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Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Fastest reading binary file reading and writing Ask Question. Asked 9 years, 9 months ago. Active 6 years, 6 months ago. Viewed 13k times. I am writing an application to read and parse files which may be 1 KB to MB in size. I have to parse it two times Extract an image contained in the file.
Parse that image To extract the contents of the image. Is there a good method or a good class library? Improve this question. Peter Mortensen Writwick Writwick 2, 6 6 gold badges 22 22 silver badges 53 53 bronze badges. This is the fastest method by a long shot. I did not include the unsafe approach of casting a byte array of freshly read data into a structure because I prefer to avoid unsafe code if at all possible.
There are plenty of articles and newsgroup posts about using the Marshal class in order to torture raw bits into a struct. This approach is functionally almost identical to the FileStream. Read approach, but I provided it as a more apples-to-apples comparison to the other BinaryReader approach. The code is as follows:. I assumed that this would be the slowest method for filling my data structures --it was certainly the least sexy approach. Using the BinaryReader to populate the individual fields of my structures was more than twice as fast as the other methods.
These results are highly sensitive to the number of fields in your structure. If you are concerned about performance, I recommend testing both approaches. I found that, at about 40 fields, the results for the three approaches were almost equivalent, and beyond that, the block reading approaches gained an upper hand.
It has facilities to generate sample data and benchmark the three reading approaches with dynamic and cached EOF sensing. BinaryReader is used to read primitive data types as binary values in a particular encoding stream. BinaryReader works with Stream object i. BinaryReader class has three overloaded constructors to work with binary data.
By default, BinaryReader uses UTF-8 encoding to read data until we specify other character encodings while creating its object. The above statement initializes a new instance of BinaryReader based on the specified stream inputStream by using UTF-8 encoding. This statement initializes a new instance of BinaryReader based on the specified stream i nputStream and encoding specified by encoding. This statement works the same as the above two statements with an extra parameter of type Boolean which is used to specify if the user wants to leave the stream open after the object of BinaryReader is disposed of.
In the above statement, File. Open method returns an object of FileStream and thus it helps in creating the object of BinaryReader. BinaryReader is used to read binary information i. Binary file stores data in a way which can be easily understood by a machine but for human it is very difficult to understand such data. To help understand such data BinaryReader is used.
In order to work with BinaryReader, we first need to import System. IO namespace in our code. While creating an instance of BinaryReader we provide stream to read from then we can optionally specify the character encoding to be used if we do not specify encoding, by default UTF-8 encoding is used. Byte swapping, on the other hand, referred to the process required to rearrange bytes in a structure due to a potential difference in the way that processors ordered bytes.
Most Intel processors expect that integers of the bit variety will align along a 4-byte boundary. Compilers know this. So when presented with a structure that would cause an integer to not be lined up on an address that is a multiple of four, compilers have three choices.
First, they can choose to add some nonusable white space into the structure so that the starting address for the integer is a multiple of four. This is the most common implementation. Second, they can rearrange the fields so that the integers are all aligned on a multiple of four. Because this causes some other interesting problems, it's less frequently used.
The third option is to allow an integer to be in the structure in a nonmultiple of four and then put code in place to move the integer to and from a scratch space which is a multiple of four. This involves a little extra overhead with each reference, but can be useful when being compact is very important. The compiler will process the same structure the same way and all will be well.
In contrast, some programmers learned how to get the compiler to leave their structures alone. Byte swapping: Big endians versus little endians Big and little endian refers to two different ways that an integer can be stored in a computer.
Since an integer is typically more than one byte, the question becomes whether the most significant byte is the one that's read and stored first. The least significant byte is the one that changes most frequently. That is, if you continually add one to an integer the least significant byte changes times as frequently as the next least significant byte. Different kinds of processors store integers differently.
Intel processors typically store integers in little endian format, in other words, little end first. Most other processors store integers in big endian format.
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