Today i'm cutting video at work (yea me!), and I came across a strange video format, an MOD file format with an companion MOI file.
I found this article online from the wiki, and I wanted to write a file format handler, but I'm not sure how to begin.
I want to write a file format handler to read the information files, has anyone ever done this and how would I begin?
Edit:
Thanks for all the suggestions, I'm going to attempt this tonight, and I'll let you know. The MOI files are not very large, maybe 5KB in size at most (I don't have them in front of me).
You're in luck in that the MOI format at least spells out the file definition. All you need to do is read in the file and interpret the results based on the file definition.
Following the definition, you should be able to create a class that could read and interpret a file which returns all of the file format definitions as properties in their respective types.
Reading the file requires opening the file and generally reading it on a byte-by-byte progression, such as:
using(FileStream fs = File.OpenRead(path-to-your-file)) {
while(true) {
int b = fs.ReadByte();
if(b == -1) {
break;
}
//Interpret byte or bytes here....
}
}
Per the wiki article's referenced PDF, it looks like someone already reverse engineered the format. From the PDF, here's the first entry in the format:
Hex-Address: 0x00
Data Type: 2 Byte ASCII
Value (Hex): "V6"
Meaning: Version
So, a simplistic implementation could pull the first 2 bytes of data from the file stream and convert to ASCII, which would provide a property value for the Version.
Next entry in the format definition:
Hex-Address: 0x02
Data Type: 4 Byte Unsigned Integer
Value (Hex):
Meaning: Total size of MOI-file
Interpreting the next 4 bytes and converting to an unsigned int would provide a property value for the MOI file size.
Hope this helps.
If the files are very large and just need to be streamed in, I would create a new reader object that uses an unmanagedmemorystream to read the information in.
I've done a lot of different file format processing like this. More recently, I've taken to making a lot of my readers more functional where reading tends to use 'yield return' to return read only objects from the file.
However, it all depends on what you want to do. If you are trying to create a general purpose format for use in other applications or create an API, you probably want to conform to an existing standard. If however you just want to get data into your own application, you are free to do it however you want. You could use a binaryreader on the stream and construct the information you need within your app, or get the reader to return objects representing the contents of the file.
The one thing I would recommend. Make sure it implements IDisposable and you wrap it in a using!
Related
I am trying to open and read a bunch of geo-referenced timelog files that are in binary format. They supposedly follow the ISO-11783 (ISOBUS) standard for agricultural machinery, but after reading 100s of pages of the standard I cannot figure out how to read the files either with a hex editor or programmatically with .NET c#. I know the timelog comes in file-pairs: an xml file and a binary file. The binary file, for example, is named TLG00004.bin and in notepad it looks like this (partial):
and when I open that file in Visual Studio 2015 (Community) as a binary file the hex looks like this:
which does not help me. I don't even know how to begin reading this as a byte stream in code (or anything else for that matter).
I know the file is supposed to look like this in human readable form:
(TimeStart, PositionNorth, PositionEast, PositionStatus, # DLV, DLV 0, PDV 0, DLV 1, PDV 1, DLV 2, PDV 2,...) it can have up to 255 DLV-PDV pairs which I believe are 32-bit integers. An example was shown as: (2005-05-02T16:32:00,51.00678,6.03489,1,2,0,10,1,15)
Little hints I have seen in the documentation indicate to me this must be utf-8 and perhaps base64 encoding with little endian and no Byte Order Mark. But I tried opening this in the free version of Hexinator and can't (human) read it using any of the dozens of encodings in that app, including utf-8, 16, 32...
I know this is not normal programming stuff but am throwing it out there to see if I'm lucky enough that someone has done this before and sees this. Any hints or resource-pointing would find me grateful, and I would be very thankful if someone can share any code that reads this kind of file.
Your data seems to follow the ISO 11783-10 standard for "Log data binary file structure" data exchange.
You will need to unpack your binary data into data types according to the specification. For example, the first 32 bits of the data are the milliseconds since midnight stored as a 32 bit unsigned integer. The next 16 bits are the days since 1980-01-01 stored as a 16 bit unsigned integer.
Unpacking binary data is programming language specific and some programming languages have useful libraries to assist in shifting through binary data.
As your question is about the general parsing of ISOBUS and I'm not proficient in your given language (C#), I can only give you an initial pointer.
BinaryReader looks to be the ideal way of unpacking a binary file by reading a number of bits from a stream and advancing the pointer through it:
using (BinaryReader reader = new BinaryReader(File.Open(fileName, FileMode.Open)))
{
milliSecondsSinceMidnight = reader.ReadUInt32();
daysSince1980 = reader.ReadUInt16();
}
If you need further help, you can now ask a specific question about byte parsing in C#.
