stream, probably custom, that allows it to read chunks of the file at a time? What should the class interface look like?
Predicated on the above having "yes", would that class need to handle seek operations, which would be a problem if the underlying file is gzip compressed?
Short anser: no, not possible.
Long(er) answer: ANTLR4 can potentially use unlimited lookahead, so it relies on the stream to seek to any position with no delay or parsing speed will drop to nearly a hold. For that reason all runtimes use a normal file stream that reads in the entire file at once.
There were discussions/attempts in the past to create a stream that buffers only part of the input, but I haven't heard of anything that actually works.
The Preview application on the Mac allows one to merge multiple PDF files, although the functionality is rather obscure. I'm writing a utility in Haskell that needs to perform a similar task, that is, merge an arbitrary number of PDF files into one new file.
Does anyone have a suggestion as to where to start with this? Obviously if there's a library on Hackage that will do most of the work out of the box that would be ideal, but if not, then some pointers about where to start would be very much appreciated.
I'm working on pdf library, that supports parsing and generating. It is low level, higher level tools are in todo list yet (because it is hard to design good high level API).
Here is an example of unpacking and decrypting of PDF file. It is easy to implement PDF merging, but you need to be familiar with PDF internals.
ADDED:
I create a basic example of merging PDF files in Haskell. 150 lines of code total, but it lacks few features (see comments at on the top of the file). They are easy to add, so let me know if you are interested.
The PDF file format isn't that complicated. Adobe has an official specification document for it somewhere. Essentially a PDF file contains a set of numbered "objects". You'd have to get all the objects from each PDF file, renumber them so they're unique, and then you need to fiddle with the page index so all the pages actually show up.
There appear to be a couple of packages on Hackage for writing PDF files, but I don't see much for reading them. You may like to look at the source code for pdfsplit for ideas. Also HPDF.
I am planning on creating a bible app. As you know, this will involve massive text files. And as a result if poorly implemented, the application can be quite inefficient.
I am thinking of storing the large files in raw folder but I feel that this is counter-intuitive as a result of the heavy content. And would it be feasible to use a multi-line textview to display the text files from the raw folder?
Can anyone point me in the right direction? I am really desperate as I have been poring over this issue for days!!
Thanks in advance.
How about splitting the text into multiple, smaller HTML files that you can then load into a WebView?
How to read excel(2007+ xlsx) sheet using actionscript(AIR)?
as3xls
An Actionscript 3 library for reading and writing Excel files. Currently reading numbers, text, and formulas from Excel version 2.0-2003 and writing numbers, text, and dates to Excel 2.0 is supported. No server-side help is needed.
SUPPORT INFORMATION
Documentation and samples are at http://code.google.com/p/as3xls/
I wrote this: https://github.com/childoftv/as3-xlsx-reader I'd love to know if it helps
Do you have any idea how... Inefficient this is?
Excel uses a complex setup for files, and unless you want to write a full-scale parser for its spreadsheets (which, believe me, will be difficult, alone to figure out what the format chars do), you'd be better off finding another solution.
Say, using a "save to XML" option would make your job a few thousand times easier, without exaggeration. AS3 has no native support for Excel, there is no real point for it to have such. But it has great integrated methods for working with XML.
If possible, save the Excel files to XML and parse those.
Better still, use databases, and parse them as XML through PHP.
I did a search and came up with this: http://code.google.com/p/php-excel-reader/
Once you've got it in PHP, passing it on to Flash is no problem at all. I'd recommend turning it into straight arrays of objects and converting it to AMF3 via Zend_Amf, AMFPHP or WebOrb, whichever one you're most comfortable with. You can then create tables, manipulate the data or whatever you like. It'd also be a lot faster and lighter than using XML.
PK
I took a look at the xlsx breakdown and it would take me 1 week to write an xlsx writer that could do basic formatting and formulas. I've only spent 1 hour perusing through the directories in an xlsx file and all you'd have to do is create the same directory structure...mostly cut and paste some strings..and then zip it and call it xlsx.
I tried this theory by manually making an xlsx file using 7zip. I downloaded childoftv's reader and, though I don't need the reader, the package includes a few zip/unzip classes that would prove helpful for anyone who wants to make a xlsx writer.
Long story short, the setup isn't complex, somebody just has to take a week out of their busy schedule to do it. I need this functionality so if nobody's done it yet, then I'll have to. Hopefully my search will find something better than a forum where the general consensus is "it's too hard, give up."
How does one combine several resources for an application (images, sounds, scripts, xmls, etc.) into a single/multiple binary file so that they're protected from user's hands? What are the typical steps (organizing, loading, encryption, etc...)?
This is particularly common in game development, yet a lot of the game frameworks and engines out there don't provide an easy way to do this, nor describe a general approach. I've been meaning to learn how to do it, but I don't know where to begin. Could anyone point me in the right direction?
