No worries. Pesto's answer looks very promising. Kim Stebel Kim Stebel That's right - Ruby was meant for other stuff probably, but we have a pretty big Rails application already and we just faced this need to operate with binary files. See stackoverflow. As this question pops up as top google result when searching for "ruby write binary", and this answer is actually showed as relevant blurb directly in the search results: Ruby is perfectly fine for what OP laid out.
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Podcast Making Agile work for data science. Stack Gives Back To perform a write operation on the file Ruby provides various methods and ways, all the operations performed on any file system will be done with the File class of the ruby.
File class system allows the developer to use the various method on it like open, new and write to perform the writing work on the file system, it allows us to write either in append add new contents on the existing content with newlines mode or on normal write , in Ruby, the shortest way to write the content will be done with the method , write here write method will work in a various mode like append and write.
We have various ways and methods available in Ruby to write the contents on the file like we can use new, we can use open in append mode and write mode, we can use the direct-write method write is also available in a various mode like append mode and write mode. Let us discuss all these possible ways of writing on any file. We can perform the write operation using the new Ruby keyword. Opening the file for the write mode, here we are opening the file for the write purpose and writing the content on the file.
We can explain the below example in the following steps. Below is a simple example where we are opening a file test. Looking at the implementation from the outside-in, you can see the general structure of the BMP::Writer class. Pixels are stored in a two-dimensional array, and all the interesting things happen at the time you write the image out to file:.
The following code shows how BMP::Writer builds up this header and writes it to file:. Out of the five fields in this header, only the file size ended up being dynamic. I was able to treat the pixel array offset as a constant because the headers for 24 bit color images take up a fixed amount of space. The file size computations 1 will make sense later once we examine the way that the pixel array gets encoded. The tool that makes it possible for us to convert these various field values into binary sequences is Array pack.
If you note that the file size of our reference image is 2x2 bitmap is 70 bytes, it becomes clear what pack is actually doing for us when we examine the byte by byte values in the following example:.
The byte sequence for the file header exactly matches that of our reference image, which indicates that the proper bitmap file header is being generated. After figuring out how to encode the file header, the next step was to work on the DIB header, which includes some metadata about the image and how it should be displayed on the screen:.
The pack statement in the above code works in a very similar fashion as the code that writes out the BMP file header, with one exception: it needs to handle signed bit little endian integers. The most interesting thing to note about this code is that each row of pixels ends up getting padded with some null characters. This is to ensure that each row of pixels is aligned on WORD boundaries 4 byte sequences.
This is a semi-arbitrary limitation that has to do with file storage constraints, but things like this are common in binary files. Sometimes calculations like this are provided for you in format specifications, other times you need to derive them yourself.
Choosing to work with only 24bit per pixel images allowed me to skirt the question of how to generalize this computation to an arbitrary amount of bits per pixel. Overwrites the existing file if the file exists. If the file does not exist, creates a new file for reading and writing. The file pointer is at the end of the file if the file exists. That is, the file is in the append mode. If the file does not exist, it creates a new file for writing. Read and write mode. The file opens in the append mode.
If the file does not exist, it creates a new file for reading and writing. So, gets reads a line from standard input, and aFile.
You can use the method sysread to read the contents of a file. You can open the file in any of the modes when using the method sysread. This statement will output the first 20 characters of the file. The file pointer will now be placed at the 21st character in the file. You can use the method syswrite to write the contents into a file. You need to open the file in write mode when using the method syswrite. This method belongs to the class File.
The class File is a subclass of the class IO. The class IO also has some methods, which can be used to manipulate files. One of the IO class methods is IO.
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