I want to create a binary file and store string data in it, I used this sample:
FileStream fs = new FileStream("c:\\test.data", FileMode.Create);
BinaryWriter bw = new BinaryWriter(fs);
bw.Write(Encoding.ASCII.GetBytes("david stein"));
bw.Close();
but when I opened created file by this sample (test.data) in notepad, it has string data in it ("david stein"), now my question is that whats the difference between this binary writing and text writing when the result is string?
I'm looking to create a data in binary file until user can not open and read my data by note pad and if user open it in notepad see real binary data .
in some files when you open theme in text editors you can not read file content like jpg files contents,they do not use any encryption methods,what about it?how can i wite my data like this?
now my question is that whats the difference between this binary writing and text writing when the result is string?
The data in a file is always "a sequence of bytes". In this case, the sequence of bytes you've written is "the bytes representing the text 'david stein'" in the ASCII encoding. So yes, if you open the file in any editor which tries to interpret the bytes as text in a way which is compatible with ASCII, you'll see the text "david stein". Really it's just a load of bytes though - it all depends on how you interpret them.
If you'd written:
File.WriteAllText("c:\\test.data", "david stein", Encoding.ASCII);
you'd have ended up with the exact same sequence of bytes. There are any number of ways you could have created a file with the same bytes in. There's nothing about File.WriteAllText which "marks" the file as text, and there's nothing about FileStream or BinaryWriter which marks the file as binary.
EDIT: From comments:
I'm looking to create a data in binary file until user can not open and read my data by note pad
Well, there are lots of ways of doing that with different levels of security. Ideally, you'd want some sort of encryption - but then the code reading the data would need to be able to decrypt it as well, which means it would need to be able to get a key. That then moves the question to "how do I store a key".
If you only need to verify the data in the file (e.g. check that it matches something from elsewhere) then you could use a cryptographic hash instead.
If you only need to prevent the most casual of snoopers, you could use something which is basically just obfuscation - a very weak form of encryption with no "key" as such. Anyone who dceompiled your code would easily be able to get at the data in that case, but you may not care too much about that.
It all depends on your requirements.
All data is binary. A text file is binary data that happens to be a limited subset that represent valid characters, but it's still binary.
The way text editors typically differentiate a text file from a binary file is they scan a certain portion of the file for zero values, \0. These never exist in text-only files and almost always exist in binary files.
C#.NET 4.0
I'm having an interesting problem here with reading a custom file archive format. In C#, I wrote a program that creates an archive header (some overhead info about the archive as a whole, number of files, those kinds of things). It then takes an input file to be stored, reads and bytes, and then writes some overhead about the file (filename, type, size and such) and then the actual file data. I can also extract files from the archive through this program. To test it, I stored a png image and extracted it by reading the filesize from the overhead and then allocating an array of bytes of that size, pulled the filedata into that array, and then wrote it with a streamwriter. No big deal, worked fine. Now, we go to the C++ side...
C++
My C++ program needs to read the filedata in, determine the filetype, and then pass it off to the appropriate processing class. The processing classes were giving errors, which they shouldn't have. So I decided to write the filedata out fro the C++ program after reading it using fwrite(), and the resulting file appears to be damaged? In a nutshell, this is the code being used to read the file...
unsigned char * data = 0;
char temp = 0;
__int64 fileSize = 0;
fread(&fileSize, sizeof(__int64), 1, _fileHandle);
data = new unsigned char[fileSize];
for (__int64 i = 0; i < fileSize; i++)
{
fread(&temp, 1, 1, _fileHandle);
data[i] = temp;
}
(I'm at work right now, so I just wrote this from memory. However, I'm 99% positive it's accurate to my code at home. I'm also not concerned with non MS Standards at the moment, so please bear with the __int64.)
I haven't gone through all 300 something thousand bytes to determine if everything is consistent, but the first 20 or so bytes that I looked at appear to be correct. I don't exactly see why there is a problem. Is there something funny about fread()? I also to double check the file in the archive, removed all the archive overhead and saved just the image data to a new png image with notepad, which worked fine.
Should I be reading this differently? Is there something wrong with using fread() to read in this data?
Given that the first n bytes appear to be correct, did you by chance forget to open the file in binary mode ("rb")? If you didn't then it's helpfully converting any sequences of \r\n into \n for you which would obviously not be what you want.
Since this question is tagged C++ did you consider using the canonical C++ approach of iostreams rather than the somewhat antiquated FILE* streams from C?
I am curious as to how applications generate their own data that is used with the application itself. For example, if you take any kind of PC game's save file or some sort of program that generates binary data like Photoshop's PSD files or .torrent files for BitTorrent applications, I'd assume they are all specific to the corresponding application and that the authors of that application programmed the way this data was created. My first question is: is that true? I am 99% positive that it is binary data because when opening a PSD file or a .torrent file in Notepad++, it's easy to see that it's nothing that can be read by a human...