There are lots of ways to do this. m_pGladiator has some good ideas, especially with seralization. I would like to make a few other comments.
First, if you are going to pack a bunch of resources into a single file (I call these packfiles), then I think that you should work to avoid loading the whole file and then deseralizing out of that file into memory. The simple reason is that it's more memory. That's really not a problem on PC's I guess, but it's good practice, and it's essential when working on the console. While we don't (currently) serialize objects as m_pGladiator has suggested, we are moving towards that.
There are two types of packfiles that you might have. One would be a file where you want arbitrary access to the contents of the files. A second type might be a collection of files where you need all of those files when loading a level. A basic example might be:
An audio packfile might contain all the audio for your game. You might only need to load certain kinds of audio for the menus or interface screens and different sets of audio for the levels. This might fall intot he first category above.
A type that falls into the second category might be all models/textures/etc for a level. You basically want to load the entire contents of this file into the game at load time because you will (likely) need all of it's contents while a player is playing that level or section.
many of the packfiles that we build fall into the second category. We basically package up the level contents, and then compresses them with something like zlib. When we load one of these at game time, we read a small amount of the file, uncompress what we've read into a memory buffer, and then repeat until the full file has been read into memory. The buffer we read into is relatively small while final destination buffer is large enough to hold the largest set of uncompressed data that we need. This method is tricky, but again, it saves on RAM, it's an interesting exercise to get working, and you feel all nice and warm inside because you are being a good steward of system resources. once the packfile has been completely uncompressed into it's destinatino buffer, we run a final pass on the buffer to fix up pointer locations, etc. This method only works when you write out your packfile as structures that the game knows. In other words, our packfile writing tools share struct (or classses) with the game code. We are basically writing out and compressing exact representations of data structures.
If you simply want to cut down on the number of files that you are shipping and installing on a users machine, you can do with something like the first kind of packfile that I describe. Maybe you have 1000s of textures and would just simply like to cut down on the sheer number of files that you have to zip up and package. You can write a small utility that will basically read the files that you want to package together and then write a header containing the files and their offsets in the packfile, and then you can write the contents of the file, one at a time, one after the other, in your large binary file. At game time, you can simply load the header of this packfile and store the filenames and offsets in a hash. When you need to read a file, you can hash the filename and see if it exists in your packfile, and if so, you can read the contents directly from the packfile by seeking to the offset and then reading from that location in the packfile. Again, this method is basically a way to pack data together without regards for encryption, etc. It's simply an organizational method.
But again, I do want to stress that if you are going a route like I or m_pGladiator suggests, I would work hard to not have to pull the whole file into RAM and then deserialize to another location in RAM. That's a waste of resources (that you perhaps have plenty of). I would say that you can do this to get it working, and then once it's working, you can work on a method that only reads part of the file at a time and then decompresses to your destination buffer. You must use a comprsesion scheme that will work like this though. zlib and lzw both do (I believe). I'm not sure about an MD5 algorithm.
Hope that this helps.
do as Java: pack it all in a zip, and use an filesystem-like API to read directly from there.
Personally, I never used the already available tools to do that. If you want to prevent your game to be hacked easily, then you have to develop your own resource manipulation engine.
First of all read about serializing objects. When you load a resource from file (graphic, sound or whatever), it is stored in some object instance in the memory. A game usually uses dozens of graphical and sound objects. You have to make a tool, which loads them all and stores them in collections in the memory. Then serialize those collections into a binary file and you have every resource there.
Then you can use for example MD5 or any other encryption algorithm to encrypt this file.
Also, you can use zlib or other compression library to make this big binary file a bit smaller.
In the game, you should load the encrypted binary file and unpack it. Then decrypt it. Then deserialize the object collections and you have all resources back in memory.
Of course you can make this more comprehensive by storing in different binary files the resources for different levels and so on - there are plenty of variants, depending on what you want. Also you can first zip, then encrypt, or make other combinations of the steps.
Short answer: yes.
In Mac OS 6,7,8 there was a substantial API devoted to this exact task. Lookup the "Resource Manager" if you are interested. Edit: So does the ROOT physics analysis package.
Not that I know of a good tool right now. What platform(s) do you want it to work on?
Edited to add: All of the two-or-three tools of this sort that I am away of share a similar struture:
The file starts with a header and index
There are a series of blocks some of which may have there own headers and indicies, some of which are leaves
Each leaf is a simple serialization of the data to be stored.
The whole file (or sometimes individual blocks) may be compressed.
Not terribly hard to implement your own, but I'd look for a good existing one that meets your needs first.
For future people, like me, who are wondering about this same topic, check out the two following links:
http://www.sfml-dev.org/wiki/en/tutorials/formatdat
http://archive.gamedev.net/reference/programming/features/pak/