My second question is: if I wanted to make an application that generates its own data in binary format (no plain-text or anything that's easily manipulated), how would I go about handling this data? I can vaguely picture generating this data and saving it to a file in binary format, but I am really stuck on how I'd handle this data when it's needed by the application again. Since this type of data is not plain text and can't be treated as a string or anything like that, how is it that applications create and handle/parse their own binary data (or any binary data in general)?
I can obviously see that when you open a PSD file, Photoshop opens and it displays whatever the PSD file contained. But how do many applications handle these formats? I am just not seeing how to parse this specific data (or binary data in general) and programmatically do what you want to with it.
Well, as a simple example, let's take bitmaps.
Bitmaps have a standard file structure, which is defined by the info header and file header.
On the wikipedia article (link: http://en.wikipedia.org/wiki/BMP_file_format) you'll see that the info header has a well defined format, as well as the file header.
Each of these is written as binary as is, and is read in as binary as is. Then, the actually bitmap image is written out as binary.
In other applications, the application may choose to do a custom plain text format, in which case it must be written to in a consistent manner or have some support for versioning so you can use newer features in the file.
Look up on serialization though, it's a rather broad topic and there are lots of approaches to this.
Edit: Here is a code sample (not optimal) for reading (or writing, with the right modifications) in bitmaps:
// Tell visual studio to align on 2-byte boundary
// Necessary so if you write to file, it only writes 14 bytes and not 16.
#pragma pack(2)
struct BMIH
{
short bfType;
long bfSize;
short bfReserved0;
short bfReserved1;
long bOffbits;
};
#pragma pack(8)
struct BMFH
{
long biSize;
long biWidth;
long biHeight;
short biPlanes;
short biBitCount;
long biCompression;
long biImageSize;
long biXPelsPerMeter;
long biYPelsPerMeter;
long biClrUsed;
long biClrImportant;
};
BMIH infoheader;
BMFH fileheader;
std::fstream file(filename.c_str(), std::ios::in | std::ios::binary);
// Read in info and file headers
file.read((char *) &infoheader, sizeof(infoheader));
file.read((char *) &fileheader, sizeof(fileheader));
// Calculate size of image
int size = fileheader.biHeight * fileheader.biWidth;
int bytes = size * fileheader.biBitCount / 8;
// Read in the image to a buffer
unsigned char data = new unsigned char[bytes];
file.read((char *) td.data, bytes);
file.close();
That code is actually a drastic simplification and completely ignores all sorts of issues, such as what happens if the file headers or data are corrupt, if the file isn't incomplete, etc. But it's just meant as a proof of concept. The #pragmas are actually visual studio specific for enforcing proper alignment of the headers.
When we write this out to a file, we might not actually say "Okay, now write out this integer". Instead, we want to write it as a binary format. For example, code that you might (but shouldn't) use to write it would look like:
// Assume for arguments sake these data structures came pre-filled
BMFH fileheader;
BMIH infoheader;
unsigned char *data;
int size = fileheader.biHeight * fileheader.biWidth;
int bytes = size * fileheader.biBitCount / 8;
std::fstream file("MyImage.bitmap", std::ios::out | std::ios::binary);
file.write((char *) &infoheader, sizeof(BMIH));
file.write((char *) &fileheader, sizeof(BMFH));
file.write((char *) data, sizeof(unsigned char) * bytes);
Read up on Binary Serialization on MSDN. The .Net Framework goes a long way to helping with this.
Yes, Many applications leverage some sort of application-specific binary formats that can not be easily manipulated. To create your own binary format, there are some options:
Binary Serialization Technique
Using IO classes to manually read and write bytes and actually creating a random access file.
I am writing a program to diff, and copy entire files or segments based on changes on either end (Rsync-esque... but more like Unison). The main idea is to keep my music folder (all mp3s) up to date over multiple locations.
I'd like to send segmented updates if only small portions of the file have changed, as opposed to copying the entire file. For this, I need a way to diff segments of the file.
I initially tried generating hashes for blocks of every file (Every n bytes I'd hash the segment). I noticed that when I changed one attribute (id3v2 tag on an mp3) all the hashed blocks would change. This makes sense, as I would guess the header is growing as it acquired new information.
This leads me to my actual question. I would like to know how to determine the length of an mp3's header, so I could create 2 comparable hashes.
1) The meta info of the file (header)
2) The actual mpeg stream with audio (This hash should remain unchanged if all I do is alter tag info)
Am I missing anything else?
Thanks!
Ty
If all you want to check the length of is id3v2 tags, then you can find out information about its structure at http://www.id3.org/id3v2.4.0-structure.
If you read the first 3 bytes, and they are equal to "ID3", then skip to the 7th byte, then read the header size. Be careful though, because the size is stored as a "synchsafe integer".
If you want to determine the header information, you'll either:
a) need to use a mp3 library that can do the parsing for you, or
b) go to the mp3 specification and parse it out as needed.
I wound up using TagLibSharp. developer.novell.com/wiki/index.php/TagLib_Sharp